Dysfunctional family

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Dysfunctional_family 

 

A dysfunctional family affects familial ties and creates conflicts in the same family space.

A dysfunctional family is a family in which conflict, misbehavior, and often child neglect or abuse on the part of individual parents occur continuously and regularly, leading other members to accommodate such actions. Children sometimes grow up in such families with the understanding that such a situation is normal. Dysfunctional families are primarily a result of two adults, one typically overtly abusive and the other codependent, and may also be affected by substance abuse or other forms of addiction, or sometimes by an untreated mental illness. Parents having grown up in a dysfunctional family may over-correct or emulate their own parents. In some cases, the dominant parent will abuse or neglect their children and the other parent will not object, misleading a child to assume blame.

Perceptions and historical context

A common misperception of dysfunctional families is the mistaken belief that the parents are on the verge of separation and divorce. While this is true in a few cases, often the marital satisfaction is very strong as the parents' faults actually complement each other. In short, they have nowhere else to go. However, this does not necessarily mean the family's situation is stable. Any major stressor, such as relocation, unemployment/underemployment, physical or mental illness, natural disaster, etc., can cause existing difficulties affecting the children to become much worse.

Dysfunctional families pervade all strata of society regardless of social, financial or intellectual status. Nevertheless, until recent decades, professionals (therapists, social workers, teachers, counselors, clergy, etc.) did not take the concept of a dysfunctional family seriously, especially not with reference to the middle and upper classes. Any intervention would have been seen as violating the sanctity of marriage and increasing the probability of divorce, which was socially unacceptable at the time. Historically, society expected the children of dysfunctional families to obey their parents (ultimately the father), and to cope with the situation alone.

Examples

Dysfunctional family members have common features and behavior patterns as a result of their experiences within the family structure. This tends to reinforce the dysfunctional behavior, either through enabling or perpetuation. The family unit can be affected by a variety of factors.

Common features

Nearly universal

Some features are common to most dysfunctional families:

• Lack of empathy, understanding, and sensitivity towards certain family members, while expressing extreme empathy or appeasement towards one or more members who have real or perceived "special needs". In other words, one family member continuously receives far more than they deserve, while another is marginalized.
• Denial (refusal to acknowledge abusive behavior, possibly believing that the situation is normal or even beneficial; also known as the "elephant in the room".)
• Inadequate or missing boundaries for self (e.g. tolerating inappropriate treatment from others, failing to express what is acceptable and unacceptable treatment, tolerance of physical, emotional or sexual abuse.)
• Disrespect of others' boundaries (e.g. physical contact that other person dislikes; breaking important promises without just cause; purposefully violating a boundary another person has expressed.)
• Extremes in conflict (either too much fighting or insufficient peaceful arguing between family members.)
• Unequal or unfair treatment of one or more family members due to their birth order, gender, age, family role (mother, etc.), abilities, race, caste, etc. (may include frequent appeasement of one member at the expense of others, or an uneven/inconsistent enforcement of rules.)

Not universal

Though not universal among dysfunctional families, and by no means exclusive to them, the following features are typical of dysfunctional families:

• Abnormally high levels of jealousy or other controlling behaviors.
• Conflict influenced by marital status:
  • Between separated or divorced parents, usually related to, or arising from their breakup.
  • Conflict between parents who remain married, often for the perceived "sake" of the children, but whose separation or divorce would in fact remove a detrimental influence on those children (must be evaluated on a case-by-case basis, as a breakup may harm children.)
  • Parents who wish to divorce, but cannot due to financial, societal (including religious), or legal reasons.
• Children afraid to talk (within or outside the family) about what is happening at home, or are otherwise fearful of their parents.
• Abnormal sexual behavior such as adultery, promiscuity, or incest.
• Lack of time spent together, especially in recreational activities and social events ("We never do anything as a family.")
• Parents insist that they treat their children fairly and equitably when that is not the case.
• Family members (including children) who disown each other, or refuse to be seen together in public (either unilaterally or bilaterally.)

Specific examples

There are certain times where families can become dysfunctional due to specific situational examples. Some of these include difficulty integrating into a new culture, strain in the relationship between nuclear and extended family members, children in a rebellion phase, and ideological differences in belief systems.

Laundry List

The program "Adult Children of Alcoholics" includes something labeled as a "Laundry List". The Laundry List is core literature of the program Adult Children of Alcoholics. This list has 14 different statements that relate to being an adult child of a parent with an alcohol addiction. These statements provide commentary on how children have been affected by the trauma of having alcoholic parents. Some highlights of the statements include, "confusing love and pity", "having low self-esteem", and having a "loss of identity". The Laundry list is a helpful tool in group therapy in order to show families that they are not alone in their struggles.

Parenting

Unhealthy signs

Unhealthy parenting signs, which could lead to a family becoming dysfunctional include:

• Unrealistic expectations
• Ridicule
• Conditional love
• Disrespect; especially contempt
• Emotional intolerance (family members not allowed to express the "wrong" emotions.)
• Social dysfunction or isolation (for example, parents unwilling to reach out to other families—especially those with children of the same gender and approximate age, or do nothing to help their "friendless" child.)
• Stifled speech (children not allowed to dissent or question authority.)
• Denial of an "inner life" (children are not allowed to develop their own value systems.)
• Being under- or over-protective
• Apathy ("I don't care!")
• Belittling ("You can't do anything right!")
• Shame ("Shame on you!")
• Bitterness (regardless of what is said, using a bitter tone of voice.)
• Hypocrisy ("Do as I say, not as I do.")
• Lack of forgiveness for minor misdeeds or accidents
• Judgmental statements or demonization ("You are a liar!")
• Being overly critical and withholding proper praise. (experts say 80–90% praise, and 10–20% constructive criticism is the most healthy.)
• Double standards or giving "mixed messages" by having a dual system of values (i.e. one set for the outside world, another when in private, or teaching divergent values to each child.)
• The absentee parent (seldom available for their child due to work overload, alcohol/drug abuse, gambling, or other addictions.)
• Unfulfilled projects, activities, and promises affecting children ("We'll do it later.")
• Giving to one child what rightly belongs to another
• Gender prejudice (treats one gender of children fairly; the other unfairly.)
• Discussion and exposure to sexuality: either too much, too soon or too little, too late
• Faulty discipline based more on emotions or family politics than on established rules (e.g., punishment by "surprise".)
• Having an unpredictable emotional state due to substance abuse, personality disorder(s), or stress
• Parents always (or never) take their children's side when others report acts of misbehavior, or teachers report problems at school
• Scapegoating (knowingly or recklessly blaming one child for the misdeeds of another)
• "Tunnel vision" diagnosis of children's problems (for example, a parent may think their child is either lazy or has learning disabilities after he falls behind in school despite recent absence due to illness.)
• Older siblings given either no or excessive authority over younger siblings with respect to their age difference and level of maturity.
• Frequent withholding of consent ("blessing") for culturally common, lawful, and age-appropriate activities a child wants to take part in
• The "know-it-all" (has no need to obtain child's side of the story when accusing, or listen to child's opinions on matters which greatly impact them.)
• Regularly forcing children to attend activities for which they are extremely over- or under-qualified (e.g. using a preschool to babysit a typical nine-year-old boy, taking a young child to poker games, etc.)
• Either being a miser ("scrooge") in totality or selectively allowing children's needs to go unmet (e.g. a father will not buy a bicycle for his son because he wants to save money for retirement or "something important".)
• Disagreements about nature and nurture (parents, often non-biological, blame common problems on child's heredity, when faulty parenting may be the actual cause.)

Dysfunctional styles

"Children as pawns"

One common dysfunctional parental behavior is a parent's manipulation of a child in order to achieve some outcome adverse to the other parent's rights or interests. Examples include verbal manipulation such as spreading gossip about the other parent, communicating with the parent through the child (and in the process exposing the child to the risks of the other parent's displeasure with that communication) rather than doing so directly, trying to obtain information through the child (spying), or causing the child to dislike the other parent, with insufficient or no concern for the damaging effects of the parent's behavior on the child. While many instances of such manipulation occur in shared custody situations that have resulted from separation or divorce, it can also take place in intact families, where it is known as triangulation.

List of other dysfunctional styles

• "Using" (destructively narcissistic parents who rule by fear and conditional love.)
• Abusing (parents who use physical violence, or emotionally, or sexually abuse their children.)
• Perfectionist (fixating on order, prestige, power, or perfect appearances, while preventing their child from failing at anything.)
• Dogmatic or cult-like (harsh and inflexible discipline, with children not allowed, within reason, to dissent, question authority, or develop their own value system.)
• Inequitable parenting (going to extremes for one child while continually ignoring the needs of another.)
• Deprivation (control or neglect by withholding love, support, necessities, sympathy, praise, attention, encouragement, supervision, or otherwise putting their children's well-being at risk.)
• Abuse among siblings (parents fail to intervene when a sibling physically or sexually abuses another sibling.)
• Abandonment (a parent who willfully separates from their children, not wishing any further contact, and in some cases without locating alternative, long-term parenting arrangements, leaving them as orphans.)
• Appeasement (parents who reward bad behavior—even by their own standards—and inevitably punish another child's good behavior in order to maintain the peace and avoid temper tantrums. "Peace at any price.")
• Loyalty manipulation (giving unearned rewards and lavish attention trying to ensure a favored, yet rebellious child will be the one most loyal and well-behaved, while subtly ignoring the wants and needs of their most loyal child currently.)
• "Helicopter parenting" (parents who micro-manage their children's lives or relationships among siblings—especially minor conflicts.)
• "The deceivers" (well-regarded parents in the community, likely to be involved in some charitable/non-profit works, who abuse or mistreat one or more of their children.)
• "Public image manager" (sometimes related to above, children warned to not disclose what fights, abuse, or damage happens at home, or face severe punishment "Don't tell anyone what goes on in this family".)
• "The paranoid parent" (a parent having persistent and irrational fear accompanied by anger and false accusations that their child is up to no good or others are plotting harm.)
• "No friends allowed" (parents discourage, prohibit, or interfere with their child from making friends of the same age and gender.)
• Role reversal (parents who expect their minor children to take care of them instead.)
• "Not your business" (children continuously told that a particular brother or sister who is often causing problems is none of their concern.)
• Ultra-egalitarianism (either a much younger child is permitted to do whatever an older child may, or an older child must wait years until a younger child is mature enough.)
• "The guard dog" (a parent who blindly attacks family members perceived as causing the slightest upset to their esteemed spouse, partner, or child.)
• "My baby forever" (a parent who will not allow one or more of their young children to grow up and begin taking care of themselves.)
• "The cheerleader" (one parent "cheers on" the other parent who is simultaneously abusing their child.)
• "Along for the ride" (a reluctant de facto, step, foster, or adoptive parent who does not truly care about their non-biological child, but must co-exist in the same home for the sake of their spouse or partner) (See also: Cinderella effect).
• "The politician" (a parent who repeatedly makes or agrees to children's promises while having little to no intention of keeping them.)
• "It's taboo" (parents rebuff any questions children may have about sexuality, pregnancy, romance, puberty, certain areas of human anatomy, nudity, etc.)
• Identified patient (one child, usually selected by the mother, who is forced into going to therapy while the family's overall dysfunction is kept hidden.)
• Münchausen syndrome by proxy (a much more extreme situation than above, where the child is intentionally made ill by a parent seeking attention from physicians and other professionals.)

Dynamical

Coalitions are subsystems within families with more rigid boundaries and are thought to be a sign of family dysfunction.

• The isolated family member (either a parent or child up against the rest of the otherwise united family.)
• Parent vs. parent (frequent fights amongst adults, whether married, divorced, or separated, conducted away from the children.)
• The polarized family (a parent and one or more children on each side of the conflict.)
• Parents vs. kids (intergenerational conflict, generation gap or culture shock dysfunction.)
• The balkanized family (named after the three-way war in the Balkans where alliances shift back and forth.)
• Free-for-all (a family that fights in a "free-for-all" style, though may become polarized when range of possible choices is limited.)

Children

Unlike divorce, and to a lesser extent, separation, there is often no record of an "intact" family being dysfunctional. As a result, friends, relatives, and teachers of such children may be completely unaware of the situation. In addition, a child may be unfairly blamed for the family's dysfunction, and placed under even greater stress than those whose parents separate.

The six basic roles

Children growing up in a dysfunctional family have been known to adopt or be assigned one or more of the following six basic roles:

• The Golden Child (also known as the Hero or Superkid): a child who becomes a high achiever or overachiever outside the family (e.g., in academics or athletics) as a means of escaping the dysfunctional family environment, defining themselves independently of their role in the dysfunctional family, currying favor with parents, or shielding themselves from criticism by family members.
• The Problem Child, Rebel, or Truth Teller: the child who a) causes most problems related to the family's dysfunction or b) "acts out" in response to preexisting family dysfunction, in the latter case often in an attempt to divert attention paid to another member who exhibits a pattern of similar misbehavior.
  • A variant of the "problem child" role is the Scapegoat, who is unjustifiably assigned the "problem child" role by others within the family or even wrongfully blamed by other family members for those members' own individual or collective dysfunction, often despite being the only emotionally stable member of the family.
• The Caretaker: the one who takes responsibility for the emotional well-being of the family, often assuming a parental role; the intra-familial counterpart of the "Good Child"/"Superkid."
• The Lost Child or Passive Kid: the inconspicuous, introverted, quiet one, whose needs are usually ignored or hidden.
• The Mascot or Family Clown: uses comedy to divert attention away from the increasingly dysfunctional family system.
• The Mastermind: the opportunist who capitalizes on the other family members' faults to get whatever they want; often the object of appeasement by grown-ups.

Effects on children

Children of dysfunctional families, either at the time, or as they grow older, may also:

• Lack the ability to be playful, or childlike, and may "grow up too fast"; conversely they may grow up too slowly, or be in a mixed mode (e.g. well-behaved, but unable to care for themselves.)
• Have moderate to severe mental health issues, including possible depression, anxiety, and suicidal thoughts.
• Become addicted to drugs, including cigarettes or alcohol, especially if parents or friends have done the same.
• Developing behavioral addictions to such things like gambling, excessive spending, video games, pornography, or food; the latter often resulting in obesity or/and other physical health issues.
• Bully or harass others, or be an easy victim thereof (possibly taking a dual role in different settings.)
• Be in denial regarding the severity of the family's situation.
• Have mixed feelings of love–hate towards certain family members.
• Become a sex offender, possibly including pedophilia.
• Have difficulty forming healthy relationships within their peer group (usually due to shyness or a personality disorder.)
• Spend an inordinate amount of time alone watching television, playing video games, surfing the Internet, listening to music, going out for late night drives alone, and engaging in other activities which lack in-person social interaction.
• Feel angry, anxious, depressed, isolated from others, or unlovable.
• Have a speech disorder (related to emotional abuse.)
• Distrust others or even have paranoia.
• Become a juvenile delinquent and turn to a life of crime (with or without dropping out of school), and possibly become a gang member as well.
• Struggle academically at school or academic performance declines unexpectedly.
• Have low self-esteem or a poor self image with difficulty expressing emotions.
• Do not pay close attention to their own physical or mental health
• May be at risk of self-harm or suicide.
• Exhibits lack of organization in their day-to-day lives.
• Rebel against parental authority, or conversely, uphold their family's values in the face of peer pressure, or even try to take an impossible "middle ground" that pleases no one.
• Turning the tables by abusing their abusive elderly parents, upon the former reaching adulthood.
• Think only of themselves to make up the difference of their childhoods (as they are still learning the balance of self-love.)
• Have little self-discipline when parents are not around, such as compulsive spending, procrastinating too close to deadlines, etc. (unfamiliar, inchoate, and seemingly lax or avoidable real-world consequences vs. known, concrete, and rigidly imposed parental consequences.)
• Find an (often abusive) spouse or partner at a young age, or run away from home.
• Become pregnant or a parent of illegitimate children.
• Be at risk of becoming poor or homeless, even if the family is already wealthy or middle-class.
• Live a reclusive lifestyle without any spouse, partner, children, or friends.
• Have auto-destructive or potentially self-damaging behaviors.
• Join a cult to find the acceptance they never had at home, or at a minimum, have differing philosophical or religious beliefs from what they were previously taught.
• Strive (as young adults) to live far away from particular family members or the family as a whole, possibly spending much more time with extended family.
• Perpetuate dysfunctional behaviors in other relationships (especially their own children.)

Positive Outcomes

Although there are many negative outcomes that came come from growing up in a dysfunctional household, the brain can be able to produce positive ones as well. As discussed in the article, "Adult Children of Dysfunctional Families", resilience is something that can come out of these obstacles in children's lives and make for a brighter future. Resilience is defined as something positive that is able to be brought forth from negative experiences in childhood. (Resilience in Adult Children of Alcoholics: A Nonpathological Approach to Social Work Practice). This refers to the ability for children who go through many hardships with their parents growing up to be able to take those hardships and learn from them in order to develop better coping strategies and find meaning in their futures. For example, when children find themselves in a dysfunctional family life, they may take the route of either isolating themselves, or reaching out for help. When children reach out for help, they can develop resiliency over time by fostering positive relationships with guidance counselors, or other trusted adults that will continue to stay strong after they become adults themselves.

Resilience is also something that can be strengthened through community settings and positive interactions with others. A dysfunctional family can create a large amount of trauma for children that they may carry into their adult lives. Although different families may create different types of trauma for children, the way that trauma is processed is very similar. When children are able to bond and help each other through the process of dealing with trauma, they can find comfort, which in turn promotes resiliency. What trauma tends to do is make people feel like there is something wrong with them, and they should keep themselves away from the rest of society. This is why recognizing that one is not alone in their struggles is an extremely powerful thing.

Resources and Hope

The organization Adult Children of Alcoholics and Dysfunctional Families (ACA) serves as an extremely useful tool in providing support for people who come from a dysfunctional childhood where their caretakers suffered with alcoholism. What the ACA does that is hold a twelve step program that is designed to create emotional healing in adult children. By doing this, the program hopes to see the adult children equally as worthy as help and support as the people in their families who faced the alcoholism themselves. There are multiple kinds of meetings that the organization holds in order to bring resources to all different groups (women, men, LGBTQ+, teens, young adults). These meeting settings also have different formats, so that people can be met where they are in their individual healing journey. For example, one could view a guest speaker's presentation before they go into any formal counseling. This is an significant aspect to the resource of meeting's, because some people feel too overwhelmed by certain settings to even begin the process. It is better for a person to join the organization at all, than to be too nervous to go to a full-blown meeting and be turned away forever.

In popular culture

• Films about dysfunctional families
• Television series about dysfunctional families
  • Animated television series about dysfunctional families

Backscatter X-ray

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Backscatter_X-ray 

 

Backscatter technology produces an image that resembles a chalk etching.

Backscatter X-ray is an advanced X-ray imaging technology. Traditional X-ray machines detect hard and soft materials by the variation in x-ray intensity transmitted through the target. In contrast, backscatter X-ray detects the radiation that reflects from the target. It has potential applications where less-destructive examination is required, and can operate even if only one side of the target is available for examination.

The technology is one of two types of whole-body imaging technologies that have been used to perform full-body scans of airline passengers to detect hidden weapons, tools, liquids, narcotics, currency, and other contraband. A competing technology is millimeter wave scanner. One can refer to an airport security machine of this type as a "body scanner", "whole body imager (WBI)", "security scanner" or "naked scanner".

Deployments at airports

In the United States, the FAA Modernization and Reform Act of 2012 required that all full-body scanners operated in airports by the Transportation Security Administration use "Automated Target Recognition" software, which replaces the picture of a nude body with the cartoon-like representation. As a result of this law, all backscatter X-ray machines formerly in use by the Transportation Security Administration were removed from airports by May 2013, since the agency said the vendor (Rapiscan) did not meet their contractual deadline to implement the software.

In the European Union, backscatter X-ray screening of airline passengers was banned in 2012 to protect passenger safety.

Technology

Backscatter technology is based on the Compton scattering effect of X-rays, a form of ionizing radiation. Unlike a traditional X-ray machine, which relies on the transmission of X-rays through the object, backscatter X-ray detects the radiation that reflects from the object and forms an image. The backscatter pattern is dependent on the material property and is good for imaging organic material.

In contrast to millimeter wave scanners, which create a 3D image, backscatter X-ray scanners will typically only create a 2D image. For airport screening, images are taken from both sides of the human body.

Backscatter X-ray was first applied in a commercial low-dose personnel scanning system by Dr. Steven W. Smith. Smith developed the Secure 1000 whole-body scanner in 1992 and then sold the device and associated patents to Rapiscan Systems, who now manufactures and distributes the device.

Large scale

Some backscatter X-ray scanners can scan much larger objects, such as trucks and containers. This scan is much faster than a physical search and could potentially allow a larger percentage of shipping to be checked for smuggled items, weapons, drugs, or people.

There are also gamma-ray-based systems coming to market.

In May 2011, the Electronic Privacy Information Center filed suit against the United States Department of Homeland Security (DHS) under the Freedom of Information Act, claiming that DHS had withheld nearly 1000 pages of documents related to the Z backscatter vans and other mobile backscatter devices.

Concerns

See also: Full body scanner § Controversies

Legality

Since in addition to weapons, these machines are designed to be capable of detecting drugs, currency and contraband, which have no direct effect on airport security and passenger safety, some have argued that the use of these full body scanners is a violation of the 4th Amendment to the United States Constitution and can be construed as an illegal search and seizure.

Privacy

An image of Susan Hallowell, Director of the Transportation Security Administration's research lab taken with backscatter x-ray system.

Backscatter x-ray technology has been proposed as an alternative to personal searches at airport and other security checkpoints easily penetrating clothing to reveal concealed weapons. It raises privacy concerns about what is seen by the person viewing the scan. Some worry that viewing the image violates confidential medical information, such as the fact a passenger uses a colostomy bag, has a missing limb or wears a prosthesis, or is transgender.

The ACLU and the Electronic Privacy Information Center are opposed to this use of the technology. The ACLU refers to backscatter x-rays as a "virtual strip search". According to the Transportation Security Administration (TSA), in one trial 79 percent of the public opted to try backscatter over the traditional pat-down in secondary screening.

It is "possible for backscatter X-raying to produce photo-quality images of what's going on beneath our clothes", thus, many software implementations of the scan have been designed to distort private areas. According to the TSA, further distortion is used in the Phoenix airport's trial system where photo-quality images are replaced by chalk outlines. The TSA has also commented that screening procedures such as having the screener viewing the image located far away from the person being screened could be a possibility.

In light of this, some journalists have expressed concern that this blurring may allow people to carry weapons or certain explosives aboard by attaching the object or substance to their genitals.

The British newspaper The Guardian has revealed concern among British officials that the use of such scanners to scan children may be illegal under the Protection of Children Act 1978, which prohibits the creation and distribution of indecent images of children. This concern may delay the introduction of routine backscatter scanning in UK airports, which had been planned in response to the attempted Christmas Day 2009 attack on Northwest Airlines Flight 253.

The Fiqh Council of North America have also issued the following fatwa in relation to full-body scanners:

It is a violation of clear Islamic teachings that men or women be seen naked by other men and women. Islam highly emphasizes haya (modesty) and considers it part of faith. The Quran has commanded the believers, both men and women, to cover their private parts.

In August 2010, it was reported that U.S. Marshals (part of the Department of Justice), saved thousands of images from a low resolution mm wave scanner: This machine does not show details of human anatomy, and is a different kind of machine from the one used in airports. TSA, part of the Department of Homeland Security, said that its scanners do not save images and that the scanners do not have the capability to save images when they are installed in airports, but later admitted that the scanners are required to be capable of saving images for the purpose of evaluation, training and testing.

Health effects

Unlike cell phone signals, or millimeter-wave scanners, the energy being emitted by a backscatter X-ray is a type of ionizing radiation that breaks chemical bonds. Ionizing radiation is considered carcinogenic even in very small doses but at the doses used in airport scanners this effect is believed to be negligible for an individual. If 1 million people were exposed to 520 scans in one year, one study estimated that roughly four additional cancers would occur due to the scanner, in contrast to the 600 additional cancers that would occur from the higher levels of radiation during flight.

Since the scanners do not have a medical purpose, the United States Food and Drug Administration (FDA) does not need to subject them to the same safety evaluations as medical X-rays. However, the FDA has created a webpage comparing known estimates of the radiation from backscatter X-ray body scanners to that of other known sources, which cites various reasons they deem the technology to be safe.

Four professors at the University of California, San Francisco, among them members of NAS and an expert in cancer and imaging, in an April 2010 letter to the presidential science and technology advisor raised several concerns about the validity of the indirect comparisons the Food and Drug Administration used in evaluating the safety of backscatter x-ray machines. They argued that the effective dose is higher than claimed by the TSA and the body scanner manufacturers because the dose was calculated as if distributed throughout the whole body, whereas most of the radiation is absorbed in the skin and tissues immediately underneath. Other professors from the radiology department at UCSF disagree with the claims of the signing four professors.

The UCSF professors requested that additional data be made public detailing the specific data regarding sensitive areas, such as the skin and certain organs, as well as data on the special (high-risk) population. In October 2010, the FDA and TSA responded to these concerns. The letter cites reports which show that the specific dose to the skin is some 89,000 times lower than the annual limit to the skin established by the NCRP. Regarding the UCSF concerns over the high-risk population to sensitive organs, the letter states that such an individual "would have to receive more than 1,000 screenings to begin to approach the annual limit".

John Sedat, the principal author of the UCSF letter, responded in November 2010 that the White House's claim that full-body scanners pose no health risks to air travelers is in error, adding that the White House statement has "many misconceptions, and we will write a careful answer pointing out their errors."

In a December 2, 2010 letter to the House of Representatives, Dr. Steven Smith, inventor of the body scanner in 1991, stated that the concerns of Brenner and UCSF regarding the skin dose of backscatter scanners is incorrect and the result of a confusion between dose and imaging penetration. Smith demonstrated this difference with two experiments using plastic (with a similar rate of absorption as body tissue), copper (the image subject), and an x-ray scanner. The dose-penetration experiment shows that 5 and 50 mm (0.20 and 1.97 in) plastic samples absorb 5% and 50% of the beam intensity respectively, whereas the imaging penetration experiment shows that 4.8 and 10 mm (0.19 and 0.39 in) plastic samples reduce the image darkness by 23% and 50% respectively. Dr. Smith states that those who calculate high skin dosage have incorrectly used the shallow imaging penetration value of a few millimeters (c. 0.16 in), whereas the actual dosage is calculated by the deeper dose penetration.

The TSA has also made public various independent safety assessments of the Secure 1000 Backscatter X-ray Scanner.

Radiation safety authorities including the National Council on Radiation Protection and Measurements, The Health Physics Society and the American College of Radiology, have stated that there is no specific evidence that full-body scans are unsafe. The Secure 1000 Backscatter X-ray scanner was developed in 1992 by Dr. Steve Smith. The scanner has been studied extensively for almost 20 years by the leading independent radiation safety authorities in the United States. Experimental and epidemiological data do not support the proposition, however, that there is a threshold dose of radiation below which there is no increased risk of cancer.

The UK Health Protection Agency has completed an analysis of the X-ray dose from backscatter scanners and has written that the dose is extremely low and "about the same as people receive from background radiation in an hour".

The Health Physics Society (HPS) reports that a person undergoing a backscatter scan receives approximately 0.05 μSv (0.005 mrem) of radiation; American Science and Engineering Inc. reports 0.09 μSv (0.009 mrem). At the high altitudes typical of commercial flights, naturally occurring cosmic radiation is considerably higher than at ground level. The radiation dose for a six-hour flight is 20 μSv (2 mrem) – 200 to 400 times larger than a backscatter scan. The Nuclear Regulatory Commission limits radiation exposure to the public to less than 1 mSv (100 mrem) per year from nuclear power plants. While this is not specifically for airline-associated radiation, the limit is an effective proxy for understanding what level is deemed safe by a regulatory agency.

According to a draft standard on the United States FDA website, the allowable dose from a scan would be 0.1 μSv, and that report uses a model whereby a 0.01 μSv dose increases an individual's risk of death by cancer during his or her lifetime by 5×10⁻¹⁰. Since the dose limit is ten times higher than 0.01 μSv, their model would predict one additional cancer death per 200 million scans. Since the airports in the UK handled 218 million passengers in 2009, if all passengers in the UK were scanned at the maximum dosage, then each year this would produce on average one additional cancer death (since there would be 200 million scans per year that the scanners were in operation), though usually each death would not occur in the same year as the particular scan that caused it, since the cancer may take years to grow. In addition, additional people would be given cancer but would die from other causes.

There may not yet be evidence of hereditary effects of x-rays administered by backscatter scanners, but backscatter scanners use the same kind of x-ray photons as are produced in medical x-ray machines but expose the subject at a considerably lower dose, so it is possible that the results from medical radiology may be relevant, at least until a study is done of any effects specific to backscatter x-ray machines. Fathers exposed to medical diagnostic x-rays are more likely to have infants who contract leukemia, especially if exposure is closer to conception or includes two or more X-rays of the lower gastrointestinal (GI) tract or lower abdomen. In medical radiography the x-ray beam is adjusted to expose only the area of which an image is required, so that generally shielding is applied to the patient to avoid exposing the gonads, whereas in an airport backscatter scan, the testicles of men and boys will be deliberately subjected to the direct beam in order to check for weapons in the underpants, and some radiation will also reach the ovaries of female subjects. A linear dose-response relationship has been observed between x-ray dose and double-strand breaks in DNA in human sperm.

Extrapolations of cancer risk from minuscule exposures to radiation across large populations, however, are not supported by analysis by the National Council on Radiation Protection (NCRP). On May 26, 2010 NCRP issued a press release to address such comments about full body scanners that are compliant with ANSI N43.17. In Commentary No.16 issued on May 26, 2010, it reads as follows:

As stated in NCRP Report No. 121 (1995), Principles and Application of Collective Dose in Radiation Protection, the summation of trivial average risks over very large populations or time periods into a single value produces a distorted image of risk, completely out of perspective with risks accepted every day, both voluntarily and involuntarily.

According to NCRP, the use of statistical extrapolations that predict 1 death for every 200 million persons scanned for example (as above) is an unrealistic over-estimation.

Other scientists at Columbia University have made the following statements in support of the safety of body scanners:

"A passenger would need to be scanned using a backscatter scanner, from both the front and the back, about 200,000 times to receive the amount of radiation equal to one typical CT scan," said Dr. Andrew J. Einstein, director of cardiac CT research at Columbia University Medical Center in New York City.

"Another way to look at this is that if you were scanned with a backscatter scanner every day of your life, you would still only receive a tenth of the dose of a typical CT scan," he said.

By comparison, the amount of radiation from a backscatter scanner is equivalent to about 10 minutes of natural background radiation in the United States, Einstein said. "I believe that the general public has nothing to worry about in terms of the radiation from airline scanning," he added.

For moms-to-be, no evidence supports an increased risk of miscarriage or fetal abnormalities from these scanners, Einstein added.

"A pregnant woman will receive much more radiation from cosmic rays she is exposed to while flying than from passing through a scanner in the airport," he said.

Furthermore, other scientists claim the health effects of backscatter are well understood whereas those from millimeter wave scanners are not:

"From a radiation standpoint there has been no evidence that there is really any untoward effect from the use of this device [backscatter scanner], so I would not be concerned about it from a radiation dose standpoint – the issues of personal privacy are a different thing," he said.

The health effects of the more common millimeter wave scanner are largely unknown, and at least one expert believes a safety study is warranted.

"I am very interested in performing a National Council on Radiation Protection and Measurements study on the use of millimeter-wave security screening systems," said Thomas S. Tenforde, council president.

However, no long-term studies have been done on the health effects of millimeter wave scanners.

Experts evaluating backscatter x-ray machine technology have also argued that defects in the machines, damage from normal wear-and-tear, or software errors could focus an intense dose of radiation on just one spot of the body. For example, Dr. Peter Rez, a professor of physics at Arizona State University, has said, "The thing that worries me the most, is not what happens if the machine works as advertised, but what happens if it doesn't", adding that a potential malfunction of the machine could increase the radiation dose.

The designers and manufacturers of backscatter X-ray scanners claim that the scanners are designed to prevent the occurrence of these kinds of errors. The scanners' safety requirements include fail-safe controls and multiple overlapping interlocks. These features, combined with fault analysis, ensure that failure of any subsystem results in non-operation of the x-ray generator to prevent accidental exposures. In the United States, the TSA requires that certification to the ANSI N43.17 safety standard is performed by a third party and not by the manufacturer themselves.

The European Commission issued a report stating that backscatter x-ray scanners pose no known health risk, and that "assuming all other conditions equal", that backscatter x-ray scanners, which expose people to ionizing radiation, should not be used when millimeter-wave scanners that "have less effects on the human body" are available.

However, the European Commission report provides no data substantiating its claim that "all other conditions are equal". One area where backscatter X-ray scanners can provide better performance than MM wave scanners, for example, is in the inspection of the shoes, groin and armpit regions of the body.

In a study published in the Archives of Internal Medicine on March 28, 2011 researchers at the University of California "calculated that fully implementing backscatter scanners would not significantly increase the lifetime risk of cancer for travelers." The researchers calculated that for every 100 million passengers who flew seven one-way flights, there would be one additional cancer.

Efficacy

In March 2012, scientist and blogger Jonathan Corbett demonstrated the ineffectiveness of the technology by publishing a viral video showing how he was able to get a metal box through backscatter x-ray and millimeter wave scanners (including the currently-used "Automated Target Recognition" scanners) in two US airports. In April 2012, Corbett released a second video interviewing a TSA screener, who described firearms and simulated explosives passing through the scanners during internal testing and training.

Backscatter scanners installed by the TSA until 2013 were unable to screen adequately for security threats inside hats and head coverings, casts, prosthetics and loose clothing. This technology limitation of current scanners often requires these persons to undergo additional screening by hand or other methods and can cause additional delay or feelings of harassment.

The next generation of backscatter scanners are able to screen these types of clothing, according to manufacturers; however, these machines are not currently in use in public airports.

In Germany, field tests on more than 800,000 passengers over a 10-month trial period concluded that scanners were effective, but not ready to be deployed in German airports due to a high rate of false alarms. The Italian Civil Aviation Authority removed scanners from airports after conducting a study that revealed them to be inaccurate and inconvenient. The European Commission decided to effectively ban backscatter machines. In a 2011 staff report by Republican Members of Congress about the TSA, airport body scanners were described as "ineffective" and "easily thwarted".

Safety regulations and standards

In the US, manufacturers of security related equipment can apply for protection under the SAFETY act, which limits their financial liability in product liability cases to the amount of their insurance coverage. The Rapiscan Secure 1000 was listed in 2006.

In the US, an X-ray system can be considered to comply with requirements for general purpose security screening of humans if the device complies with American National Standards Institute (ANSI) Standard #N43.17.

In the most general sense, N43.17 states that a device can be used for general purpose security screening of humans if the dose to the subject is less than 0.25 μSv (25 μrem) per examination and complies with other requirements of the standard. This is comparable to the average dose due to background radiation (i.e. radioactivity within the surrounding environment) at sea level in 1.5 hours; it is also comparable to the dose from cosmic rays when traveling in an airplane at cruising altitude for two minutes.

Many types of X-ray systems can be designed to comply with ANSI N43.17 including transmission X-ray, backscatter X-ray and gamma ray systems. Not all backscatter X-ray devices necessarily comply with ANSI N43.17; only the manufacturer or end user can confirm compliance of a particular product to the standard.

ANSI standards use a standard of measurement algorithm called "effective dose" that considers the different exposure of all parts of the body and then weights them differently. The interior of the human body is given more weight in this survey, and the exterior, including the skin organ, are given less weight.

Technical countermeasures

Some people wish to prevent either the loss of privacy or the possibility of health problems or genetic damage that might be associated with being subjected to a backscatter X-ray scan. One company sells X-ray absorbing underwear which is said to have X-ray absorption equivalent to 0.5 mm (0.020 in) of lead. Another product, Flying Pasties, "are designed to obscure the most private parts of the human body when entering full body airport scanners", but their description does not seem to claim any protection from the X-ray beam penetrating the body of the person being scanned.

Isotope analysis

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Isotope_analysis 

 

Magnetic sector mass spectrometer used in isotope ratio analysis, through thermal ionization

Isotope analysis is the identification of isotopic signature, abundance of certain stable isotopes of chemical elements within organic and inorganic compounds. Isotopic analysis can be used to understand the flow of energy through a food web, to reconstruct past environmental and climatic conditions, to investigate human and animal diets, for food authentification, and a variety of other physical, geological, palaeontological and chemical processes. Stable isotope ratios are measured using mass spectrometry, which separates the different isotopes of an element on the basis of their mass-to-charge ratio.

Tissues affected

Isotopic oxygen is incorporated into the body primarily through ingestion at which point it is used in the formation of, for archaeological purposes, bones and teeth. The oxygen is incorporated into the hydroxylcarbonic apatite of bone and tooth enamel.

Bone is continually remodelled throughout the lifetime of an individual. Although the rate of turnover of isotopic oxygen in hydroxyapatite is not fully known, it is assumed to be similar to that of collagen; approximately 10 years. Consequently, should an individual remain in a region for 10 years or longer, the isotopic oxygen ratios in the bone hydroxyapatite would reflect the oxygen ratios present in that region.

Teeth are not subject to continual remodelling and so their isotopic oxygen ratios remain constant from the time of formation. The isotopic oxygen ratios, then, of teeth represent the ratios of the region in which the individual was born and raised. Where deciduous teeth are present, it is also possible to determine the age at which a child was weaned. Breast milk production draws upon the body water of the mother, which has higher levels of ¹⁸O due to the preferential loss of ¹⁶O through sweat, urine, and expired water vapour.

While teeth are more resistant to chemical and physical changes over time, both are subject to post-depositional diagenesis. As such, isotopic analysis makes use of the more resistant phosphate groups, rather than the less abundant hydroxyl group or the more likely diagenetic carbonate groups present.

Applications

Isotope analysis has widespread applicability in the natural sciences. These include numerous applications in the biological, earth and environmental sciences.

Archaeology

Reconstructing ancient diets

Archaeological materials, such as bone, organic residues, hair, or sea shells, can serve as substrates for isotopic analysis. Carbon, nitrogen and zinc isotope ratios are used to investigate the diets of past people; these isotopic systems can be used with others, such as strontium or oxygen, to answer questions about population movements and cultural interactions, such as trade.

Carbon isotopes are analysed in archaeology to determine the source of carbon at the base of the foodchain. Examining the ¹²C/¹³C isotope ratio, it is possible to determine whether animals and humans ate predominantly C3 or C4 plants. Potential C3 food sources include wheat, rice, tubers, fruits, nuts and many vegetables, while C4 food sources include millet and sugar cane. Carbon isotope ratios can also be used to distinguish between marine, freshwater, and terrestrial food sources.

Carbon isotope ratios can be measured in bone collagen or bone mineral (hydroxylapatite), and each of these fractions of bone can be analysed to shed light on different components of diet. The carbon in bone collagen is predominantly sourced from dietary protein, while the carbon found in bone mineral is sourced from all consumed dietary carbon, included carbohydrates, lipids, and protein.

To obtain an accurate picture of palaeodiets, it is important to understand processes of diagenesis that may affect the original isotopic signal. It is also important for the researcher to know the variations of isotopes within individuals, between individuals, and over time.

Sourcing archaeological materials

Isotope analysis has been particularly useful in archaeology as a means of characterization. Characterization of artifacts involves determining the isotopic composition of possible source materials such as metal ore bodies and comparing these data to the isotopic composition of analyzed artifacts. A wide range of archaeological materials such as metals, glass and lead-based pigments have been sourced using isotopic characterization. Particularly in the Bronze Age Mediterranean, lead isotope analysis has been a useful tool for determining the sources of metals and an important indicator of trade patterns. Interpretation of lead isotope data is, however, often contentious and faces numerous instrumental and methodological challenges. Problems such as the mixing and re-using of metals from different sources, limited reliable data and contamination of samples can be difficult problems in interpretation.

Ecology

All biologically active elements exist in a number of different isotopic forms, of which two or more are stable. For example, most carbon is present as ¹²C, with approximately 1% being ¹³C. The ratio of the two isotopes may be altered by biological and geophysical processes, and these differences can be utilized in a number of ways by ecologists. The main elements used in isotope ecology are carbon, nitrogen, oxygen, hydrogen and sulfur, but also include silicon, iron, and strontium.

Stable isotope analysis in aquatic ecosystems

Stable isotopes have become a popular method for understanding aquatic ecosystems because they can help scientists in understanding source links and process information in marine food webs. These analyses can also be used to a certain degree in terrestrial systems. Certain isotopes can signify distinct primary producers forming the bases of food webs and trophic level positioning. The stable isotope compositions are expressed in terms of delta values (δ) in permil (‰), i.e. parts per thousand differences from a standard. They express the proportion of an isotope that is in a sample. The values are expressed as:

δX = [(R_sample / R_standard) – 1] × 10³

where X represents the isotope of interest (e.g., ¹³C) and R represents the ratio of the isotope of interest and its natural form (e.g., ¹³C/¹²C). Higher (or less negative) delta values indicate increases in a sample's isotope of interest, relative to the standard, and lower (or more negative) values indicate decreases. The standard reference materials for carbon, nitrogen, and sulfur are Pee Dee Belamnite limestone, nitrogen gas in the atmosphere, and Cañon Diablo meteorite respectively. Analysis is usually done using a mass spectrometer, detecting small differences between gaseous elements. Analysis of a sample can cost anywhere from $30 to $100. Stable isotopes assist scientists in analyzing animal diets and food webs by examining the animal tissues that bear a fixed isotopic enrichment or depletion vs. the diet. Muscle or protein fractions have become the most common animal tissue used to examine the isotopes because they represent the assimilated nutrients in their diet. The main advantage to using stable isotope analysis as opposed to stomach content observations is that no matter what the status is of the animal's stomach (empty or not), the isotope tracers in the tissues will give us an understanding of its trophic position and food source. The three major isotopes used in aquatic ecosystem food web analysis are ¹³C, ¹⁵N and ³⁴S. While all three indicate information on trophic dynamics, it is common to perform analysis on at least two of the previously mentioned 3 isotopes for better understanding of marine trophic interactions and for stronger results.

Hydrogen-2

The ratio of ²H, also known as deuterium, to ¹H has been studied in both plant and animal tissue. Hydrogen isotopes in plant tissue are correlated with local water values but vary based on fractionation during photosynthesis, transpiration, and other processes in the formation of cellulose. A study on the isotope ratios of tissues from plants growing within a small area in Texas found tissues from CAM plants were enriched in deuterium relative to C4 plants. Hydrogen isotope ratios in animal tissue reflect diet, including drinking water, and have been used to study bird migration and aquatic food webs.

Carbon-13

Carbon isotopes aid us in determining the primary production source responsible for the energy flow in an ecosystem. The transfer of ¹³C through trophic levels remains relatively the same, except for a small increase (an enrichment < 1 ‰). Large differences of δ¹³C between animals indicate that they have different food sources or that their food webs are based on different primary producers (i.e. different species of phytoplankton, marsh grasses.) Because δ¹³C indicates the original source of primary producers, the isotopes can also help us determine shifts in diets, both short term, long term or permanent. These shifts may even correlate to seasonal changes, reflecting phytoplankton abundance. Scientists have found that there can be wide ranges of δ¹³C values in phytoplankton populations over a geographic region. While it is not quite certain as to why this may be, there are several hypotheses for this occurrence. These include isotopes within dissolved inorganic carbon pools (DIC) may vary with temperature and location and that growth rates of phytoplankton may affect their uptake of the isotopes. δ¹³C has been used in determining migration of juvenile animals from sheltered inshore areas to offshore locations by examining the changes in their diets. A study by Fry (1983) studied the isotopic compositions in juvenile shrimp of south Texas grass flats. Fry found that at the beginning of the study the shrimp had isotopic values of δ¹³C = -11 to -14‰ and 6-8‰ for δ¹⁵N and δ³⁴S. As the shrimp matured and migrated offshore, the isotopic values changed to those resembling offshore organisms (δ¹³C= -15‰ and δ¹⁵N = 11.5‰ and δ³⁴S = 16‰).

Sulfur-34

While there is no enrichment of ³⁴S between trophic levels, the stable isotope can be useful in distinguishing benthic vs. pelagic producers and marsh vs. phytoplankton producers. Similar to ¹³C, it can also help distinguish between different phytoplankton as the key primary producers in food webs. The differences between seawater sulfates and sulfides (c. 21‰ vs -10‰) aid scientists in the discriminations. Sulfur tends to be more plentiful in less aerobic areas, such as benthic systems and marsh plants, than the pelagic and more aerobic systems. Thus, in the benthic systems, there are smaller δ³⁴S values.

Nitrogen-15

Nitrogen isotopes indicate the trophic level position of organisms (reflective of the time the tissue samples were taken). There is a larger enrichment component with δ¹⁵N because its retention is higher than that of ¹⁴N. This can be seen by analyzing the waste of organisms. Cattle urine has shown that there is a depletion of ¹⁵N relative to the diet. As organisms eat each other, the ¹⁵N isotopes are transferred to the predators. Thus, organisms higher in the trophic pyramid have accumulated higher levels of ¹⁵N ( and higher δ¹⁵N values) relative to their prey and others before them in the food web. Numerous studies on marine ecosystems have shown that on average there is a 3.2‰ enrichment of ¹⁵N vs. diet between different trophic level species in ecosystems. In the Baltic sea, Hansson et al. (1997) found that when analyzing a variety of creatures (such as particulate organic matter (phytoplankton), zooplankton, mysids, sprat, smelt and herring,) there was an apparent fractionation of 2.4‰ between consumers and their apparent prey.

In addition to trophic positioning of organisms, δ¹⁵N values have become commonly used in distinguishing between land derived and natural sources of nutrients. As water travels from septic tanks to aquifers, the nitrogen rich water is delivered into coastal areas. Waste-water nitrate has higher concentrations of ¹⁵N than the nitrate that is found in natural soils in near shore zones. For bacteria, it is more convenient for them to uptake ¹⁴N as opposed to ¹⁵N because it is a lighter element and easier to metabolize. Thus, due to bacteria's preference when performing biogeochemical processes such as denitrification and volatilization of ammonia, ¹⁴N is removed from the water at a faster rate than ¹⁵N, resulting in more ¹⁵N entering the aquifer. ¹⁵N is roughly 10-20‰ as opposed to the natural ¹⁵N values of 2-8‰. The inorganic nitrogen that is emitted from septic tanks and other human-derived sewage is usually in the form of ${\displaystyle {\text{NH}}_4^{+}}$. Once the nitrogen enters the estuaries via groundwater, it is thought that because there is more ¹⁵N entering, that there will also be more ¹⁵N in the inorganic nitrogen pool delivered and that it is picked up more by producers taking up N. Even though ¹⁴N is easier to take up, because there is much more ¹⁵N, there will still be higher amounts assimilated than normal. These levels of δ¹⁵N can be examined in creatures that live in the area and are non migratory (such as macrophytes, clams and even some fish). This method of identifying high levels of nitrogen input is becoming a more and more popular method in attempting to monitor nutrient input into estuaries and coastal ecosystems. Environmental managers have become more and more concerned about measuring anthropogenic nutrient inputs into estuaries because excess in nutrients can lead to eutrophication and hypoxic events, eliminating organisms from an area entirely.

Oxygen-18

Analysis of the ratio of ¹⁸O to ¹⁶O in the shells of the Colorado Delta clam was used to assess the historical extent of the estuary in the Colorado River Delta prior to construction of upstream dams.

Forensic science

A recent development in forensic science is the isotopic analysis of hair strands. Hair has a recognisable growth rate of 9-11mm per month or 15 cm per year. Human hair growth is primarily a function of diet, especially drinking water intake. The stable isotopic ratios of drinking water are a function of location, and the geology that the water percolates through. ⁸⁷Sr, ⁸⁸Sr and oxygen isotope variations are different all over the world. These differences in isotopic ratio are then biologically 'set' in our hair as it grows and it has therefore become possible to identify recent geographic histories by the analysis of hair strands. For example, it could be possible to identify whether a terrorist suspect had recently been to a particular location from hair analysis. This hair analysis is a non-invasive method which is becoming very popular in cases that DNA or other traditional means are bringing no answers.

Isotope analysis can be used by forensic investigators to determine whether two or more samples of explosives are of a common origin. Most high explosives contain carbon, hydrogen, nitrogen and oxygen atoms and thus comparing their relative abundances of isotopes can reveal the existence of a common origin. Researchers have also shown that analysis of the ¹²C/¹³C ratios can locate the country of origin for a given explosive.

Stable isotopic analysis has also been used in the identification of drug trafficking routes. Isotopic abundances are different in morphine grown from poppies in south-east Asia versus poppies grown in south-west Asia. The same is applied to cocaine that is derived from Bolivia and that from Colombia.

Traceability

See also: Traceability

Stable isotopic analysis has also been used for tracing the geographical origin of food, timber, and in tracing the sources and fates of nitrates in the environment.

Geology

Main article: Isotope geochemistry

Hydrology

In isotope hydrology, stable isotopes of water (²H and ¹⁸O) are used to estimate the source, age, and flow paths of water flowing through ecosystems. The main effects that change the stable isotope composition of water are evaporation and condensation. Variability in water isotopes is used to study sources of water to streams and rivers, evaporation rates, groundwater recharge, and other hydrological processes.

Paleoclimatology

The ratio of ¹⁸O to ¹⁶O in ice and deep sea cores is temperature dependent, and can be used as a proxy measure for reconstructing climate change. During colder periods of the Earth's history (glacials) such as during the ice ages, ¹⁶O is preferentially evaporated from the colder oceans, leaving the slightly heavier and more sluggish ¹⁸O behind. Organisms such as foraminifera which combine oxygen dissolved in the surrounding water with carbon and calcium to build their shells therefore incorporate the temperature-dependent ¹⁸O to ¹⁶O ratio. When these organisms die, they settle out on the sea bed, preserving a long and invaluable record of global climate change through much of the Quaternary. Similarly, ice cores on land are enriched in the heavier ¹⁸O relative to ¹⁶O during warmer climatic phases (interglacials) as more energy is available for the evaporation of the heavier ¹⁸O isotope. The oxygen isotope record preserved in the ice cores is therefore a "mirror" of the record contained in ocean sediments.

Oxygen isotopes preserve a record of the effects of the Milankovitch cycles on climate change during the Quaternary, revealing an approximately 100,000-year cyclicity in the Earth's climate.