BMC Public Health 2008, 8:72 http://www.biomedcentral.com/1471-2458/8/72 Table 3: Adjusted* geometric means (95% confidence interval) by quartile of creatinine corrected urinary cadmium and smoking status. Quartile 1 < 0.18 µg/g Quartile 2 0.18–0.33 µg/g Quartile 3 0.34–0.62 µg/g Quartile 4 ≥ 0.63 µg/g p-trend Total testosterone, ng/mL Never smokers Former smokers Current smokers Total estradiol, pg/mL Never smokers Former smokers Current smokers SHBG, nmol/L Never smokers Former smokers Current smokers Androstanediol glucuronide, ng/mL Never smokers Former smokers Current smokers Estimated free testosterone, ng/mL Never smokers Former smokers Current smokers Estimated free estradiol, pg/mL Never smokers Former smokers Current smokers Estradiol*1000/total testosterone Never smokers Former smokers Current smokers Total testosterone/SHBG Never smokers Former smokers Current smokers Estradiol*1000/SHBG Never smokers Former smokers Current smokers 5.03 (4.68, 5.41) 4.34 (3.91, 4.81) 5.74 (5.08, 6.48) 31.7 (29.0, 34.6) 33.0 (30.1, 36.2) 40.2 (36.3, 44.5) 32.4 (29.6, 35.3) 36.2 (30.6, 42.8) 39.3 (34.7, 44.5) 12.9 (12.0, 13.8) 14.0 (11.8, 16.7) 12.1 (9.8, 14.9) 0.102 (0.094, 0.111) 0.083 (0.075, 0.091) 0.109 (0.097, 0.123) 0.81 (0.73, 0.90) 0.84 (0.75, 0.94) 1.00 (0.90, 1.10) 6.67 (6.06, 7.35) 8.08 (6.96, 9.37) 7.41 (6.75, 8.14) 0.539 (0.490, 0.593) 0.416 (0.364, 0.474) 0.507 (0.456, 0.563) 3.60 (3.09, 4.19) 3.35 (2.70, 4.15) 3.75 (3.30, 4.27) 4.88 (4.27, 5.58) 4.16 (3.60, 4.80) 5.78 (5.34, 6.27) 34.0 (31.4, 36.7) 33.0 (31.0, 35.0) 39.1 (37.0, 41.3) 32.6 (29.8, 35.6) 32.2 (29.7, 34.8) 36.3 (31.7, 41.6) 11.3 (9.9, 13.0) 11.8 (10.3, 13.6) 12.5 (10.0, 15.4) 0.099 (0.088, 0.111) 0.084 (0.071, 0.099) 0.114 (0.106, 0.123) 0.86 (0.79, 0.94) 0.86 (0.80, 0.92) 0.99 (0.92, 1.05) 7.37 (6.08, 8.93) 8.41 (7.36, 9.60) 7.15 (6.62, 7.72) 0.520 (0.470, 0.575) 0.448 (0.382, 0.525) 0.552 (0.491, 0.621) 3.83 (3.37, 4.36) 3.77 (3.37, 4.20) 3.95 (3.44, 4.53) 4.12 (3.26, 5.22) 4.52 (4.20, 4.87) 6.09 (5.81, 6.39) 34.3 (30.8, 38.2) 32.6 (30.8, 34.4) 44.3 (42.3, 46.5) 31.3 (27.1, 36.1) 37.3 (33.5, 41.7) 33.7 (31.0, 36.6) 11.7 (9.7, 14.0) 10.5 (9.7, 11.3) 10.8 (8.7, 13.3) 0.084 (0.063, 0.112) 0.086 (0.079, 0.093) 0.129 (0.121, 0.137) 0.89 (0.78, 1.00) 0.82 (0.78, 0.87) 1.16 (1.09, 1.23) 8.81 (6.75, 11.50) 7.62 (7.02, 8.28) 7.71 (7.25, 8.19) 0.457 (0.337, 0.619) 0.420 (0.380, 0.464) 0.628 (0.575, 0.685) 4.03 (3.29, 4.93) 3.20 (2.90, 3.53) 4.84 (4.35, 5.38) 4.24 (3.24, 5.55) 4.49 (4.05, 4.98) 6.39 (5.86, 6.96) 30.2 (23.6, 38.7) 33.5 (31.0, 36.2) 43.2 (40.7, 45.8) 32.5 (26.8, 39.3) 37.8 (34.1, 41.8) 37.6 (33.2, 42.7) 13.1 (11.0, 15.7) 11.7 (9.6, 14.4) 11.0 (9.3, 12.9) 0.085 (0.064, 0.114) 0.084 (0.076, 0.093) 0.126 (0.117, 0.136) 0.77 (0.60, 1.00) 0.84 (0.77, 0.91) 1.09 (1.01, 1.17) 7.54 (6.20, 9.17) 7.89 (7.10, 8.77) 7.16 (6.58, 7.79) 0.453 (0.332, 0.619) 0.412 (0.370, 0.459) 0.588 (0.535, 0.646) 3.42 (2.62, 4.45) 3.25 (2.86, 3.70) 4.22 (3.66, 4.86) 0.06 0.49 0.12 0.97 0.73 0.26 0.88 0.28 0.71 0.80 0.64 0.53 0.14 0.97 0.09 0.92 0.87 0.39 0.16 0.71 0.51 0.25 0.59 0.31 0.88 0.52 0.72 *Adjusted for age (continuous) and race-ethnicity (non-Hispanic white, non-Hispanic black, Mexican-American, and other), serum cotinine (continuous), household income (< $20,000 and ≥ $20,000), physical activity (none, 1–2, and ≥ 3 times a week), alcohol consumption (< 12 and ≥ 12 drinks in the past year), percent body fat (continuous), blood lead (log-transformed, continuous), and serum selenium (continuous) were relatively small: the largest study included 263 par- ticipants, and their combined sample size was 701. Addi- tionally, three of these studies did not report smoking adjusted results [10-12], although smoking was included in stepwise regression algorithms. The importance of tobacco use as a confounder of the cadmium-sex hor- mone relationship may differ across populations due to varying levels of cadmium in tobacco, prevalence of tobacco use, and exposure to cadmium from other sources (e.g., occupational exposure, food, air pollution). How- ever, our analysis indicates that studies of the association of cadmium with sex steroid hormones need to carefully control for tobacco use. Our findings pertain to low-level chronic environmental cadmium exposure and may not be generalizable to envi- ronmental or occupational settings involving higher dos- ages of cadmium. Indeed, differences in cadmium levels may account for the inconsistent results in previous research. Additionally, urinary cadmium reflects predom- inantly cumulative long-term exposure and we cannot rule out short-term effects of cadmium exposure on sex steroid hormone levels. Our analysis was based on single measures of sex steroid hormones in plasma and of cad- mium in spot urine samples, all of which were subject to substantial within person variability and laboratory meas- urement error. Consequently, we cannot exclude the exist- ence of a modest association between urine cadmium and sex steroid hormone levels. However, the inconsistent findings in experimental models and the lack of a clearly delineated biological mechanism that could explain an effect of chronic environmental cadmium exposure on sex Page 5 of 7 (page number not for citation purposes)