Of those chemicals, 219 had not been previously identified as potential carcinogens, Ruthann Rudel, director of research for the Silent Spring Institute and co-author of the new study, told EHN. The findings come in a study out this week in Environmental Health Perspectives.
While scientists have known for decades that higher levels of estrogen and progesterone are linked to breast cancer, experts say that safety screening to test U.S. consumer products rarely looks at how chemicals affect the production of those hormones.
"The way that chemicals are tested now, they are really missing breast-related effects," said Rudel. "We have to do a much better job checking for these effects when we test chemicals."
Environmental chemicals and hormone production
A postdoctoral fellow in the National Cancer Institute's Experimental Immunology Branch, pipetting DNA samples into a tube. (Credit: National Cancer Institute)
Scientists have historically used animal studies to understand whether chemicals pose a threat to humans. Animal studies take time and money, though, leading researchers and regulators to increasingly use high-throughput tests to more quickly screen chemicals for hormone disruption and other potentially disease-inducing effects. With these high-throughput tests, researchers expose cells and other molecules to chemicals to see whether they trigger any changes.
Researchers from the Silent Spring Institute, a non-profit that studies the environmental causes of breast cancer, decided to look through 2018 EPA ToxCast safety data on roughly 1,800 chemicals to see how many caused cells to increase estrogen and progesterone.
Laura Vandenberg, associate professor of environmental health sciences at the University of Massachusetts Amherst who was not involved in the study, told EHN that one of the characteristics toxicologists commonly look for is whether a chemical mimics estrogen. To date, though, there has been little focus on whether chemicals could actually cause cells to produce more estrogen or progesterone.
Related: Pesticide DDT linked to increased breast cancer risk generations after exposure
Rudel and a colleague found that 296 chemicals increased one or both of the hormones. Some of the hormone-increasing chemicals include the pesticide atrazine, the fungicide imazalil, and hair dye ingredient 1-4, benzenediamine. Vandenberg said she was disturbed but not shocked to see that so many of these chemicals increase hormone production in cells as "many of these chemicals (like pesticides) were designed to be biologically active."
The Silent Spring researchers then looked through carcinogen and reproductive toxicity databases, like California's Prop 65 list, to see which of these chemicals were already on those lists. The researchers found that roughly a third had been identified as carcinogenic, toxic to development and reproduction, or both. But they also found that many of the chemicals on their list "hadn't been tested or evaluated," for impacts to those systems, Rudel said.
Scientists have known for some time now that estrogen and progesterone contribute to breast cancer because both hormones stimulate breast cell growth, increasing the risk of uncontrolled cell growth and DNA damage. Around 70% of breast cancer cases respond to these hormones, and treatment for this disease commonly involves using drugs that inhibit estrogen.
"What we know is that a woman's own production of estrogen is actually one of the biggest risk factors for breast cancer," Vandenberg said, adding that early puberty and delayed menopause, which give the body more time to produce estrogen, have been linked to higher rates of breast cancer.
Women’s health focus
"My worry is that women's health always gets sort of short shrift," University of Massachusetts Amherst researcher Laura Vandenberg told EHN. (Credit: Vonecia Carswell/Unsplash)
Rudel said that their list of hormone-increasing chemicals provides a good starting point for both toxicity and human exposure research. "There hasn't been a super systematic approach to what chemicals should be studied in breast cancer (epidemiological) studies," she added.
The researchers also found that even for chemicals that had been previously scrutinized, past risk often didn't look at or dismissed mammary gland impacts. For example, although a multi-generational toxicology study showed that exposure to dichlorophenol, a chemical in some pesticides and disinfectants, stiffened and whitened breast tissue in all doses, the authors of that study didn't take those effects into consideration when determining what a safe dose of that chemical is.
And a lot of the animal tests used by regulators only look at a couple of the hundreds of ducts in the mammary gland, which is "treated as sufficient—and it's not," Vandenberg said.
"My worry is that women's health always gets sort of short shrift, and there's a little bit of an attitude of breast cancer as a disease of the old, and therefore, it's not a priority for regulatory agencies," she said, stressing that no one at those agencies had actually said that.
How to limit your chemical exposure
Researchers also don't have a great sense of how we're exposed to many of the chemicals on the list, Rudel added.
Silent Spring has a mobile app, Detox Me, that allows people to scan consumer product barcodes and other features to try to minimize their exposure to toxic chemicals.
Banner photo: Woman performing a breast self-examination. (Credit: National Cancer Institute)
But evidence is mounting that another facet of contemporary life—routine exposure to endocrine-disrupting chemicals—could be worsening the diabetes epidemic. In a review article out last month in Advances in Pharmacology, researchers say it's vital that doctors and policymakers take environmental health into account as they seek to stem the global rise in diabetes.
"We often attribute patient's disease risk to individual choices, and we don't necessarily think about how systems and environments play into disease risk," Dr. Robert Sargis, lead author and an endocrinologist at the University of Illinois at Chicago, told EHN.
The new review article surveyed more than 200 animal, cell, clinical, and epidemiological studies, finding that exposure to endocrine disruptors is a "novel but under-appreciated" diabetes risk factor.
Global uptick in diabetes
Diabetes has been on the rise globally — in 1980, 108 million people around the world had diabetes; now, more than 420 million people have the disease, according to the World Health Organization. While type 1 diabetes is an autoimmune disease that occurs when our bodies don't produce enough insulin, more common type 2 diabetes occurs when we develop resistance to insulin, a hormone produced by the pancreas that helps us convert sugar into energy.
Obesity, which has tripled around the world since 1975, is a main risk factor in developing type 2 diabetes.
Dr. Carolina Solis-Herrera, assistant professor of Medicine in the Division of Diabetes at the University of Texas Health at San Antonio, told EHN that family history is another risk. "If one of your parents has type 2 diabetes, your risk of developing diabetes over time is about 30 percent," she said. "And if both of your parents have type 2 diabetes, your risk can go up to 60 percent." Other conditions — like heart disease, high cholesterol, hypertension and polycystic ovary syndrome — can also put someone more at risk for developing diabetes.
The authors of the new review say that while calorie-rich diets, lack of exercise, sleeping issues, and genetic risk factors clearly play a major role in the diabetes epidemic, those factors fail to fully account for "the dramatic rise and spread" of diabetes.
How endocrine disruptors contribute to diabetes
Over the past couple of decades, researchers have examined what role endocrine disruptors —chemicals that impact our bodies' hormone making system — have on diabetes. We come in contact with endocrine disruptors in items like receipts, contaminated food, and cosmetics, as well as by breathing in air pollution. Researchers have found, according to Sargis, that certain endocrine disruptors such as PCBs, arsenic, and DDT can impair our ability to make insulin, make us more insulin-resistant, and, in some cases, do both. Some endocrine disruptors, like BPA, have also been linked to obesity.
Dr. Ángel Nadal Navajas, a professor of physiology at the Miguel Hernandez University of Elche in Spain who was not involved with the study, told EHN endocrine disruptors alone don't cause diabetes "but exposure to endocrine disruptors increases (one's) probability of developing type two diabetes. It's one more factor, and for some people, it's going to be a major factor."
There have been extensive human studies linking BPA, a compound used in plastics and canned food lines that mimics estrogen hormones, to diabetes. "I don't think there is any doubt the connection is there," said Nadal Navajas.
There have also been epidemiological studies showing associations between diabetes and exposure to arsenic, organochlorine pesticides, air pollution, and other endocrine disruptors, according to the review. While some of endocrine disruptors looked at, like DDT, have been banned, they don't break down readily in the environment or in our bodies. The authors call for more research into how endocrine disruptors could affect type 1 and gestational diabetes, which occurs when glucose levels rise during pregnancy and puts both mother and child at a greater risk for type 2 diabetes.
In the U.S., Indigenous, Latinx, and Black people have a greater risk of developing diabetes, and of suffering complications from the disease. Some of these populations are also exposed to more to endocrine disruptors from air pollution and other sources because of where they live and what they do for work.
While this disproportionate exposure could be contributing to the higher levels of diabetes in these communities, it's difficult to tease out the link "because people who are exposed to endocrine-disrupting chemicals are also probably the same ones who have limited access to healthy food and limited access to health care," Dr. Lisa Goldman Rosas, an assistant professor of epidemiology and population health at Stanford University, told EHN.
Environmental health training and oversight
With new chemicals coming out all the time with limited federal oversight, Sargis and Nadal Navajas both said we need to come up with better ways to test chemical safety en masse. Europe has already started doing that with a recent project to develop better ways to test the hormone-disrupting effects of new chemicals before they come onto the market.
In the meantime, doctors, and the medical schools that train them, need to better take into account environmental health components that could put patients at risk for developing diabetes, or influence their disease trajectory, said Sargis.
"We (tend to) approach medicine as a one-on-one relationship with the patient and the physician, and that sort of neglects these external factors," he said, adding that this was in part because physicians have limited environmental health training.
Banner photo credit: National Human Genome Research Institute
The declaration, signed by more than 30 local organizations and 25 individuals so far, explains that rates of several kinds of cancer are "strikingly high" in the region—higher than state and national rates—with disproportionate burdens on people of color and marginalized communities. It calls on leaders across a diverse range of sectors—local businesses and elected officials, foundations and nonprofits, research institutions and health care facilities—to take concrete actions aimed at reducing people's exposure to cancer-causing chemicals in the region.
"We all know someone who has been affected by cancer, whether it's an immediate family member or a partner's cousin or a friend," Alyssa Lyon, a co-author of the declaration and director of the Black Environmental Collective, an environmental and racial equity advocacy group, told EHN. "This is an issue that permeates everyone's communities and sits right at the intersection of equity and environmental justice."
While there are local initiatives aimed at reducing smoking and promoting healthy lifestyles, the declaration's authors note other factors play a role in cancer rates. A recent study estimated that even if everyone in Allegheny County (which encompasses Pittsburgh) had quit smoking 20 years ago, lung cancer rates would only be 11 percent lower—due in part to the region's long-standing problems with carcinogenic pollution in air and water.
The group that authored the declaration, the Cancer & Environment Network of Southwestern Pennsylvania, grew out of a national symposium on cancer and the environment hosted in Pittsburgh in 2019.
"I've never experienced anything quite like what happened at the end of that symposium," Dani Wilson, executive director of Our Clubhouse, a Pittsburgh-based cancer patient support organization, told EHN. "After learning what we did, no one there wanted to just walk away."
Two years and one pandemic later, the group is calling for "bold action on a cancer prevention strategy that is often overlooked: reducing environmental chemicals that are put into our air, water, food, homes, workplaces, and products," according to the declaration.
"We want this to be transformational—not just a promise toward a better future, but an actual blueprint for a way forward," Lyon said. "If everyone does their own small part, we can collectively create big changes."
“Unnecessary” exposures to cancer-causing toxics
The declaration states that residents of southwestern Pennsylvania are "exposed unnecessarily to environmental carcinogens," and explains that while exposure to any one pollutant may only pose a small increased risk of cancer for an individual, widespread exposures can result in a significant rise of cancer cases in the region.
Among those exposures they list:
- Air pollution, pointing to research showing that 96 percent of counties nationwide have lower cancer risks from hazardous air pollutants than Allegheny County.
- Emissions from oil and gas wells, which have been shown to increase rates of childhood leukemia
- Carcinogens, such as bromodichloromethane and Hexavalent chromium, in the region's drinking water
- Radon, which is the second leading cause of lung cancer in the U.S. behind smoking and is ubiquitous in Pennsylvania
- Carcinogens in consumer products like cosmetics, furniture, building materials, and home and garden pest control products
"These issues didn't just go away during the pandemic," Olivia Benson, chief operating officer for the Forbes Funds, a foundation that supports southwestern Pennsylvania nonprofits, told EHN. "We know these types of environmental exposures disproportionately affect marginalized people and people of color."
The Forbes Funds signed onto the declaration, but Benson signed as an individual, too. Her grandmother and an aunt who lived in southwestern Pennsylvania died "too young" as a result of breast cancer and ovarian cancer, respectively. She pointed to research showing that Black women in southwestern Pennsylvania have some of the highest mortality rates in the country.
"I can't help but wonder, if environmental justice and racial equity were centered here...would they still be here today?"
Following the science on cancer
The declaration references 15 scientific studies, and the group also published a companion document with more in-depth science.
"Everything in the declaration is driven by science," Polly Hoppin, one of the researchers who helped organize the 2019 symposium on cancer and the environment that spurred the creation of the Cancer and Environment Network of Southwestern Pennsylvania, told EHN. Hoppin is a former Senior Advisor at the U.S. Department of Health and Human Services and Environmental Protection Agency and the program director at the Lowell Center for Sustainable Production at the University of Massachusetts. She also serves as a facilitator for the Network.
In the science document, the authors used data from the National Cancer Institute's cancer registry to describe national trends in cancer rates and show how locally cancer rates generally mirror national trends, but several cancer types associated with environmental exposures are higher than state and national rates.
These include elevations in lung cancer, leukemias, and thyroid cancer across multiple counties in the region (although not always in both males and females), and elevated rates of childhood cancers in Greene County, Washington County, and Westmoreland counties.
The document points to research showing that among the more than 200 air pollutants detected in emissions from oil and gas wells, nearly two dozen are considered known or suspected carcinogens (an investigation into the cause of numerous cases of rare childhood cancers in the region is ongoing).
Polly Hoppin at the 2019 cancer and environment symposium. (Credit: Kristina Marusic for EHN)
The science companion document also delves into the most recent science on the ways exposure to air pollution, water pollution, pesticides, and carcinogens in consumer products can cause cancer to develop, then reviews the specific exposures happening in southwestern Pennsylvania.
For example, it references data from the U.S. Environmental Protection Agency's National Air Toxics Assessment showing that Allegheny is in the worst 4 percent of counties in the nation for cancer risk from all forms of toxic air pollution (including traffic and industrial emissions), and in the worst 1 percent of counties nationwide for cancer risk specifically from air pollution caused by industrial manufacturing—and notes that nearly 90 percent of those emissions come from U.S. Steel's Clairton Coke Works facility.
In a discussion about the region's drinking water, the science companion document points to research showing that public drinking utilities in Pittsburgh and its suburbs frequently report potentially dangerous levels of suspected carcinogens like bromodichloromethane, hexavalent chromium and chloroform. In rural parts of the state, there have been more than 300 confirmed cases of private drinking water wells being contaminated by the oil and gas industry.
Because these issues are so widespread and come from such diverse sources, Benson said, no single group can tackle the problem on their own.
"This is a problem that requires system-level change to address," she said.
Finding solutions to the pollution
The declaration lays out a series of priorities for diverse groups, including:
- Speak up about exposures to carcinogens, and mobilize community institutions—including childcare centers, schools, businesses and places of worship—to take their own steps to reduce pollution and create healthy environment (for community leaders)
- Protect workers and fence-line communities from exposure to toxic chemicals used and released in manufacturing by implementing state-of-the-art operations that reduce pollution and preserve resources (for businesses)
- Enforce laws and regulations and issue substantial and escalating fines to companies that repeatedly violate regulations and pollute the food we eat, the air we breathe and the water we drink (for public officials)
- Advocate for health care institutions—for example via procurement policies—to purchase safer products and specify healthy building materials for construction and renovation (for health care professionals)
- Hold government decision makers accountable for implementing and enforcing policies that protect public health and increase reliance on safer alternatives over time (for environmental and public health advocates)
- Encourage collaboration across sectors and systems approaches to catalyze change at the scale needed (for philanthropic organizations)
- Prioritize research and development to meet necessary societal needs with materials, technologies and chemistries that do not contribute to cancers and other health problems (for research institutions)
The authors believe southwestern Pennsylvania is uniquely positioned to make meaningful changes to reduce local cancer rates because of the region's high volume of research institutions, healthcare facilities, and effective nonprofit organizations.
Lyon noted that Pittsburgh is among the top metropolitan areas in the U.S. for both number of charitable foundations and per capita investment by foundations.
"Pittsburgh is so small that means we all have one degree of separation from the top person at a foundation," she said. "That means we can afford to put all the right minds in a room together and figure out what equity for everyone in the city really looks like."
Banner photo: 2019 cancer and environment symposium. (Credit: Kristina Marusic for EHN)