Persistent organic pollutant

From Wikipedia, the free encyclopedia

Persistent organic pollutants (POPs) are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. Because of their persistence, POPs bioaccumulate with potential adverse impacts on human health and the environment. The effect of POPs on human and environmental health was discussed, with intention to eliminate or severely restrict their production, by the international community at the Stockholm Convention on Persistent Organic Pollutants in 2001.

 

Many POPs are currently or were in the past used as pesticides, solvents, pharmaceuticals, and industrial chemicals. Although some POPs arise naturally, for example volcanoes and various biosynthetic pathways, most are man-made via total synthesis.

Consequences of persistence

POPs typically are halogenated organic compounds (see lists below) and as such exhibit high lipid solubility. For this reason, they bioaccumulate in fatty tissues. Halogenated compounds also exhibit great stability reflecting the nonreactivity of C-Cl bonds toward hydrolysis and photolytic degradation. The stability and lipophilicity of organic compounds often correlates with their halogen content, thus polyhalogenated organic compounds are of particular concern. They exert their negative effects on the environment through two processes, long range transport, which allows them to travel far from their source, and bioaccumulation, which reconcentrates these chemical compounds to potentially dangerous levels. Compounds that make up POPs are also classed as PBTs (Persistent, Bioaccumulative and Toxic) or TOMPs (Toxic Organic Micro Pollutants).

Long-range transport

POPs enter the gas phase under certain environmental temperatures and volatize from soils, vegetation, and bodies of water into the atmosphere, resisting breakdown reactions in the air, to travel long distances before being re-deposited. This results in accumulation of POPs in areas far from where they were used or emitted, specifically environments where POPs have never been introduced such as Antarctica, and the Arctic circle. POPs can be present as vapors in the atmosphere or bound to the surface of solid particles. POPs have low solubility in water but are easily captured by solid particles, and are soluble in organic fluids (oils, fats, and liquid fuels). POPs are not easily degraded in the environment due to their stability and low decomposition rates. Due to this capacity for long-range transport, POP environmental contamination is extensive, even in areas where POPs have never been used, and will remain in these environments years after restrictions implemented due to their resistance to degradation.

Bioaccumulation

Bioaccumulation of POPs is typically associated with the compounds high lipid solubility and ability to accumulate in the fatty tissues of living organisms for long periods of time. Persistent chemicals tend to have higher concentrations and are eliminated more slowly. Dietary accumulation or bioaccumulation is another hallmark characteristic of POPs, as POPs move up the food chain, they increase in concentration as they are processed and metabolized in certain tissues of organisms. The natural capacity for animals gastrointestinal tract concentrate ingested chemicals, along with poorly metabolized and hydrophobic nature of POPs makes such compounds highly susceptible to bioaccumulation. Thus POPs not only persist in the environment, but also as they are taken in by animals they bioaccumulate, increasing their concentration and toxicity in the environment.

Stockholm Convention on Persistent Organic Pollutants

State parties to the Stockholm Convention on Persistent Organic Pollutants

The Stockholm Convention was adopted and put into practice by the United Nations Environment Programme (UNEP) on May 22, 2001. The UNEP decided that POP regulation needed to be addressed globally for the future. The purpose statement of the agreement is "to protect human health and the environment from persistent organic pollutants." As of 2014, there are 179 countries in compliance with the Stockholm convention. The convention and its participants have recognized the potential human and environmental toxicity of POPs. They recognize that POPs have the potential for long range transport and bioaccumulation and biomagnification. The convention seeks to study and then judge whether or not a number of chemicals that have been developed with advances in technology and science can be categorized as POPs or not. The initial meeting in 2001 made a preliminary list, termed the "dirty dozen," of chemicals that are classified as POPs. As of 2014, the United States of America has signed the Stockholm Convention but has not ratified it. There are a handful of other countries that have not ratified the convention but most countries in the world have ratified the convention.

Compounds on the Stockholm Convention list

In May 1995, the United Nations Environment Programme Governing Council investigated POPs. Initially the Convention recognized only twelve POPs for their adverse effects on human health and the environment, placing a global ban on these particularly harmful and toxic compounds and requiring its parties to take measures to eliminate or reduce the release of POPs in the environment. 

1. Aldrin, an insecticide used in soils to kill termites, grasshoppers, Western corn rootworm, and others, is also known to kill birds, fish, and humans. Humans are primarily exposed to aldrin through dairy products and animal meats.
2. Chlordane, an insecticide used to control termites and on a range of agricultural crops, is known to be lethal in various species of birds, including mallard ducks, bobwhite quail, and pink shrimp; it is a chemical that remains in the soil with a reported half-life of one year. Chlordane has been postulated to affect the human immune system and is classified as a possible human carcinogen. Chlordane air pollution is believed the primary route of humane exposure.
3. Dieldrin, a pesticide used to control termites, textile pests, insect-borne diseases and insects living in agricultural soils. In soil and insects, aldrin can be oxidized, resulting in rapid conversion to dieldrin. Dieldrin’s half-life is approximately five years. Dieldrin is highly toxic to fish and other aquatic animals, particularly frogs, whose embryos can develop spinal deformities after exposure to low levels. Dieldrin has been linked to Parkinson's disease, breast cancer, and classified as immunotoxic, neurotoxic, with endocrine disrupting capacity. Dieldrin residues have been found in air, water, soil, fish, birds, and mammals. Human exposure to dieldrin primarily derives from food.
4. Endrin, an insecticide sprayed on the leaves of crops, and used to control rodents. Animals can metabolize endrin, so fatty tissue accumulation is not an issue, however the chemical has a long half-life in soil for up to 12 years. Endrin is highly toxic to aquatic animals and humans as a neurotoxin. Human exposure results primarily through food.
5. Heptachlor, a pesticide primarily used to kill soil insects and termites, along with cotton insects, grasshoppers, other crop pests, and malaria-carrying mosquitoes. Heptachlor, even at every low doses has been associated with the decline of several wild bird populations – Canada geese and American kestrels. In laboratory tests have shown high-dose heptachlor as lethal, with adverse behavioral changes and reduced reproductive success at low-doses, and is classified as a possible human carcinogen. Human exposure primarily results from food.
6. Hexachlorobenzene (HCB), was first introduced in 1945–59 to treat seeds because it can kill fungi on food crops. HCB-treated seed grain consumption is associated with photosensitive skin lesions, colic, debilitation, and a metabolic disorder called porphyria turcica, which can be lethal. Mothers who pass HCB to their infants through the placenta and breast milk had limited reproductive success including infant death. Human exposure is primarily from food.
7. Mirex, an insecticide used against ants and termites or as a flame retardant in plastics, rubber, and electrical goods. Mirex is one of the most stable and persistent pesticides, with a half-life of up to 10 years. Mirex is toxic to several plant, fish and crustacean species, with suggested carcinogenic capacity in humans. Humans are exposed primarily through animal meat, fish, and wild game.
8. Toxaphene, an insecticide used on cotton, cereal, grain, fruits, nuts, and vegetables, as well as for tick and mite control in livestock. Widespread toxaphene use in the US and chemical persistence, with a half-life of up to 12 years in soil, results in residual toxaphene in the environment. Toxaphene is highly toxic to fish, inducing dramatic weight loss and reduced egg viability. Human exposure primarily results from food. While human toxicity to direct toxaphene exposure is low, the compound is classified as a possible human carcinogen.
9. Polychlorinated biphenyls (PCBs), used as heat exchange fluids, in electrical transformers, and capacitors, and as additives in paint, carbonless copy paper, and plastics. Persistence varies with degree of halogenation, an estimated half-life of 10 years. PCBs are toxic to fish at high doses, and associated with spawning failure at low doses. Human exposure occurs through food, and is associated with reproductive failure and immune suppression. Immediate effects of PCB exposure include pigmentation of nails and mucous membranes and swelling of the eyelids, along with fatigue, nausea, and vomiting. Effects are transgenerational, as the chemical can persist in a mother’s body for up to 7 years, resulting in developmental delays and behavioral problems in her children. Food contamination has led to large scale PCB exposure.
10. Dichlorodiphenyltrichloroethane (DDT) is probably the most infamous POP. It was widely used as insecticide during WWII to protect against malaria and typhus. After the war, DDT was used as an agricultural insecticide. In 1962, the American biologist Rachel Carson published Silent Spring, describing the impact of DDT spraying on the US environment and human health. DDT’s persistence in the soil for up to 10–15 years after application has resulted in widespread and persistent DDT residues throughout the world including the arctic, even though it has been banned or severely restricted in most of the world. DDT is toxic to many organisms including birds where it is detrimental to reproduction due to eggshell thinning. DDT can be detected in foods from all over the world and food-borne DDT remains the greatest source of human exposure. Short-term acute effects of DDT on humans are limited, however long-term exposure has been associated with chronic health effects including increased risk of cancer and diabetes, reduced reproductive success, and neurological disease.
11. Dioxins are unintentional by-products of high-temperature processes, such as incomplete combustion and pesticide production. Dioxins are typically emitted from the burning of hospital waste, municipal waste, and hazardous waste, along with automobile emissions, peat, coal, and wood. Dioxins have been associated with several adverse effects in humans, including immune and enzyme disorders, chloracne, and are classified as a possible human carcinogen. In laboratory studies of dioxin effects an increase in birth defects and stillbirths, and lethal exposure have been associated with the substances. Food, particularly from animals, is the principal source of human exposure to dioxins.
12. Polychlorinated dibenzofurans are by-products of high-temperature processes, such as incomplete combustion after waste incineration or in automobiles, pesticide production, and polychlorinated biphenyl production. Structurally similar to dioxins, the two compounds share toxic effects. Furans persist in the environment and classified as possible human carcinogens. Human exposure to furans primarily results from food, particularly animal products.

New POPs on the Stockholm Convention list

Since 2001, this list has been expanded to include some polycyclic aromatic hydrocarbons (PAHs), brominated flame retardants, and other compounds. Additions to the initial 2001 Stockholm Convention list are as following POPs:

• Chlordecone, a synthetic chlorinated organic compound,is primarily used as an agricultural pesticide, related to DDT and Mirex. Chlordecone is toxic to aquatic organisms, and classified as a possible human carcinogen. Many countries have banned chlordecone sale and use, or intend to phase out stockpiles and wastes.
• α-Hexachlorocyclohexane (α-HCH) and β-Hexachlorocyclohexane (β-HCH) are insecticides as well as by-products in the production of lindane. Large stockpiles of HCH isomers exist in the environment. α-HCH and β-HCH are highly persistent in the water of colder regions. α-HCH and β-HCH has been linked Parkinson's and Alzheimer's disease.
• Hexabromodiphenyl ether (hexaBDE) and heptabromodiphenyl ether (heptaBDE) are main components of commercial octabromodiphenyl ether (octaBDE). Commercial octaBDE is highly persistent in the environment, whose only degradation pathway is through debromination and the production of bromodiphenyl ethers, which can increase toxicity.
• Lindane (γ-hexachlorocyclohexane), a pesticide used as a broad spectrum insecticide for seed, soil, leaf, tree and wood treatment, and against ectoparasites in animals and humans (head lice and scabies). Lindane rapidly bioconcentrates. It is immunotoxic, neurotoxic, carcinogenic, linked to liver and kidney damage as well as adverse reproductive and developmental effects in laboratory animals and aquatic organisms. Production of lindane unintentionally produces two other POPs α-HCH and β-HCH.^{[citation needed]}
• Pentachlorobenzene (PeCB), is a pesticide and unintentional byproduct. PeCB has also been used in PCB products, dyestuff carriers, as a fungicide, a flame retardant, and a chemical intermediate. PeCB is moderately toxic to humane, while highly toxic to aquatic organisms.
• Tetrabromodiphenyl ether (tetraBDE) and pentabromodiphenyl ether (pentaBDE) are industrial chemicals and the main components of commercial pentabromodiphenyl ether (pentaBDE). PentaBDE has been detected in humans in all regions of the world.
• Perfluorooctanesulfonic acid (PFOS) and its salts are used in the production of fluoropolymers. PFOS and related compounds are extremely persistent, bioaccumulating and biomagnifying. The negative effects of trace levels of PFOS have not been established.
• Endosulfans are insecticides to control pests on crops such coffee, cotton, rice and sorghum and soybeans, tsetse flies, ectoparasites of cattle. They are used as a wood preservative. Global use and manufacturing of endosulfan has been banned under the Stockholm convention in 2011, although many countries had previously banned or introduced phase-outs of the chemical when the ban was announced. Toxic to humans and aquatic and terrestrial organisms, linked to congenital physical disorders, mental retardation, and death. Endosulfans' negative health effects are primarily liked to its endocrine disrupting capacity acting as an antiandrogen.
• Hexabromocyclododecane (HBCD) is a brominated flame retardant primarily used in thermal insulation in the building industry. HBCD is persistent, toxic and ecotoxic, with bioaccumulative and long-range transport properties.

Health effects

POP exposure may cause developmental defects, chronic illnesses, and death. Some are carcinogens per IARC, possibly including breast cancer. Many POPs are capable of endocrine disruption within the reproductive system, the central nervous system, or the immune system. People and animals are exposed to POPs mostly through their diet, occupationally, or while growing in the womb. For humans not exposed to POPs through accidental or occupational means, over 90% of exposure comes from animal product foods due to bioaccumulation in fat tissues and bioaccumulate through the food chain. In general, POP serum levels increase with age and tend to be higher in females than males.

Studies have investigated the correlation between low level exposure of POPs and various diseases. In order to assess disease risk due to POPs in a particular location, government agencies may produce a human health risk assessment which takes into account the pollutants' bioavailability and their dose-response relationships.

Endocrine disruption

The majority of POPs are known to disrupt normal functioning of the endocrine system. Low level exposure to POPs during critical developmental periods of fetus, newborn and child can have a lasting effect throughout its lifespan. A 2002 study summarizes data on endocrine disruption and health complications from exposure to POPs during critical developmental stages in an organism’s lifespan. The study aimed to answer the question whether or not chronic, low level exposure to POPs can have a health impact on the endocrine system and development of organisms from different species. The study found that exposure of POPs during a critical developmental time frame can produce a permanent changes in the organisms path of development. Exposure of POPs during non-critical developmental time frames may not lead to detectable diseases and health complications later in their life. In wildlife, the critical development time frames are in utero, in ovo, and during reproductive periods. In humans, the critical development timeframe is during fetal development.

Reproductive system

The same study in 2002 with evidence of a link from POPs to endocrine disruption also linked low dose exposure of POPs to reproductive health effects. The study stated that POP exposure can lead to negative health effects especially in the male reproductive system, such as decreased sperm quality and quantity, altered sex ratio and early puberty onset. For females exposed to POPs, altered reproductive tissues and pregnancy outcomes as well as endometriosis have been reported.

Gestational weight gain and newborn head circumference

A Greek study from 2014 investigated the link between maternal weight gain during pregnancy, their PCB-exposure level and PCB level in their newborn infants, their birth weight, gestational age, and head circumference. The lower the birth weight and head circumference of the infants was, the higher POP levels during prenatal development had been, but only if mothers had either excessive or inadequate weight gain during pregnancy. No correlation between POP exposure and gestational age was found. A 2013 case-control study conducted 2009 in Indian mothers and their offspring showed prenatal exposure of two types of organochlorine pesticides (HCH, DDT and DDE) impaired the growth of the fetus, reduced the birth weight, length, head circumference and chest circumference.

Additive and synergistic effects

Evaluation of the effects of POPs on health is very challenging in the laboratory setting. For example, for organisms exposed to a mixture of POPs, the effects are assumed to be additive. Mixtures of POPs can in principle produce synergistic effects. With synergistic effects, the toxicity of each compound is enhanced (or depressed) by the presence of other compounds in the mixture. When put together, the effects can far exceed the approximated additive effects of the POP compound mixture.

In urban areas and indoor environments

Traditionally it was thought that human exposure to POPs occurred primarily through food, however indoor pollution patterns that characterize certain POPs have challenged this notion. Recent studies of indoor dust and air have implicated indoor environments as a major sources for human exposure via inhalation and ingestion. Furthermore, significant indoor POP pollution must be a major route of human POP exposure, considering the modern trend in spending larger proportions of life indoor. Several studies have shown that indoor (air and dust) POP levels to exceed outdoor (air and soil) POP concentrations.

Control and removal in the environment

Current studies aimed at minimizing POPs in the environment are investigating their behavior in photo catalytic oxidation reactions. POPs that are found in humans and in aquatic environments the most are the main subjects of these experiments. Aromatic and aliphatic degradation products have been identified in these reactions. Photochemical degradation is negligible compared to photocatalytic degradation. A method of removal of POPs from marine environments that has been explored is adsorption. It occurs when an absorbable solute comes into contact with a solid with a porous surface structure. This technique was investigated by Mohamed Nageeb Rashed of Aswan University, Egypt. Current efforts are more focused on banning the use and production of POPs worldwide rather than removal of POPs.

Environmental impact of pharmaceuticals and personal care products

From Wikipedia, the free encyclopedia

A vervet monkey with a stolen box of aspirin that was not securely stored.

 

The environmental effect of pharmaceuticals and personal care products (PPCPs) is currently being widely investigated. PPCPs include substances used by individuals for personal health or cosmetic reasons and the products used by agribusiness to boost growth or health of livestock. More than twenty million tons of PPCPs are produced every year. PPCPs have been detected in water bodies throughout the world. The effects of these chemicals on humans and the environment are not yet known, but to date there is no scientific evidence that they affect human health.

Further research is needed to evaluate the risks of toxicity, persistence, and bioaccumulation. PPCPs encompass environmental persistent pharmaceutical pollutants (EPPPs) and are one type of persistent organic pollutants. They are not removed from wastewater by conventional methods. The European Union has declared pharmaceutical residues with the potential of contamination of water and soil to be "priority substances".

Overview

Since the 1990s, water contamination by pharmaceuticals has been an environmental issue of concern. In addition, it is important to note that many public health professionals in the United States began writing reports of pharmaceutical contamination in waterways in the 1970s.” Most pharmaceuticals are deposited in the environment through human consumption and excretion, and are often filtered ineffectively by municipal sewage treatment plants which are not designed to manage them. Once in the water, they can have diverse, subtle effects on organisms, although research is still limited. Pharmaceuticals may also be deposited in the environment through improper disposal, runoff from sludge fertilizer and reclaimed wastewater irrigation, and leaky sewer pipes. In 2009, an investigative report by Associated Press concluded that U.S. manufacturers had legally released 271 million pounds of compounds used as drugs into the environment, 92% of which was the industrial chemicals phenol and hydrogen peroxide, which are also used as antiseptics. It could not distinguish between drugs released by manufacturers as opposed to the pharmaceutical industry. It also found that an estimated 250 million pounds of pharmaceuticals and contaminated packaging were discarded by hospitals and long-term care facilities. The series of articles led to a hearing conducted by the U.S. Senate Subcommittee on Transportation Safety, Infrastructure Security, and Water Quality. This hearing was designed to address the levels of pharmaceutical contaminants in U.S. drinking water. This was the first time that pharmaceutical companies were questioned about their waste disposal methods. "No federal regulations or laws were created as a result of the hearing." "Between the years of 1970-2018 more than 3000 pharmaceutical chemicals were manufactured, but only 17 are screened or tested for in waterways." Alternately, "There are no studies designed to examine the effects of pharmaceutical contaminated drinking water on human health.” In parallel, the European Union is the second biggest consumer in the world (24% of the world total) after the USA and in the majority of EU Member States, around 50% of unused human medicinal products is not collected to be disposed of properly. In the EU, between 30 and 90% of the orally administered doses are estimated to be excreted as the active substances in the urine.

The term environmental persistent pharmaceutical pollutants (EPPP) was suggested in the 2010 nomination of pharmaceuticals and environment as an emerging issue to Strategic Approach to International Chemicals Management (SAICM) by the International Society of Doctors for the Environment (ISDE).

Safe disposal

Depending on the sources and ingredients, there are various ways in which the public can dispose of pharmaceutical and personal care products in acceptable ways. The most environmentally safe disposal method is to take advantage of a community drug take-back programs that collect drugs at a central location for proper disposal. Several local public health departments in the United States have initiated these programs. In addition, the United States Drug Enforcement Administration (DEA) periodically promotes local take-back programs, as well as the National Take Back Initiative.

Currently, take-back programs are funded by state or local health departments or are volunteer programs through pharmacies or health care providers. In recent years, the proposition that pharmaceutical companies should be responsible for their products “from the cradle to the grave,” has been gaining traction. This philosophy suggests that the manufacturers should fund the proper disposal of pharmaceutical products. Take-back programs should exist in every community, and, if further information is required on this, city officials should be contacted. If no such program exists locally, the Environmental Protection Agency and the Office of National Drug Control Policy suggest that consumers do the following:

1. take the prescription drugs out of their original containers;
2. mix drugs with cat litter or used coffee grounds;
3. place the mixture into a disposable container with a lid, such as a sealable bag;
4. cover up any personal identification with a black marker that is on the original pill containers;
5. place these containers in the bag with the mixture, seal them, and place them in the trash.

This will hopefully keep these chemicals separated from the open environment and especially water bodies long enough for them to naturally break down. 

When these substances find their way into water, it is much more difficult to deal with them. Water treatment facilities use different processes in order to minimize or fully eliminate these pollutants. This is done by using sorption where suspended solids are removed by sedimentation. Another method used is biodegradation, and through this method microorganisms, such as bacteria and fungi, feed on or break down these pollutants thus eliminating them from the contaminated media.

Types

Illicit drugs such as ecstasy (above) can be found in waterways.

 

Pharmaceuticals, or prescription and over-the-counter medications made for human use or veterinary or agribusiness purposes, are common PPCPs found in the environment. There are nine classes of pharmaceuticals included in PPCPs: hormones, antibiotics, lipid regulators, nonsteroidal anti-inflammatory drugs, beta-blockers, antidepressants, anticonvulsants, antineoplastics, and diagnostic contrast media.

Personal care products have four classes: fragrances, preservatives, disinfectants, and sunscreen agents. These products may be found in cosmetics, perfumes, menstrual care products, lotions, shampoos, soaps, toothpastes, and sunscreen. These products typically enter the environment when passed through or washed off the body and into the ground or sewer lines, or when disposed of in the trash, septic tank, or sewage system.

Traces of illicit drugs can be found in waterways and may even be carried by money.

Routes into the environment

More attention has been devoted of late to PPCPs in the environment. Two causes may contribute to this: PPCPs are actually increasing in the environment due to widespread use and/or analytical technology is better able to detect PPCPs in the environment. These substances enter the environment directly or indirectly. Direct methods include contamination of surface water by hospitals, households, industries, or wastewater treatment plants. Direct contamination can also affect the sediment and soil.

It is generally assumed (albeit hardly verified) that the production of pharmaceuticals in industrialised countries is well controlled and unharmful to the environment, due to the local legal restrictions usually required to permit production. However, a substantial fraction of the global production of pharmaceuticals takes place in low-cost production countries like India and China. Recent reports from India demonstrate that such production sites may emit very large quantities of e.g. antibiotics, yielding levels of the drugs in local surface waters higher than those found in the blood of patients under treatment.

The major route for pharmaceutical residues to reach the aquatic environment is most probably by excretion from patients undergoing pharma treatment. Since many pharmaceutical substances are not metabolized in the body they may be excreted in biologically active form, usually via the urine. Furthermore, many pharmaceutical substances are not fully taken up from the intestine (following oral administration in patients) into their blood stream. The fraction not taken up into the blood stream will remain in the gut and eventually be excreted via the faeces. Hence, both urine and faeces from treated patients contain pharmaceutical residues. Between 30 and 90% of the orally administered dose is generally excreted as active substance in the urine.

An additional source to environmental pollution with pharmaceuticals is improper disposal of unused or expired drug residues. In European countries take-back systems for such residues are usually in place (although not always utilized to full extent) while in e.g. the US only voluntary initiatives on a local basis exist. Though most of the waste goes to incineration and people are asked to throw unused or expired pharmaceuticals into the household waste investigations in Germany showed that up to 24% of liquid pharmaceuticals and 7% of tablets or ointments are disposed always or at least “rarely” via the toilet or sink.

Proper destruction of pharma residues should yield rest products without any pharmaceutical or ecotoxic activity. Furthermore, the residues should not act as components in the environmental formation of new such products. Incineration at a high temperature (more than 1000 degrees Celsius) is considered to fulfill the requirements, but even following such incineration residual ashes from the incineration should be properly taken care of.

Pharmaceuticals used in veterinary medicine, or as additives to animal food, pose a different problem, since they are excreted into soil or possibly open surface waters. It is well known that such excretions may affect terrestrial organisms directly, leading to extinction of exposed species (e.g. dung-beetles). Lipid-soluble pharma residues from veterinary use may bind strongly to soil particles, with little tendency to leak out to ground water or to local surface waters. More water-soluble residues may be washed out with rain or melting snow and reach both ground water and surface water streams.

Presence in the environment

Methods of PPCP entry into the environment from residential homes via septic and sewage systems.

 

The use of pharmaceuticals and personal care products (PPCPs) is on the rise with an estimated increase from 2 billion to 3.9 billion annual prescriptions between 1999 and 2009 in the United States alone. PPCPs enter into the environment through individual human activity and as residues from manufacturing, agribusiness, veterinary use, and hospital and community use. In Europe, the input of pharmaceutical residues via domestic waste water is estimated to be around 80% whereas 20% is coming from hospitals. Individuals may add PPCPs to the environment through waste excretion and bathing as well as by directly disposing of unused medications to septic tanks, sewers, or trash. Because PPCPs tend to dissolve relatively easily and do not evaporate at normal temperatures, they often end up in soil and water bodies. 

Some PPCPs are broken down or processed easily by a human or animal body and/or degrade quickly in the environment . However, others do not break down or degrade easily. The likelihood or ease with which an individual substance will break down depends on its chemical makeup and the metabolic pathway of the compound.

A 2002 study by the U.S. Geological Survey found detectable quantities of one or more chemicals in 80 percent of a sampling of 139 susceptible streams in 30 states. The most common pharmaceuticals detected were nonprescription drugs; detergents, fire retardants, pesticides, natural and synthetic hormones, and an assortment of antibiotics and prescription medications were also found.

A 2006 study found detectable concentrations of 28 pharmaceutical compounds in sewage treatment plant effluents, surface water, and sediment. The therapeutic classes included antibiotics, analgesics and anti-inflammatories, lipid regulators, beta-blockers, anti-convulsant, and steroid hormones. Although most chemical concentrations were detected at low levels (nano-grams/Liter (ng/L)), there are uncertainties that remain regarding the levels at which toxicity occurs and the risks of bioaccumulation of these pharmaceutical compounds.

A study published in late 2014 reported a spike in the levels of ecstasy, ketamine, caffeine and acetaminophen in nearby rivers coinciding with a Taiwanese youth event attended by around 600,000 people. In 2018, shellfish in Puget Sound, waters that receive treated sewage from the Seattle area, tested positive for oxycodone.

Besides the identified input from human medicine there appears diffuse pollution for example from pharmaceuticals used in agriculture, too. Investigations in Germany, France and Scotland showed traces of PPCPs upstream of waste water treatment plant effluents to rivers, too.

Effects

Human

The scope of human exposure to pharmaceuticals and personal care products from the environment is a complex function of many factors. These factors include the concentrations, types, and distribution of pharmaceuticals in the environment; the pharmacokinetics of each drug; the structural transformation of the chemical compounds either through metabolism or natural degradation processes; and the potential bioaccumulation of the drugs. More research is needed to determine the effects on humans of long-term exposure to low levels of PPCPs. The full effects of mixtures of low concentrations of different PPCPs is also unknown.

"The U.S. EPA risk assessment states that the acceptable daily intake (ADI) of pharmaceuticals is around 0.0027 mg/kg‐day." Due to the lack of research of toxicity guidelines and their effects on human health it is difficult to determine a healthy dosage for water contaminated by pharmaceuticals. "The pharmaceutical sample size tested does not give a full representation of human exposure. Only 17 out of 3000 prescriptions are screened for in drinking water."

In addition, “The EPA and FDA regulations state that a drug or chemical is not considered harmful until clear evidence shows that a substance causes harm". This means that we are not testing or screening for thousands of contaminants in our drinking water. Health risk assessments have not been conducted to provide concrete evidence to link pharmaceutical contamination and adverse human health effects. 

"However adverse health outcomes are displayed in aquatic organisms. Fish living near water treatment plants have been reported to be feminized." "Some male fish started to develop ovaries and other feminized characteristic due to pharmaceutical pollution some species have decreased in population due to exposure of EE2 and other hormonal ECD substances."

Although research has shown that PPCPs are present in water bodies throughout the world, no studies have shown a direct effect on human health. However, the absence of empirical data cannot rule out the possibility of adverse outcomes due to interactions or long-term exposures to these substances. Because the amounts of these chemicals in the water supply may be in the parts per trillion or parts per billion, it is difficult to chemically determine the exact amounts present. Many studies have therefore been focused to determining if the concentrations of these pharmaceuticals exist at or above the accepted daily intake (ADI) at which the designed biological outcomes can occur.

PPCPS: shelves with tampons, women's sanitary towels, tooth brushes, health and body care products

 

In addition to the growing concerns about human health risks from pharmaceutical drugs via environmental exposures, many researchers have speculated about the potential for inducing an antibiotic resistance. One study found 10 different antibiotics in sewage treatment effluents, surface water, and sediments. Some microbiologists believe that if antibiotic concentrations are higher than the minimum inhibitory concentrations (MICs) of a species of pathogenic bacteria, a selective pressure would be exerted and, as a result, antibiotic resistance would be selectively promoted. It has also been proven that at even sub-inhibitory concentrations (e.g., one-fourth of the MIC), several antibiotics are able to have an effect on gene expression (e.g., as shown for the modulation of expression of toxin-encoding genes in Staphylococcus aureus).

For reference the MIC of erythromycin that is effective against 90 percent of lab grown Campylobacter bacteria, the most common food-borne pathogen in the United States, is 60 ng/mL. One study found that the average concentration of erythromycin, a commonly prescribed antibiotic, was 0.09 ng/mL in water treatment plant effluents,. Additionally, transfer of genetic elements among bacteria has been observed under natural conditions in wastewater treatment plants, and selection of resistant bacteria has been documented in sewers receiving wastewaters from pharmaceutical plants. Moreover, antibiotic resistant bacteria may also remain in sewage sludge and enter the food chain if the sludge is not incinerated but used as fertilizer on agricultural land.

The relationship between risk perception and behavior is multifaceted. Risk management is most effective once the motivation behind the behavior of disposing unused pharmaceuticals is understood. There was little correlation found between the perception of risk and knowledge regarding pharmaceutical waste according to a study conducted by Cook and Bellis in 2001. This study cautioned against the effectiveness of attempting to change the public’s behavior on these health issues by warning them of the risks associated with their actions.

It is advised to take careful measures to inform the public in a way that does not impart guilt but rather public awareness. For example, a study carried out by Norlund and Garvill in Sweden (2003) that found that some people may make a personal sacrifice in terms of comfort because they feel that it would be helpful to reduce further environmental damage caused by the use of cars. Awareness of air pollution problems was a factor in their decision to take action on a more environmentally favorable choice of transportation. Thus, the goal of Bound’s project encapsulates whether the perception of risk associated with pharmaceuticals has an effect on the way in which medication is commonly disposed. 

In order to conduct this study, the pharmaceuticals were grouped by their therapeutic action in order to help participants identify them. The eight therapeutic groups are listed below: antibacterials, antidepressants, antihistamines, antiepileptics, hormone treatments, and lipid regulators. Next, a survey was created to examine the disposal patterns of the participants and their perception of the existing risk or threat against the environment. Respondents were asked the following questions in part one of the survey: 1. When and how they disposed of pharmaceuticals. 2. How they perceive the risk to the environment posed by pharmaceuticals. 3. To differentiate between the risks associated with different classed of pharmaceuticals. Part two of the survey involved each of the eight pharmaceutical groups described above individually. Finally, the third part asked information about the age, sex, profession, postcode, and education of participants. The sample size of participants was precise in comparison to the actual distribution of males and females in the UK: Sample- 54.8 percent were female and 45.2 percent male vs. Actual- the UK of 51.3 percent female to 48.7 percent male. Results showed that when a medication must be discarded, 63.2 percent of participants throw them in a bin, 21.8 percent return them to a pharmacist, and 11.5 percent dispose of them via the toilet/sink, while the remaining 3.5 percent keep them. Only half of the respondents felt like pharmaceuticals could potentially be harmful to the environment. Upon examination of factors relevant to risk perception, there was no definite link found between perception and education or income.

Dr. Bound noted that participation in altruistic activities such as Environmental Conservation groups may provide members with the ability to better grasp the effects of their actions in the environment. In regards to the aquatic environment, it is hard for one to perceive the favorable effects of properly disposing medication. There also exists the plausibility that a person’s behavior will only be affected if there is a severe risk to themselves or humans as opposed to an environmental threat. Even though there are serious threats of pharmaceutical pollution resulting in the feminization of certain fish, they have a lower priority because they are not easily understood or experienced by the general public. In Jonathan P. Bound’s opinion, the provision of information about exactly how to go about disposing unused medication properly in conjunction with risk education may have a more positive and forceful effect.

Recommendations

Several recommendations and initiatives have been made to prevent pharmaceutical pollution in the environment. Important practices include:

• Educating patients on the importance of proper unused drug disposal,
• Educating physicians and patients of proper drug disposal,
• Encouraging pharmaceutical industries to implement strategies for proper disposal of drugs or recycling strategies, and
• Requiring hospitals to implement better management practices for disposing pharmaceutical waste.

First, it is imperative that patients become educated on pharmaceutical pollution and its hazardous effects on humans, animals, and the overall environment. By educating patients on proper disposal of unused drugs, steps are being taken to further prevent pharmaceutical waste in the environment. Consumers should take precautions before tossing out drugs in the trash or flushing them down the toilet. Community take-back programs have been set up for consumers to bring back unused drugs for proper disposal. Another initiative is for pharmacies to serve as a take-back site for proper drug disposal such as implementing recycling bins for customers to bring back unused or expired medicines while they’re shopping. In addition, medical foundations could receive these medicines to administer them to people who need them, while destroying those that are in excess or expired. Furthermore, educating physicians and patients on the importance of proper drug disposal and the environmental concern will help further reduce pharmaceutical waste. 

Also, implementing initiatives for hospitals to focus on better practices for hazardous waste disposal may prove to be beneficial. The US EPA encourages hospitals to develop efficient pharmaceutical disposal practices by giving them grants. This incentive may be very beneficial to other hospitals worldwide. 

Additionally, “It is critical for us to develop an analytical method of identifying, testing, and regulating the amount of pharmaceuticals in the water systems”. Data must be collected in order to accurately measure the prevalence of pharmaceuticals in drinking water. “Multiple Health risk assessments should be conducted to understand the effects of prolonged exposure to pharmaceuticals in drinking water”.

Community-based programs should be developed to monitor exposure and health outcomes. We should encourage the pharmaceutical industry to develop technology that extracts pharmaceuticals from waterways. “Extensive research must be conducted to determine the amount of pharmaceutical contamination in the environment and its effects on animals and marine life”.

We must remember that many pharmaceuticals pass through the human body unchanged, so it is best for human excrement to not go into waterways, even after conventional treatment, which can also not remove these chemicals. It is therefore preferable for human feces and urine to go into fertile soil, where they will receive more effective treatment by numerous microbes found there, over longer amounts of time, and stay away from waterways, via the use of Urine-diverting Dry Toilets, Composting Toilets, and ArborLoos. As mentioned below, constructed wetlands are efficient at removing these chemicals, but it is better for them to not go into water in the first place.

Environmental

While the full effects of most PPCPs on the environment are not understood, there is concern about the potential they have for harm because they may act unpredictably when mixed with other chemicals from the environment or concentrate in the food chain. Additionally, some PPCPs are active at very low concentrations, and are often released continuously in large or widespread quantities. 

A class of antidepressants may be found in frogs and can significantly slow their development

 

Because of the high solubility of most PPCPs, aquatic organisms are especially vulnerable to their effects. Researchers have found that a class of antidepressants may be found in frogs and can significantly slow their development. The increased presence of estrogen and other synthetic hormones in waste water due to birth control and hormonal therapies has been linked to increased feminization of exposed fish and other aquatic organisms. The chemicals within these PPCP products could either affect the feminization or masculinization of different fishes, therefore affecting their reproductive rates.

In addition to being found only in waterways, the ingredients of some PPCPs can also be found in the soil. Since some of these substances take a long time or cannot be degraded biologically, they make their way up the food chain. Information pertaining to the transport and fate of these hormones and their metabolites in dairy waste disposal is still being investigated, yet research suggest that the land application of solid wastes is likely linked with more hormone contamination problems. Not only does the pollution from PPCPs affect marine ecosystems, but also those habitats that depend on this polluted water. 

There are various concerns about the effects of pharmaceuticals found in surface waters and specifically the threats against rainbow trout exposed to treated sewage effluents. Analysis of these pharmaceuticals in the blood plasma of fish compared to human therapeutic plasma levels have yielded vital information providing a means of assessing risk associated with medication waste in water. In a study by Dr. Jerker Fick from Umeå University rainbow trout were exposed to undiluted, treated sewage water at three different sits in Sweden. They were exposed for a total of 14 days while 25 pharmaceuticals were measured in the blood plasma at different levels for analysis. The progestin Levonorgestrel was detected in fish blood plasma at concentrations between 8.5 and 12 ng mL-1 which exceed the human therapeutic plasma level. Studies show that the measured effluent level of Levonorgestrel in the three areas was shown to reduce the fertility of the rainbow trout.

The three sites chosen for field exposures were in located in Stockholm, Gothenburg, and Umeå. They were chosen according to their varying degrees of treatment technologies, geographic locations, and size. The effluent treatment includes active sludge treatment, nitrogen and phosphorus removal (except in Umeå), primary clarification, and secondary clarification. Juvenile rainbow trout were procured from Antens fiskodling AB, Sweden and Umlax AB, Sweden. The fish were exposed to aerated, undiluted, treated effluent. Since all of the sites underwent sludge treatment, it can be inferred that they are not representative of the low end of treatment efficacy. Of the 21 pharmaceuticals that were detected in the water samples, 18 were identified in the effluent, 17 in the plasma portion, and 14 pharmaceuticals were found in both effluent and plasma.

Current research

There are traces pharmaceuticals in waterways that have an adverse effect on the environment.

 

Starting in the mid-1960s, ecologists and toxicologists began to express concern about the potential adverse effects of pharmaceuticals in the water supply, but it wasn’t until a decade later that the presence of pharmaceuticals in water was well documented. Studies in 1975 and 1977 found clofibric acids and salicylic acids at trace concentrations in treated water. Widespread concern about and research into the effect of PPCPs largely started in the early 1990s. Until this time, PPCPs were largely ignored because of their relative solubility and containment in waterways compared to more familiar pollutants like agrochemicals, industrial chemicals, and industrial waste and byproducts.

Since then, a great deal of attention has been directed to the ecological and physiological risk associated with pharmaceutical compounds and their metabolites in water and the environment. In the last decade, most research in this area has focused on steroid hormones and antibiotics. There is concern that steroid hormones may act as endocrine disruptors. Some research suggests that concentrations of ethinylestradiol, an estrogen used in oral contraceptive medications and one of the most commonly prescribed pharmaceuticals, can cause endocrine disruption in aquatic and amphibian wildlife in concentrations as low as 1 ng/L.

Current research on PPCPs aims to answer these questions:

• What is the effect of exposure to low levels of PPCPs over time?
• What is the effect of exposure to mixtures of chemicals?
• Are the effects acute (short-term) or chronic (long-term)?
• Are certain populations, such as the elderly, very young, or immuno-compromised, more vulnerable to the effects of these compounds?
• 

• Jaipur cows eating trash, which may contain medicines and supplements that will pass through their system and enter the environment
  What is the effect of PPCPs on bacterial, fungal, and aquatic life?
• Are the levels of antibiotics in the aquatic environment sufficient to promote antibiotic resistance?
• What is the effect of exposure to steroid hormones on animal and human populations?

Pharmacoenvironmentology

Pharmacoenvironmentology is an extension of pharmacovigilance as it deals specifically with the environmental and ecological effects of drugs given at therapeutic doses. Pharmacologists with this particular expertise (known as a pharmacoenvironmentologist) become a necessary component of any team assessing different aspects of drug safety in the environment. We must look at the effects of drugs not only in medical practice, but also at its environmental effects. Any good clinical trial should look at the impact of particular drugs on the environment. Things we need to address in pharmacoenvironmentology are drugs and their exact concentration in different parts of the environment.

Pharmacoenvironmentology is a specific domain of pharmacology and not of environmental studies.This is because it deals with drugs entering through living organisms through elimination.

Ecopharmacovigilance

Pharmacovigilance is a new branch of science, which was born in 1960 after the incidence of the thalidomide disaster. Thalidomide is a teratogen and caused horrific birth abnormalities. The thalidomide disaster lead to the present day approach to drug safety and adverse event reporting.

According to the EPA, pharamacovigilance is science aiming to capture any adverse effects of pharmaceuticals in humans after use. However, ecopharmacovigilance is the science, and activities concerning detection, assessment, understanding, and prevention of adverse effects of pharmaceuticals in the environment which affect humans and other animal species. There has been a growing focus among scientists about the impact of drugs on the environment. In recent years, we have been able to see human pharmaceuticals that are being detected in the environment which most are typically found on surface water.

The importance of ecopharmacovigilance is to monitor adverse effects of pharmaceuticals on humans through environmental exposure. Due to this relatively new field of science, researchers are continuously developing and understanding the impacts of pharmaceuticals in the environment and its risk on human and animal exposure. Environmental risk assessment is a regulatory requirement in the launch of any new drug. This precaution has become a necessary step towards the understanding and prevention of adverse effects of pharmaceutical residue in the environment. It is important to note that pharmaceuticals enter the environment from the excretion of drugs after human use, hospitals, and improper disposal of unused drugs from patients.

Ecopharmacology

Ecopharmacology concerns the entry of chemicals or drugs into the environment through any route and at any concentration disturbing the balance of ecology (ecosystem), as a consequence. Ecopharmacology is a broad term that includes studies of “PPCPs” irrespective of doses and route of entry into environment.

The geology of a karst aquifer area assists with the movement of PPCPs from the surface to the ground water. Relatively soluble bedrock creates sinkholes, caves and sinking streams into which surface water easily flows, with minimal filtering. Since 25% of the population get their drinking water from karst aquifers, this affects a large number of people. A 2016 study of karst aquifers in southwest Illinois found that 89% of water samples had one or more PPCP measured. Triclocarban (an antimicrobial) was the most frequently detected PPCP, with gemfibrozil (a cardiovascular drug) the second most frequently detected. Other PPCPs detected were trimethoprim, naproxen, carbamazepine, caffeine, sulfamethoxazole, and fluoxetine. The data suggests that septic tank effluent is a probable source of PPCPs.

Fate of pharmaceuticals in sewage treatment plants

Sewage treatment plants use physical, chemical, and biological processes to remove nutrients and contaminants from waste water.

 

Sewage treatment plants (STP) work with physical, chemical, and biological processes to remove nutrients and contaminants from waste water. Usually the STP is equipped with an initial mechanical separation of solid particles (cotton buds, cloth, hygiene articles etc.) appearing in the incoming water. Following this there may be filters separating finer particles either occurring in the incoming water or developing as a consequence of chemical treatment of the water with flocculating agents.

Many STPs also include one or several steps of biological treatment. By stimulating the activity of various strains of microorganisms physically their activity may be promoted to degrade the organic content of the sewage by up to 90% or more. In certain cases more advanced techniques are used as well. The today most commonly used advanced treatment steps especially in terms of micropollutants are:

• Membranes (which may be used instead of the biological treatment),
• Ozonation,
• Activated carbon (powdered or granulated),
• UV treatment,
• Treatment with ferrate and
• Sand filtration (which is sometimes added as a last step after the aforementioned).

PPCPs are difficult to remove from wastewater with conventional methods. Some research shows the concentration of such substances is even higher in water leaving the plant than water entering the plant. Many factors including environmental pH, seasonal variation, and biological properties affect the ability of a STP to remove PPCPs.

A 2013 study of a drinking water treatment plant, found that of 30 PPCPs measured at both the source water and the drinking water locations, 76% of PPCPs were removed, on average, in the water treatment plant. Ozonation was found to be an efficient treatment process for the removal of many PPCPs. However, there are some PPCPs that were not removed, such as DEET used as mosquito spray, nonylphenol which is a surfactant used in detergents, the antibiotic erythromycin, and the herbicide atrazine.

Several research projects are running to optimize the use of advanced sewage treatment techniques under different conditions. The advanced techniques will increase the costs for the sewage treatment substantially. In a European cooperation project between 2008 and 2012 in comparison 4 hospital waste water treatment facilities were developed in Switzerland, Germany, The Netherlands and Luxembourg to investigate the elimination rates of concentrated waste water with pharmaceutical “cocktails” by using different and combined advanced treatment technologies. Especially the German STP at Marienhospital Gelsenkirchen showed the effects of a combination of membranes, ozone, powdered activated carbon and sand filtration. But even a maximum of installed technologies could not eliminate 100% of all substances and especially radiocontrast agents are nearly impossible to eliminate. The investigations showed that depending on the installed technologies the treatment costs for such a hospital treatment facility may be up to 5.50 € per m². Other studies and comparisons expect the treatment costs to increase up to 10%, mainly due to energy demand. It is therefore important to define best available technique before extensive infrastructure investments are introduced on a wide basis. 

The fate of incoming pharmaceutical residues in the STP is unpredictable. Some substances seem to be more or less completely eliminated, while others pass the different steps in the STP unaffected. There is no systematic knowledge at hand to predict how and why this happens. 

Pharmaceutical residues that have been conjugated (bound to a bile acid) before being excreted from the patients may undergo de-conjugation in the STP, yielding higher levels of free pharmaceutical substance in the outlet from the STP than in its incoming water. Some pharmaceuticals with large sales volumes have not been detected in the incoming water to the STP, indicating that complete metabolism and degradation must have occurred already in the patient or during the transport of sewage from the household to the STP.

Regulation

In the United States, “There are no federal regulations limiting the levels of pharmaceuticals in wastewater or drinking water”, according to EPA. Three birth controls substances and one antibiotic were added to the pharmaceuticals contaminant candidate list (CCL 3). EPA states that they are 8 pharmaceuticals that are classified as hazardous waste. Out of 3000 pharmaceuticals EPA has only evaluated 100 of them leaving numerous of unscreened compounds in the water.” In 2008, EPA proposed an amendment to the Universal Waste Rule to address pharmaceutical wastes.” However, no action on the Rule has occurred since the hearing in the U.S. senate in 2009”.

The Clean Water Act (CWA), Safe Drinking Water Act (SDWA), and the Universal Waste Regulations under the Resource Conservation and Recovery Act (RCRA) do little to protect the American population from pharmaceutical contamination in waterways. The EPA has the ability to implement governmental regulations to insure that the public has access to water that is free of pharmaceutical pollution however, no laws have been enacted even though “ the U.S. Government Accountability Office (GAO) reports that some research has demonstrated potential impact on human health from exposure to pharmaceuticals found in drinking water, such as antibiotics and EE2 substances that interfere with human hormone development”.

The EPA and other governmental agencies are not focused on this issue. They are not demanding any changes or regulations for Pharmaceutical pollution. They did not review the 3000 Pharmaceutical substances to determine their effect on human health. There are no long term studies or health assessments created to examine how this affects us or the environment.

Treatment methods

PPCPs are emerging pollutants, which pose potential risks on the environment and health. They are the result of many sectors, such as household consumption, industrial, farming, medicine, and aquaculture. However, because of the toxic and intractable characteristics, these pollutants cannot be removed by a traditional wastewater treatment plant in an effective way. Hence, they are becoming more and more universal. The fact that conventional wastewater treatment processes could not eradicate PPCPs completely has been highlighted. In final effluents, high concentrations of PPCPs can be detected, and these contaminants can accumulate in rivers, sludge, soil, and biosolids. A study pointed out that organic pollutants, including PPCPs, appeared in 80% of 139 U.S. streams from 1999 to 2000. As such, environmental pollution caused by PPCPs are becoming more and more serious. Therefore, the removal of PPCPs is an urgent topic in the treatment of wastewater. Up to now, the methods used for the removal of PPCPs can be roughly divided into three categories, including physical, chemical, and biological methods.

Physical adsorption processes

The most common physical process is adsorption. It is usually used to remove traceable organic pollutants in water. Generally, carbon-based materials, which include biochar, activated carbon, graphene and graphene oxide, and carbon nanotubes, are applied to adsorb PPCPs from aqueous solution. Different materials have a different adsorption capacity for PPCPs. As for these materials, carbon nanotubes have the highest adsorption capacity, while the adsorption capacity adjusted with the surface chemistry and properties of carbon nanotubes. By comparison, activated carbon as a traditional adsorbent has a wide application in adsorption of PPCPs from wastewater. Although physical adsorption processes are regarded as an advanced technology, and developing fast in the field of treatment methods, there are still some problems that should be addressed in future research, like the production of carbon nanotubes, the high cost of graphene, and the absorption of macromolecular substances.

Biological degradation processes

Microbial degradation is regarded as an essential method for the removal of organic pollutants. The processes have numerous advantages, like economical input costs, and mild operational conditions. In these processes, microorganisms can make use of their metabolic functions to degrade the contaminants and in some cases several microbes cooperate with each other to achieve this goal. Pure cultures, mixed cultures, and activated sludge processes can be used in these processes, while an activated sludge process is widely used as a biological treatment in the conventional wastewater treatment plants. Constructed wetlands show great promise and are discussed below.

Chemical advanced oxidation processes

Advanced chemical oxidation processes are effective in removing PPCPs from wastewater. These include ozonation, Fenton oxidation, ionizing radiation, and UV treatment, are efficient in the degradation of recalcitrant organic pollutants in aqueous solution. Among these, ozonation is the most widely used oxidation method for the removal of PPCPs.

Combined chemical and biological methods

Because some PPCPs are highly resistant and toxic to microorganisms, it can be difficult for biological methods to eliminate them on their own. On the other hand, advanced chemical oxidation processes behave well in removing persistent pollutants, but the intermediates produced during the treatment process are sometimes more resistant to oxidation. Thus, if using one of these two methods to treat pollutants, the process requires long times and high energy inputs, resulting in a high cost. In order to overcome the shortfalls of using a single method, combinations of biological and chemical processes have increasingly been applied in recent years. In the first stage, advanced chemical oxidation processes are used for pre-treatment to transform persistent pollutants into the biodegradable intermediates. Then, biological methods are applied to degrade them. Combined systems are being shown to be efficient and cost effective.

Examples

Blister packs

80% of pills in the world are packed with blister packaging, which is the most convenient type for several reasons. Blister packs have two main components, the “lid” and the “blister” (cavity). Lid is mainly manufactured with aluminum (Al) and paper. The Cavity consists of polyvinyl chloride (PVC), polypropylene (PP), polyester (PET) or aluminum (Al). If users employ proper disposal methods, all these materials can be recycled and the harmful effects to the environment can be minimized. However, a problem arises with the improper disposal either by burning or disposing as normal household waste. 

Burning of blister packs directly causes air pollution by the combustion products of polypropylene ([C₃H₆]_n), polyester ([C₁₀H₈O₄]_n), and polyvinyl chloride ([CH₂CHCl]_n). The combustion reactions and products of these chemicals are mentioned below. 

The basic configuration of blister packaging

[C₃H₆]_n + 9n/2 O₂ → 3n CO₂ +3n H₂O

[C₁₀H₈O₄]_n + 10n O₂ → 10n CO₂ +4n H₂O

[CH₂CHCl]_n + 2n O₂ → n CO₂ + n H₂O + n HCl + n CO 

Even though polypropylene and polyester is harmful to the environment, the most toxic effect is due to the combustion of polyvinyl chloride since it produces hydrochloric acid (HCl) which is an irritant in the lower and upper respiratory tract that can cause adverse to human beings.

The disposal of blister packs as normal waste, will forbid recycling process and eventually accumulate in soil or water, which will result soil and water pollution since bio-degradation processes of compounds like PVC, PP and PET are very slow. As a result, ecologically damaging effects like disturbances of the habitats and movements can be seen. Ingestion by the animals, affect the secretion of gastric enzymes and steroid hormones that can decrease the feeding stimuli and may also cause problems in reproduction. At low pH, aluminum can increase its solubility according to the following equation. As a result, the negative effects of both aquatic and terrestrial ecosystems can be generated.

2Al_(s)+ 6H⁺ → 2Al³⁺ _(aq) + 3H_{2 (g)} 

By employing proper disposal methods, all manufacturing materials of blister packs like PP, PE, PVC and Al can be recycled and the adverse effects to the environment can be minimized. Even though, the synthesis of these polymers relatively simple, the recycling process can be very complex since the blister packs contain metals and polymers together.

As the first step of recycling, separation of Al and Polymers using the hydrometallurgical method which uses hydrochloric acid (HCl)  can be incorporated. Then PVC can be recycled by using mechanical or chemical methods. The most recent trend is to use biodegradable, eco-friendly “bio plastics” which are also called as biopolymers such as derivatives of starch, cellulose, protein, chitin and xylan for pharmaceutical packaging, to reduce the hostile effects to the environment.

Nail polish remover

Nail polish remover has the ability to enter bodies of water and soil after entering landfills or by precipitation, such as rain or snow. However, due to acetone's high volatility, most of it that enters the bodies of water and soil will evaporate again and re-enter the atmosphere. Not all of the acetone molecules will evaporate again, and so, when acetone remains in the bodies of water or soil, a reaction will occur. Nail polish remover evaporates easily because acetone's intermolecular forces are weak. An acetone molecule can't attract other acetone molecules easily because its hydrogens are not slightly positive. The only force that holds acetone molecules together is its permanent dipoles which are weaker than hydrogen bonds.

Nail polish remover contains acetone.

 

Since nail polish remover is a solvent, it will dissolve in water. When acetone dissolves in water, it hydrogen bonds with water. The more nail polish remover that enters the hydrosphere will increase the concentration of acetone and then increase the concentration of the solution created when acetone and water bonds. If enough nail polish remover is disposed, it can reach the lethal dose level for aquatic life. 

Nail polish remover can also enter the lithosphere by landfills and by precipitation. However, it will not bind to the soil. Microorganisms in the soil will decompose acetone. The consequence of microorganisms decomposing acetone is the risk it has to cause oxygen depletion in bodies of water. The more acetone readily available for microorganism decomposition leads to more microorganisms reproduced and thus oxygen depletion because more microorganisms use up the available oxygen. 

When nail polish remover evaporates, acetone enters the atmosphere in the gaseous phase. In the gaseous phase, acetone can undergo photolysis and breakdown into carbon monoxide, methane, and ethane. When temperatures are between 100 - 350 degrees Celsius, the following mechanism occurs:

(CH₃)2CO + hv → CH₃ + CH₃CO

CH₃CO → CH₃+ CO

CH₃+ (CH₃)2CO → CH4 + CH2COCH₃

2CH₃ → C2H6

A second pathway that nail polish remover can enter in the atmosphere is reacting with hydroxyl radicals. When acetone reacts with hydroxyl radicals, its main product is methylglyoxal. Methylglyoxal is an organic compound that is a by-product of many metabolic pathways. It is an intermediate precursor for many advanced glycation end-products, that are formed for diseases such as diabetes or neurodegenerative diseases. The following reaction occurs: 

(CH₃)2CO + ·OH → CH₃C(O)OH + ·CH₃

CH₃C(O)OH + ·CH₃→ CH₃C(O)COH + 3H+

Case study

The Location of the Pearl River Delta

Pearl River, South China

It is well known that releasing antibiotics into the water can lead to antibiotic resistance. In the recent decade, the Pearl River has been altered by antibiotics. A study found that concentrations of antibiotics were lower than those in the estuary, and decreased from the east side to the west side. A series of phenomena showed that the primary sources of antibiotics came from river tributaries and terrigenous sources and there were frequent human activities and hydraulic conditions along the west banks of the river. Seasonal variations happened in most of the detected antibiotics in water as well. Additionally, the TOC content of sediments, and the pH of water affected the performance of antibiotics. The highest concentrations of antibiotics were found downstream of Guangdong Province, which was affected severely by nearby densely populated megacities, like Shenzhen, Hong Kong, and Macau. These have an adverse impact on people there.

The coast of Guangdong, South China

The coast of Guangdong is a place polluted by another representative contaminant, plastic debris. After an extended period of observation, scientists found that the beach was a place that would help the fragmentation of plastic debrisinto highly fragmented plastic particles that can attach to small organisms. Through the process of washback, the plastic debris may be transported into the water, and make an adverse impact on a wide range of marine life at different trophic levels. It is noticeable that polystyrene (PS) foams and fragments, and microplastics account for a great percentage of plastic debris on the beach. Most of the polystyrenes degrade within a year on average, and could not be observed in deep beach sediment. Thus, coastal beaches store highly fragmented and degraded micro-plastics. However, they may be active and return to the water.

An alternative best management practice for PPCPs treatment – the application of constructed wetlands

Structures of constructed wetlands: (a) surface flow (SF-CW); (b) horizontal subsurface flow (HSSF-CW); and (c) vertical subsurface flow (VSSF-CW).

 

In recent years, scientists have been trying to find a way to handle PPCPs, but most of the advanced treatment processes are too expensive to apply in large scale. As such, a low-cost alternative approach for PPCPs treatment is of great significance for the environment. Based on this purpose, increasing concerns have been raised on constructed wetlands, which are cheaper in construction, operation, maintenance and monitoring. Actually, constructed wetlands have been proved to be effective for removal of conventional contaminants in wastewater treatment. However, applying constructed wetlands to deal with these issues is a totally new application in the field.

Important components of constructed wetlands

Substrate

Based on several researches and further analysis for various constructed wetlands, scientists found that gravel is the most common substrate materials for the removal of PPCPs in constructed wetlands. The gravel substrate is efficient for some certain PPCPs which are difficult to be biodegraded but with relatively high hydrophobicity. On the other hand, according to a set of experiments, it is reported that light expanded clay aggregate as a sorbent in constructed wetlands performs well for the treatment of the acidic compounds and alkaline with positive charge.

Vegetation

Vegetation plays an important part in directly taking up several organic pollutants from wastewater in constructed wetlands. With the function of diffusion, the organic pollutants like PPCPs can be transported within plants. That means, theses pollutants cannot move into the plant tissues through the plant roots and some specific transporters. Generally, the physico-chemical characteristics of PPCPs, such as hydrophobicity, water solubility, and concentration, affect the diffusion of the compounds. After being soaked up by plants, the degradation may happen in metabolism processes. Due to the activities of microbial populations, there are numerous biological processes occurring in the rhizosphere. However, the toxicity of PPCPs to plants is a nonnegligible issue.

Microbes

The processes of transformation and mineralization of nutrients and organic pollutants are primarily dependent on microbes in constructed wetlands, and the microbial degradation processes can occur in both the aerobic and the anaerobic environments with the participation of diverse microorganisms, like fungi, specific protozoa, heterotrophic bacteria, and autotrophic bacteria. The chemical structures of organic pollutants strongly affect the degradation processes. Some contaminations with simple structures owning high water solubility and low absorptivity, so degradation via microorganisms will be easier. However, for PPCPs, which are xenobiotic organic pollutants with totally different compounds, they are degraded relatively slowly. Even though there are non-specific enzymes, the rate of degradation is still slower.

Pending questions

• Is there a temperature at which PPCPs are burned and destroyed? Would they thus be eliminated when materials are made into biochar?
• Are there artificial colorings that degrade under similar conditions to PPCPs and could be used as proxies in low-tech experiments of how to eliminate PPCPs?
• Ultraviolet light is known to degrade PPCPs. How long would urine need to lay in the sun in transparent bottles to destroy the PPCPs before its use as fertilizer?
• Do soil microbes develop or evolve the ability to break down PPCPs over time? If a person who consumes a pharmaceutical uses a Urine-diverting Dry Toilet, in which the urine is dispersed into fertile soil among plants, would the microbes eventually decompose this chemical entirely? After how much time? Which types of pharmaceuticals would break down faster and which slower?
• Are there types of PPCPs that cannot enter into the roots of plants because their molecules are simply too large?
• When essential oils are extracted from plants, would PPCPs pass into them, stay in the cauldron, or be destroyed by the heat?