Effect Measure Modification of Blood Lead-Air Lead Slope Factors
Background: There is abundant literature finding that blood lead (PbB) levels are directly influenced by susceptibility factors including race and ethnicity, age, and housing. However, no study has explored how susceptibility factors influence the PbB-air lead (PbA) relationship nationally.
Objective: The objective is to evaluate if susceptibility factors, including age group, sex, housing age, and race/ethnicity, act as effect measure modifiers on the PbB-PbA relationship.
Methods: Participant level PbB data from the 1999-2008 National Health and Nutrition Examination Survey (NHANES) were merged with PbA data from the U.S. Environmental Protection Agency. Linear mixed effects models were run with and without an PbA interaction term for age group, sex, housing age, or race/ethnicity to determine if those factors are effect measure modifiers. Models were run for all ages combined and for five age brackets (1-5 yr, 6-11 yr, 12-19 yr, 20-59 yr, ≥60 yr). Results: Age group and race/ethnicity were determined to be effect measure modifiers in the all-ages model and for some age groups. Being a child (1-5 yr, 6-11 yr, 12-19 yr) and being of Mexican-American ethnicity increased the effect estimate in the PbB-PbA model. Living in older housing (built prior to 1950) decreased the effect estimate for all models except for the 1-5 yr group, where older housing was an effect measure modifier.
Conclusion: The effect of PbA concentrations on PbB levels was enhanced by childhood and by Mexican-American ethnicity. The results for effect measure modification are consistent with the peer-reviewed literature of time-activity patterns, ventilation, and toxicokinetics.
Methods: Participant level PbB data from the 1999-2008 National Health and Nutrition Examination Survey (NHANES) were merged with PbA data from the U.S. Environmental Protection Agency. Linear mixed effects models were run with and without an PbA interaction term for age group, sex, housing age, or race/ethnicity to determine if those factors are effect measure modifiers. Models were run for all ages combined and for five age brackets (1-5 yr, 6-11 yr, 12-19 yr, 20-59 yr, ≥60 yr). Results: Age group and race/ethnicity were determined to be effect measure modifiers in the all-ages model and for some age groups. Being a child (1-5 yr, 6-11 yr, 12-19 yr) and being of Mexican-American ethnicity increased the effect estimate in the PbB-PbA model. Living in older housing (built prior to 1950) decreased the effect estimate for all models except for the 1-5 yr group, where older housing was an effect measure modifier.
Conclusion: The effect of PbA concentrations on PbB levels was enhanced by childhood and by Mexican-American ethnicity. The results for effect measure modification are consistent with the peer-reviewed literature of time-activity patterns, ventilation, and toxicokinetics.