Environment and Cancer: The Links Are Elusive

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Environment and Cancer: The Links Are Elusive

By GINA KOLATA
Published: December 13, 2005
Correction Tuesday, Decemeber 20, 2005
The New York Times

When Mike Gallo learned he had cancer, a B cell lymphoma, two years ago, his friends and relatives told him that they knew how he got it.

His cancer, Dr. Gallo's friends said, was obviously caused by the dioxin that he had worked with for three decades in his laboratory. After all, the Environmental Protection Agency classifies dioxin as a probable human carcinogen. And among the cancers that it may increase the risk for, in high doses, is lymphoma.

Dr. Michael A. Gallo, director of the National Institute for Environmental Health Sciences Center of Excellence at the Robert Wood Johnson Medical School in New Brunswick, N.J., tells his well-meaning advisers that he does not think so.

"I say, 'No, I know my blood levels of dioxin,' " Dr. Gallo said, explaining that he measured them when he worked with the chemical. His levels, he said, are low. And there is no way to make a leap from such low levels of dioxin to his cancer.

Yet many of his friends and relatives remain convinced.

"That's the way people think," Dr. Gallo said. "If you get cancer, there has to be a reason."

And there may be a reason, he and other scientists say. But pinning cancer on trace levels of poisons in the environment or even in the workplace is turning out to be a vexing task. There has been recent progress in addressing the issue, but the answers that many people believe must be out there remain elusive.

"It's an area where there's certainly been a lot of heat and not a lot of light for some time," said Robert Hoover, director of the epidemiology and biostatistics program at the National Cancer Institute. For the most part, Dr. Hoover said, "we are down to speculations based on some data but without having the information we need."

Members of advocacy groups agree that there is much to learn, but they say the questions are too important to brush off by saying the research is difficult or the questions complex.

"Science is very specific," said Linda Gillick, a founder of Ocean of Love, a support group for children with cancer in Ocean County, N.J. "Sometimes you have to think outside the box."

Barbara Brenner, executive director of the Breast Cancer Action Coalition, an advocacy group in San Francisco, said that at the very least people should look for the least toxic alternative to chemicals in common use that may cause cancer.

Having had breast cancer twice, Ms. Brenner is impassioned by the cause. "I have a firsthand experience, and I would do anything - anything - to keep someone else from having that experience," she said.

Researchers, for their part, say they have not given up the quest. In their search for answers, they are trying a variety of methods. They are looking for reliable ways to detect environmental exposures and determine whether they are linked to cancer risk. They are studying the bewildering array of factors that can determine a chemical's effects on individual people. And they are looking at cancer statistics and asking whether there are blips in cancer rates that may point to an environmental cause.

The effort is important, Dr. Hoover said. While most scientists think that only a tiny fraction of cancers might be caused by low levels of environmental poisons, these are cancers that could, in theory, be avoided.

"All it takes is the political will to ban them or impose regulations to minimize exposure, and the cancers are gone," Dr. Hoover said.

The problem is to decide which chemicals might be causing cancer, and in whom.

Some scientists, like Aaron Blair, an epidemiologist at the National Cancer Institute, see hints that environmental pollutants like pesticides, diesel exhaust in cities and workplaces and small particles in the air may instigate cancer.

But, Dr. Blair says, there is a huge problem in following up on these hints because scientists need to figure out who was exposed to what and when the exposure occurred. Asking people is not much help. Most people do not know what they were exposed to, and even if they think they know, they often are wrong, he said.

So Dr. Blair and his colleagues decided to try for the greatest possible rigor by focusing on one group, farmers, that is not only routinely exposed to pesticides that may increase cancer risk, but also keeps excellent records of exposure.

Copyright 2006The New York Times Company