Search This Blog

Friday, March 6, 2020

Sustainable forest management

From Wikipedia, the free encyclopedia
Sustainable forest management is the management of forests according to the principles of sustainable development. Sustainable forest management has to keep the balance between three main pillars: ecological, economic and socio-cultural. Successfully achieving sustainable forest management will provide integrated benefits to all, ranging from safeguarding local livelihoods to protecting the biodiversity and ecosystems provided by forests, reducing rural poverty and mitigating some of the effects of climate change.

The "Forest Principles" adopted at The United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro in 1992 captured the general international understanding of sustainable forest management at that time. A number of sets of criteria and indicators have since been developed to evaluate the achievement of SFM at the global, regional, country and management unit level. These were all attempts to codify and provide for independent assessment of the degree to which the broader objectives of sustainable forest management are being achieved in practice. In 2007, the United Nations General Assembly adopted the Non-Legally Binding Instrument on All Types of Forests. The instrument was the first of its kind, and reflected the strong international commitment to promote implementation of sustainable forest management through a new approach that brings all stakeholders together.

Definition

A definition of SFM was developed by the Ministerial Conference on the Protection of Forests in Europe (FOREST EUROPE), and has since been adopted by the Food and Agriculture Organization (FAO). It defines sustainable forest management as:
The stewardship and use of forests and forest lands in a way, and at a rate, that maintains their biodiversity, productivity, regeneration capacity, vitality and their potential to fulfill, now and in the future, relevant ecological, economic and social functions, at local, national, and global levels, and that does not cause damage to other ecosystems.
In simpler terms, the concept can be described as the attainment of balance – balance between society's increasing demands for forest products and benefits, and the preservation of forest health and diversity. This balance is critical to the survival of forests, and to the prosperity of forest-dependent communities. 

For forest managers, sustainably managing a particular forest tract means determining, in a tangible way, how to use it today to ensure similar benefits, health and productivity in the future. Forest managers must assess and integrate a wide array of sometimes conflicting factors – commercial and non-commercial values, environmental considerations, community needs, even global impact – to produce sound forest plans. In most cases, forest managers develop their forest plans in consultation with citizens, businesses, organizations and other interested parties in and around the forest tract being managed. The tools and visualization have been recently evolving for better management practices.

The Food and Agriculture Organization of the United Nations, at the request of Member States, developed and launched the Sustainable Forest Management Toolbox in 2014, an online collection of tools, best practices and examples of their application to support countries implementing sustainable forest management.

Because forests and societies are in constant flux, the desired outcome of sustainable forest management is not a fixed one. What constitutes a sustainably managed forest will change over time as values held by the public change.

Criteria and indicators

Deforestation of native rain forest in Rio de Janeiro City for extraction of clay for civil construction
Deforestation of native rain forest in Rio de Janeiro City for extraction of clay for civil engineering (2009 picture). An example of non sustainable forest management.

Criteria and indicators are tools which can be used to conceptualise, evaluate and implement sustainable forest management. Criteria define and characterize the essential elements, as well as a set of conditions or processes, by which sustainable forest management may be assessed. Periodically measured indicators reveal the direction of change with respect to each criterion.

Criteria and indicators of sustainable forest management are widely used and many countries produce national reports that assess their progress toward sustainable forest management. There are nine international and regional criteria and indicators initiatives, which collectively involve more than 150 countries. Three of the more advanced initiatives are those of the Working Group on Criteria and Indicators for the Conservation and Sustainable Management of Temperate and Boreal Forests (also called the Montréal Process), Forest Europe, and the International Tropical Timber Organization. Countries who are members of the same initiative usually agree to produce reports at the same time and using the same indicators. Within countries, at the management unit level, efforts have also been directed at developing local level criteria and indicators of sustainable forest management. The Center for International Forestry Research, the International Model Forest Network and researchers at the University of British Columbia have developed a number of tools and techniques to help forest-dependent communities develop their own local level criteria and indicators. Criteria and Indicators also form the basis of third-party forest certification programs such as the Canadian Standards Association's Sustainable Forest Management Standards and the Sustainable Forestry Initiative Standard.

There appears to be growing international consensus on the key elements of sustainable forest management. Seven common thematic areas of sustainable forest management have emerged based on the criteria of the nine ongoing regional and international criteria and indicators initiatives. The seven thematic areas are:
  • Extent of forest resources
  • Biological diversity
  • Forest health and vitality
  • Productive functions and forest resources
  • Protective functions of forest resources
  • Socio-economic functions
  • Legal, policy and institutional framework.
This consensus on common thematic areas (or criteria) effectively provides a common, implicit definition of sustainable forest management. The seven thematic areas were acknowledged by the international forest community at the fourth session of the United Nations Forum on Forests and the 16th session of the Committee on Forestry. These thematic areas have since been enshrined in the Non-Legally Binding Instrument on All Types of Forests as a reference framework for sustainable forest management to help achieve the purpose of the instrument.

On January 5, 2012, the Montréal Process, Forest Europe, the International Tropical Timber Organization, and the Food and Agriculture Organization of the United Nations, acknowledging the seven thematic areas, endorsed a joint statement of collaboration to improve global forest related data collection and reporting and avoiding the proliferation of monitoring requirements and associated reporting burdens.

Ecosystem approach

The Ecosystem Approach has been prominent on the agenda of the Convention on Biological Diversity (CBD) since 1995 . The CBD definition of the Ecosystem Approach and a set of principles for its application were developed at an expert meeting in Malawi in 1995, known as the Malawi Principles. The definition, 12 principles and 5 points of "operational guidance" were adopted by the fifth Conference of Parties (COP5) in 2000. The CBD definition is as follows
The ecosystem approach is a strategy for the integrated management of land, water and living resources that promotes conservation and sustainable use in an equitable way. Application of the ecosystem approach will help to reach a balance of the three objectives of the Convention. An ecosystem approach is based on the application of appropriate scientific methodologies focused on levels of biological organization, which encompasses the essential structures, processes, functions and interactions among organisms and their environment. It recognizes that humans, with their cultural diversity, are an integral component of many ecosystems.
Sustainable forest management was recognized by parties to the Convention on Biological Diversity in 2004 (Decision VII/11 of COP7) to be a concrete means of applying the Ecosystem Approach to forest ecosystems. The two concepts, sustainable forest management and the ecosystem approach, aim at promoting conservation and management practices which are environmentally, socially and economically sustainable, and which generate and maintain benefits for both present and future generations. In Europe, the MCPFE and the Council for the Pan-European Biological and Landscape Diversity Strategy (PEBLDS) jointly recognized sustainable forest management to be consistent with the Ecosystem Approach in 2006.

Independent certification

Growing environmental awareness and consumer demand for more socially responsible businesses helped third-party forest certification emerge in the 1990s as a credible tool for communicating the environmental and social performance of forest operations. 

There are many potential users of certification, including: forest managers, scientists, policy makers, investors, environmental advocates, business consumers of wood and paper, and individuals.

With third-party forest certification, an independent organization develops standards of good forest management, and independent auditors issue certificates to forest operations that comply with those standards. Forest certification verifies that forests are well-managed – as defined by a particular standard – and chain-of-custody certification tracks wood and paper products from the certified forest through processing to the point of sale.

This rise of certification led to the emergence of several different systems throughout the world. As a result, there is no single accepted forest management standard worldwide, and each system takes a somewhat different approach in defining standards for sustainable forest management.

In its 2009–2010 Forest Products Annual Market Review United Nations Economic Commission for Europe/Food and Agriculture Organization stated: "Over the years, many of the issues that previously divided the (certification) systems have become much less distinct. The largest certification systems now generally have the same structural programmatic requirements."

Third-party forest certification is an important tool for those seeking to ensure that the paper and wood products they purchase and use come from forests that are well-managed and legally harvested. Incorporating third-party certification into forest product procurement practices can be a centerpiece for comprehensive wood and paper policies that include factors such as the protection of sensitive forest values, thoughtful material selection and efficient use of products.

There are more than fifty certification standards worldwide, addressing the diversity of forest types and tenures. Globally, the two largest umbrella certification programs are:
The area of forest certified worldwide is growing slowly. PEFC is the world's largest forest certification system, with more than two-thirds of the total global certified area certified to its Sustainability Benchmarks.

In North America, there are three certification standards endorsed by PEFC – the Sustainable Forestry Initiative, the Canadian Standards Association's Sustainable Forest Management Standard, and the American Tree Farm System. FSC has five standards in North America – one in the United States and four in Canada.

While certification is intended as a tool to enhance forest management practices throughout the world, to date most certified forestry operations are located in Europe and North America. A significant barrier for many forest managers in developing countries is that they lack the capacity to undergo a certification audit and maintain operations to a certification standard.

Forest governance

Countries participating in the UNREDD program and/or Forest Carbon Partnership Facility.
  UN-REDD participants
  Forest Carbon Partnership Facility participants
  participants in both

Although a majority of forests continue to be owned formally by government, the effectiveness of forest governance is increasingly independent of formal ownership. Since neo-liberal ideology in the 1980s and the emanation of the climate change challenges, evidence that the state is failing to effectively manage environmental resources has emerged. Under neo-liberal regimes in the developing countries, the role of the state has diminished and the market forces have increasingly taken over the dominant socio-economic role. Though the critiques of neo-liberal policies have maintained that market forces are not only inappropriate for sustaining the environment, but are in fact a major cause of environmental destruction. Hardin's tragedy of the commons (1968) has shown that the people cannot be left to do as they wish with land or environmental resources. Thus, decentralization of management offers an alternative solution to forest governance.

The shifting of natural resource management responsibilities from central to state and local governments, where this is occurring, is usually a part of broader decentralization process. According to Rondinelli and Cheema (1983), there are four distinct decentralization options: these are: (i) Privatization – the transfer of authority from the central government to non-governmental sectors otherwise known as market-based service provision, (ii) Delegation – centrally nominated local authority, (iii) Devolution – transfer of power to locally acceptable authority and (iv) Deconcentration – the redistribution of authority from the central government to field delegations of the central government. The major key to effective decentralization is increased broad-based participation in local-public decision making. In 2000, the World Bank report reveals that local government knows the needs and desires of their constituents better than the national government, while at the same time, it is easier to hold local leaders accountable. From the study of West African tropical forest, it is argued that the downwardly accountable and/or representative authorities with meaningful discretional powers are the basic institutional element of decentralization that should lead to efficiency, development and equity. This collaborates with the World Bank report in 2000 which says that decentralization should improve resource allocation, efficiency, accountability and equity "by linking the cost and benefit of local services more closely".

Many reasons point to the advocacy of decentralization of forest. (i) Integrated rural development projects often fail because they are top-down projects that did not take local people's needs and desires into account. (ii) National government sometimes have legal authority over vast forest areas that they cannot control, thus, many protected area projects result in increased biodiversity loss and greater social conflict. Within the sphere of forest management, as state earlier, the most effective option of decentralization is "devolution"-the transfer of power to locally accountable authority. However, apprehension about local governments is not unfounded. They are often short of resources, may be staffed by people with low education and are sometimes captured by local elites who promote clientelist relation rather than democratic participation. Enters and Anderson (1999) point that the result of community-based projects intended to reverse the problems of past central approaches to conservation and development have also been discouraging.

Broadly speaking, the goal of forest conservation has historically not been met when, in contrast with land use changes; driven by demand for food, fuel and profit. It is necessary to recognize and advocate for better forest governance more strongly given the importance of forest in meeting basic human needs in the future and maintaining ecosystem and biodiversity as well as addressing climate change mitigation and adaptation goal. Such advocacy must be coupled with financial incentives for government of developing countries and greater governance role for local government, civil society, private sector and NGOs on behalf of the "communities".

National Forest Funds

The development of National Forest Funds is one way to address the issue of financing sustainable forest management. National forest funds (NFFs) are dedicated financing mechanisms managed by public institutions designed to support the conservation and sustainable use of forest resources. As of 2014, there are 70 NFFs operating globally.

Forest genetic resources

Appropriate use and long-term conservation of forest genetic resources (FGR) is a part of sustainable forest management. In particular when it comes to the adaptation of forests and forest management to climate change. Genetic diversity ensures that forest trees can survive, adapt and evolve under changing environmental conditions. Genetic diversity in forests also contributes to tree vitality and to the resilience towards pests and diseases. Furthermore, FGR has a crucial role in maintaining forest biological diversity at both species and ecosystem levels.

Selecting carefully the forest reproductive material with emphasis on getting a high genetic diversity rather than aiming at producing a uniform stand of trees, is essential for sustainable use of FGR. Considering the provenance is crucial as well. For example in relation to climate change, local material may not have the genetic diversity or phenotypic plasticity to guarantee good performance under changed conditions. A different population from further away, which may have experienced selection under conditions more like those forecast for the site to be reforested, might represent a more suitable seed source.

Regional action

Russia

In 2019 after severe wildfires and public pressure the Russian government decided to take a number of measures for more effective forest management, what is considered as a big victory for the Environmental movement

Indonesia

In August 2019, a court in Indonesia stopped the construction of a dam that could heavily hurt forests and villagers in the area

United States of America

In the beginning of the year 2020 the "Save the Redwoods League" after a successful crowdfunding campaign bought " Alder Creek" a piece of land 583 acres large, with 483 big Sequoia trees including the 5th largest tree in the world. The organizations plan to make there forest thinning that is a controversial operation

Superfund

From Wikipedia, the free encyclopedia

Comprehensive Environmental Response, Compensation, and Liability Act of 1980
Great Seal of the United States
Long titleAn act to provide for liability, compensation, cleanup, and emergency response for hazardous substances released into the environment and the cleanup of inactive hazardous waste disposal sites.
Acronyms (colloquial)CERCLA
NicknamesSuperfund
Enacted bythe 96th United States Congress
Citations
Public lawP.L. 96-510
Statutes at Large94 Stat. 2767
Codification
Titles amended42 (Public Health)
U.S.C. sections created42 U.S.C. § 9601 et seq.
Legislative history
Major amendments
Superfund Amendments and Reauthorization Act of 1986;
Emergency Planning and Community Right-to-Know Act of 1986
United States Supreme Court cases
United States v. Bestfoods, 524 U.S. 51 (1998)

The United States federal Superfund law is officially known as the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). The federal Superfund program, administered by the U.S. Environmental Protection Agency (EPA) is designed to investigate and clean up sites contaminated with hazardous substances. Sites managed under this program are referred to as "Superfund" sites. There are 40,000 federal Superfund sites across the country, and approximately 1,600 of those sites have been listed on the National Priorities List (NPL). Sites on the NPL are considered the most highly contaminated and undergo longer-term remedial investigation and remedial action (cleanups).

The EPA seeks to identify parties responsible for hazardous substances releases to the environment (polluters) and either compel them to clean up the sites, or it may undertake the cleanup on its own using the Superfund (a trust fund) and seek to recover those costs from the responsible parties through settlements or other legal means.

Approximately 70% of Superfund cleanup activities historically have been paid for by the potentially responsible parties (PRPs), the latter reflecting the polluter pays principle. However, 30% of the time the responsible party either cannot be found or is unable to pay for the cleanup. In these circumstances, taxpayers pay for the cleanup. Through the 1980s, most of the funding came from a tax passed on to the consumers of petroleum and chemical products. However, in 1995, Congress chose not to renew this tax and the burden of the cost was shifted to tax payers. Since 2001, most of the cleanup of hazardous waste sites has been funded through taxpayers generally. Despite its name, the program has suffered from under-funding, and Superfund NPL cleanups have decreased to a mere 8 in 2014, out of over 1,200.

The EPA and state agencies use the Hazard Ranking System (HRS) to calculate a site score (ranging from 0 to 100) based on the actual or potential release of hazardous substances from a site. A score of 28.5 places a site on the National Priorities List, eligible for long-term, remedial action (i.e., cleanup) under the Superfund program. As of August 9, 2016, there were 1,328 sites listed; an additional 391 had been delisted, and 55 new sites have been proposed.

The Superfund law also authorizes federal natural resource agencies, primarily the Environmental Protection Agency (EPA), states and Native American tribes to recover natural resource damages caused by hazardous substances, though most states have and most often use their own versions of a state Superfund law. CERCLA created the Agency for Toxic Substances and Disease Registry (ATSDR).

The primary goal of a Superfund cleanup is to reduce the risks to human health and human health in the environment through a combination of cleanup, engineered controls like caps and site restrictions such as groundwater use restrictions. A secondary goal is to return the site to productive use as a business, recreation or as a natural ecosystem. Identifying the intended reuse early in the cleanup often results in faster and less expensive cleanups. EPA's Superfund Redevelopment Initiative provides tools and support for site redevelopment.

History

Workers in hazmat suits check the status of a cleanup site

CERCLA was enacted by Congress in 1980 in response to the threat of hazardous waste sites, typified by the Love Canal disaster in New York, and the Valley of the Drums in Kentucky. It was recognized that funding would be difficult, since the responsible parties were not easily found, and so the Superfund was established to provide funding through a taxing mechanism on certain industries and to create a comprehensive liability framework to be able to hold a broader range of parties responsible. The initial Superfund trust fund to clean up sites where a polluter could not be identified, could not or would not pay (bankruptcy or refusal), consisted of about $1.6 billion and then increased to $8.5 billion. Initially, the framework for implementing the program came from the oil and hazardous substances National Contingency Plan.

The EPA published the first Hazard Ranking System (HRS) in 1981, and the first National Priorities List (NPL) in 1983. Implementation in early years, during the Reagan administration, was ineffective, with only 16 of the 799 Superfund sites cleaned up and only $40 million of $700 million in recoverable funds from responsible parties collected. The mismanagement of the program under Anne Gorsuch Burford, Reagan's first chosen Administrator of the agency, led to a congressional investigation and the reauthorization of the program in 1986 through an act amending CERCLA.

The Superfund Amendments and Reauthorization Act of 1986 (SARA) added minimum cleanup requirements in Section 121, and required that most cleanup agreements with polluters be entered in federal court as a consent decree subject to public comment (section 122). This was to address sweetheart deals between industry and the Reagan-era EPA that Congress had discovered.

In 1994, President Bill Clinton proposed a new Superfund reform bill, Executive Order (E.O) 12898, which called for federal agencies to make achieving environmental justice a requirement by addressing low income populations and minority populations that have experienced disproportionate adverse health and environmental effects as a result of their programs, policies, and activities. The regional offices of the Environmental Protection Agency now had to apply required guidelines for its managers to take into consideration data analysis, managed public participation, and economic opportunity when considering the geography of toxic waste site remediation. Some environmentalists and industry lobbyists saw the Clinton administration’s environmental justice policy as an improvement, but the bill did not get bipartisan support. The newly elected Republican Congress made numerous unsuccessful efforts to significantly weaken the law. The Clinton Administration then adopted some industry favored reforms as policy and blocked most major changes.

Until the mid-1990s, most of the funding came from a tax on the petroleum and chemical industries, reflecting the polluter pays principle. Even though by 1995 nearly $4 billion in fees were in the Superfund, Congress chose not to reauthorize collection of these and by 2003 the Superfund was empty.

In 2001, the Environmental Protection Agency used funds from the Superfund program to institute the cleanup of anthrax on Capitol Hill after the 2001 Anthrax Attacks. It was the first time the agency dealt with a biological release rather than a chemical or oil spill.

According to a 2015 U.S. Government Accountability Office report, since 2001, most of the funding for cleanups of hazardous waste sites has come from taxpayers; a state pays 10 percent of cleanup costs in general and at least 50 percent of cleanup costs if the state operated the facility responsible for contamination. By 2013 funding had decreased from $2 billion in 1999 to less than $1.1 billion (in constant dollars).

From 2000-2015, Congress allocated about $1.26 billion of general revenue to the Superfund program each year. Consequently, less than half the number of sites were cleaned up from 2001 to 2008, compared to before. The decrease continued during the Obama Administration, and since under the direction of EPA Administrator Gina McCarthy Superfund cleanups decreased even more from 20 in 2009 to a mere 8 in 2014.

The preliminary 2018 Trump Administration Superfund budget would cut the program by $330 million out of its nearly $1.1 billion budget, a 30% reduction to the Environmental Protection Agency program.

Provisions

CERCLA authorizes two kinds of response actions:
  1. Removal actions. These are typically short-term response actions, where actions may be taken to address releases or threatened releases requiring prompt response. Removal actions are classified as: (1) emergency; (2) time-critical; and (3) non-time critical. Removal responses are generally used to address localized risks such as abandoned drums containing hazardous substances, and contaminated surface soils posing acute risks to human health or the environment.
  2. Remedial actions. These are usually long-term response actions. Remedial actions seek to permanently and significantly reduce the risks associated with releases or threats of releases of hazardous substances, and are generally larger more expensive actions. They can include measures such as using containment to prevent pollutants from migrating, and combinations of removing, treating, or neutralizing toxic substances. These actions can be conducted with federal funding only at sites listed on the EPA National Priorities List (NPL) in the United States and the territories. Remedial action by responsible parties under consent decrees or unilateral administrative orders with EPA oversight may be performed at both NPL and non-NPL sites, commonly called Superfund Alternative Sites in published EPA guidance and policy documents.
A potentially responsible party (PRP) is a possible polluter who may eventually be held liable under CERCLA for the contamination or misuse of a particular property or resource. Four classes of PRPs may be liable for contamination at a Superfund site:
  1. the current owner or operator of the site;
  2. the owner or operator of a site at the time that disposal of a hazardous substance, pollutant or contaminant occurred;
  3. a person who arranged for the disposal of a hazardous substance, pollutant or contaminant at a site; and
  4. a person who transported a hazardous substance, pollutant or contaminant to a site, who also has selected that site for the disposal of the hazardous substances, pollutants or contaminants.
The liability scheme of CERCLA changed commercial and industrial real estate, making sellers liable for contamination from past activities, meaning they can’t pass liability onto unknowing buyers without any responsibility. Buyers also have to be aware of future liabilities.

The CERCLA also required the revision of the National Oil and Hazardous Substances Pollution Contingency Plan 9605(a)(NCP). The NCP guides how to respond to releases and threatened releases of hazardous substances, pollutants, or contaminants. The NCP established the National Priorities List, which appears as Appendix B to the NCP, and serves as EPA´s information and management tool. The NPL is updated periodically by federal rulemaking.

The identification of a site for the NPL is intended primarily to guide the EPA in:
  • Determining which sites warrant further investigation to assess the nature and extent of risks to human health and the environment
  • Identifying what CERCLA-financed remedial actions may be appropriate
  • Notifying the public of sites the EPA believes warrant further investigation
  • Notifying PRPs that the EPA may initiate CERCLA-financed remedial action
Including a site on the NPL does not itself require PRPs to initiate action to clean up the site, nor assign liability to any person. The NPL serves informational purposes, notifying the government and the public of those sites or releases that appear to warrant remedial actions.

The key difference between the authority to address hazardous substances and pollutants or contaminants is that the cleanup of pollutants or contaminants, which are not hazardous substances, cannot be compelled by unilateral administrative order.

Despite the name, the Superfund trust fund lacks sufficient funds to clean up even a small number of the sites on the NPL. As a result, the EPA typically negotiates consent orders with PRPs to study sites and develop cleanup alternatives, subject to EPA oversight and approval of all such activities. The EPA then issues a Proposed Plans for remedial action for a site on which it takes public comment, after which it makes a cleanup decision in a Record of Decision (ROD). RODs are typically implemented under consent decrees by PRPs or under unilateral orders if consent cannot be reached. If a party fails to comply with such an order, it may be fined up to $37,500 for each day that non-compliance continues. A party that spends money to clean up a site may sue other PRPs in a contribution action under the CERCLA. CERCLA liability has generally been judicially established as joint and several among PRPs to the government for cleanup costs (i.e., each PRP is hypothetically responsible for all costs subject to contribution), but CERCLA liability is allocable among PRPs in contribution based on comparative fault. An "orphan share" is the share of costs at a Superfund site that is attributable to a PRP that is either unidentifiable or insolvent. The EPA tries to treat all PRPs equitably and fairly. Budgetary cuts and constraints can make more equitable treatment of PRPs more difficult.

Procedures

A national map of Superfund sites. Red indicates currently on final National Priority List, yellow is proposed, green is deleted (usually meaning having been cleaned up). This map is as of October 2013.

Upon notification of a potentially hazardous waste site, the EPA conducts a Preliminary Assessment/Site Inspection (PA/SI), which involves records reviews, interviews, visual inspections, and limited field sampling. Information from the PA/SI is used by the EPA to develop a Hazard Ranking System (HRS) score to determine the CERCLA status of the site. Sites that score high enough to be listed typically proceed to a Remedial Investigation/Feasibility Study (RI/FS).

The RI includes an extensive sampling program and risk assessment that defines the nature and extent of the site contamination and risks. The FS is used to develop and evaluate various remediation alternatives. The preferred alternative is presented in a Proposed Plan for public review and comment, followed by a selected alternative in a ROD. The site then enters into a Remedial Design phase and then the Remedial Action phase. Many sites include long-term monitoring. Once the Remedial Action has been completed, reviews are required every five years, whenever hazardous substances are left onsite above levels safe for unrestricted use.
  • The CERCLA information system (CERCLIS) is a database maintained by the EPA and the states that lists sites where releases may have occurred, must be addressed, or have been addressed. CERCLIS consists of three inventories: the CERCLIS Removal Inventory, the CERCLIS Remedial Inventory, and the CERCLIS Enforcement Inventory.
  • The Superfund Innovative Technology Evaluation (SITE) program supports development of technologies for assessing and treating waste at Superfund sites. The EPA evaluates the technology and provides an assessment of its potential for future use in Superfund remediation actions. The SITE program consists of four related components: the Demonstration Program, the Emerging Technologies Program, the Monitoring and Measurement Technologies Program, and Technology Transfer activities.
  • A reportable quantity (RQ) is the minimum quantity of a hazardous substance which, if released, must be reported.
  • A source control action represents the construction or installation and start-up of those actions necessary to prevent the continued release of hazardous substances (primarily from a source on top of or within the ground, or in buildings or other structures) into the environment.
  • A section 104(e) letter is a request by the government for information about a site. It may include general notice to a potentially responsible party that CERCLA-related action may be undertaken at a site for which the recipient may be responsible. This section also authorizes the EPA to enter facilities and obtain information relating to PRPs, hazardous substances releases, and liability, and to order access for CERCLA activities. The 104(e) letter information-gathering resembles written interrogatories in civil litigation.
  • A section 106 order is a unilateral administrative order issued by EPA to PRP(s) to perform remedial actions at a Superfund site when the EPA determines there may be an imminent and substantial endangerment to the public health or welfare or the environment because of an actual or threatened release of a hazardous substance from a facility, subject to treble damages and daily fines if the order is not obeyed.
  • A remedial response is a long-term action that stops or substantially reduces a release of a hazardous substance that could affect public health or the environment. The term remediation, or cleanup, is sometimes used interchangeably with the terms remedial action, removal action, response action, remedy, or corrective action.
    • A nonbinding allocation of responsibility (NBAR) is a device, established in the Superfund Amendments and Reauthorization Act, that allows the EPA to make a nonbinding estimate of the proportional share that each of the various responsible parties at a Superfund site should pay toward the costs of cleanup.
  • Relevant and appropriate requirements are those United States federal or state cleanup requirements that, while not "applicable," address problems sufficiently similar to those encountered at the CERCLA site that their use is appropriate. Requirements may be relevant and appropriate if they would be "applicable" except for jurisdictional restrictions associated with the requirement.

Implementation

Polluted Martin's Creek on the Kin-Buc Landfill Superfund site in Edison, New Jersey

As of 9 August 2016, there were 1,328 sites listed on the National Priority List; an additional 391 had been delisted, and 55 new sites were proposed.

Historically about 70 percent of Superfund cleanup activities have been paid for by potentially responsible party (PRPs). When the party either cannot be found or is unable to pay for the cleanup, the Superfund law originally paid for toxic waste cleanups through a tax on petroleum and chemical industries. The chemical and petroleum fees were intended to provide incentives to use less toxic substances. Over five years, $1.6 billion was collected, and the tax went to a trust fund for cleaning up abandoned or uncontrolled hazardous waste sites.

The last full fiscal year (FY) in which the Department of the Treasury collected the tax was 1995. At the end of FY 1996, the invested trust fund balance was $6.0 billion. This fund was exhausted by the end of FY 2003; Since that time superfund sites for which the potentially responsible parties could not pay have been paid for from the general fund appropriated by Congress.

Hazard Ranking System

The Hazard Ranking System is a scoring system used to evaluate potential relative risks to public health and the environment from releases or threatened releases of hazardous wastes at uncontrolled waste sites. Under the Superfund program, the EPA and state agencies use the HRS to calculate a site score (ranging from 0 to 100) based on the actual or potential release of hazardous substances from a site through air, surface water or groundwater. A score of 28.5 places the site on the National Priorities List, making the site eligible for long-term remedial action (i.e., cleanup) under the Superfund program.

Environmental discrimination

Federal actions to address the disproportionate health and environmental disparities that minority and low-income populations face through Executive Order (E.O) 12898 required federal agencies to make environmental justice central to their programs and policies. Superfund sites have been shown to impact minority communities the most. Despite legislation specifically designed to ensure equity in Superfund listing, marginalized populations still experience a lesser chance of successful listing and cleanup than areas with higher income levels. After the executive order had been put in place, there persisted a discrepancy between the demographics of the communities living near toxic waste sites and their listing as Superfund sites, which would otherwise grant them federally funded cleanup projects. Communities with both increased minority and low-income populations were found to have lowered their chances of site listing after the executive order, while on the other hand, increases in income led to greater chances of site listing. Of the populations living within 1 mile radius of a Superfund site, 44% of those are minorities despite only being around 37% of the nation's population. It has also been shown that the government responds slower to community demands from minority communities than from white communities. Superfund sites near white communities are reputed to have better clean-up, harsher penalties for polluters, and a larger tax-base of funding than minority communities.

Case studies in African American communities

In 1978, residents of the rural black community of Triana, Alabama were found to be contaminated with DDT and PCB, some of whom had the highest levels of DDT ever recorded in human history. The DDT was found in high levels in Indian Creek, which many residents relied on for sustenance fishing. Although this major health threat to residents of Triana was discovered in 1978, the federal government did not act until 5 years later after the mayor of Triana filed a class-action lawsuit in 1980. 

In West Dallas, Texas, a mostly African American and Latino community, a lead smelter poisoned the surrounding neighborhood, elementary school, and day cares for more than five decades. Dallas city officials were informed in 1972 that children in the proximity of the smelter were being exposed to lead contamination. The city sued the lead smelters in 1974, then reduced its lead regulations in 1976. It wasn't until 1981 that the EPA commissioned a study on the lead contamination in this neighborhood, and found the same results that had been found a decade earlier. In 1983, the surrounding day cares had to close due to the lead exposure while the lead smelter remained operating. It was later revealed that EPA Deputy Administrator John Hernandez had deliberately stalled the clean up of the lead-contaminated hot spots. It wasn't until 1993 that the site was declared a Superfund site, and at the time it was one of the largest ones. However, it was not until 2004 when the EPA completed the clean-up efforts and eliminated the lead pollutant sources from the site. 

The Afton community of Warren County, North Carolina is one of the most prominent environmental injustice cases and is often pointed to as the roots of the environmental justice movement. PCB's were illegally dumped into the community and then it eventually became a PCB landfill. Community leaders pressed the state for the site to be cleaned up for an entire decade until it was finally detoxified. However, this decontamination did not return the site to its pre-1982 conditions. There has been a call for reparations to the community which has not yet been met. 

Bayview-Hunters Point, San Francisco, a historically African American community, has faced persistent environmental discrimination due to the poor remediation efforts of the San Francisco Naval Shipyard, a federally declared Superfund site. The negligence of multiple agencies to adequately clean this site has led Bayview residents to be subject to high rates of pollution, gentrification, and has been tied to high rates of cancer, asthma, and overall higher health hazards than other regions of San Francisco.

Case studies in Native American communities

One example is the Church Rock uranium mill spill on the Navajo Nation. It was the largest radioactive spill in the US, but received a long delay in government response and cleanup after being placed as a lower priority site. Two sets of five-year clean up plans have been put in place by US Congress, but contamination from the Church Rock incident has still not been completely cleaned up. Today, uranium contamination from mining during the Cold War era remains throughout the Navajo Nation, posing health risks to the Navajo community. 

Cuts to the EPA's funding and resources would hinder the regulation and remediation of Superfund sites. This would perpetuate the exposure to health risks that adjacent communities face from proximity to the Superfund site. Delays in government response to Superfund conditions increases the exposure of health risks to proximate communities.

Accessing data

The data in the Superfund Program are available to the public.
  • EPA Superfund Information Systems: Report and Product Descriptions
  • EPA Superfund Information Systems: Superfund Product Order Form
  • TOXMAP was a Geographic Information System (GIS) from the Division of Specialized Information Services of the United States National Library of Medicine (NLM) that was deprecated on December 16, 2019. The application used maps of the United States to help users visually explore data from the EPA Toxics Release Inventory (TRI) and Superfund programs. TOXMAP was a resource funded by the US Federal Government. TOXMAP's chemical and environmental health information is taken from NLM's Toxicology Data Network (TOXNET), PubMed, and other authoritative sources.

Future challenges

While the simple and relatively easy sites have been cleaned up, EPA is now addressing a residual number of difficult and massive sites such as large-area mining and sediment sites, which is tying up a significant amount of funding. Also, while the federal government has reserved funding for cleanup of federal facility sites, this cleanup going much more slowly. The delay is due to a number of reasons, including EPA’s limited ability to require performance, difficulty of dealing with Department of Energy radioactive wastes, and the sheer number of federal facility sites.

Polychlorinated biphenyl

From Wikipedia, the free encyclopedia

Polychlorinated biphenyl
Polychlorinated biphenyl structure.svg
Chemical structure of PCBs. The possible positions of chlorine atoms on the benzene rings are denoted by numbers assigned to the carbon atoms.
Identifiers
UN number UN 2315
Properties
C12H10−xClx
Molar mass Variable
Appearance Light yellow or colorless, thick, oily liquids
Hazards
NFPA 704 (fire diamond)
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
2
1
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

PCB warning label on a power transformer known to contain PCBs.

A polychlorinated biphenyl (PCB) is an organic chlorine compound with the formula C12H10−xClx. Polychlorinated biphenyls were once widely deployed as dielectric and coolant fluids in electrical apparatus, carbonless copy paper and in heat transfer fluids.

Because of their longevity, PCBs are still widely in use, even though their manufacture has declined drastically since the 1960s, when a host of problems were identified. With the discovery of PCBs' environmental toxicity, and classification as persistent organic pollutants, their production was banned by United States federal law in 1978, and by the Stockholm Convention on Persistent Organic Pollutants in 2001. The International Agency for Research on Cancer (IARC), rendered PCBs as definite carcinogens in humans. According to the U.S. Environmental Protection Agency (EPA), PCBs cause cancer in animals and are probable human carcinogens. Many rivers and buildings, including schools, parks, and other sites, are contaminated with PCBs and there has been contamination of food supplies with the substances.

Some PCBs share a structural similarity and toxic mode of action with dioxins. Other toxic effects such as endocrine disruption (notably blocking of thyroid system functioning) and neurotoxicity are known. The maximum allowable contaminant level in drinking water in the United States is set at zero, but because of the limitations of water treatment technologies, a level of 0.5 parts per billion is the de facto level.

The bromine analogues of PCBs are polybrominated biphenyls (PBBs), which have analogous applications and environmental concerns.

Physical and chemical properties

Physical properties

The compounds are pale-yellow viscous liquids. They are hydrophobic, with low water solubilities: 0.0027–0.42 ng/L for Aroclors, but they have high solubilities in most organic solvents, oils, and fats. They have low vapor pressures at room temperature. They have dielectric constants of 2.5–2.7, very high thermal conductivity, and high flash points (from 170 to 380 °C).

The density varies from 1.182 to 1.566 g/cm3. Other physical and chemical properties vary widely across the class. As the degree of chlorination increases, melting point and lipophilicity increase, and vapour pressure and water solubility decrease.

PCBs do not easily break down or degrade, which made them attractive for industries. PCB mixtures are resistant to acids, bases, oxidation, hydrolysis, and temperature change. They can generate extremely toxic dibenzodioxins and dibenzofurans through partial oxidation. Intentional degradation as a treatment of unwanted PCBs generally requires high heat or catalysis.

PCBs readily penetrate skin, PVC (polyvinyl chloride), and latex (natural rubber). PCB-resistant materials include Viton, polyethylene, polyvinyl acetate (PVA), polytetrafluoroethylene (PTFE), butyl rubber, nitrile rubber, and Neoprene.

Structure and toxicity

PCBs are derived from biphenyl, which has the formula C12H10, sometimes written (C6H5)2. In PCBs, some of the hydrogen atoms in biphenyl are replaced by chlorine atoms. There are 209 different chemical compounds in which one to ten chlorine atoms can replace hydrogen atoms. PCBs are typically used as mixtures of compounds and are given the single identifying CAS number 1336-36-3 . About 130 different individual PCBs are found in commercial PCB products.

Toxic effects vary depending on the specific PCB. In terms of their structure and toxicity, PCBs fall into two distinct categories, referred to as coplanar or non-ortho-substituted arene substitution patterns and noncoplanar or ortho-substituted congeners. 

Structures of the twelve dioxin-like PCBs
Coplanar or non-ortho
The coplanar group members have a fairly rigid structure, with their two phenyl rings in the same plane. It renders their structure similar to polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans, and allows them to act like PCDDs, as an agonist of the aryl hydrocarbon receptor (AhR) in organisms. They are considered as contributors to overall dioxin toxicity, and the term dioxins and dioxin-like compounds is often used interchangeably when the environmental and toxic impact of these compounds is considered.
Noncoplanar
Noncoplanar PCBs, with chlorine atoms at the ortho positions can cause neurotoxic and immunotoxic effects, but only at concentrations much higher than those normally associated with dioxins. They do not activate the AhR, and are not considered part of the dioxin group. Because of their lower toxicity, they are of less concern to regulatory bodies.
Di-ortho-substituted, non-coplanar PCBs interfere with intracellular signal transduction dependent on calcium which may lead to neurotoxicity. ortho-PCBs can disrupt thyroid hormone transport by binding to transthyretin.

Alternative names

Commercial PCB mixtures were marketed under the following names:

Aroclor mixtures

The only North American producer, Monsanto Company, marketed PCBs under the trade name Aroclor from 1930 to 1977. These were sold under trade names followed by a four-digit number. In general, the first two digits refer to the product series as designated by Monsanto (e.g. 1200 or 1100 series); the second two numbers indicate the percentage of chlorine by mass in the mixture. Thus, Aroclor 1260 is a 1200 series product and contains 60% chlorine by mass. It is a myth that the first two digits referred to the number of carbon atoms; the number of carbon atoms do not change in PCBs. The 1100 series was a crude PCB material which was distilled to create the 1200 series PCB product.

The exception to the naming system is Aroclor 1016 which was produced by distilling 1242 to remove the highly chlorinated congeners to make a more biodegradable product. "1016" was given to this product during Monsanto's research stage for tracking purposes but the name stuck after it was commercialized.

Different Aroclors were used at different times and for different applications. In electrical equipment manufacturing in the US, Aroclor 1260 and Aroclor 1254 were the main mixtures used before 1950; Aroclor 1242 was the main mixture used in the 1950s and 1960s until it was phased out in 1971 and replaced by Aroclor 1016.

Production

One estimate (2006) suggested that 1 million tonnes of PCBs had been produced. 40% of this material was thought to remain in use. Another estimate put the total global production of PCBs on the order of 1.5 million tonnes. The United States was the single largest producer with over 600,000 tonnes produced between 1930 and 1977. The European region follows with nearly 450,000 tonnes through 1984. It is unlikely that a full inventory of global PCB production will ever be accurately tallied, as there were factories in Poland, East Germany, and Austria that produced unknown amounts of PCBs. In East region of Slovakia there is still 21 500 tons of PCBs stored.

Applications

The utility of PCBs is based largely on their chemical stability, including low flammability and high dielectric constant. In an electric arc, PCBs generate incombustible gases.

Use of PCBs is commonly divided into closed and open applications. Examples of closed applications include coolants and insulating fluids (transformer oil) for transformers and capacitors, such as those used in old fluorescent light ballasts, hydraulic fluids, lubricating and cutting oils, and the like. In contrast, the major open application of PCBs was in carbonless copy ("NCR") paper, which even presently results in paper contamination.

Other open applications were as plasticizers in paints and cements, stabilizing additives in flexible PVC coatings of electrical cables and electronic components, pesticide extenders, reactive flame retardants and sealants for caulking, adhesives, wood floor finishes, such as Fabulon and other products of Halowax in the U.S., de-dusting agents, waterproofing compounds, casting agents. It was also used as a plasticizer in paints and especially "coal tars" that were used widely to coat water tanks, bridges and other infrastructure pieces.

Environmental transport and transformations

PCBs have entered the environment through both use and disposal. The environmental fate of PCBs is complex and global in scale.

Water

Because of their low vapour pressure, PCBs accumulate primarily in the hydrosphere, despite their hydrophobicity, in the organic fraction of soil, and in organisms. The hydrosphere is the main reservoir. The immense volume of water in the oceans is still capable of dissolving a significant quantity of PCBs.

As the pressure of ocean water increases with depth, PCBs become heavier than water and sink to the deepest ocean trenches where they are concentrated.

Air

A small volume of PCBs has been detected throughout the earth's atmosphere. The atmosphere serves as the primary route for global transport of PCBs, particularly for those congeners with one to four chlorine atoms.

In the atmosphere, PCBs may be degraded by hydroxyl radicals, or directly by photolysis of carbon–chlorine bonds (even if this is a less important process).

Atmospheric concentrations of PCBs tend to be lowest in rural areas, where they are typically in the picogram per cubic meter range, higher in suburban and urban areas, and highest in city centres, where they can reach 1 ng/m3 or more. In Milwaukee, an atmospheric concentration of 1.9 ng/m3 has been measured, and this source alone was estimated to account for 120 kg/year of PCBs entering Lake Michigan. In 2008, concentrations as high as 35 ng/m3, 10 times higher than the EPA guideline limit of 3.4 ng/m3, have been documented inside some houses in the U.S.

Volatilization of PCBs in soil was thought to be the primary source of PCBs in the atmosphere, but research suggests ventilation of PCB-contaminated indoor air from buildings is the primary source of PCB contamination in the atmosphere.

Biosphere

In the biosphere, PCBs can be degraded by the sun, bacteria or eukaryotes, but the speed of the reaction depends on both the number and the disposition of chlorine atoms in the molecule: less substituted, meta- or para-substituted PCBs undergo biodegradation faster than more substituted congeners.

In bacteria, PCBs may be dechlorinated through reductive dechlorination, or oxidized by dioxygenase enzyme. In eukaryotes, PCBs may be oxidized by the cytochrome P450 enzyme.

Biomagnification is the increasing concentration of a substance, such as a toxic chemical, in the tissues of tolerant organisms at successively higher levels in a food chain.
 
Like many lipophilic toxins, PCBs undergo biomagnification and bioaccumulation primarily due to the fact that they are easily retained within organisms. Plastic pollution, specifically Microplastics, are a major contributor of PCB's into the biosphere and especially into marine environments. PCB's concentrate in marine environments because freshwater systems, like rivers, act as a bridge for plastic pollution to be transported from terrestrial environments into marine environments. It has been estimated that 88-95% of marine plastic is exported into the ocean by just 10 major rivers. An organism can accumulate PCBs by consuming other organisms that have previously ingested PCB's from terrestrial, freshwater, or marine environments. The concentration of PCB's within an organism will increase over their lifetime; this process is called bioaccumulation. PCB concentrations within an organism also change depending upon which trophic level they occupy. When an organism occupies a high trophic level, like orcas or humans, they will accumulate more PCB's than an organism that occupies a low trophic level, like phytoplankton. If enough organisms with a trophic level are killed due to the accumulation of toxins, like PCB, a trophic cascade can occur. PCB's can cause harm to human health or even death when eaten. PCBs can be transported by birds from aquatic sources onto land via feces and carcasses.

Biochemical metabolism

Overview

PCBs undergo xenobiotic biotransformation, a mechanism used to make lipophilic toxins more polar and more easily excreted from the body. The biotransformation is dependent on the number of chlorine atoms present, along with their position on the rings. Phase I reactions occur by adding an oxygen to either of the benzene rings by Cytochrome P450. The type of P450 present also determines where the oxygen will be added; phenobarbital (PB)-induced P450s catalyze oxygenation to the meta-para positions of PCBs while 3-methylcholanthrene (3MC)-induced P450s add oxygens to the orthometa positions. PCBs containing orthometa and metapara protons can be metabolized by either enzyme, making them the most likely to leave the organism. However, some metabolites of PCBs containing orthometa protons have increased steric hindrance from the oxygen, causing increased stability and an increased chance of accumulation.

Species dependent

Metabolism is also dependent on the species of organism; different organisms have slightly different P450 enzymes that metabolize certain PCBs better than others. Looking at the PCB metabolism in the liver of four sea turtle species (green, olive ridley, loggerhead and hawksbill), green and hawksbill sea turtles have noticeably higher hydroxylation rates of PCB 52 than olive ridley or loggerhead sea turtles. This is because the green and hawksbill sea turtles have higher P450 2-like protein expression. This protein adds three hydroxyl groups to PCB 52, making it more polar and water-soluble. P450 3-like protein expression that is thought to be linked to PCB 77 metabolism, something that was not measured in this study.

Temperature dependent

Temperature plays a key role in the ecology, physiology and metabolism of aquatic species. The rate of PCB metabolism was temperature dependent in yellow perch (Perca flavescens). In fall and winter, only 11 out of 72 introduced PCB congeners were excreted and had halflives of more than 1,000 days. During spring and summer when the average daily water temperature was above 20 °C, persistent PCBs had halflives of 67 days. The main excretion processes were fecal egestion, growth dilution and loss across respiratory surfaces. The excretion rate of PCBs matched with the perch's natural bioenergetics, where most of their consumption, respiration and growth rates occur during the late spring and summer. Since the perch is performing more functions in the warmer months, it naturally has a faster metabolism and has less PCB accumulation. However, multiple cold-water periods mixed with toxic PCBs with coplanar chlorine molecules can be detrimental to perch health.

Sex dependent

Enantiomers of chiral compounds have similar chemical and physical properties, but can be metabolized by the body differently. This was looked at in bowhead whales (Balaena mysticetus) for two main reasons: they are large animals with slow metabolisms (meaning PCBs will accumulate in fatty tissue) and few studies have measured chiral PCBs in cetaceans. They found that the average PCB concentrations in the blubber were approximately four times higher than the liver; however, this result is most likely age- and sex-dependent. As reproductively active females transferred PCBs and other poisonous substances to the fetus, the PCB concentrations in the blubber were significantly lower than males of the same body length (less than 13 meters).

Health effects

Labelling transformers containing PCBs

The toxicity of PCBs varies considerably among congeners. The coplanar PCBs, known as nonortho PCBs because they are not substituted at the ring positions ortho to (next to) the other ring, (such as PCBs 77, 126 and 169), tend to have dioxin-like properties, and generally are among the most toxic congeners. Because PCBs are almost invariably found in complex mixtures, the concept of toxic equivalency factors (TEFs) has been developed to facilitate risk assessment and regulation, where more toxic PCB congeners are assigned higher TEF values on a scale from 0 to 1. One of the most toxic compounds known, 2,3,7,8-tetrachlorodibenzo[p]dioxin, a PCDD, is assigned a TEF of 1.

Exposure and excretion

In general, people are exposed to PCBs overwhelmingly through food, much less so by breathing contaminated air, and least by skin contact. Once exposed, some PCBs may change to other chemicals inside the body. These chemicals or unchanged PCBs can be excreted in feces or may remain in a person's body for years, with half lives estimated at 10–15 years. PCBs collect in body fat and milk fat. PCBs biomagnify up the food web and are present in fish and waterfowl of contaminated aquifers. Human infants are exposed to PCBs through breast milk or by intrauterine exposure through transplacental transfer of PCBs and are at the top of the food chain.

Signs and symptoms

Humans

The most commonly observed health effects in people exposed to extremely high levels of PCBs are skin conditions, such as chloracne and rashes, but these were known to be symptoms of acute systemic poisoning dating back to 1922. Studies in workers exposed to PCBs have shown changes in blood and urine that may indicate liver damage. In Japan in 1968, 280 kg of PCB-contaminated rice bran oil was used as chicken feed, resulting in a mass poisoning, known as Yushō disease, in over 1800 people. Common symptoms included dermal and ocular lesions, irregular menstrual cycles and lowered immune responses. Other symptoms included fatigue, headaches, coughs, and unusual skin sores. Additionally, in children, there were reports of poor cognitive development. Women exposed to PCBs before or during pregnancy can give birth to children with lowered cognitive ability, immune compromise, and motor control problems.

There is evidence that crash dieters that have been exposed to PCBs have an elevated risk of health complications. Stored PCBs in the adipose tissue become mobilized into the blood when individuals begin to crash diet. PCBs have shown toxic and mutagenic effects by interfering with hormones in the body. PCBs, depending on the specific congener, have been shown to both inhibit and imitate estradiol, the main sex hormone in females. Imitation of the estrogen compound can feed estrogen-dependent breast cancer cells, and possibly cause other cancers, such as uterine or cervical. Inhibition of estradiol can lead to serious developmental problems for both males and females, including sexual, skeletal, and mental development issues. In a cross-sectional study, PCBs were found to be negatively associated with testosterone levels in adolescent boys.

High PCB levels in adults have been shown to result in reduced levels of the thyroid hormone triiodothyronine, which affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate. It also resulted in reduced immunity and increased thyroid disorders.

Animals

Animals that eat PCB-contaminated food even for short periods of time suffer liver damage and may die. In 1968 in Japan, 400,000 birds died after eating poultry feed that was contaminated with PCBs. Animals that ingest smaller amounts of PCBs in food over several weeks or months develop various health effects, including anemia; acne-like skin conditions (chloracne); liver, stomach, and thyroid gland injuries (including hepatocarcinoma), and thymocyte apoptosis. Other effects of PCBs in animals include changes in the immune system, behavioral alterations, and impaired reproduction. PCBs that have dioxin-like activity are known to cause a variety of teratogenic effects in animals. Exposure to PCBs causes hearing loss and symptoms similar to hypothyroidism in rats.

Cancer

In 2013, the International Agency for Research on Cancer (IARC) classified dioxin-like PCBs as human carcinogens. According to the U.S. EPA, PCBs have been shown to cause cancer in animals and evidence supports a cancer-causing effect in humans. Per the EPA, studies have found increases in malignant melanoma and rare liver cancers in PCB workers.

In 2013, the International Association for Research on Cancer (IARC) determined that the evidence for PCBs causing non-Hodgkin lymphoma is "limited" and "not consistent". In contrast an association between elevated blood levels of PCBs and non-Hodgkin lymphoma had been previously accepted. PCBs may play a role in the development of cancers of the immune system because some tests of laboratory animals subjected to very high doses of PCBs have shown effects on the animals' immune system, and some studies of human populations have reported an association between environmental levels of PCBs and immune response.

History

Old power transformers are a major source of PCBs. Even units not originally filled with PCB may be contaminated, since PCB and oil mix freely and any given transformer may have been refilled from hoses or tanks also used with PCBs.

In 1865 the first "PCB-like" chemical was discovered, and was found to be a byproduct of coal tar. Years later in 1881, German chemists synthesized the first PCB in a laboratory. Between then and 1914, large amounts of PCBs were released into the environment, to the extent that there are still measurable amounts of PCBs in feathers of birds currently held in museums.

In 1935, Monsanto Chemical Company (now Solutia Inc) took over commercial production of PCBs from Swann Chemical Company which had begun in 1929. PCBs, originally termed "chlorinated diphenyls", were commercially produced as mixtures of isomers at different degrees of chlorination. The electric industry used PCBs as a non-flammable replacement for mineral oil to cool and insulate industrial transformers and capacitors. PCBs were also commonly used as heat stabilizer in cables and electronic components to enhance the heat and fire resistance of PVC.

In the 1930s, the toxicity associated with PCBs and other chlorinated hydrocarbons, including polychlorinated naphthalenes, was recognized because of a variety of industrial incidents. Between 1936 and 1937, there were several medical cases and papers released on the possible link between PCBs and its detrimental health effects. In 1936 a U.S. Public health Service official described the wife and child of a worker from the Monsanto Industrial Chemical Company who exhibited blackheads and pustules on their skin. The official attributed these symptoms to contact with the worker's clothing after he returned from work. In 1937, a conference about the hazards was organized at Harvard School of Public Health, and a number of publications referring to the toxicity of various chlorinated hydrocarbons were published before 1940.

In 1947 Robert Brown reminded chemists that Arochlors were "objectionably toxic. Thus the maximum permissible concentration for an 8-hr. day is 1 mg/m3 of air. They also produce a serious and disfiguring dermatitis".

In 1954 Japan, Kanegafuchi Chemical Co. Ltd. (Kaneka Corporation) first produced PCBs, and continued until 1972.

Through the 1960s Monsanto Chemical Company knew increasingly more about PCBs' harmful effects on humans and the environment, per internal leaked documents released in 2002, yet PCB manufacture and use continued with few restraints until the 1970s.

In 1966, PCBs were determined by Swedish chemist Sören Jensen to be an environmental contaminant. Jensen, according to a 1994 article in Sierra, named chemicals PCBs, which previously, had simply been called "phenols" or referred to by various trade names, such as Aroclor, Kanechlor, Pyrenol, Chlorinol and others. In 1972, PCB production plants existed in Austria, West Germany, France, the UK, Italy, Japan, Spain, the USSR and the US.

In the early 1970s, Ward B. Stone of the New York State Department of Environmental Conservation (NYSDEC) first published his findings that PCBs were leaking from transformers and had contaminated the soil at the bottom of utility poles.

There have been allegations that Industrial Bio-Test Laboratories engaged in data falsification in testing relating to PCBs. In 2003, Monsanto and Solutia Inc., a Monsanto corporate spinoff, reached a US$700 million settlement with the residents of West Anniston, Alabama who had been affected by the manufacturing and dumping of PCBs. In a trial lasting six weeks, the jury found that "Monsanto had engaged in outrageous behavior, and held the corporations and its corporate successors liable on all six counts it considered – including negligence, nuisance, wantonness and suppression of the truth."

Existing products containing PCBs which are "totally enclosed uses" such as insulating fluids in transformers and capacitors, vacuum pump fluids, and hydraulic fluid, are allowed to remain in use. The public, legal, and scientific concerns about PCBs arose from research indicating they are likely carcinogens having the potential to adversely impact the environment and, therefore, undesirable as commercial products. Despite active research spanning five decades, extensive regulatory actions, and an effective ban on their production since the 1970s, PCBs still persist in the environment and remain a focus of attention.

Pollution due to PCBs

Belgium

In 1999, the Dioxin Affair occurred when 50 kg of PCB transformer oils were added to a stock of recycled fat used for the production of 500 tonnes of animal feed, eventually affecting around 2,500 farms in several countries. The name Dioxin Affair was coined from early misdiagnosis of dioxins as the primary contaminants, when in fact they turned out to be a relatively small part of the contamination caused by thermal reactions of PCBs. The PCB congener pattern suggested the contamination was from a mixture of Aroclor 1260 & 1254. Over 9 million chickens, and 60,000 pigs were destroyed because of the contamination. The extent of human health effects has been debated, in part because of the use of differing risk assessment methods. One group predicted increased cancer rates, and increased rates of neurological problems in those exposed as neonates. A second study suggested carcinogenic effects were unlikely and that the primary risk would be associated with developmental effects due to exposure in pregnancy and neonates. Two businessmen who knowingly sold the contaminated feed ingredient received two-year suspended sentences for their role in the crisis.

Italy

The Italian company Caffaro, located in Brescia, specialized in producing PCBs from 1938 to 1984, following the acquisition of the exclusive rights to use the patent in Italy from Monsanto. The pollution resulting from this factory and the case of Anniston, in the US, are the largest known cases in the world of PCB contamination in water and soil, in terms of the amount of toxic substance dispersed, size of the area contaminated, number of people involved and duration of production.

The values reported by the local health authority (ASL) of Brescia since 1999 are 5,000 times above the limits set by Ministerial Decree 471/1999 (levels for residential areas, 0.001 mg/kg). As a result of this and other investigations, in June 2001, a complaint of an environmental disaster was presented to the Public Prosecutor's Office of Brescia. Research on the adult population of Brescia showed that residents of some urban areas, former workers of the plant, and consumers of contaminated food, have PCB levels in their bodies that are in many cases 10-20 times higher than reference values in comparable general populations. PCBs entered the human food supply by animals grazing on contaminated pastures near the factory, especially in local veal mostly eaten by farmers' families. The exposed population showed an elevated risk of Non-Hodgkin lymphoma, but not for other specific cancers.

Japan

In 1968, a mixture of dioxins and PCBs got into rice bran oil produced in northern Kyushu. Contaminated cooking oil sickened more than 1860 people. The symptoms were called Yushō disease.

In Okinawa, high levels of PCB contamination in soil on Kadena Air Base were reported in 1987 at thousands of parts per million, some of the highest levels found in any pollution site in the world.

Republic of Ireland

In December 2008, a number of Irish news sources reported testing had revealed "extremely high" levels of dioxins, by toxic equivalent, in pork products, ranging from 80 to 200 times the EU's upper safe limit of 1.5 pg WHO-TEQDFP/μg i.e. 0.12 to 0.3 parts per billion.

Brendan Smith, the Minister for Agriculture, Fisheries and Food, stated the pork contamination was caused by PCB-contaminated feed that was used on 9 of Ireland's 400 pig farms, and only one feed supplier was involved. Smith added that 38 beef farms also used the same contaminated feed, but those farms were quickly isolated and no contaminated beef entered the food chain. While the contamination was limited to just 9 pig farms, the Irish government requested the immediate withdrawal and disposal of all pork-containing products produced in Ireland and purchased since 1 September 2008. This request for withdrawal of pork products was confirmed in a press release by the Food Safety Authority of Ireland on December 6.

It is thought that the incident resulted from the contamination of fuel oil used in a drying burner at a single feed processor, with PCBs. The resulting combustion produced a highly toxic mixture of PCBs, dioxins and furans, which was included in the feed produced and subsequently fed to a large number of pigs.

Kenya

In Kenya, a number of cases have been reported in the 2010s of thieves selling transformer oil, stolen from electric transformers, to the operators of roadside food stalls for use in deep frying. When used for frying, it is reported that transformer oil lasts much longer than regular cooking oil. The downside of this misuse of the transformer oil is the threat to the health of the consumers, due to the presence of PCBs.

Slovakia

The chemical plant Chemko in Strážske (east Slovakia) was an important producer of polychlorinated biphenyls for the former communist bloc (Comecon) until 1984. Chemko contaminated a large part of east Slovakia, especially the sediments of the Laborec river and reservoir Zemplínska šírava.

Slovenia

Between 1962 and 1983, the Iskra Kondenzatorji company in Semič (White Carniola, Southeast Slovenia) manufactured capacitors using PCBs. Due to the wastewater and improperly disposed waste products, the area (including the Krupa and Lahinja rivers) became highly contaminated with PCBs. The pollution was discovered in 1983, when the Krupa river was meant to become a water supply source. The area was sanitized then, but the soil and water are still highly polluted. Traces of PCBs were found in food (eggs, cow milk, walnuts) and Krupa is still the most PCB-polluted river in the world.

Spain

Several cetacean species have very high mean blubber PCB concentrations likely to cause population declines and suppress population recovery. Striped dolphins, bottlenose dolphins and killer whales were found to have mean levels that markedly exceeded all known marine mammal PCB toxicity thresholds. The western Mediterranean Sea and the south-west Iberian Peninsula were identified as “hotspots”.

United Kingdom

Monsanto manufactured PCBs at its chemical plant in Newport, South Wales, until the mid- to late-1970s. During this period, waste matter, including PCBs, from the Newport site was dumped at a disused quarry near Groes-faen, west of Cardiff, and Penhros landfill site from where it continues to be released in waste water discharges.

United States

Alabama

PCBs (manufactured through most of the 20th century until the early 2000s) originating from Monsanto Chemical Company in Anniston, Alabama were dumped into Snow Creek, which then spread to Choccolocco Creek, then Logan Martin Lake. In the early 2000s, class action lawsuits were settled by local land owners, including those on Logan Martin Lake, and Lay Reservoir (downstream on the Coosa River), for the PCB pollution. Donald Stewart, former Senator from Alabama, first learned of the concerns of hundreds of west Anniston residents after representing a church which had been approached about selling its property by Monsanto. Stewart went on to be the pioneer and lead attorney in the first and majority of cases against Monsanto and focused on residents in the immediate area known to be most polluted. Other attorneys later joined in to file suits for those outside the main immediate area around the plant; one of these was the late Johnnie Cochran.

In 2007, the highest pollution levels remained concentrated in Snow and Choccolocco Creeks. Concentrations in fish have declined and continue to decline over time; sediment disturbance, however, can resuspend the PCBs from the sediment back into the water column and food web.

Great Lakes

In 1976 environmentalists found PCBs in the sludge at Waukegan Harbor, the southwest end of Lake Michigan. They were able to trace the source of the PCBs back to the Outboard Marine Corporation that was producing boat motors next to the harbor. By 1982, the Outboard Marine Corporation was court-ordered to release quantitative data referring to their PCB waste released. The data stated that from 1954 they released 100,000 tons of PCB into the environment, and that the sludge contained PCBs in concentrations as high as 50%.

In 1989, during construction near the Zilwaukee bridge, workers uncovered an uncharted landfill containing PCB-contaminated waste which required $100,000 to clean up.

Much of the Great Lakes area were still heavily polluted with PCBs in 1988, despite extensive remediation work.

Indiana

From the late 1950s through 1977, Westinghouse Electric used PCBs in the manufacture of capacitors in its Bloomington, Indiana, plant. Reject capacitors were hauled and dumped in area salvage yards and landfills, including Bennett's Dump, Neal's Landfill and Lemon Lane Landfill. Workers also dumped PCB oil down factory drains, which contaminated the city sewage treatment plant. The City of Bloomington gave away the sludge to area farmers and gardeners, creating anywhere from 200 to 2,000 sites, which remain unaddressed.

Over 2 million pounds of PCBs were estimated to have been dumped in Monroe and Owen counties. Although federal and state authorities have been working on the sites' environmental remediation, many areas remain contaminated. Concerns have been raised regarding the removal of PCBs from the karst limestone topography, and regarding the possible disposal options. To date, the Westinghouse Bloomington PCB Superfund site case does not have a Remedial Investigation/Feasibility Study (RI/FS) and Record of Decision (ROD), although Westinghouse signed a US Department of Justice Consent Decree in 1985. The 1985 consent decree required Westinghouse to construct an incinerator that would incinerate PCB-contaminated materials. Because of public opposition to the incinerator, however, the State of Indiana passed a number of laws that delayed and blocked its construction. The parties to the consent decree began to explore alternative remedies in 1994 for six of the main PCB contaminated sites in the consent decree. Hundreds of sites remain unaddressed as of 2014. Monroe County will never be PCB-free, as noted in a 2014 Indiana University program about the local contamination.

On 15 February 2008, Monroe County approved a plan to clean up the three remaining contaminated sites in the City of Bloomington, at a cost of $9.6 million to CBS Corp., the successor of Westinghouse. In 1999, Viacom bought CBS, so they are current responsible party for the PCB sites.

Massachusetts

Pittsfield, in western Massachusetts, was home to the General Electric (GE) transformer, capacitor, and electrical generating equipment divisions. The electrical generating division built and repaired equipment that was used to power the electrical utility grid throughout the nation. PCB-contaminated oil routinely migrated from GE's 254-acre (1.03 km2) industrial plant located in the very center of the city to the surrounding groundwater, nearby Silver Lake, and to the Housatonic River, which flows through Massachusetts, Connecticut, and down to Long Island Sound. PCB-containing solid material was widely used as fill, including oxbows of the Housatonic River. Fish and waterfowl who live in and around the river contain significant levels of PCBs and are not safe to eat.

New Bedford Harbor, which is a listed Superfund site, contains some of the highest sediment concentrations in the marine environment.

Investigations into historic waste dumping in the Bliss Corner neighborhood have revealed the existence of PCBs, among other hazardous materials, buried into soil and waste material.

Missouri

In 1982 Martha C. Rose Chemical Inc. began processing and disposing of materials contaminated with PCB's in Holden, Missouri, a small rural community about 40 miles east of Kansas City. From 1982 until 1986, nearly 750 companies, including General Motors Corp., Commonwealth Edison, Illinois Power Co. and West Texas Utilities, sent millions of pounds of PCB contaminated materials to Holden for disposal. Instead, according to prosecutors, the company began storing the contaminated materials while falsifying its reports to the EPA to show they had been removed. After investigators learned of the deception, Rose Chemical was closed and filed for bankruptcy. The site had become the nation's largest waste site for the chemical PCB. In the four years the company was operational, the EPA inspected it four times and assessed $206,000 in fines but managed to collect only $50,000.

After the plant closed the state environmental agency found PCB contamination in streams near the plant and in the city's sewage treatment sludge. A 100,000 square-foot warehouse and unknown amounts of contaminated soil and water around the site had to be cleaned up. Most of the surface debris, including close to 13 million pounds of contaminated equipment, carcasses and tanks of contaminated oil, had to be removed. Walter C. Carolan, owner of Rose Chemical, and five others pleaded guilty in 1989 to committing fraud or falsifying documents. Carolan and two other executives served sentences of less than 18 months; the others received fines and were placed on probation. Cleanup costs at the site are estimated at $35 million.

New York

Pollution of the Hudson River is largely due to dumping of PCBs by General Electric from 1947 to 1977. GE dumped an estimated 1.3 million pounds of PCBs into the Hudson River during these years. This pollution caused a range of harmful effects to wildlife and people who eat fish from the river or drink the water.

Love Canal is a neighborhood in Niagara Falls, New York that was heavily contaminated with toxic waste including PCBs. Eighteen Mile Creek in Lockport, New York is an EPA Superfund site for PCBs contamination.

PCB pollution at the State Office Building in Binghamton was responsible for what is now considered to be the first indoor environmental disaster in the United States. In 1981, a transformer explosion in the basement spewed PCBs throughout the entire 18-story building. The contamination was so severe that cleanup efforts kept the building closed for 13 years.

North Carolina

One of the largest deliberate PCB spills in American history occurred in the summer of 1978 when 31,000 gallons (117 m^3) of PCB-contaminated oil were illegally sprayed by the Ward PCB Transformer Company in 3-foot (0.91 m) swaths along the roadsides of some 240 miles (390 km) of North Carolina highway shoulders in 14 counties and at the Fort Bragg Army Base. The crime, known as "the midnight dumpings", occurred over nearly 2 weeks, as drivers of a black-painted tanker truck drove down one side of rural Piedmont highways spraying PCB-laden waste and then up the other side the following night.

Under Governor James B. Hunt, Jr., state officials then erected large, yellow warning signs along the contaminated highways that read: "CAUTION: PCB Chemical Spills Along Highway Shoulders." The illegal dumping is believed to have been motivated by the passing of the Toxic Substances Control Act (TSCA), which became effective on August 2, 1978 and increased the expense of chemical waste disposal.

Within a couple of weeks of the crime, Robert Burns and his sons, Timothy and Randall, were arrested for dumping the PCBs along the roadsides. Burns was a business partner of Robert "Buck" Ward, Jr., of the Ward PCB Transformer Company, in Raleigh. Burns and sons pleaded guilty to state and Federal criminal charges; Burns received a three to five-year prison sentence. Ward was acquitted of state charges in the dumping, but was sentenced to 18 months prison time for violation of TSCA.

Cleanup and disposal of the roadside PCBs generated controversy, as the Governor's plan to pick up the roadside PCBs and to bury them in a landfill in rural Warren County were strongly opposed in 1982 by local residents. In October 2013, at the request of the South Carolina Department of Health and Environmental Control (SCDHEC), the City of Charlotte, North Carolina decided to stop applying sewage sludge to land while authorities investigated the source of PCB contamination. In February 2014, the City of Charlotte admitted PCBs have entered their sewage treatment centers as well.

After the 2013 SCDHEC had issued emergency regulations the City of Charlotte discovered high levels of PCBs entering its sewage waste water treatment plants, where sewage is converted to sewage sludge. The city at first denied it had a problem, then admitted an "event" occurred in February 2014, and in April that the problem had occurred much earlier. The city stated that its very first test with a newly changed test method revealed very high PCB levels in its sewage sludge farm field fertilizer. Because of the widespread use of the contaminated sludge, SCDHEC subsequently issued PCB fish advisories for nearly all streams and rivers bordering farm fields that had been applied with city waste.

Ohio

The Clyde cancer cluster (also known as the Sandusky County cancer cluster) is a childhood cancer cluster that has affected many families in Clyde, Ohio and surrounding areas. PCBs were found in soil in a public park within the area of the cancer cluster.

In Akron, Ohio, soil was contaminated and noxious PCB-laden fumes had been put into the air by an electrical transformer deconstruction operation from the 1930s to the 1960s.

South Carolina

From 1955 until 1977, the Sangamo Weston plant in Pickens, SC, used PCBs to manufacture capacitors, and dumped 400,000 pounds of PCB contaminated wastewater into the Twelve Mile Creek. In 1990, the EPA declared the 228 acres (0.92 km2) site of the capacitor plant, its landfills and the polluted watershed, which stretches nearly 1,000 acres (4.0 km2) downstream to Lake Hartwell as a Superfund site. Two dams on the Twelve Mile Creek are to be removed and on Feb. 22, 2011 the first of two dams began to be dismantled. Some contaminated sediment is being removed from the site and hauled away, while other sediment is pumped into a series of settling ponds.

In 2013, the state environmental regulators issued a rare emergency order, banning all sewage sludge from being land applied or deposited on landfills, as it contained very high levels of PCBs. The problem had not been discovered until thousands of acres of farm land in the state had been contaminated by the hazardous sludge. A criminal investigation to determine the perpetrator of this crime was launched.

Washington

As of 2015, several bodies of water in the state of Washington were contaminated with PCBs, including the Columbia River, the Duwamish River, Green Lake, Lake Washington, the Okanogan River, Puget Sound, the Spokane River, the Walla Walla River, the Wenatchee River, and the Yakima River. A study by Washington State published in 2011 found that the two largest sources of PCB flow into the Spokane River were City of Spokane stormwater (44%) and municipal and industrial discharges (20%).

PCBs entered the environment through paint, hydraulic fluids, sealants, inks and have been found in river sediment and wild life. Spokane utilities will spend $300 million to prevent PCBs from entering the river in anticipation of a 2017 federal deadline to do so. In August 2015 Spokane joined other U.S cities like San Diego and San Jose, California, and Westport, Massachusetts. in seeking damages from Monsanto.

Wisconsin

From 1954 until 1971, the Fox River in Appleton, Wisconsin had PCBs deposited into it from Appleton Paper/NCR, P.H. Gladfelter, Georgia Pacific and other notable local paper manufacturing facilities. The Wisconsin DNR estimates that after wastewater treatment the PCB discharges to the Fox River due to production losses ranged from 81,000 kg to 138,000 kg. (178,572 lbs. to 304,235 lbs). The production of Carbon Copy Paper and its byproducts led to the discharge into the river. Fox River clean up is ongoing.

Pacific Ocean

Polychlorinated biphenyls have been discovered in organisms living in the Mariana trench in the Pacific Ocean. Levels were as high as 1,900 nanograms per gram of amphipod tissue in the organisms analyzed.

Regulation

In 1972 the Japanese government banned the production, use, and import of PCBs.

In 1973, the use of PCBs in "open" or "dissipative" sources, such as plasticisers in paints and cements, casting agents, fire retardant fabric treatments and heat stabilizing additives for PVC electrical insulation, adhesives, paints and waterproofing, railroad ties was banned in Sweden.

In 1976, concern over the toxicity and persistence (chemical stability) of PCBs in the environment led the United States Congress to ban their domestic production, effective January 1, 1978, via the Toxic Substances Control Act. As the agency that was charged with implementing TSCA, the EPA banned new manufacturing of PCBs, but it allowed their continued use for electrical equipment for economic reasons. In 1979 and future years, the EPA continued to regulate PCB usage and disposal.

In 1981, the UK banned closed uses of PCBs in new equipment, and nearly all UK PCB synthesis ceased; closed uses in existing equipment containing in excess of 5 litres of PCBs were not stopped until December 2000.

Modern sources include pigments, which may be used in inks for paper or plastic products.

Methods of destruction

Physical

PCBs are technically attractive because of their inertness, which includes their resistance to combustion. Nonetheless, they can be effectively destroyed by incineration at 1000 °C. When combusted at lower temperatures, they convert in part to more hazardous materials, including dibenzofurans and dibenzodioxins. When conducted properly, the combustion products are water, carbon dioxide, and hydrogen chloride. In some cases, the PCBs are combusted as a solution in kerosene. PCBs have also been destroyed by pyrolysis in the presence of alkali metal carbonates.
Thermal desorption is highly effective at removing PCBs from soil.

Chemical

PCBs are fairly chemically unreactive, this property being attractive for its application as an inert material. They resist oxidation. Many chemical compounds are available to destroy or reduce the PCBs. Commonly, PCBs are degraded by basis mixtures of glycols, which displace some or all chloride. Also effective are reductants such as sodium or sodium naphthenide. Vitamin B12 has also shown promise.

Microbial

Some micro-organisms degrade PCBs by reducing the C-Cl bonds. Microbial dechlorination tends to be rather slow-acting in comparison to other methods. Enzymes extracted from microbes can show PCB activity. In 2005, Shewanella oneidensis biodegraded a high percentage of PCBs in soil samples. A low voltage current can stimulate the microbial degradation of PCBs.

Fungal

There is research showing that some ligninolytic fungi can degrade PCBs.

Delayed-choice quantum eraser

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Delayed-choice_quantum_eraser A delayed-cho...