Some science behind the scenes

Endocrine disruptors

Endocrine disruptors are chemicals that at certain doses, can interfere with the endocrine (or hormone system) in mammals. Any system in the body controlled by hormones, can be derailed by hormone disruptors. Hormones work at very small doses (part per billion ranges) thus it takes very little to disrupt the body's endocrine systems. Endocrine disruption can occur via higher than normal doses of the body's own hormones [via the food chain for example] or via chemicals that can compete with natural hormones for receptors or destroy the receptors.

Humans can be affected, but EDCs in the environment may also be related to reproductive and infertility problems in wildlife including aquatic life. Clearly any wildlife or other animals in the food chain can directly affect humans if they are ingested [eaten] and the toxins are still present. 

Symptoms

The types of problems caused by these chemicals include 

Cancer - cancerous tumors, breast cancer, prostate cancer, thyroid and other cancers

Developmental defects – birth defects and deformations of the body (including limbs). The critical period of development for most organisms is between the transition from a fertilized egg, into a fully formed infant. As the cells begin to grow and differentiate, there are critical balances of hormones and protein changes that must occur. Therefore, a dose of disrupting chemicals may do substantial damage to a developing fetus (baby)

Brain damage - learning disabilities, severe attention deficit disorder, autism, cognitive and brain development problems. Most critical stages of development occur in utero, where the fertilized egg divides, rapidly developing every structure of a fully formed baby, including much of the wiring in the brain. Interfering with the hormonal communication in utero can have profound effects both structurally and toward brain development.

Sexual development problems - such as feminizing of males or masculine effects on females, etc, “male and female reproduction, breast development , reduced fertility, male and female reproductive tract abnormalities, and skewed male/female sex ratios, loss of fetus, menstrual problems, changes in hormone levels; early puberty. For example, phthalates in pregnant women’s urine was linked in one study to subtle, but specific, genital changes in their male infants – a shorter, more female-like anogenital distance and associated incomplete descent of testes and a smaller scrotum and penis. In another study, researchers found that a common flame retardant, PBDE-47, affects the reproductive system and thyroid gland of female rats in doses of the order of those to which humans are exposed. Xenoestrogens, for example, imitate estrogen. Synthetic xenoestrogens include PCBs BPA and phthalates all of which have estrogenic effects on a living organism.

Thyroid problemsobesity and other metabolic disorders

Immune system problems – especially impaired immune functions 

Causes

The following lists just some of the main chemicals implicated, this is not an exhaustive list I will try to add observations if I find any relevant extra chemicals

Bisphenol A (BPA) - Bisphenol A is commonly found in plastic bottles, plastic food containers, dental materials, and the linings of metal food and infant formula cans. Another exposure comes from receipt paper commonly used at grocery stores and restaurants, because today the paper is commonly coated with a BPA containing clay for printing purposes.

BPA is a known endocrine disruptor, and numerous studies have found that laboratory animals exposed to low levels of it have elevated rates of diabetes, mammary and prostate cancers, decreased sperm count, reproductive problems, early puberty, obesity, and neurological problems.

Long-chain alkylphenols - The long-chain alkylphenols are used extensively as precursors to detergents, as additives for fuels and lubricants, polymers, and as components in phenolic resins. These compounds are also used as building block chemicals that are also used in making fragrances, thermoplastic elastomers, antioxidants, oil field chemicals and fire retardant materials. They are also found in tires, adhesives, coatings, carbonless copypaper and high performance rubber products. Nonylphenol is considered to be a low-level endocrine disruptor owing to its tendency to mimic estrogen

DDT - Dichloro-diphenyl-trichloroethane (DDT) was first used as a pesticide in 1936. Its use for agricultural purposes has since been prohibited by national legislation of most countries, but its use as a control against malaria vectors is permitted. As early as 1946, the harmful effects of DDT on bird, beneficial insects, fish, and marine invertebrates were seen in the environment. Recent studies suggest DDT may inhibit the proper development of female reproductive organs that adversely affects reproduction into maturity. Additional studies suggest that a marked decrease in fertility in adult males may be due to DDT exposure.

Polychlorinated biphenyls (PCBs) - are a class of chlorinated compounds used as industrial coolants and lubricants. The effects of acute exposure to PCBs were well known within the companies who used PCBs even early on. Direct skin contact results in a severe acne-like condition called chloracne. Exposure increases the risk of skin cancer, liver cancer, and brain cancer. Recent studies show the endocrine interference of certain PCB congeners is toxic to the liver and thyroid, increases childhood obesity in children and may increase the risk of developing diabetes.

Polybrominated diphenyl ethers (PBDEs) - are a class of compounds found in flame retardants used in plastic cases of televisions and computers, electronics, carpets, lighting, bedding, clothing, car components, foam cushions and other textiles.
PBDEs have the potential to disrupt thyroid hormone balance. PBDE's contribute to a variety of neurological and developmental deficits, including behavioural problems, low intelligence and learning disabilities. Many of the most common PBDE's were banned in the European Union in 2006.

Phthalates - are found in some soft toys, flooring, medical equipment, cosmetics and air fresheners. They are of potential health concern because they are known to disrupt the endocrine system of animals, and some research has implicated them in the rise of birth defects of the male reproductive system. California and Europe have banned them from toys. One phthalate, Bis(2-ethylhexyl) phthalate (DEHP), used in medical tubing, catheters and blood bags, may harm sexual development in male infants. Similarly, phthalates may play a causal role in disrupting masculine neurological development.  Vinyl products such as shower curtains were found to contain more than 10% by weight of DEHP, which when present in dust has been associated with asthma and wheezing in children

Perfluorooctanoic acid PFOA - exerts hormonal effects including alteration of thyroid hormone levels. Blood serum levels of PFOA were associated with an increased time to pregnancy — or "infertility" — in a 2009 study. PFOA exposure is associated with decreased semen quality. PFOA appeared to act as an endocrine disruptor by a potential mechanism on breast maturation in young girls. A C8 Science Panel status report noted an association between exposure in girls and a later onset of puberty.

Parabens – Parabens is a class of chemicals that has been associated with reproductive-tract issues. It has been detected in consumer products, for example, three sunscreens that did not list parabens on the label.

Other suspected endocrine disruptors -

  • polychlorinated dibenzo-dioxins (PCDDs)
  • furans (PCDFs)
  • polycyclic aromatic hydrocarbons (PAHs)
  • phenol derivatives
  • a number of pesticides (most prominent being organochlorine insecticides like endosulfan, Kepone(chlordecone)
  • the herbicide atrazine
  • the fungicide vinclozolin
  • the contraceptive 17-alpha ethinylestradiol

Sources

All people are exposed to chemicals with, for example, estrogenic effects in their everyday life, because endocrine disrupting chemicals are found in low doses in thousands of products. In fact, almost all plastic products, including those advertised as "BPA free", have been found to leach endocrine-disrupting chemicals. 

Food - Food is a major mechanism by which people are exposed to pollutants. Diet is thought to account for up to 90% of a person's PCB and DDT body burden. In a study of 32 different common food products from three grocery stores in Dallas, fish and other animal products were found to be contaminated with PBDE. Since these compounds are fat soluble, it is likely they are accumulating from the environment in the fatty tissue of animals we eat. 

Indoor air - With the increase in household products containing pollutants and the decrease in the quality of building ventilation, indoor air has become a significant source of pollutant exposure. Residents living in homes with wood floors treated in the 1960s with PCB-based wood finish have a much higher body burden than the general population. Recent studies suggest that contaminated house dust, not food, may be the major source of PBDE in our bodies. One study estimated that ingestion of house dust accounts for up to 82% of our PBDE body burden. 

Consumer goods - consumer goods are another potential source of exposure to endocrine disruptors, for example, household cleaning and personal care products "If a consumer used the alternative surface cleaner, tub and tile cleaner, laundry detergent, bar soap, shampoo and conditioner, facial cleanser and lotion, and toothpaste [he or she] would potentially be exposed to at least 19 compounds: 2 parabens, 3 phthalates, MEA, DEA, 5 alkylphenols, and 7 fragrances."

Government action

There has been controversy over endocrine disruptors, with some groups calling for swift action by regulators to remove them from the market, and regulators and other scientists calling for 'further study'.

The European Union has implemented sales and use restrictions on certain applications in which nonylphenols are used because of their alleged "toxicity, persistence, and the liability to bioaccumulate" but the United States EPA has taken a slower approach to make sure that action is based on "sound science".

Bisphenol A, until 2010 a common component in the plastic used to manufacture plastic baby bottles, has been banned in most countries.

In 2013 the WHO and the United Nations Environment Programme released a study, the most comprehensive report on EDCs to date, calling for more research, but they did nothing.

Observations

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