Tuesday, October 11, 2011

Fine-particle soot found to cause lung cancer in non-smokers

This is a study that has just appeared in the American Journal of Respiratory and Critical Case Medicine

Abstract at http://ajrccm.atsjournals.org/cgi/content/abstract/201106-1011OCv1


Here are a few quick excerpts from the full study (which requires a paid subscription):

DISCUSSION

This large prospective study showed clear positive associations between mean long-term ambient fine particulate matter air pollution concentrations and lung cancer mortality in lifelong never smokers. Each 10 μg/m3 increase in PM2.5 concentrations was associated with a 15-27% increase in the relative risk of lung cancer death after detailed adjustment for a number of potential confounders including passive smoking, occupational exposures, and radon. The
association was similar in men and women and across categories of attained age and educational attainment but was stronger in those with a normal BMI or a history of asthma or any CLD at enrollment. Findings were robust to the adjustment of a variety of socio-demographic ecological covariates at different time points in the model.

Strengths of this study include the examination of lung cancer mortality in a large cohort of 188,699 lifelong never smokers to eliminate potential residual confounding by cigarette smoking status; an extended 26-year follow-up time period (1982-2008) with a total of 1,100 observed lung cancer deaths; detailed prospectively collected individual-level lung cancer risk factor data;
and the availability of ecological measures of residential radon concentrations and sociodemographic characteristics to examine potential confounding by radon and community-level factors.

Although previous studies examining associations between PM2.5 and lung cancer adjusting for cigarette smoking history have generally reported positive findings, there remains concern regarding potential residual confounding by cigarette smoking status; previous studies of non-smokers were also limited by the small numbers of lung cancer cases...

Ambient fine particulate matter comprises a diverse group of air pollutants that may be deposited and retained in the deep branches of the respiratory system, the chemical composition of which varies widely and may include a variety of adsorbed organic compounds, transition metals, ions, and minerals capable of inducing toxic biological effects Long-term exposure to fine particulate air pollution may lead to increased lung cancer risk through inflammatory injury,
reactive oxygen species production, and oxidative damage to DNA. Genotoxic and
mutagenic effects have also been demonstrated in laboratory studies.

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