Air pollution, which has already been linked to a range of health problems, may put women at risk of for another deadly disease.
A ground breaking new study suggests pollution from traffic is associated with the risk of breast cancer.
The study has been conducted by researchers from The Research Institute of the MUHC (RI MUHC; Dr. Mark Goldberg), McGill University (Drs. Goldberg, Dan Crouse and Nancy Ross), and Université de Montréal (Dr. France Labrèche).
"We`ve been watching breast cancer rates go up for some time. 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," says study co-author Dr. Mark Goldberg, a researcher at The RI MUHC.
Dr. Goldberg and his colleagues approached the problem by combining data from several studies.
First, they used the results of their 2005-2006 study to create two air pollution "maps" showing levels of nitrogen dioxide (NO2), a by-product of vehicular traffic, in different parts of Montreal in 1996 and 10 years earlier in 1986.
Then, they charted the home addresses of women diagnosed with breast cancer in a 1996-97 study onto the air pollution maps. Their findings were startling. The incidence of breast cancer was clearly higher in areas with higher levels of air pollution.
"We found a link between post-menopausal breast cancer and exposure to nitrogen dioxide (NO2), which is a ``marker`` for traffic-related air pollution", says Dr. Goldberg.
"Across Montreal, levels of NO2 varied between 5 ppb to over 30 ppb. We found that risk increased by about 25 per cent 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."
These disturbing results must be interpreted with great caution, warns Dr. Goldberg. "First of all, this doesn’t mean NO2 causes breast cancer," he explains. "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."
The study has been published in the prestigious journal Environmental Health Perspectives.