Our Understanding of Endocrine-Disrupting Chemicals
Gaining knowledge of endocrine-disrupting chemicals (EDCs) and their impacts on our health—“What needs to be tested?” and “Which regulations will protect us?”—is a evolving process that started decades ago.
The 1962 book Silent Spring, Rachel Carson’s seminal examination of the effects of pesticides and chemical sprays, set the stage for the modern environmental movement. Yet the groundwork for concerns about EDCs was laid four years earlier. In 1958, endocrinologist Roy Hertz proposed that certain chemicals found in feedlots could find their way into the human body and mimic hormone activity.
Throughout the 1960s, researchers began to notice strange reproductive patterns in wildlife across the United States. Policymakers responded, founding the National Institute of Environmental Health Sciences (NIEHS) in 1969 and the Environmental Protection Agency (EPA) in 1970.
In the early 1970s, the tragic health impacts of diethylstilbestrol (DES), an estrogen-based drug that was thought to prevent miscarriage, introduced the possibility of hormone disruption as a threat to human health and development that sparked intensive study of estrogens in the environment.
In 1991, a Wingspread conference brought together experts from ecology to biology to toxicology, who reached consensus that environmental chemicals could interfere with the endocrine system in humans and animals with long-term consequences. The meeting codified the concept of endocrine disruption.
In 1996, the EPA assembled its own task force, the Endocrine Disruption Screening and Testing Advisory Committee (EDSTAC), comprised of representatives from industry, government, environmental and public health groups, worker safety groups, and academia. As EDSTAC worked to develop a scientific screening program to guide regulatory decisions on the endocrine effects of chemicals, the US government released its first requests for applications for EDC research.
In 1998, the NIEHS/EPA Children’s Environmental Health and Disease Prevention Research Centers began studying individual, regional, national, and global environmental exposures and the effects on children’s health.
The World Health Organization (WHO) released its Global Assessment of the State of the Science of Endocrine Disruptors in 2002. It examined animal and human case studies—including studies of the reproductive, neurobehavioral, and immune systems as well as cancer—and proposed a framework for assessing endocrine disruptors. In 2012, the WHO updated these assessments (see below).
In 2009, the Endocrine Society released its first scientific statement on EDCs, presenting evidence-based prespectives and identifying areas requiring additional research. This was a landmark, comprehensive review of EDC research whose key points included:
“The evidence for adverse reproductive outcomes (infertility, cancers, malformations) from exposure to endocrine-disrupting chemicals is strong, and there is mounting evidence for effects on other endocrine systems, including thyroid, neuroendocrine, obesity and metabolism, and insulin and glucose homeostasis.”
“Effects of endocrine-disrupting chemicals may be transmitted to further generations through germline epigenetic modifications or from continued exposure of offspring to the environmental insult.”
Effects shown in animals may also occur in humans, due to the similarities of endocrine systems across species.
Effects on early development are a special concern, as these effects are often irreversible.
The effects may not become evident until later in life.
During this time, the Endocrine Society continued to explain how science supports policy decisions. In 2015, the Society published it's own update in the second EDC scientific statement, which comprehensively reviewed what is known about EDCs and what gaps still exist.
As more research reported the negative effects of chemicals that interfere with hormone action, more medical and scientific societies voiced concern over EDCs. The American Medical Association called for improved oversight (2009), the American Public Health Association called for “a precautionary approach to reducing American exposure,” (2010) and the American Chemical Society recommended expanded education and research, updated testing protocols, and the development of safer EDC alternatives (2012–2015).
These calls to action have yielded practical tools for identifying EDCs, new testing methods, and greater collaboration among scientists tackling this vast problem.