*[Enwl-eng] Breast Cancer Tied to Environmental Exposures

[ENWLine]

*Breast cancer ties to environment probed*

Stephanie M. Lee
Updated 5:41 pm, Tuesday, February 26, 2013

Marika Holmgren will never be sure why she was diagnosed with breast
cancer at 37. She was a devoted athlete and vegetarian. Cancer ran in
her family, but not breast cancer.

Six years and many rounds of chemotherapy and surgeries later, Holmgren
has for now won the battle. But she still wonders why the battle even began.

Could it have been the chemicals in the blush and lipstick she once wore
daily? Did it matter that she lives in Half Moon Bay, where breast
cancer rates exceed the state average?

"When I got diagnosed, I really started to understand how many women
were out there with very few risk factors, including myself," she said.
"It makes us start to wonder, what can we be doing to lower those
numbers and increase prevention and eradicate environmental risk factors?"

Breast cancer has many possible causes, but genetic risk factors are
estimated to explain at most 27 percent of cases. A large chunk of the
rest, experts say, is likely related to the environment. Polluted air
and water, toxic chemicals in products, and socioeconomic conditions
such as someone's hometown can all play a role.

But because the environment is so complex, it's difficult to ferret out
precisely which factor - or factors - lead to breast cancer, which is
both the most common cancer and the leading cause of cancer deaths among
women worldwide.

"There's not one smoking gun," said Jeanne Rizzo, president of the
Breast Cancer Fund in San Francisco.

Rizzo was an expert on a federal advisory panel that said this month
that more research should focus on understanding the link between breast
cancer and the environment.

The panel noted that just 10 percent of recent breast cancer research
funded by the National Institutes of Health and the U.S. Department of
Defense - the two federal agencies that spend the most on breast cancer
- focuses on environmental health.

While much remains unknown about the relationship between the disease
and the environment, scientists nationwide and in the Bay Area have made
inroads into understanding the toxicity of factors such as pesticides,
income and immigration status.

And they've looked at how those factors affect the mammary gland at
different stages of life, including puberty and menopause. Human and
animal studies suggest that breast cancer may, in some cases, stem from
exposure to an environmental carcinogen as far back as the womb.

"We wouldn't want to suggest that the environment is the most important
cause or is the only cause of breast cancer. But it's a very
understudied cause and it's also the one that points toward prevention,"
said Dr. Megan Schwarzman, a research scientist at UC Berkeley's School
of Public Health.

"If we can understand what chemicals are raising the risk of breast
cancer, that's a place where we can prevent the disease," Schwarzman
said. "How much better is that than trying to treat it after the fact?"

With the Natural Resources Defense Council, an environmental action
nonprofit in San Francisco, Schwarzman directed a yearlong research
effort called the Breast Cancer and Chemicals Policy Project. In 2010,
scientists with the project recommended ways that companies could
evaluate the chemicals they produce for their risk of causing breast cancer.

They said that chemicals should be checked, for instance, to see if they
are endocrine disruptors. These disturb the endocrine system's function
in a way that may promote the formation and growth of cancer cells.
Bisphenol-A, a building block of hard plastics, is one such compound.

Chemicals can wreak havoc in a woman years after she is exposed to them,
making it hard to pinpoint blame, Schwarzman said.

"It may not be that the chemical comes in and mutates DNA and develops
into a tumor," she said.

"It may be that a developing fetus exposed in the womb has altered
breast development that predisposes that tissue to cancer later in life."

Toxic substances are stirring public health concerns and legislative
debate. Pending in Congress is the Safe Chemicals Act, a bill that would
update the nation's 1976 regulations of industrial chemicals.

Generational effects

Even if some dangerous compounds end up being banned, Barbara Cohn, at
the Public Health Institute in Berkeley, has found that they can affect
women's bodies for decades after they are outlawed.

Cohn is studying more than 15,000 Bay Area mothers and their offspring
who are enrolled in the Child Health and Development Studies, a project
that launched in 1959.

For more than 50 years, researchers have tracked the women and their
blood samples.

This cross-generational data has led to hundreds of studies on the
long-term effects of environmental and lifestyle factors on pregnancy,
birth weight, infant mortality and diseases.

About 10,000 women who were once young daughters of the first study
participants now have daughters and granddaughters of their own. And 110
of those 10,000 have developed breast cancer, Cohn said.

"Every pregnant woman has chemicals in their bodies," Cohn said. "The
question is, do some combinations of them, and some mothers in
combination with the chemicals, produce a situation that means the
daughters are at risk?"

DDT and cancer

One chemical that Cohn has connected to the disease is DDT, an
insecticide that was once ubiquitous but was banned in the United States
in the 1970s due to its likely carcinogenicity.

In a 2007 study, Cohn found that women who had high levels of DDT and
went through adolescence starting in the mid-1940s, when the pesticide
came into widespread use, had a five-fold increased risk of developing
breast cancer as adults.

As the women in the Child Health and Development Studies project
continue to grow and bear children, researchers plan to parse their
blood for signs of newer toxicants, such as flame retardants, which
started appearing in furniture in the mid-1970s.

"The fourth generation is not exposed to what the original pregnant
woman was exposed to," Cohn said, "but a whole slew of other things that
may influence risk down the road."

Hometown risk

Just as it was difficult to avoid breathing in pesticides in the 1950s,
it's hard to change basic facts of life that can have a hand in breast
cancer - such as the place where one lives.

Marin County, for example, has one of the highest rates of the disease
in the world, and scientists believe this has to do with some factor
other than the land itself.

Birthplace may also make a difference. A Chinese American woman born
stateside has greater odds of developing breast cancer than a woman who
is born in China and immigrates to the United States.

The longer these women spend in the United States, the more their breast
cancer rates resemble or even exceed those of non-Hispanic white women.

That was the conclusion of Scarlett Gomez, a research scientist at the
Cancer Prevention Institute of California in Fremont, who examined data
from cases from 1998 to 2004.

"Some of it can certainly be explained by the increased uptick of
Westernization among some Asian groups," she said. "They come here,
start eating more Americanized food and higher-fat diets."

Early puberty in girls

One great concern to researchers is that the age at which puberty begins
has been steadily dropping, which is thought to be a major risk factor
in breast cancer. At ages 7 and 8, some girls are already starting to
develop breasts and pubic hair.

"That's new, and it has to mean there's some change in the environment,"
said Dr. Robert Hiatt, chair of UCSF's Department of Epidemiology and
Biostatistics.

Hiatt is co-leading a six-year study in the Bay Area, along with
researchers in Cincinnati and New York City, of a total of 1,200 girls
and their blood, genetics, diet, physical activity, chemical exposure
and socioeconomic status.

He has found that breathing in secondhand tobacco smoke can lower the
age of puberty onset. He's also found, in a yet-to-be-published paper,
that growing up in a low-income household somehow correlates with
earlier puberty.

Hiatt is still working on explaining why. Marika Holmgren and other
cancer patients will be among the many interested in learning the answers.

"People can't change genetics, but we can change the environment,"
Holmgren said.

"And if we can start to advocate for changes so other women of the next
generation don't have to go through this, that to me is a no-brainer."

Stephanie M. Lee is a San Francisco Chronicle staff writer. E-mail:
sl...@sfchronicle.com Twitter: @stephaniemlee




http://www.sfgate.com/bayarea/article/Breast-cancer-ties-to-environment-probed-4310594.php


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