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Breast cancer more likely in polluted areas

Women living in areas with worse air pollution have higher breast cancer risk

Louise Prime

Thursday, 07 October 2010

Breast cancer risk is higher in women who live in areas with worse traffic-related air pollution, research from Canada has shown.

Researchers combined several sources of data to produce ‘maps’ of air pollution – represented by levels of nitrogen dioxide (NO2), produced by motor vehicles – across different parts of Montreal, for 1986 and then for 1996. They also mapped the home addresses of women who had developed breast cancer, and then compared the sets of maps. Their findings are published online in the journal Environmental Health Perspectives.

They found that women who lived in the areas with higher levels of air pollution were much more likely to develop breast cancer than those living in areas of lower pollution.

Study co-author Dr Mark Goldberg, from McGill University, said: “Across Montreal, levels of NO2 varied between 5ppb to over 30ppb. We found that [breast cancer] risk increased by about 25% with every increase of NO2 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.”

But he warns that the results must be interpreted with caution: “This doesn’t mean NO2 causes breast cancer … 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. NO2 is only a marker, not the actual carcinogenic agent.”

And he further warns: “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.”

His co-author Dr France Labrèche, from the University of Montreal, adds: “Some studies published in the US have also shown possible links between cancer and air pollution. 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. From a public health standpoint, this possible link also argues for actions aimed at reducing traffic-related air pollution in residential areas.”

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