01.What you need to know
With bad news stories about bisphenol A (BPA) appearing with increasing frequency, consumers are becoming more aware and concerned about the insidious effects that minute quantities of chemicals may cause. Known to have hormonal effects, BPA has been linked – although not necessarily conclusively – with all sorts of hormone-related health problems including asthma, obesity and diabetes, ADHD, breast and prostate cancers and reproductive abnormalities.
Because of its hormonal action, BPA is classified as an endocrine disrupting chemical (EDC). The endocrine system is a series of ductless glands that secrete hormones directly into the blood to regulate various body functions. Apart from the gonads, which produce sex hormones (oestrogen and testosterone), there is also the thyroid gland (thyroid hormone), adrenal glands (adrenaline), pancreas (insulin) and pituitary gland (growth hormone). Body fat, muscle, heart, liver, intestines and kidneys have secondary endocrine functions and 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. While BPA may be one of the highest-profile endocrine disruptors, it’s not the only one we’re regularly exposed to.
Other known EDCs include:
- synthetic chemicals used as industrial solvents/lubricants and their by products (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.
Meanwhile, 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.
Endocrine disorders have also been observed in animals, wild and domestic. Studies have confirmed EDCs as the cause of many, although not all, of these disorders, and in some cases can account for their increase.
Who is most vulnerable to the effects of EDCs?
Much remains unknown 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.
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 a 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?
While 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 are other animals (including humans), yet less sensitive to others. Even within a species some breeds are more sensitive than others.
At what doses are EDCs most potent?
A major difficulty in establishing which chemicals are dangerous and under what circumstances is that 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.
What are the potential interactions?
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
Some jurisdictions adopt the precautionary approach when it comes to the regulation of 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.