The recent WHO report which declared that diesel exhaust causes cancer was widely picked up by various news media. Diesel fumes are of a slightly different composition than gasoline fumes and since 1989, they were deemed as a ‘possible carcinogen’ and now have been upgraded to a definite threat to human health.
Diesel exhaust, however, affects people in a similar fashion to secondhand smoke. Those who are regularly exposed have a higher chance of getting cancer. The WHO study looked at a population of 12,000 underground miners over the course of the past 60 years. Those regularly exposed to diesel exhaust had three times the rate of lung cancer deaths as their peers. Apart from mines, urban air does contain amounts of diesel exhaust as well as particulates in suspension, which cannot always be avoided. This is something that the WHO acknowledges in the report, as stated below:
“Large populations are exposed to diesel exhaust in everyday life, whether through their occupation or through the ambient air. People are exposed not only to motor vehicle exhaust but also to exhaust from other diesel engines, including from other modes of transport (e.g. diesel trains and ships) and from power generators.”
Although ambient urban air does contain diesel exhaust, it is most harmful in enclosed places like mines or housing complexes that are located near facilities that emit a lot of diesel. The study however, does not take into account exhaust from diesel generators which are a common source of backup power in countries like India. Most of these are used in shopping complexes, small-scale industries and even houses, often without proper ventilation.
Environmental concerns in North America, Europe and elsewhere over the past two decades have resulted in tighter emission standards for both diesel and gasoline. The report notes that there is, “strong interplay between standards and technology – standards drive technology and new technology enables more stringent standards.” This for the most part is true, engine manufacturers need not come up with more efficient designs if there is no pressure to do so. Diesel engines are especially challenging because the fuel itself needs to have a much lower sulfur content to burn more efficiently.