27 November 2013

An estimated 6% of lung cancer deaths in the United States and the United Kingdom—11,000 deaths per year—may be due to diesel exhaust, according to a new study published in the Environmental Health Perspectives by an international team led by Roel Vermeulen of the University of Utrecht.

The analysis and calculations conducted in the study are based on data from three prior studies of workers—two of truckers and one of non-metal miners—as well as national death statistics for the United States and United Kingdom. In these previous studies, truckers and miners were exposed to emissions from old, uncontrolled diesel engines during the 1970s, 1980s and 1990s. It is not clear if the results are applicable to modern, emission-controlled diesel engines.

The study found that truckers and miners exposed over their careers to diesel exhaust face a risk of deadly lung cancer that is almost 70 times higher than the risk considered acceptable under US occupational standards. The scientists estimated the lifetime risk for these workers at up to 689 extra lung cancer deaths per 10,000 workers exposed. In comparison, one cancer death per 1,000 workers is used to set federal workplace standards.

Even in non-occupational settings, people in urban areas can still face a lifetime risk of lung cancer that is 10 times higher than the acceptable risk used in US health standards, concluded the study. An estimated 21 per 10,000 people exposed to the amount of diesel exhaust commonly found near US highways would be at risk of dying of lung cancer over their lifetime. That compares to the risk of one death per 100,000 people that is used to set air quality standards.

The study estimated that 4.8% of lung cancer deaths in the United States and the United Kingdom is due to occupational exposure to diesel exhaust, while 1.3% is due to environmental exposures to the exhaust.

The researchers said their estimates “are far from precise and depend on broad assumptions.” But they said their findings are “generally consistent” with past findings. Other factors, such as smoking, were not taken into account. They used the assumption that smoking does not modify effects of diesel exhaust.

Last year the World Health Organization, after reviewing health data for workers, classified diesel exhaust carcinogenic to humans (IARC Group 1). That decision was also based on analysis of exposure data with uncontrolled diesel engines from the last century.

The population of old, uncontrolled diesel engines has declined substantially over the past years in the United States, Europe, Japan and other countries that adopted stringent diesel emission standards. However, uncontrolled, high emission diesels are still common in nonroad applications—such as in construction and farm machinery—as well as in many countries around the world that still have relaxed diesel emission requirements.

Source: Environmental Health Sciences