How EDCs affect us
The endocrine system is a series of ductless glands that secrete hormones directly into the blood to regulate various body functions. The glands include:
- gonads – produces sex hormones (oestrogen and testosterone)
- thyroid – produces thyroid hormone
- adrenal – produce adrenaline
- pancreas – produces insulin
- pituitary – produces growth hormone
Body fat, muscle, heart, liver, intestines and kidneys have secondary endocrine functions and also produce hormones.
Many substances affect our endocrine systems. When ingested, absorbed or inhaled into the body, these substances interfere with the production, action and/or elimination of our naturally present hormones.
Which EDCs should we be worried about?
BPA may be one of the highest-profile endocrine disruptors, but we're regularly exposed to plenty of others.
Other known EDCs include:
- synthetic chemicals used as industrial solvents/lubricants and their byproducts (polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), dioxins)
- plasticisers (phthalates)
- pesticides (methoxychlor, chlorpyrifos, dichlorodiphenyltrichloroethane (DDT) and tributyltin)
- fungicides (vinclozolin)
- pharmaceutical agents (diethylstilbestrol)
Although rarely called endocrine disruptors, natural substances such as soy and beta-sitosterol also have hormonal effects, while pharmaceuticals including hormone replacement therapy and the oral contraceptive pill have endocrine-disrupting effects.
Another concern is that of an estimated 50,000 chemicals in use today, very few have been tested for endocrine effects. Even of the 800 or so chemicals suspected to be endocrine disruptors, only a small proportion of these have been tested.
Endocrine disorders on the rise
Endocrine disorders are on the rise worldwide and include:
- low semen quality and fertility in young men
- genital malformations, such as non-descending testes (cryptorchidisms) and penile malformations (hypospadias) in baby boys
- premature birth and low birth weight
- neurobehavioural disorders associated with thyroid disruption in children (autism, attention deficit disorders and learning disabilities)
- endocrine-related cancers (breast, endometrial, ovarian, prostate, testicular and thyroid)
- earlier onset of breast development in young girls, which is a risk factor for breast cancer, obesity and type-2 diabetes.
Studies have confirmed EDCs as the cause of many, although not all, of these disorders - and in some cases can account for their increase. Endocrine disorders have also been observed in wild and domestic animals.
Who is most vulnerable to the effects of EDCs?
Our age and developmental stage plays a critical role in how, or even if, endocrine disruptors have an effect. Humans and other animals are most vulnerable to EDCs during critical periods of development, such as during foetal development and puberty. And there can be a long time between exposure to an endocrine disruptor and when the effects are manifested, and these can span several generations – so, a pregnant woman's exposure may ultimately affect her grandchildren.
Acknowledging the vulnerability of the developing foetus and infant, the Danish government has compiled an English-version consumer brochure for pregnant women explaining how they can avoid exposure to known and suspected endocrine disruptors while pregnant and breastfeeding, and for their baby after birth (information which could be useful for any consumer wishing to avoid them).
What do lab tests reveal?
There's a lot we don't know about the effects of EDCs. There are many obstacles facing researchers trying to establish whether a substance is an endocrine disruptor and under what circumstances.
Although a lot information about endocrine disruption has come from lab animals, animal testing doesn't always correlate well from one species to another. For example, rats are more sensitive to some chemicals than other animals (including humans), yet less sensitive to others. Even within a species some breeds are more sensitive than others.
Many endocrine disruptors have different effects at different doses. The problem arises when scientists only study very large doses, and if proven safe they assume it's still safe at lower doses.
However, there's increasing evidence that very low doses of certain chemicals have an equally or more potent effect as high doses. The effect may be the same as the high dose, where an intermediate dose shows no effect. Or the effect may be different but equally problematic. For example, pregnant mice given large doses of an oestrogenic drug called diethylstilbestrol have extremely skinny offspring, while very low doses produce obese offspring. Alternatively, some endocrine disruptors may have an effect at medium doses, but have none at very high or very low doses.
Testing also often overlooks the combined effects of more than one EDC – they may magnify, alter or cancel out any endocrine effects they have individually. This applies to products such as cosmetics or pesticides, which contain a raft of chemicals that could alter the effects of EDCs. Studies on herbicides containing glyphosate, for example, found that the formulation of the product in which it was contained was the major determinant of endocrine effects, rather than the concentration of glyphosate.
Test conditions vs normal use
Finally, just because a product contains known EDCs, they may not actually be in a form that causes a problem. The Danish environmental protection agency tested various products containing EDCs, including mobile phone covers, work gloves, sleeping mats, sneakers and handbags, and found the chemicals didn't migrate from the products under simulated conditions of normal use. On the other hand, for decades it was assumed that BPA wouldn't cause problems because it was safely locked up in polycarbonate plastic – but when heated or washed in harsh detergents, it was released.
The precautionary approach vs wait-and-see
Some jurisdictions adopt the precautionary approach when it comes to regulating known or suspected endocrine disruptors: this means banning EDCs from certain or all applications.
Relevant Australian authorities, including the Therapeutic Goods Administration (TGA), Food Standards Australia New Zealand (FSANZ), the Australian Pesticides & Veterinary Medicines Authority (APVMA), the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) and the various state and local environmental and water authorities are taking a wait-and-see approach, until there are more definitive research results.
EDCs in consumer products
Bisphenol A (BPA)
- polycarbonate plastics, including food and beverage containers
- linings of tins and jar lids
The oestrogenic properties of BPA were identified in the 1930s when researchers were looking to treat symptoms relating to menopause, menstruation, nausea in pregnancy and prevention of miscarriages. It wasn't pursued for this use, but rather for its plasticising properties – by the 1950s BPA was used in epoxy resins for protective coatings, linings and adhesives, then later for making clear, hard polycarbonate plastic.
BPA's endocrine-disrupting properties arose as an issue for research scientists in the 1990s, where its presence in water bottles and polycarbonate animal cages, as well as polycarbonate laboratory equipment, was producing unexpected experimental effects.
Having established that the BPA in polycarbonate was the source of contamination, the observed oestrogenic effects were not surprising. But the fact it was leaching out of plastic in quantities that could cause significant effects was unexpected, and given its ubiquity in a variety of consumer goods, the implications were enormous.
Studies on animals and in vitro testing on human cells have linked BPA exposure with breast and prostate cancers, obesity, neurobehavioural problems and reproductive abnormalities. Because babies and young children are more vulnerable to its effects due to their development stage and rates of metabolism, products for this group have caused the most concern. BPA is more likely to leach from containers into food and beverages if the containers are heated or the contents are acidic, while harsh detergents can break down the plastics causing BPA to be released.
BPA has been banned or voluntarily withdrawn from use in baby bottles in Australia, Canada, the US, Turkey and some European and Asian countries, and banned for use in linings of jars and tins for food aimed at children under three in France and Sweden. An American BPA producer famously required customers to agree it wouldn't be used in products aimed at children under three.
What you can do: While it's difficult to know whether BPA is in tin or jar linings, you can avoid polycarbonate plastics used in water bottles and other food containers (a number "7" in the recycling triangle means the plastic is polycarbonate or "other", and a sign it may contain BPA).
- cosmetics with sun protection, e.g. lip balm, make-up and moisturiser
Some chemical sunscreens, including widely used octyl methoxycinnamate (also called OMC or ethylhexyl methoxy cinnamate), as well as 4-methylbenzylidene camphor (4-MBC) and benzophenone 3, have been found in some studies to have developmental and reproductive effects, as well as thyroid effects from OMC. Most studies look at the chemicals in isolation, whereas in reality there is often more than one chemical sunscreen used in a preparation, not to mention other potential endocrine disruptors, such as parabens. The combined effects of these aren't known.
What you can do: Choose sunscreens with physical blockers, such as zinc oxide or titanium dioxide.
- food wrap
- cosmetics such as fragrances, lotions and nail polish
Phthalates are common chemicals primarily used as plasticisers in manufacturing flexible vinyl plastic found in flooring, food wrap and medical devices. They are also found in cosmetics and personal-care products, such as fragrances, lotions and nail polish, and pharmaceuticals where they're used in coatings for timed-release pills. As such, we eat, breathe and absorb them through our skin. They have been linked with endometriosis and early puberty in girls, and reproductive organ abnormalities and reduced fertility in males. They can also act on the thyroid, and have been linked with obesity.
What you can do: Some of the dangerous phthalates have been banned in cosmetics and children's toys in Europe, and toys in the US. Only one phthalate has been banned in Australian toys. As they're often found in fragrances such as air fresheners, you can avoid perfumed personal care and household products.
- cosmetic and personal care products.
Parabens are preservatives used in many cosmetic and personal care products and have been found to have oestrogenic effects. The larger the molecule, the greater the effect, with the smaller molecule parabens being the safest, including methyl paraben which is the most commonly used. The European Scientific Committee on Consumer Safety conducted a review of parabens in consumer goods, and determined that they didn't pose a risk in the quantities permitted in such products. However the Danish government has banned the use of some of the larger-molecule parabens (propyl-, isopropyl-, butyl- and isobutyl-parabens) in products for children up to three years old as a precautionary measure, as children might be especially vulnerable to endocrine effects. This is of particular concern if products are used on broken skin, such as nappy rash.
What you can do: Check the ingredients list for propyl-, isopropyl-, butyl- and isobutyl-parabens.
Pesticides and herbicides
Many pesticides are endocrine disruptors, including some that have been banned but persist in the environment, and those that have been banned in some countries but not Australia, and some still widely in use including DDT, endosulfan, synthetic pyrethroids and chlorpyrifos.
DDT has an oestrogenic effect, and although it has been banned in most countries for several decades, it persists in the environment and the food chain. It's still used in some countries for mosquito control where observable short-term malaria deaths are a greater concern than potential longer-term endocrine effects.
Atrazine is a selective herbicide used on animal feed crops, sugar cane and forestry plantations, and canola crops. Apart from food residues, it can also enter the water supply, and has been linked with neuroendocrine effects. The Australian regulatory authorities determined that it doesn't pose a risk, but will continue to monitor research.
Glyphosate (the active ingredient in Roundup weed killer) is widely used throughout the world in agriculture, parks and home gardens, and has been linked with endocrine-disruption effects related to growth, sexual development and reproduction. Various food crops (soy, canola, corn, cotton, sugar beet) have been genetically modified so they're resistant to glyphosate.
What you can do: Wash all fruit and vegetables before eating them. Where possible avoid buying imported fresh, canned or frozen produce from countries with dubious pesticide regulation. Buy GM-free to avoid plant foods (such as canola and soy) that are tolerant to pesticides.
- antibacterial soap and hand wash
- cleaning cloths
- cutting boards
Triclosan is an antibacterial compound found in soap, hand wash and toothpaste, as well as other consumer products such as cleaning cloths and cutting boards. It interferes with the thyroid hormone and is oestrogenic. The US Food and Drug Administration (FDA) is currently reviewing the safety of triclosan, pointing out that while it's "not currently known to be hazardous to humans", tests on mammals and other animals have shown hormonal effects that warrant further scientific and regulatory review. There are also concerns that it may contribute to antibiotic resistance. The FDA also points out that there's no evidence that it has any extra health benefits over soap and water. According to the precautionary principle, it may be better to avoid it.
What you can do: Use soap and water. Many "antibacterial" soaps and toothpastes in the supermarket contain triclosan (liquid soaps and toothpaste) and triclocarban (bar soaps), so check the label.
- hair dyes
- topical treatments for acne, seborrhoeic dermatitis, eczema, psoriasis, corns and warts
Resorcinol is used as an antiseptic and disinfectant. Resorcinol is currently on the European Union's Category 1 list of endocrine disruptors, and has been linked to thyroid disease when used in large quantities on broken skin over a long period of time.
What you can do: Look for hair dye that's resorcinol-free, and don't overuse products containing resorcinol on broken skin.
Perfluoroalkyl acids (PFOA)
- furniture upholstery, carpets, weatherproof clothing (e.g. Gore-Tex)
- coatings for non-stick cookware (Teflon)
- fast-food paper wrappers/containers
Their resistance to solvents, acids and bases as well as their non-stick quality and heat resistance makes these chemicals highly useful in a variety of consumer products, including stain- and water-repellent coatings and treatments for textiles (such as furniture upholstery, carpets, weatherproof clothing – think Gore-Tex), coatings for non-stick cookware (Teflon) and paper fast-food wrappers/containers.
Components of the polymers, in particular PFOA, have been linked with thyroid disease. While the WHO/UN Environment Programme (UNEP) has listed PFOA as a potential obesogen (a substance which may lead to obesity), a panel of expert scientists established to look into the effects of PFOA on people working in and living near a production factory determined that although it is probably associated with increased blood cholesterol, there was no evidence of a link with obesity or metabolic syndrome.
What you can do: Look for PFOA-free, rather than Teflon, non-stick cookware. If you have Teflon cookware at home, use it at low temperatures, and if it's peeling throw it away – you don't want little bits in your food.
- The Endocrine Society is an international organisation of professionals concerned with endocrinology research and clinical practice. Its members include clinicians, researchers, educators, industry professionals and health professionals. They have provided a comprehensive review of the science behind endocrine disruptors.
- The WHO and United Nations Environment Programme's report on EDCs was released in February 2013.
- The Danish Ministry of the Environment has information and a consumer-friendly pamphlet (in English) for pregnant women on how to avoid EDCs.