Wednesday, October 6, 2010

Air pollution could increase breast cancer risk: study

Traffic-related air pollution may put women at risk for breast cancer, according to a new study from Quebec.
The study, published in the journal Environmental Health Perspectives, looks at links between the risk of breast cancer, a leading cause of death from cancer in women, and traffic pollution.
Researchers from McGill University and the Université de Montréal charted incidences of breast cancer and compared them with pollution maps.
“We’ve been watching breast cancer rates go up for some time,” study co-author Mark Goldberg, a researcher at McGill University Health Centre, said in a release on Wednesday.
“Nobody really knows why, and only about one-third of cases are attributable to known risk factors. Since no one had studied the connection between air pollution and breast cancer using detailed air pollution maps, we decided to investigate it.”
Dr. Goldberg and his colleagues combined data from several studies. They created two air pollution maps which showed levels of nitrogen dioxide, a byproduct of vehicle traffic, in different parts of Montreal in 1996 and 10 years earlier in 1986.
Then, the research team looked at the home addresses of women diagnosed with breast cancer in a 1996-97 study and charted that onto the air pollution maps.
The team says its results were “startling,” and showed the incidence of breast cancer was increased in areas with higher levels of air pollution.
“We found a link between post-menopausal breast cancer and exposure to nitrogen dioxide (NOsub2/sub), which is a marker for traffic-related air pollution,” Dr. Goldberg said in the release.
“Across Montreal, levels of NOsub2/sub varied between five parts per billion to over 30 parts per billion. We found that risk increased by about 25% with every increase of NOsub2/sub of five parts per billion.
“Another way of saying this is that women living in the areas with the highest levels of pollution were almost twice as likely to develop breast cancer as those living in the least polluted areas.”
Dr. Goldberg warns, however, that the study must be interpreted with caution.
“First of all, this doesn’t mean NOsub2/sub causes breast cancer,” he said. “This gas is not the only pollutant created by cars and trucks, but where it is present, so are the other gases, particles and compounds we associate with traffic — some of which are known carcinogens.”
Dr. Goldberg said the study can be subject to unknown variables and that some areas of uncertainty remain.
“For example, we don’t know how much the women in the study were exposed to pollution while at home or at work, because that would depend on their daily patterns of activity, how much time they spend outdoors and so on,” Dr. Goldberg said.
“At the moment, we are not in a position to say with assurance that air pollution causes breast cancer. However, we can say that the possible link merits serious investigation,” the team said in its release.
Studies published in the U.S, have also shown possible links between cancer and air pollution.
The study was funded by a research grant from the Canadian Cancer Society and another one from the Canadian Institutes of Health Research.

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