Exposure to certain types of inhaled particles in occupational settings and in the environment has been linked to increases in lung cancer risk. The December Journal of Occupational and Environmental Medicine, official publication of the American College of Occupational and Environmental Medicine (ACOEM), is a special issue providing updates on particles and cancer.
"A remarkable consistency exists among many types of studies for some particles in terms of their ability to cause cancer," writes Dr. Robert J. McCunney of Massachusetts Institute of Technology in an introductory editorial. "But how does one sort out the disparate results among many studies and make effective decisions in minimizing risk of cancer among people exposed to particles at work or in the environment?" The articles in the special issue—highlights of a recent MIT-sponsored conference—provide new insights into the lung cancer risks associated with particle exposure.Several studies focus on a particle called carbon black—a fine powder made from incomplete combustion of petroleum that is widely used in the rubber and printing industries. The results of previous studies of workers exposed to carbon black have been unclear: although there was evidence of an increased risk of lung cancer, there was no clear relationship between cancer rates and the level of carbon black exposure.
The new studies provide further evidence of increased risk among workers exposed to carbon black, with lung cancer rates 80 to 120 percent higher than in the general population. Again, however, there is no clear "dose-response" link. The findings are consistent with the recent International Agency for Research on Cancer conclusion that carbon black is "possibly carcinogenic," but that there is not enough scientific evidence to confirm that it was a cancer-causing agent in humans.
The special issue also includes new research on other particles with possible links to cancer, such as titanium dioxide. One paper looks at how inhaled particles affect levels of pro-inflammatory and anti-inflammatory substances in the lungs, which might help to explain how particles lead to the development of lung cancer.
Another study looks at air pollution as a contributor to death from asthma. The special issue also includes a commentary by Dr. McCunney on recent studies suggesting that computed tomography scans might be an effective way to screen for early-stage lung cancers in workers with certain occupational exposures, as well as in smokers.
The studies in the special issue help to advance scientific understanding of the relationships between particles and cancer. Dr. McCunney underscores the need for further research in key areas, including how size, shape, and other particle characteristics affect their behavior in the atmosphere and their impact on health; the best ways of measuring exposure to specific particles; the mechanisms underlying the toxic effects of particles, including possible new approaches to recognizing early health effects; and how best to interpret the often "limited and conflicting data" on the health risks of particle exposure.
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