High levels of occupational cadmium exposure have been associated with immunotoxic effects, but less is known about the impact of lower level exposures in the general population, typically due to smoking and diet. The present study examined blood cadmium levels in relation to white blood cell (WBC) and differential counts in a national sample of adults in the U.S. (NHANES 1999-2002). The sample included 5,382 adults ages 20-69 with WBC in the normal range (3.5-11 X 10^6 cells/ml). Cadmium, WBC and differential counts were measured in blood specimens. Linear regression models and estimated means adjusted for sample weights, age, sex, race, education, body mass index, recent infection, C-reactive protein, and blood lead level. Increased cadmium level from the lowest (Q1 < / = 0.2 ug/L) to the highest quartile (Q4 mean 1.2 ug/L, range 0.7-8.5) was associated with significantly higher WBC counts, ranging from a Q1 mean of 6.48 X 10^6 cells/ml (95% Confidence Limit, CL 6.39, 6.56) to a Q4 mean of 7.45 (95% CL 7.30, 7.60) (Q4-Q1 = 0.97, p < 0.0001), primarily due to differences in neutrophil count. Significant differences in mean WBC were seen in current smokers (Q4-Q1 = 0.51, p = 0.043), but not in non-smokers. Smoking status accounted for most of the observed association in women, but not in men, where a smoking-adjusted difference in the means persisted (Q4-Q1 = 0.63, p < 0.0001). In these cross-sectional analyses, elevated cadmium was associated with higher WBC in a representative sample of the general population. Differences in association by smoking and gender could reflect the influence of exposure route (i.e., inhaled versus ingested) and the possible contribution of occupational exposures in men.
American Journal of Epidemiology. Abstracts of the 2nd North American Congress of Epidemiology, June 21-24, 2006, Seattle, Washington