Endocrine Disruptors

1.   What are endocrine disruptors?
2.   How can my family be exposed to EDs?
3.   What are the health effects of endocrine disruptors?
4.   Are there medical tests to see if my family has been exposed to endocrine
      disruptors?
6.   References

What are endocrine disruptors?

Endocrine disruptors (EDs) are environmental chemicals that affect the function of the endocrine system, the system involving the glands and hormones of the body. The endocrine system coordinates the functions of various organs and systems in the body. EDs may disrupt the endocrine system in several ways:
  • they may act as "imposters" of naturally occurring hormones
  • they may block the action of hormones
  • they may alter the chemical message sent by hormones
  • they may disrupt the production of hormones or hormone receptors (proteins used to receive information from hormones)
Most EDs act like naturally occurring estrogens in the body. However, some EDs block androgens (male sex hormones such as testosterone). The theory of endocrine disruptors gained credibility from a number of studies demonstrating reproductive problems in wildlife exposed to certain environmental chemicals. For example, alligators exposed to an organochlorine pesticide, diclofol experienced various reproductive abnormalities. [3] Also, certain birds exposed to the organochlorine pesticide DDT failed to reproduce. [4]

EDs are a diverse class of chemicals. They include:
  • certain pesticides (DDT)
  • industrial chemicals (PCBs, dioxins)
  • phthalates
  • phenols (bisphenol A, alkylphenol)
  • plant hormones (phytoestrogens)

How can my family be exposed to EDs?

Exposure to each major class of EDs - pesticides, industrial chemicals, phthalates, phenol compounds, and plant hormones - will be discussed separately.

Pesticides

Pesticides are widely used for many purposes, including home, garden, commercial, and agricultural pest control. Thus, the potential for human exposure to these chemicals is great. Among the pesticides that may act as EDs, DDT is perhaps the most widely studied. Due to its negative reproductive effects on wildlife and tendency persist in the environment, DDT was banned in the U.S. in 1987. However, DDT is still used extensively in certain developing countries and may enter the U.S. from imported produce. One of the few remaining pesticides in this class still in use is lindane (Kwell), which is used mainly for treatment of head lice.

In general, pesticides can enter the body through the lungs, the mouth, and the skin. Each class of pesticide will differ somewhat in the specific way it is absorbed.

Young children may be at particularly increased risk of pesticide exposure for several reasons:
  • their tendency to explore their environment with their mouths
  • their closeness to the ground
  • their increased time playing outdoors
To learn more about pesticide exposure, click here.

Industrial Chemicals

Two industrial chemicals suspected as EDs are PCBs and dioxins. Each will be discussed separately.

PCBs

PCBs, or polychlorinated biphenyls, are members of a chemical family that were widely used in the past in industry as lubricants, coatings, and insulation materials for dielectric equipment like transformers and capacitors.

PCBs were also used in common consumer items such as hydraulic fluid, fluorescent lights, televisions, and other appliances. Because PCBs tend to persist for long periods in the environment and have negative effects on wildlife, they were banned from use in the U.S. in 1977.

PCBs have been released into the environment from several sources:
  • Poorly maintained hazardous waste dumps and city landfills
  • Illegal or improper dumping of hydraulic fluids/coolants
  • Leaks from electrical transformers and other equipment
  • Burning of medical, industrial, or city waste
  • From older consumer goods like televisions
To learn more about exposure to PCBs, click here.

Dioxins

Polychlorinated dibenzodioxins, commonly called dioxins, are a family of chemical compounds unintentionally produced by a variety of industrial processes, including:
  • PVC plastic manufacturing
  • Manufacturing of certain industrial chemicals and pesticides
  • burning of medical /city wastes
  • the chlorine bleaching process of pulp and paper mills
Not all members of this family are equally toxic. Based on animal studies, the most toxic member of this family is considered to be 2,3,7,8- tetrachlorodibenzodioxin (TCDD), or dioxin. Perhaps the most publicized dioxin exposure was from Agent Orange. This was a chemical mixture heavily contaminated with dioxin that served as a defoliant agent during the Vietnam War.

To learn more about exposure to dioxins, click here.

Phthalates

Phthalates are chemicals used as plasticizers, or plastic softeners. They make normally rigid plastics easier to bend. Phthalates are used in a variety of consumer products, including:
  • plastics in food and beverage containers
  • PVC pipes
  • vinyl toys or products for children
  • lining of metal cans
  • medical supplies
  • automotive parts
Exposure to phthalates may occur through:
  • Food -
    People may be exposed to pthalates by eating food stored or cooked in plastic containers or drinking beverages from plastic containers.
  • Direct Injection -
    Certain medical procedures can put phthalates directly into the blood- stream. This may occur from certain medical products wrapped in plastic such as intra- venous (IV) tubing, IV bags, and indwelling catheters.
  • Water -
    Drinking water may contain low levels of pthalates. However, the levels found in water tend to be extremely low. Also, well water near certain hazardous waste sites may be contaminated with phthalates.
  • Air -
    People may be exposed to low concentrations of pthalates in indoor and workplace air. People can also be exposed to phthalates when they receive treatments involving inhalation of gases, such as during anesthesia prior to surgery.
Phenol compounds

The two members of this class of chemicals thought to be EDs are bisphenol A and alkylphenol. Each will be discussed separately.
  • Bisphenol A
    Bisphenol A is a chemical used in the production of epoxy resins and polycarbonate plastics. It may be found in the following consumer products:
    • food and drink packages
    • baby bottles
    • lacquers coating certain metal products
    • cans and bottle tops water pipes
    • some polymers used in dental treatment

      Exposure may occur from:
      • leaching of the chemical from cans into food
      • leaching from plastic bottles into food or drink
      • leaching from dental products into the mouth
  • Alkylphenol
    Alkylphenols are chemicals used in a variety of consumer goods. They may be found in:
    • liquid clothes detergents
    • The spermicidal lubricant nonoxynol-9 used in some condoms
    • some pesticide formulations

      Exposure may occur through:
      • Skin -
        Absorption across skin may happen from shampoos, cosmetics, and laundry detergents. The spermicide nonoxynol-9 may be absorbed across skin or mucous membranes from condom use.
      • Food -
        Eating food from fields spread with sewage sludge containing alkylphenols may result in exposure to alkylphenols.
      • Water -
        Drinking water from polluted rivers may result in alkylphenol exposure. Drinking well water near certain hazardous waste sites may result in exposure as well.
      • Air -
        Breathing fumes from pesticide sprays may cause exposure to alkylphenols. Alkylphenols may also be present as background outdoor air pollutants.
    Plant Hormones

    The family of plant hormones suspected to act as endocrine disruptors (EDs) are called phytoestrogens. They are very similar to natural human estrogens, but tend to be much weaker than human estrogens. Phytoestrogens are in:
    • soy products
    • citrus fruits
    • licorice
    • certain grains (wheat, alfalfa)
    • fennel
    • celery
    Exposure to phytoestrogens occurs mainly through food. This may include eating tofu, soy-milk, and other soy products. Infants may be exposed through soy-based formula.
    What are the health effects of endocrine disruptors?

    The health effects from endocrine disruptors (EDs) will depend on:
    • the specific ED involved
    • the level of exposure
    • the timecourse of exposure (hours, days, years)
    • the underlying health status of the exposed individual
    Very little is known about the possible effects of EDs on humans. Most of the available evidence comes from studies of animals or cell cultures (cells grown in laboratory settings). We will discuss general health trends that may involve one or more EDs as well as the known or suspected health effects from individual EDs (pesticides, fungicides, industrial chemicals, phthalates, phenols, and plant hormones).

    General Health Trends - Male Reproductive problems
    • Testicular cancer
      Several studies suggest that testicular cancer is increasing around the world. Some scientists believe that endocrine disrupting chemicals could be a cause for this increase. [6][7][57]
    • Sperm Counts
      Several studies suggest that sperm counts are decreasing in developed countries. Some scientists suspect that EDs may be a possible cause for this decrease. [6][7][58]
    • Male reproductive abnormalities
      There is limited evidence that male reproductive problems such as cryptorchidism and hypospadias are increasing around the world. [73] Crytporchidism is a condition where one or both testicles does not descend properly into the scrotum. Hypospadias is a condition where the urethra (opening on the penis where urine or semen comes out) opens on the underside rather than on the end of the penis. Some scientists suspect that EDs may be a possible cause for the increase in these conditions. [9][56][59]
    General Health Trends - Female reproductive problems
    • Breast cancer
      Several studies suggest that breast cancer is increasing around the world. Some scientists believe that EDs may be one cause of this increase. [60]
    • Early puberty
      Some research suggests that girls in the US are entering puberty earlier than in the past. [12] Some scientists believe that EDs may be one cause of this trend
    Health effects of specific EDs (pesticides, fungicides)
    • Pesticides
      There are two main types of pesticides, the organo- chlorines and the organophosphates, and each type has a different set of effects. The two types are each discussed separately below.
    • Organochlorine pesticides -
      Some human studies suggest that pregnant mothers exposed to organochlorine pesticides may have increased risk of spontaneous abortions (stillbirths) and early delivery of infants. [13][14]

      One human study suggests that mothers exposed to certain organochlorine pesticides may have not be able to produce milk for as long as unexposed mothers. [15]

      There has been some concern that exposure to organochlorines is associated with increased risk of breast cancer and endometrial cancer, but the weight of the available evidence argues against these associations. [16-19][87-88]

      The endocrine disrupting effects of lower levels of pesticides is still very controversial. Many studies do not support these relation- ships. However, many animal studies have given us reason for concern.

      Several animal studies suggest that animals exposed to organochlorines have problems with their menstrual cycle, problems with fertility, and decreased litter size. [20-23]
    • Organophosphate pesticides -
      One study suggests that animals exposed to organophosphate pesticides have problems with hormone regulation and egg development. [24]

      Another animal study suggests that certain organophosphates can block male sex hormones. [61]
    • Fungicides
      Several animal studies suggest that the fungicides can block male sex hormones and cause problems in sperm quality and delays in puberty. [62-64]
    Industrial Chemicals (PCBs, Dioxins)
    • PCBs
      Several human studies suggest that women exposed to PCBs may have problems with their menstrual cycle, children with abnormal growth, and increased risk of spontaneous abortion. [25][47]

      One human study suggests that boys exposed to PCBs while in the womb had shorter penis lengths than unexposed boys. [48]

      One human study suggests that girls exposed to polybrominated biphenyls during breastfeeding (closely related to PCBs) experienced an earlier start of menstrual bleeding than less exposed girls. [49]

      There has been some concern that PCBs are linked with increased risk of breast cancer, but the weight of the available evidence argues against this. [26][27]

      Some studies suggest that PCBs can alter thyroid function. There is also evidence against such an association, but there appears to be more evidence in favor of this association. [28][29]
    • Dioxins
      One study suggests that men exposed to dioxin have an altered ratio of males to female children. [30]

      Several studies of Vietnam veterans do not support a link between a father’s dioxin exposure and spontaneous abortion (stillbirth), birth defects, and developmental problems in his children. [31][34]

      Another study of Vietnam veterans shows no association between dioxin exposures and changes in levels of male reproductive hormones. [32]

      One human study suggests that together, dioxins and PCBs may cause thyroid abnormalities. [33]
    Phthalates

    One human study suggests that phthalates may cause premature puberty in young girls. [37]

    One occupational study linked exposure to phthalates in PVC plastic with increased testicular cancer. [11]

    Overall, the human evidence supporting the endocrine disrupting effects of phthalates is limited. However, several animal studies have given us reason for concern. Some animal studies suggest that phthalates can cause spontaneous abortions, birth defects, altered menstrual cycle, and other reproductive problems. [35][36][39][67]

    However, these findings are very controversial. Not all studies support the notion that phthalates are EDs. [66]

    Phenols (Bisphenol A, Alkylphenol)
    • Bisphenol A
      There is little human evidence that Bisphenol A acts as an endocrine disruptor (ED). However, several animal studies and cell culture studies have given us reason for concern:
      • One study found that Bisphenol A acts as an ED with human breast cancer cells. [40]
      • One animal study suggests that Bisphenol A may cause changes in hormone levels, menstrual cycle irregularities, delays in reproductive development, and other reproductive problems [41][70]
      • Several animal studies suggests that Bisphenol A may cause various reproductive abnormalities in males [68][69]
      • These finding are controversial. Not all studies agree with these effects of Bisphenol A. [72]
    • Alkylphenol
      There is little human evidence that alkylphenols act as EDs. However, several animal studies and cell culture studies have given us reason for concern:
      • One study found that certain alkylphenols act as EDs with human breast cancer cells. [42]
      • Several animal studies suggest that alkylphenols may negatively effect the female reproductive system. [43-45][75]
      • Another animal study suggests that alkylphenols may decrease sperm production in males. [69]
      • One animal study also suggests that alkyphenols may alter energy balance. [50]
    Phytoestrogens

    The health effects of phytoestrogens are controversial. Some studies suggest that phytoestrogens are harmful to the female reproductive system, whereas others suggest that they are actually beneficial to women.
    • Potentially harmful effects -
      One human study suggests that phytoestrogens may cause small changes in the lining of the vagina. The significance of this finding is not clear. [76]

      One human study suggests that some phytoestrogens may increase the risk of prostate cancer. [84]

      One human study suggests that phytoestrogens may increase risk of thyroid disease. [85]

      Another human study suggests that phytoestrogens may alter an infant’s ability to make cholesterol. [77] The significance of this finding is not clear.

      One animal study suggests that phytoestrogens may cause problems with the menstrual cycle. [52]

      One animal study suggests that phytoestrogens may worsen certain cancers. [79]

      Potentially beneficial effects -

      One human study suggests that phytoestrogens may lead to favorable changes in reproductive hormones in postmenopausal women. [80]

      Several laboratory studies suggests that phytoestrogens may decrease the risk of breast cancer. [81][82]

      One laboratory study suggests that phytoestrogens may decrease risk of prostate cancer. [83]

      These findings are controversial. Not all studies support these relationships. [78]

    Are there medical tests to see if my family has been exposed to endocrine disruptors?

    The answer to this question depends on the endocrine disruptor of interest. Each is discussed separately below (pesticides, industrial chemicals, phenols, phthalates, and plant hormones).
    Pesticides
    • To learn more about medical tests for pesticides, click here.
    • Industrial chemicals
    • To learn more about medical tests for PCBs, click here.
    • To learn more about medical tests for dioxins, click here.
    Phenols
    • Bisphenol A
    • There are no medical test available to measure levels of bisphenol A in the – body.
    • Alkylphenols
    • There are no medical tests available to measure levels of alkylphenols in the body.
    Phthalates

    There are medical that can measure the levels of a certain phthalate called di(2-ethylhexyl)phthalate, or DEHP. The test measures a breakdown product of DEHP called (2-ethylhexyl)phthalate, or MEHP, in the urine or blood. This test is good only for recent exposures because DEHP remains in the body for a short time. These tests are generally performed in research settings and are not routinely available in a doctor's office.

    No routine blood or urine test is available for other phthalate species such as diethyl phthalate. There are medical tests to measure levels of diethylphthalate in semen, fat, and kidney tissue. However, these tests are only useful in specialized research settings. They are not available at most doctors' offices.

    Phytoestrogens

    There are medical tests available that can measure the levels of certain phytoestrogens in the blood and saliva. These have been useful mainly in research settings and are not widely available in a doctor’s office. However, some manufacturers have advertised tests for phytoestrogens in saliva on the inter
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