The Latest in the Fight Against Endocrine Disruptors

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Kevin Bunch
December 12, 2016
A US Geological Survey scientist dissects a fish to determine possible effects from exposure to endocrine disrupting contaminants. Credit: USGS
A US Geological Survey scientist dissects a fish to determine possible effects from exposure to endocrine disrupting contaminants. Credit: USGS

A dangerous class of chemical compounds called endocrine disruptors has been known to cause health problems in wildlife and people since the 1960s. These chemical pollutants, which can come from substances like polychlorinated biphenyls (PCBs) or pesticides such as DDTs, made their way into the Great Lakes before the United States and Canada started taking steps to end their production and limit usage starting in the closing decades of the 20th century. Since then, stacks of research have discovered how dangerous these substances are to human and animal health, and efforts are underway to improve testing and filtering for them at water treatment plants.

On the binational level, progress has been made. According to the Progress Report of the Parties released earlier this year, the Canadian government has passed regulations that address some of these chemicals directly, while the US government recently amended the Toxic Substances Control Act to improve regulation. Both countries also have been funding research into these compounds. Regional and local efforts are progressing as well.

According to Dr. Carol Miller, director of the Healthy Urban Waters program at Wayne State University and member of the IJC’s Great Lakes Science Advisory Board (SAB), researchers are collaborating with the Detroit Water and Sewerage Department and the regional Great Lakes Water Authority (GLWA) to investigate methods of removing endocrine disruptors from drinking water supplies and improving testing for them in water supplies.

Miller said there has been an increasing effort to use existing drinking water monitoring stations in the Great Lakes channels to measure and track chemicals in the water – both those already identified as potentially hazardous and others just in case they are found to be hazardous in the future. Environmental chemist Dr. Miriam Diamond from the University of Toronto said major sources of endocrine disrupting chemicals are from urban areas, wastewater treatment plants and agriculture (in the form of pesticides). Due to aging infrastructure and increases in the urban population, Diamond said wastewater plants—such as those around Toronto—are being asked to contend with additional domestic sewage, industrial emissions and stormwater without sufficient money for maintenance and upgrading. Since those plants aren’t optimized to deal with these endocrine-disrupting pollutants, some can slip through and enter the water system.

Dr. Theo Colborn. Credit: Jrrochester
Dr. Theo Colborn. Credit: Jrrochester

In 1988, a scientist named Dr. Theo Colborn published research suggesting that persistent human-made chemicals in the environment were being transferred to the offspring of a variety of wildlife species that otherwise did not seem to be exhibiting any issues. The IJC brought the topic up in its 1992 sixth biennial report, where it found that the environment and future generations of people were both at significant risk from these substances. At the time, the US General Accounting Office found no federal agencies had listed any endocrine disrupting chemicals as a known or potential risk to human development or reproduction, while a Canadian government report found that the effects seen on wildlife also occur in humans.

Colborn convened a small group of scientists in 1991 who were working independently on what are now called endocrine disruptors. The scientists were each working at a variety of scales from the microscopic to full-scale wildlife; Colborn brought them together so they could begin highlighting the issue as a whole. The idea of endocrine disruptors was published in 1997 in Colborn’s book “Our Stolen Future” and received widespread attention.

One of the most important discoveries over the past 25 years is that endocrine disruptors have an impact on sexual development and that the chemicals come from man-made sources or from new uses of organic compounds, said Dr. Michael Twiss, an SAB member and biology professor at Clarkson University.

Twiss cited the discovery of feminized suckers in Lake Superior caused by chemical byproducts from the pulp and paper industry, thanks to ongoing research carried out since 1988. Those chemicals also occur naturally in trees, but can impact some species when they get into aquatic environments in excessive amounts. The industry has since made an effort to clean up its practices, due in part to research by Environment and Climate Change Canada.

“There’s often a balance among hormones, so in order for a female to be a female there’s a balance between estrogen and testosterone,” Twiss said. “Any change in that ratio (from endocrine disruptors) can throw it one way or another.”

Scientists have learned that these endocrine disrupting substances can turn “whole batteries of genes” on and off in a way that allows them to have effects for generations beyond the initial exposure to an organism, in what is called an epigenetic effect.

Generally when the concentration of a toxic substance drops below a certain amount, it becomes less poisonous. In turn, toxicity increases as the dose of the substance increases. Miller said endocrine disruptors research suggests that low and median concentrations can result in varying types of effects from what scientists would expect to see based on the impacts of high concentrations.

Scientists suggest this is because organisms naturally have hormones in their systems, and that those systems are designed to be modified by relatively low hormonal changes. Since levels of these legacy endocrine-disrupting chemicals are declining in the lakes and rivers, it’s possible concentrations of specific chemicals could cause new health risks.

In a September presentation sponsored by the Collaborative on Health and the Environment, National Institute for Environmental Health Sciences (NIEHS) Director Dr. Linda Birnbaum said that endocrine disruptors can impact a person’s sleep, mood, sexual functions and, in children, general development. These compounds can act as keys to the “locks” of hormones, and tell the body to produce particular hormones like estrogen or testosterone or ease back and shut off production. Effects can even start happening at the levels found in the “soup of chemicals” we live in – from air pollution to the food we eat and drinks we drink.

“Not all of them are artificial – some are natural,” Birnbaum said. “Some are in food, some are in drugs we take, and there are lifestyle issues. For example, drinking alcohol, smoking cigarettes or marijuana, all of those things can interfere with hormone action.”

Birnbaum estimates that up to 140,000 chemicals are currently being used commercially around the globe. With those numbers, testing each one individually isn’t practical. The NIEHS has developed a program capable of screening up to 10,000 chemicals at once, though that method doesn’t account for human genetic variability to the extent that exists in the world. Ideally, she added, chemicals would be tested in advance before getting used. The program is being used to identify which ones could have a damaging impact to human health.

Dr. Thomas Speth, an SAB member and US Environmental Protection Agency environmental engineer, said there have been some limiting factors when trying to measure the impact of endocrine disruptors. The first is that there are a suite of chemicals in the environment that need to be accounted for, and the second is how few laboratories are capable of running those investigations. Even if scientists study a mix of chemicals at once, they could still miss some that are having an impact.

There has been informative work, though. Researchers have reconstructed the history of the introduction of brominated compounds like PBDEs from archived environmental samples, and found that the compounds have much the same effect as the older compounds like DDT on fish and wildlife and likely on humans – all of which are endocrine disruptors.

Rain and the air also are major pathways. Diamond said any chemicals in the air can easily enter the water system through atmospheric deposition – the pollution of water by air pollution – or by rain. This is the major driver of endocrine disruptors getting into Lake Superior, while other lakes with higher population densities can be exposed through runoff, she added.

A huge problem is posed by chemicals already in use as building insulation or other long-lived equipment like electrical transformers that will remain in the environment for decades.

Coupled with other obstacles faced by aquatic life– like habitat loss, lack of oxygen due to severe algal blooms, and invasive species – the addition of endocrine disruption can have a major impact on the health of the lakes, she added..

Scientists collect several fish species from the Chicago River’s north branch to analyze them for endocrine disrupting chemicals and biomarkers of endocrine disruption as part of a survey that included the Great Lakes and upper Mississippi River. Credit: Clifford P. Rice, US Department of Agriculture
Scientists collect several fish species from the Chicago River’s north branch to analyze them for endocrine disrupting chemicals and biomarkers of endocrine disruption as part of a survey that included the Great Lakes and upper Mississippi River. Credit: Clifford P. Rice, US Department of Agriculture

While there has been progress in cleaning up some endocrine disruptors from waterways, the governments still have work to do to achieve the “virtual elimination” of persistent toxic chemicals called for in the 2012 Great Lakes Water Quality Agreement

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Kevin Bunch

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.