Background: Air pollution particulate matter and tobacco smoke, which contain metals that are human lung carcinogens, are associated with lung cancer risk. We conducted an ecological study to examine the association of metal air pollutants with lung cancer incidence in Texas.
Methods: During the period 1995 to 2000, 81,132 lung cancer cases were reported in Texas. We identified eight metals that (1) are in airborne particulate matter or tobacco smoke or are human lung carcinogens and (2) had consistent Environmental Protection Agency air release reporting for multiple counties from 1988 through 2000. We examined the association of metal air releases with the average annual age-adjusted primary and non-small cell lung cancer rates in the 254 Texas counties.
Results: Univariate analysis indicated the following positive associations: (1) zinc with the primary (p = 0.02) and non-small cell (p < 0.01) lung cancer rates and (2) chromium and copper with the non-small cell lung cancer rate, p = 0.01 and p = 0.01, respectively. In the multivariate analyses, risk adjusted for sex, race and ethnicity, and urbanization, zinc was positively associated with the primary (beta = 0.13, p = 0.01) and non-small cell (beta = 0.14, p = 0.02) lung cancer rates, and when interaction terms among the eight metals were included, zinc was significantly and positively associated with these rates. Smoking prevalence was similar for counties with and without releases for the eight metals.
Conclusions: The study suggests that inhalation exposure to metals, including those that are essential human nutrients, play a role in lung carcinogenesis.