TABLE 2.
Blood Lead Levels in Children and Adolescents Aged 3–19 Years, by Secondhand Smoke Exposure Levels: National Health and Nutrition Examination Survey, United States, 1999–2004
| No.(Weighted %) | Blood Lead Level, μg/dL, Geometric Mean (95% CI) | Ratio of Geometric Mean (95% CI) | |||
| Model 1 | Model 2 | Model 3 | |||
| Cotinine, μg/L | |||||
| ≤ 0.03 (Ref) | 1538 (25) | 0.91 (0.86, 0.95) | 1.00 | 1.00 | 1.00 |
| 0.031–0.074 | 1876 (25) | 1.13 (1.08, 1.19) | 1.10 (1.04, 1.16) | 1.09 (1.03, 1.15) | 1.08 (1.02, 1.15) |
| 0.075–0.44 | 1804 (25) | 1.31 (1.22, 1.40) | 1.26 (1.21, 1.32) | 1.19 (1.14, 1.24) | 1.17 (1.12, 1.23) |
| ≥ 0.441 | 1612 (25) | 1.52 (1.41, 1.62) | 1.47 (1.40, 1.55) | 1.30 (1.23, 1.37) | 1.28 (1.21, 1.35) |
| P for trenda | < .001 | < .001 | < .001 | < .001 | |
| Smokers at home, no. | |||||
| 0 (Ref) | 5484 (78) | 1.12 (1.08, 1.17) | 1.00 | 1.00 | 1.00 |
| 1 | 929 (14) | 1.46 (1.33, 1.61) | 1.26 (1.18, 1.33) | 1.16 (1.08, 1.23) | 1.14 (1.07, 1.22) |
| ≥ 2 | 417 (8) | 1.56 (1.42, 1.72) | 1.39 (1.32, 1.47) | 1.25 (1.17, 1.33) | 1.24 (1.16, 1.33) |
| P for trenda | < .001 | < .001 | < .001 | < .001 | |
Note. CI = confidence interval. Model 1 was adjusted for gender; age (continuous); race (White, Black, Mexican American, other); birth country (United States, Mexico, other); body mass index (BMI; defined as weight in kilograms divided by the square of height in meters) percentile; and survey year (1999–2000, 2001–2002, 2003–2004). Model 2 was further adjusted for household education (< high school, high school or equivalent, > high school) and poverty-to-income ratio (PIR; the ratio of the family's income to its appropriate poverty threshold as defined by the US Census Bureau [≤ 1.30, 1.31–3.50, 3.51–5.00]). Model 3 was further adjusted for year in which house was built (before 1950, 1950–1978, after 1978, unknown).
P values for trend across cotinine categories were obtained by including cotinine medians corresponding to each quartile as continuous variables in the regression models. P values for trend across categories of no. of smokers at home were obtained by including 0, 1, and 2 as continuous variables in the regression models.