Friday, 1 January 2016

A Public Health Perspective on Endocrine Disrupting Chemicals

Moving Forward: How Should We Deal with EDC’s

Some Current Flaws in the EDC Debate

In considering the problem there are important principles of human endocrine receptor function that provide a perspective and negate all animal studies referred to by industry and Health Canada. Several aspects of human endocrine receptor physiology seem to escape regulators like the FDA or Health Canada, the sunscreen industry, and unfortunately most dermatologists. They are either unwilling or unable to understand basic concepts even when the World Health Organization (WHO), The Endocrine Society, and The United Nations Environmental Program, have gone to great lengths to alert the world to the science, and the rising incidence of reproductive disorders and cancers in humans and lower species. Important aspects of human endocrine receptor function  provide a perspective (taken from WHO/UNEP ES 2012). Humans are not large rodents and human endocrine receptors function differently from mice and other lower species. Animal studies in mice and other lower species suggest that only large doses are toxic.

In humans the age of exposure is critical, and endocrinologists  now use the terminology “the developmental basis of adult disease.”  I also believe that puberty represents another period of increased vulnerability for obvious reasons. There may be a delay before the consequences are evident in adult life or later on. Furthermore, effects of different classes of EDCs may be additive or even synergistic. In humans, infinitesimally low levels of exposure— indeed, any level of exposure at all—may cause endocrine or reproductive abnormalities, particularly if exposure occurs during a critical developmental window. Surprisingly, low doses may even exert more potent effects than higher doses. EDCs may exert non-traditional dose-response curves, such as inverted-U or U-shaped curves.

Both of these concepts have been known for hormone and neurotransmitter actions, but only in the past decade have they begun to be appreciated for EDCs, which may also affect not only the exposed individual but also their children and subsequent generations. Recent evidence suggests that the mechanism of transmission may in some cases involve the germline  and may be nongenomic.  In other words, effects may be transmitted not due to mutation of the DNA sequence but rather through modifications to factors that regulate gene expression such as DNA methylation and histone acetylation.

Bisphenol A (BPA) and phthalates in plastics and tins are publicized as a source of human EDC exposure mainly by ingestion. This exposure is more tangential and incidental than sunscreen or cosmetic chemicals. The liver may metabolize and ameliorate the effects of EDCs ingested. Sunscreen chemicals absorbed through the skin obtain direct access to tissues and the brain and bypass this protective mechanism. Logical and critical thinking leads you to the unavoidable conclusion that sunscreen and cosmetic chemicals, often used on a daily basis and in combinations of products, which pass into the blood and brain, are the most important source of EDC exposure in a first world society.

How Should We Approach the Issue?
Physicians subscribe to the principle of “First do no harm” and should believe in The Precautionary Principle. It considers the limits of science and errs on the side of caution, so that action in the public interest is not delayed until the damage is done. Regulators in N. America, unlike those in Europe, seem to act only when there is incontrovertible evidence of harm, which is too late. This policy is illogical since it is criminal or unethical to do definitive studies on humans, particularly pregnant women and children. The follow-up phase would have to span a lifetime to detect effects like cancer. We believe in the Precautionary Principle and that like BPA, we have passed the point where action is necessary with respect to soluble sunscreen filters. The Industry and regulatory regime response that animal studies show no evidence that sunscreen chemicals which attain blood levels do harm is simplistic. They do not provide evidence that these chemicals are safe. Extrapolations from animal studies are largely irrelevant to the human condition. It is ironic that the soluble filters that pose a risk to human endocrine function also give UVB-biased protection, and indirectly increase the risk of cancer and photo-aging in fair skinned individuals. Conversely, insoluble particle based filters pose no risk to humans and give balanced protection that reduces the risk of cancer and photo-aging.  It is time to counsel pregnant women about the risks of soluble filters and have them make an informed choice. Infertility specialists also need to pay attention. The entire population should make their own enlightened choice between soluble and insoluble filters.

The Application of the Precautionary Principle
These excerpts from essays by Marion Nestle and CHEM Trust are helpful. The application of “precaution”, “the precautionary principle” or “the precautionary approach” recognizes that the absence of full scientific certainty shall not be used as a reason for postponing decisions where there is a risk of serious or irreversible harm.

“The application of precaution is distinctive within science-based risk management and is characterized by three basic tenets: the need for a decision, a risk of serious or irreversible harm and a lack of full scientific certainty. It is enshrined in Canadian Law repeated in numerous legislation where required to protect human health and the environment. In the administration of Food & Drugs, it is mandated that when there is a concern for human safety, however minimal, it is necessary to err on the side of caution. In this respect Bisphenol A has been banned for use in plastic containers. European countries tend to subscribe to the precautionary principle.  Sweden, for example, has also banned BPA. The precautionary principle is one of the guiding principles of current EU policy making. The precautionary principle requires all the available scientific evidence to be taken into account, including all its related complexities, contradictions and gaps which need to be considered when trying to avert serious and irreversible damage to the population.

The precautionary principle takes the limits of science into the equation and tries to ensure that action is not delayed until the damage is done (and confirmed). To say the precautionary principle is unscientific misses the point, because all available scientific information is taken into account. The precautionary principle permits decision makers to take decisions in the absence of scientific certainty if there is a sufficiently serious risk. So it requires the exercise of judgement, in other words it is a principle of policy making. It is often impossible to design and implement experiments that prove that EDCs cause the increase in diseases that we are seeing. For example, this could require exposing pregnant women to chemicals and following their children for several decades to monitor the effects. However, if there are indications from tests on cell lines as well as animal experiments that chemicals have endocrine disrupting properties, we need to act before waiting for absolute proof of harm in humans. In my opinion, where EDC effects are concerned we are already too late.

A meaningful precautionary approach requires transparency in all assessments and their underlying scenarios. These assessments should look widely at exposure routes, otherwise small-scale measures may be decided instead of more effective wide-ranging policy responses, which protect those most vulnerable. For example in the USA, the limited BPA ban in baby bottles by the FDA, left pregnant women and the unborn child at risk from all other sources of exposure to BPA. The FDA still advises  that parents should examine bottles and discard them if worn or scratched because scratches can both harbor germs and, in BPA-containing bottles, lead to greater release of BPA.  For those who want to use baby bottles and feeding cups not made with BPA, consumers should know that such products are now widely available in the U.S. market. What all this means is that the FDA is sticking to—or has to stick to—a science-based position on BPA, but it is hedging bets by urging parents and the public to apply the precautionary principle and avoid BPA whenever possible.”

Some Conclusions

This shifts the burden of protection against harm from the government to you. I believe The Precautionary Principle under Canadian Law is being ignored where soluble sunscreen filters are concerned. The case for banning them is much stronger than BPA.  We know now about how the chemical oxybenzone in sunscreen can damage to reefs, but most of us still ignore the science that soluble UV filters (benzophenone and others) are human and environmental toxins. The pharmaceutical companies, the cosmetic industry, regulators, and most physicians, continue to ignore the persuasive evidence and breach The Precautionary Principle.   

Fetal and early childhood exposure (the developmental basis of adult disease) explains the genesis of numerous endocrine disorders and the cancers linked to hormone disruptors. Puberty is another time for concern but adults and seniors should not be dismissive of the jeopardy. There are links to Alzheimer’s and Parkinson’s for those EDCs that bind to certain receptors or affect neurotransmitter functions in the brain. Fetal and early childhood  exposures are linked to metabolic syndrome, obesity, and Type 2 Diabetes later in life. Metabolic systems that control  weight and glucose levels are affected, but even adult exposure may affect your chances of becoming obese or diabetic. Gru¨n and Blumberg  have named molecules that affect normal lipid metabolism adversely to promote obesity as obesogens. Hormone disruptors are among these obesogens that increase  the storage of fat. Exposure to EDCs may reduce the chance of success if you are an adult trying to lose weight. 

I have expressed my concern about EDCs for almost a decade but few physicians are listening. Those providing care around pregnancy should  counsel patients about sunscreens with filters that attain blood levels in mother and fetus, as they would for many  medications. I am slowly being vindicated. The WHO, The United Nations Environmental Program, The European Pediatric Society, The Endocrine Society, and others issued a warning in 2012 that there is strong evidence that EDCs are affecting human health. The NIH recently described links to male infertility for the benzophenone group. Facts about hormone disruptors are slowly filtering through to mainstream media. A good review by Linda Marsa appeared in the October issue of MORE magazine. Missing is the deductive conclusion that sunscreen chemicals are the most likely way in which hormone disruptors intersect with our daily lives, given the patterns of exposure in a first world society. The European Court of Justice recently ruled in a case brought by Sweden (on behalf of the Nordic countries) that the European Commission – tasked with oversight like the FDA or Health Canada - had "unlawfully refrained from laying down rules" to identify and ban endocrine disrupting chemicals. Health Canada and the FDA hardly even discuss this issue let alone recognise there is legitimate concern over human effects. If there is a ban of benzophenone – over 65% of sunscreens globally will have to be removed from the market. A growing number of consumers are already consciously avoiding it and other soluble filters.                                                                    

© Denis K. Dudley MD 2015