Many are found in food, hair products and skincare products.
Kristina Marusic for Environmental Health
News
More than 900 chemicals commonly found in consumer products and the environment have been linked to breast cancer risk in a new study.
The study, published today in Environmental Health Perspectives,
identified 921 chemicals that increase the risk of breast cancer and found that
90% are ubiquitous in consumer products, food and drinks, pesticides,
medications and workplaces.
The list includes chemicals like parabens and phthalates,
which are commonly found in makeup, skin and hair care products; and numerous
pesticide ingredients, including malathion, atrazine and triclopyr, which are
used on food and in household pest control products in the U.S.
Breast cancer among young women has increased in recent years. Between 2010 and 2019, diagnoses among people 30 to 39 years old increased 19.4%, and among those ages 20 to 29, rates increased 5.3%. This change is too fast to be explained by genetics, so researchers have begun looking more closely at potential environmental causes for the disease.
A 2020 study found that women who used chemical hair
straighteners more than six times a year had about a 30% higher risk of breast cancer
than those who didn’t use chemical straighteners. Those products typically
contain one or more of the chemicals identified in the new study as increasing
the chances of getting breast cancer.
Women of color face greater risk. Studies have shown that
products marketed to women of color tend to be more toxic and
are more likely to contain chemicals associated with increased cancer risk
compared to products marketed to white women.
To conduct the new study, researchers at Silent Spring Institute,
a nonprofit breast cancer prevention research group, developed a new method to
quickly identify compounds that can increase the likelihood of the disease.
“We know there are lots of environmental chemicals that
can increase breast cancer risk, but we need more efficient and more effective
ways to identify them so they can be regulated and reduced,” Jennifer Kay, a
research scientist at Silent Spring Institute and lead author of the study,
told Environmental Health News (EHN).
Historically, regulators have used animal studies to determine whether chemicals cause mammary tumors in mice to assess whether they could increase breast cancer risk in humans, but these studies are slow and expensive.
In 2016, the International Agency for Research on Cancer (IARC)
published a landmark study outlining
10 ways that carcinogens cause cancer to develop. Since then, scientists and
regulators have begun working to identify chemicals that have those
characteristics as a quicker, less expensive way to determine whether exposure
to them is likely to increase cancer risk.
“What's unique about our approach is that we recognized
that breast carcinogens tend to increase hormonal activity,” Kay explained. “So
for this study, we looked at whether chemicals increase certain hormonal
activities that are known to increase breast cancer risk.”
Kay and her team looked specifically for chemicals that activate estrogen receptors in breast cells and for chemicals that cause cells to make more estrogen or progesterone, both known risk factors for breast cancer.
More than half of the chemicals on their list cause cells to make more
estrogen or progesterone and about a third activate the estrogen receptor. An
additional 278 of the chemicals on the list have previously been found to cause
mammary tumors in animal studies.
Kay noted that while there are tens of thousands of
chemicals used in commercial products in the U.S., they only had access to data
on whether chemicals interact with hormones from the U.S. Environmental
Protection Agency (EPA) for about 2,200 chemicals.
“If EPA was more comprehensive about screening chemicals
for potential hazards,” she said, “our list would likely be a lot longer.”
Children’s exposure and future breast cancer risks
Evidence also suggests that children’s exposure to these
chemicals during key developmental windows can increase their risk of
developing breast cancer later in life, and that these types of exposures can
even increase the odds of negative outcomes for multiple generations of
women.
Many of the chemicals listed in the new study are common
in products made for children. For example, many kids’ lotions and shampoos
include parabens and phthalates and the pesticide malathion is commonly used as
an ingredient in lice treatments for children.
“Kids getting exposed to these chemicals is particularly
concerning, because at younger ages kids are very vulnerable,” Kay said.
Avoiding cancer-causing chemicals
In the absence of meaningful regulations, numerous
nonprofit organizations have developed resources aimed at helping consumers
avoid chemicals that could raise their cancer risk, including Silent Spring
Institute’s Detox Me app,
the Anti-Cancer Lifestyle Program, the
Environmental Working Group’s Healthy Living App,
the MadeSafe database and Clearya.
Kay said she hopes that as a result of the study, this
method will be used to screen chemicals for other types of cancer risk and that
regulatory agencies like the EPA will use the research to more quickly identify
and regulate chemicals that could be hazardous.
“We have now found hundreds of chemicals that could
increase breast cancer risk,” she said. “We’re actively working on translating
this research for regulators, epidemiologists and cancer researchers so we can
all work together to advance breast cancer prevention.”
Kristina Marusic covers environmental
health and justice issues in Pittsburgh and Western Pennsylvania for
Environmental Health News. Her new book, "A New
War On Cancer: The Unlikely Heroes Revolutionizing Prevention,"
uncovers an emerging national movement to prevent cancer by reducing our
exposure to cancer-causing chemicals in our everyday lives.