Shedding Light on
Endocrine Disruptors
We are constantly exposed to chemicals called endocrine disruptors, particularly in plastics, but also in other products including pesticides, clothing, and cosmetics. They interfere with our hormones, critical chemicals that regulate brain chemistry, metabolism, and immune function. Hormones are particularly important during fetal development and puberty.
Even if you haven’t heard of endocrine disruptors as a group, you’re probably familiar with some individual examples.
The first to generate a public outcry was DDT, a widely used pesticide that was banned in the United States in 1972 because it interfered with the reproduction of birds. DES, a synthetic estrogen that was for a while prescribed to pregnant women, was banned in 1971 after it was linked to cervical cancer in their daughters, who were exposed to DES in the womb. More recently, you may have heard of bisphenol A or BPA, which was banned in baby bottles in 12 states during the 2010s.
But there must be other options, Chideya says. “I don’t like fatalism. That frustrates me.”
A physician and epidemiologist by training, Chideya is a program director at the National Centers for Complementary and Integrative Health (NCCIH), a branch of the National Institutes of Health (NIH). This followed previous career stops at the U.S. Centers for Disease Control and Apple.
disrupting the disruptors
The person who first tipped Gilbert off was Ana Soto of Tufts University. “She and Carlos [Sonnenschein, Soto’s scientific partner] kidnapped me at a scientific meeting,” Gilbert says with a chuckle. “They said, ‘We’re taking you to lunch. You need to hear what we have to say.’”
In 1987, a strange incident occurred in Soto’s lab. She was experimenting with human breast cells to try to understand what chemical signals cause them to proliferate in the presence of estrogen. But one year, all the breast cells in her lab started to divide, even the ones that were not supposed to have been exposed to estrogen.
A chemical called nonylphenol, used in detergents, was leaching from plastic containers into the blood supply for the cell cultures. A lightbulb went on in Soto’s head: If it could happen in her lab, it could happen anywhere.
Soon other biologists were having the same epiphany.
“That’s what I find so interesting about the origin stories,” Gilbert says. “They were not trying to find endocrine disruptors. Rather, the endocrine disruptors were anomalies in their normal research programs.”
“Tyrone Hayes [of the University of California—Berkeley] didn’t start off trying to show that atrazine was an endocrine disruptor. But he observed that it demasculinized frogs. Patricia Hunt [of Washington State University] didn’t try to find that BPA caused egg anomalies in mice. However, a technician washed mouse cages in a solution that released BPA and caused the mice to become sterile,” says Gilbert. For anyone who has read Thomas Kuhn’s Structure of Scientific Revolutions, it’s a familiar story: Paradigm shifts result from anomalies that can’t be explained by prevailing theories.
Natural androgens at low doses increase cell production in the prostate, but at high doses they inhibit it. This paradoxical behavior results from the fact that they are interfering with a complex communication system. The relationship between dose and effect is nonlinear, or “non-monotonic.” In a graph, it may be U-shaped or W-shaped.
There are other differences between endocrine disruptors and traditional poisons. As Heather Patisaul of NIH said at Chideya’s workshop, for endocrine disruptors, “the timing makes the poison.” A rat exposed to BPA as a fetus will have abnormal mammary tissue for the rest of its life, which can lead to cancer in adulthood.
Another difference is that animals and humans are likely to be exposed to poisons one at a time. Not so with endocrine disruptors; we are exposed to a cocktail of them every time we eat with plastic utensils, or apply makeup, or cook on a nonstick frying pan.
The U.S. regulatory system has not adapted to the new paradigm, remaining organized around the old convention that harm is dose-related. The U.S. Food and Drug Administration, in its most recent study of BPA, used conventional toxicology standards to conclude that the effects “were not dose-responsive,” “did not demonstrate a clear pattern of consistent responses,” and “do not suggest a plausible hazard of BPA exposure in the lower end of the dose range tested.” Soto, who runs one of the 10 academic labs that participated in the study, calls the FDA interpretation of the results “disingenuous.”
The academic labs, using methods that were more sensitive to developmental abnormalities, did find consistent, albeit non-monotonic, effects of BPA. “All that’s needed is appropriate statistics,” Soto says.
According to Soto, a better model for regulation is the one recently adopted in Europe that is “hazard-based” rather than “risk-based.” In a risk-based assessment, you try to determine a safe level of exposure based on a dose-response curve. In a hazard-based assessment, you eliminate the hazard, regardless of the level of exposure. For example, Soto said, “a new French law dictates that starting in 2025, the use of plastics is banned in school cafeterias, from kindergarten to university. Because plastics contain various known endocrine disruptors, plus thousands of chemicals that have yet to be tested for biological activity, banning plastics from cafeterias is a good way to curtail exposure to a large number of chemicals.”
Last summer, Chideya organized a first-of-its-kind workshop at NIH on the scientific evidence for actions that ordinary people can take to reduce the impact of endocrine disruptors even after they have been exposed to them (as we all have). More than 1,100 people registered for the hybrid Zoom and in-person workshop.
Fighting endocrine disruptors with education is high on Chideya’s agenda.
“There are two populations we should focus on,” she says. “One is young children before puberty, so they can start adulthood with a cleaner slate. The other is people in their early 20s and 30s who are likely to have children.”
Kids Teaching Kids
“Our goal is to help them recognize that eating a burger is not just about the food content, but also ingesting chemicals from the packaging,” says Howarth. “Also, we try to help them make better choices around personal care products.”
Howarth, like Chideya, has made multiple stops in her public health odyssey. After graduating from Swarthmore and medical school, she worked at the CDC and the N.J. Department of Health before settling down at Penn.
“I loved occupational and environmental health,” says Howarth. “That was my niche.”
At Penn’s Center of Excellence in Environmental Toxicology, she organized a summer research program in biology for high school students, which ultimately sent three of them (Arianne Wenk ’14, Ariel Parker ’15, and Hayden Dahmm ’15) to Swarthmore.
As deputy director of the new Philadelphia Regional Center for Children’s Environmental Health, Howarth has started a new and even more focused training program for high school students — focused, first, in its clientele.
“We accept preferentially students from high schools in Philadelphia that are located in ‘environmental justice’ neighborhoods,” Howarth says. “We’re aware that programs that accept the most qualified students on paper may exclude students who haven’t had as many opportunities.”
The eight-week spring program, called the Academy for Environmental Exposure Reduction, is also focused in its subject matter.
“We designed it specifically around endocrine disruptors,” Howarth says. “We thought it was very important for students to think about the impacts of these substances on their endocrine organs, their fertility, their thyroids. It is particularly relevant for people who are still growing and developing, and will soon be thinking about becoming parents.”
The course covers a lot of material in eight weeks. What is an endocrine disruptor? What is the endocrine system? What does the alphabet soup of chemical names mean?
“Then we make it more personal,” Howarth says. “We talk about food packaging and personal care and how they can protect themselves.”
practical ways to reduce plastics
- Don’t mix plastics with things you eat or drink. This includes bottles, plastic wrap, and containers — especially if you’re heating things up. Plastics often contain EDCs that can leach into the things they touch. Glass, ceramics, stainless steel and silicone are safer options.
- As much as possible, keep children and adolescents away from plastics — toys, teethers, water bottles, artificial turf, etc.Childhood and adolescence are especially vulnerable times as far as body and brain development, and hormones play key roles in these processes.
- Many commercial pesticides and herbicides are EDCs. Choose organic foods (including fruits, veggies, dairy and meat), if you can afford and access them. Don’t feel guilty if you can’t. Do they best you can. If you have to prioritize, focus on organic dairy and fruits and veggies with edible skins.
- Many personal care products — shampoos, soaps, lotions, dental floss, makeup, hair products — have EDCs. Look for ones without artificial fragrances and colors, or say that they don’t contain parabens, phthalates or PFAS. A good resource: www.ewg.org/skindeep/
- Eat fermented, probiotic foods (kraut, pickles, miso, yogurt, kombucha, etc.) and prebiotic foods every day. The commensal gut bacteria in a healthy microbiome play a critical role in detoxifying, metabolizing and clearing many EDCs, including some heavy metals.
In two years, 25 students have participated in the program.
“We’ve gotten very positive feedback about empowerment,” Howarth says. “For some of the students, it was their first chance to see a laboratory. For others, it was their first time ever on a college campus. I think that was a growth opportunity, seeing themselves on a college campus and seeing themselves in the midst of science.”
Collective Action, Individual Actions
Hormis Bedolla of Alianza Nacional de Campesinas, who has worked for 20 years picking apples, presented on how basic precautions are not followed in commercial agriculture. Workers receive little to no training on how to apply pesticides, or they get trained after they have already started using them, or they simply sign a paper saying they have been trained. Chemicals being sprayed directly on the skin is a common occurrence, Bedolla says.
Inspections by the U.S. Environmental Protection Agency are prearranged, not random. Many farmworkers are afraid to complain because they fear deportation.
“They desperately want to find solutions to the problems they and their families are experiencing,” says Chideya. “Many are running out of hope.”
One message repeated frequently at the workshop was that consumers have power. In some areas, consumers have already made a difference. Retailers like Target and Walmart sell containers labeled “BPA-free” — not because they are required to by law, but because of public outcry.
In addition, when buying food, consumers can choose items labeled organic. Although an organic label is not a panacea, buying organic still has the potential to benefit consumers as well as farmworkers. Diana Roopchand, a food scientist at Rutgers University, presented a study showing that after seven days of an organic diet, levels of pesticide byproducts in participants’ blood dropped by 60% to 95%.
There are other common-sense measures people can take even if they can’t reduce their exposure to endocrine disruptors.
“In terms of lifestyle, we had a great talk showing that the more physically active people are, the lower the levels of PFAS they had,” Chideya says.
The reason is not clear, but it’s possible that sweating flushes the chemicals from the body more rapidly.
On the dietary side, researchers shared compelling data about the mitigating effects of eating fiber and flavonoid-rich foods, taking folate (vitamin B9) supplements, and consuming probiotics to leverage the microbiome. Microorganisms are especially proficient at sequestering heavy metals, which also can act as endocrine disruptors.
“Metals are just as toxic to microbes as to us, but they have a much longer history of dealing with them,” says Jordan Bisanz, assistant professor of biochemistry and molecular biology at the Pennsylvania State University’s Eberly College of Science.
One missing ingredient is testing for BPA and other endocrine disruptors, so people — and their doctors — don’t have to fly blind. Some mail-in tests are already available, but Chideya says do your homework first.
“People should be very cautious about unregulated, unvalidated over-the-counter tests,” she says. “It’s similar to COVID-19, when lots of mail-order tests flooded the market and a bunch were not accurate. Neither a false sense of security nor alarm is helpful. There is definitely a need for [tests], but there needs to be third-party validation.”
The NIH workshop was the first of what Chideya hopes will be an ongoing dialogue with the research community, clinicians, and the public about reducing the morbidity and mortality associated with endocrine disruptors. She would like to see that dialogue at Swarthmore, too. “I would love the Swarthmore community, because it’s doing so much in terms of climate change and being responsible citizens of the world, to think about how to reduce exposure and the risk of harm to its students, faculty, and staff,” Chideya says.