written by Laura N. Vandenberg, PhD
Assistant Professor and Graduate Program Director of Environmental Health Sciences, University of Massachusetts Amherst School of Public Health and Health Sciences
Reprinted with permission from Environmental Health News
Cancer. Diabetes. Autism. Infertility. ADHD. Asthma. As the rates of these diseases increase over time, the public and researchers alike have focused on the role the environment might play in their cause and progression. Scientists in the field of environmental health sciences are not satisfied just to know that the environment contributes to human disease – they want to know how.
This week [ScienceSeptember 18-20], researchers, public health advocates, government officials, and industry spokespersons will meet at National Institutes of Health (NIH) to celebrate 25 years of scientific research on one aspect of environmental health: endocrine disrupting chemicals (EDCs). These are compounds that alter the way hormones act in the body, often by mimicking or blocking their actions. Just a few examples of widely used consumer products that contain EDCs are plastics, electronics, flooring, some personal care products, and furniture treated with some flame retardants.
Scientists funded by NIH have made tremendous strides understanding how the environment contributes to diseases that affect the lives of millions of Americans. We now recognize that EDCs can act at low doses. It is also clear that the traditional adage ‘the dose makes the poison,’ used by toxicologists for decades, is outdated and too simplistic when it comes to understanding the health effects associated with EDCs; studying high doses often does not tell the full story about a chemical’s effects. And there are periods in our life when we are more sensitive to these chemicals; exposures during vulnerable periods of development can produce effects that might not manifest until adulthood.
We also know that Americans today have hundreds of chemicals circulating in their bodies. Our babies are being born ‘pre-polluted’ with chemicals detectable in their blood, in the placenta, and in amniotic fluid because of exposure to EDCs and other contaminants during pregnancy and throughout the mother’s life.
But through research funded by NIH, we now know, for example, that bisphenol-A (BPA), a chemical commonly used in plastics and other consumer products, can mimic (and sometimes block) estrogen, disrupt thyroid hormone signaling, alter actions of male hormones, and induce obesity. We know that DDT, an insecticide that was widely used in the 1970s, can be stored in the body and increase risk of breast cancer in daughters exposed in the womb. We know that PCBs, chemicals once widely used in industrial processes, can alter development of the brain and disrupt a number of behaviors. We also know that atrazine, a common herbicide, can affect sexual development in frogs, and also alter puberty and the menstrual cycle in mammals.
More importantly, because of the dedication of hundreds of scientists in the U.S. and elsewhere, we are starting to know how these chemicals can induce diseases, even at levels of exposure lower than previously thought to be significant.
The public is often outraged to find that hormonally active compounds are detected in consumer products like food packaging, cosmetics, upholstery, cleaning products, and medical equipment. They are also upset when new studies link one of these chemicals to the myriad diseases that afflict human populations. Although these feelings are clearly understandable, as a society, we need to move beyond anger and frustration to identify solutions.
In some cases, we require better knowledge about how these chemicals are used by industry, and whether a safer alternative exists. In other cases, deciding what to do about these chemicals requires more knowledge – studies to better understand what these compounds might be doing to us, and how these compounds may act in concert – as a ‘chemical stew.’
We also fall short in developing methods to identify ‘safe’ levels of exposure. In fact, for many EDCs, scientists question whether any level is a safe level, especially when the compound could disrupt the important hormonal signaling that is essential for the health of fetuses, neonates, infants and children. And for some chemicals, we know a lot about how they act alone, but very little about how they act in mixtures – as they are experienced by many on a day-to-day basis. It is this combination of exposures – this chemical stew – that is more relevant to the human condition, and which needs to be better understood.
Finally, studies have shown that some EDCs induce effects that transfer from one generation to the next, even when the younger generations are not directly exposed. This means that grandchildren and great-grandchildren may be affected by chemical exposures experienced by their grandparents, but not by themselves. The implications of these findings are staggering, making it even more important that we understand the ways that biological information is transferred from generation to generation.
The Native Iroquois and other Native American tribes live by a principle: in all decisions, we should consider the effects on seven generations of descendants. This relatively new EDC work showing harm in great-grandchildren of exposed animals challenges our ability to protect future populations from chemicals once we know that they cause harm.
While it may sound cliché for a research scientist to advocate for funds for more research, we need a commitment from the public for research dollars to further our understanding of environmental contributions to disease. We need Congress to pass budgets that maintain or increase such funding for NIH.
In many ways, 2016 is a banner year – and there is much to celebrate in environmental health. The Endocrine Society, whose members have contributed much of the research on EDCs, celebrated its 100th Anniversary. The National Institute of Environmental Health Sciences (NIEHS), the institute within the NIH that funds much of the work on environmental health, is celebrating 50 years of environmental research.
As we celebrate 25 years of EDC research this week, it is heartening to see the significant strides we have made in the scientific arena. Yet, we must also acknowledge that much more is needed to protect the health of generations to come.
Listen to a recording of CHE’s call with NIEHS Director Linda Birnbaum: 25 Years of Endocrine Disruption Research: Insights from the Director of NIEHS