NYTimes.com Article: Looking for the Link

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Looking for the Link

August 11, 2002

By GINA KOLATA

DR. DEBORAH WINN has had breast cancer herself, so when she

speaks to women who have just received the dread diagnosis,

she understands the nagging question: Why did this happen

to me? Many people suspect environmental pollutants like

pesticides, for instance, or car exhaust. But Dr. Winn,

head of the extramural epidemiology program at the National

Cancer Institute, which conducts studies to look for

environmental causes of cancer, does not tell women that

pollutants are the cause.

" Usually, I tell them that there are a lot of factors that

combine - it's a multistep process, " Dr. Winn said. " There

is no one thing. Many aspects of your reproduction are

involved. It may have something to do with your genes and

in how you repair damage, how you metabolize estrogen. "

Dr. Winn, like many other scientists, said that the quest

for environmental causes of cancer - from chemicals in the

water to electromagnetic fields near power lines to

radiation from a cellphone - may be more daunting than the

public realizes. Conclusive evidence that any of these

things increase one's risk of cancer has never been found,

despite repeated studies. And even if there is a link,

several experts said, it may be beyond the capacity of

science to find it.

Still, the drive to blame something other than chance is a

strong one, and the issue arose again last week when a

long-awaited study of breast cancer on Long Island did not

find evidence that certain pesticides, exhaust fumes, or

cigarette smoke were linked to cancer. The $8 million

study, which was financed by Dr. Winn's group at the

National Cancer Institute, came into being because local

advocates had pressured Congress to approve it. When

earlier studies found that breast cancer rates in Nassau

and Suffolk counties on Long Island were about 3 percent

higher than the national average, advocates were certain

that this new study would find a smoking gun in the

environment.

Instead, scientists said, the investigation raised

questions about what sort of assurances research like this

can really provide.

Geri Barish, the president of 1 in 9: The Long Island

Breast Cancer Action Coalition, said that she knows that

the pollutants studied are dangerous - they cause cancer in

laboratory animals, she said. " How could they absolutely

say that a known carcinogen is not absolutely involved in

the cause of cancer? " she asked.

DR. WINN points to the study, which examined blood and

urine from more than 3,000 Long Island women for evidence

of exposure to DDT, PCB's, chlordanes or chemicals from

cigarette smoke. The scientists also looked at carpet dust,

tap water and yard soil for evidence that the chemicals

were in the women's environment. But those who got breast

cancer were no more likely to have been exposed to the

chemicals than those who didn't.

The data, she said, " were very, very conclusive. "

The

chemicals that were examined were thought to be plausible

culprits - largely because they could cause cancer in mice.

Still, Dr. Winn said, " In the study, it is clear that they

are not associated with breast cancer. "

The one tentative link was a very modest increase in risk

from exposure to polycyclic aromatic hydrocarbons,

chemicals that are in grilled food and in cigarette smoke.

But Marilie D. Gammon, the Long Island study's lead

investigator and an epidemiologist at the University of

North Carolina, discounts the connection, saying the effect

was minuscule and the risk did not go up with greater

exposure, as it should have if the chemicals were causing

breast cancer. Smokers, for example, did not have more

breast cancer than nonsmokers.

The results in Long Island were consistent with previous

studies. For example, a study published in the New England

Journal of Medicine in 1997, involving 32,826 nurses, also

found no evidence that DDT and PCB's increase the risk of

breast cancer.

The next year, Dr. Hunter, director of the Harvard

Center for Cancer Prevention, and his colleagues published

a paper in The Journal of the National Cancer Institute

that pulled together data from five studies involving 1,600

women. Again no link between exposure to the chemicals and

breast cancer was found.

" I think we have the answers for these chemicals, " Dr.

Hunter said.

BUT what if the risks are very small and the exposures took

place in the distant past? Then, Dr. Gammon said, it can

stretch the limits of science to try to find an

association.

" In some areas of science we can do wonderful things, " Dr.

Gammon said. " But there are still some very basic things we

can't do. We don't have accurate ways to measuring

pollutants from a long time ago. "

Dr. Boice, the scientific director of the

International Epidemiology Institute in Rockville, Md.,

mentions other complications. " Often the exposure you are

looking for, whether it is indoor radon or pesticides or

solvents in the water, are so low that it is difficult to

find an effect even if one is there. " In addition, he said,

it is hard even to find people who may have been exposed to

low levels of a pollutant 10 or 20 years ago. " People move,

they migrate, " he said.

Dr. Gallo, the associate director for cancer

prevention at the Wood Medical School's

cancer institute, said the same. " Looking for direct

causation is going to be impossible, " he said.

Indeed, beyond cigarette smoking, excessive sun exposure,

radon, very high concentrations of arsenic in water and,

possibly, air pollution, very few environmental causes of

cancer have been proven definitively. But advocates who

pushed for the Long Island study are not easily dissuaded.

Dr. Gammon said she had been meeting with the women, trying

to explain the limits of science. " They don't want to hear

it, " she said.

Ms. Barish said she was not at all convinced that the

pollutants were not causing breast cancer.

" I refuse to accept the fact that they didn't find

anything, " she said. " They didn't find anything conclusive

because in the scientific world it has to be exact. " But,

she added, " they couldn't say 100 percent that there wasn't

a link. " And so, Ms. Barish said, the story is not over.

" We need to do a lot more studies, " she said.

Others said it may be time to close the books. " I think it

is important that these studies have been done, " said Dr.

Barbara Hulka, an emeritus professor of epidemiology at the

University of North Carolina. " We ought to be on the

cautious side. " But this and other studies of environmental

pollutants and cancer have not found the suspected link,

she said. " There comes a point after so many studies are

done that it becomes less productive to continue that line

of work. "

http://www.nytimes.com/2002/08/11/weekinreview/11KOLA.html?ex=1030114731 & ei=1 & en\

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