Breast Cancer and Car Exhaust: New Study Finds Possible Link

Women living in the most polluted neighorhoods were twice as likely to develop breast cancer.This may be the news about breast cancer that we've all feared. A new study (ground breaking for its simple, smart design that uses maps of Montreal to correlate air quality and home addresses with the incidence of breast cancer) suggests pollution from traffic may put women at risk for developing post-menopausal breast cancer. The study, published in the prestigious journal of Environmental Health Perspectives, links the risk of breast cancer – the second leading cause of death from cancer in women – to traffic-related air pollution.

“We’ve been watching breast cancer rates go up for some time," says study co-author Dr. Mark Goldberg, a researcher at McGill University Health Center Research Institute. “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 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.”

A study of this kind can be subject to unknown errors. While the researchers tried to account as much as possible for them, 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,” says Dr. Goldberg.

Dr. Labrèche 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.”

Read about the study.

Common Environmental Toxin Linked to Obesity, Study Finds

One-quarter of babies born to women with high blood levels of a breakdown product of DDT--a persistent, ubiquitous enivronmental toxin--grew unusually fast for at least the first year of life. Such rapid growth in early infancy has put children on track to become obese. The babies' birthweights were normal, and the mothers were also normal weight, suggesting the toxins' presence triggers a hormonal cascade that accelerates growth and weight gain. 

Increasingly, data suggests that some pollutants — known colloquially as obesogens — can trigger the body to put on the pounds. In animals, these pollutants will sometimes lead a mouse to become rotund despite eating no more and exercising no less than its lean cousins.

Many obesogens — including DDE, the DDT breakdown product — have a hormonal alter ego. In the body, DDE can either turn on or block the activity of natural estrogens, female sex hormones. This pollutant also can block the activity of male sex hormones. Such properties lead scientists to describe this pesticide derivative as an endocrine disrupter. Click here to read about the study in ScienceNews.

Air Pollution and Brain Inflammation

Car exhaust and other forms of big-city pollution seem to lower IQ.Like most scientific tales, this one is partly a detective thriller. Mexico City-based pediatric neurologist, Lillian Calderon-Garciduenas, had a hunch that the megacity's notorious pollution was harming children. She was worried about widespread evidence of childhood lung and heart disease. Perhaps most troubling: something seemed to be ravaging their minds. For children enrolled in her studies, Calderon-Garciduenas was documenting cognitive impairments in memory, problem solving and judgment, and deficiencies in their sense of smell compared with age-matched children from a cleaner city 120 kilometers away. In a move Sherlock Holmes would appreciate, Calderon-Garciduenas conducted autposies of seemingly healthy Mexico City children who had died in auto accidents or from other traumatic events, and she found widespread evidence of deposits of proteins that serve as hallmarks of Alzheimer's and Parkinson's diseases.

Dr. Merrell's Tip: People living in urban environments can help their bodies process pollutants by eating a diet rich in antioxidants and anti-inflammatory substances (found in fruits, vegetablesc, fish and olive oils, dark chocolate and green tea.) Also, reduce exposure to airborne pollutants by using HEPA air filters in the bedroom (which only work when windows are kept closed.) 

Fast-forward through several years of global scientific research, and a picture begins to emerge of pollutions' effects on the brain. Increasingly, studies point to inflammation-provoking nanopollutants as a potential source of nerve cell damage. In studies of Boston 10-year-olds, researchers have found those living in areas with the highest average airborne concentrations of soot, a pollutant primarily associated with traffic, had lower IQs and lower scores on memory tests--comparable to IQ point drops identified in kids whose mothers had smoked during pregnancy.

The nose is crucial to understanding the problem. Research has identified the nasal passage as a front door that allows micro-particles of pollution to march into the brain. If the nasal tissues are inflammed, say, from allergies or sinusitis, the uptake of soot may be maginfiied.

There are mitigating factors. Not all pollution is equal. Mexico City air contains the metal manganese, which has been shown to migrate into the brain through the nose with unusual ease. And manganese is perhaps one of the most neuro-toxic metals. Genetic pre-disposition also play a roll. Calderon-Garciduenas has found that children with a particular gene variant (known as APOE-4) that predisposes them to Alzheimer's exhibit the most inflammation.

There are potential solutions. Short of moving and hoping for governments to clean up the air, the best bet is to eat an anti-inflammatory diet, rich in brightly colored fruits and vegetables and augmented with omega-3 fatty acids and specific anti-inflammatory foods like green tea, dark chocolate and the spice turmeric, which has been shown specifically to reduce the formation of amyloid-beta plaque. Calderon-Garciduenas has recently been feeding dark chocolate rich in polyphenols, a class of natural antioxidants, to inflammation-ravaged lab-mice. She has not published her study yet, but word is her prelimanary data shows great promise.

For a more detailed look at Calderon-Garciduenas research, see Destination Brain, ScienceNews, May 22.

Cancer Debate: It's the Environment

Originally appointed by the Bush administration, the President's Cancer Panel issued a 200 page report earlier this month asserting that manmade toxins are a much bigger contributor to cancer than previously thought. They point out that umblical cords typically have 300 industrial chemicals present, saying "babies are polluted before they are born." For a smart overview, read Nicholas Kristof's summary in the New York Times, and read a report on reactions from the scientific community in Discover Magazine. Also, read Jerome Groopman's take on this debate in the May 31st New Yorker.