Vehicle emissions a cancer threat?
Because of the relatively short timespan covered, only limited conclusions can be drawn in the Irish context.
However, an important omission from the feature article is that there is a consistent trend upwards in incidence for certain cancers of almost 3% per year.
Another issue worth highlighting is that the HPV virus is sexually transmitted, meaning that the risk of cervical cancer directly relates to the number of unprotected exposures to multiple partners.
In relation to the increased incidence of cancers in cities, Dr Comber seems to underestimate the potential of environmental contaminants. The WHO has attributed 2%-to-5% of cancers to environmental contaminants.
In a recent major review paper with over 300 references, Prof Vyvyan Howard of the University of Ulster, in the Journal of Nutritional and Environmental Medicine, suggests that there may be a much more significant contributor, and not just in the urban environment. This is also highlighted in the Paris Appeal (available on the web), an international declaration of the dangers associated with chemical contamination of the biosphere.
Example: benzene, a known carcinogen, is present in the air as a result of vehicle emissions — 78% from petrol engines and 10% from diesel engines. The WHO air quality guidelines for Europe state that “no safe level of exposure can be recommended”.
Microfine particles PM 10 and 2.5 are also emitted from vehicle engines, particularly diesel engines, and they are being increasingly recognised as important health determinants.
A large bus or truck with a 200kw engine will produce 80g of particulates per hour. The wonder is that there is not an even higher incidence of cancer in our gridlocked cities, but then there is a 20-year time-lag before the cancer actually appears. Are we setting ourselves up for an ever increasing annual rate?
Dr Philip Michael
Chair
Irish Doctors Environmental Association
Bandon
Co Cork
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