Breast cancer risk and the air we breathe

The article titled Traffic Pollution Study Reveals Increased Breast Cancer Risk (October 8), reporting on research conducted at McGill University Health Centre, once more demonstrated a link between breast cancer and traffic pollution. Mark Goldberg and his colleagues made it clear that nitrogen dioxide (levels of which are high in Malta) was not itself necessarily the cause of increased cancer risk; it is a “marker” of high levels of other more dangerous pollutants, which are the actual cause of breast cancer.

There is, in fact, evidence that the elements in traffic pollutants responsible for increases in breast cancer, as observed by Dr Goldberg and his colleagues, are compounds which are known as “polycylic aromatic hydrocarbons” or “PAHs”.

One analysis of air pollution concluded that traffic sources are responsible for 90 per cent of PAHs and that exposure to these mutagenic compounds in the urban air contributes to cases of lung and other cancers. It later emerged that pollution with PAHs is implicated in the causation of breast cancer. There is also a sinister dimension to this aspect of traffic pollution and, in particular, PAHs. First of all, the time lag between critical exposures and health outcomes is measured in years or even decades.

This means the damage to today’s children and young adults from exposure to traffic pollution will only become apparent in years to come. Secondly, there is evidence the damage from PAHs can be “trans-generational”. In other words, the damage can skip a generation and occur in the children of people who were exposed. This, therefore, raises the spectre of both “late effects of early exposures” and of “silent environmental heritage” from parent to child. The significance of these findings was reaffirmed by the EU in its State of the Environment report, Environment And Health And The Quality Of Life (2007),

The landmark study conducted by the American Cancer Society in 500,000 men and women who were followed from 1982 through 1998 was one of the earliest studies to establish that the fine particles in black smoke are lethal pollutants. The American Cancer Society study quantified the effects of long-term exposure to traffic pollution on mortality. The incidence of cancer and mortality and early death from all causes in areas most heavily polluted with fine particles was 17 per cent higher than that of the least polluted area. Other large-scale studies which followed replicated the findings.

The World Health Organisation and the UK Committee on the Medical Effects of Air Pollutants now endorse the evidence that exposure to traffic-related particulate air pollution is one of the most important environmental risk factors for excess mortality from cardiopulmonary disease and lung cancer.

To that is now added the causative role in breast cancer of exposure to PAHs, which also present in soot particles.

All the forgoing stresses the tremendous importance of taking steps to reduce traffic pollution.

The government – and the Health Department – has shown little concern and remains indifferent to the degree of traffic pollution in densely urbanised areas. This applies especially to the highly toxic black smoke emitted by many diesel driven vehicles, especially buses. If the scientific evidence is anything to go by, this visible smoke emission is a cause of cancer. It is both illegal and preventable. And, yet, the government does nothing to stop it. This inaction can be expected to result in significant delayed health impacts, including cancer, which will become apparent over the coming years by virtue of cumulation of effect in younger generations currently exposed.

The responsibility lies with us too. Anybody who drives a car is also part of the problem. The older among us had the privilege of growing up in the relatively clean atmosphere of decades ago.

On the other hand, given the intimidating scientific evidence of harm from traffic pollution, our prodigal use of the car is bestowing an increase in cancer rates and shortened lifespans not only on our young generation but also on their children. Every time you are about to turn on the ignition switch in your car ask yourself this question: Is this journey really necessary?

And next time you buy a car, buy the smallest, most economical and least polluting car possible or, better still, consider buying an electric car.

The scientific evidence referred to is reviewed in part IV of the think tank report Towards A Low Carbon Society - The Nation’s Health, Energy Security And Fossil Fuels, available at www.tppi.org.mt/cms/index.php/reports.