Contribution of particle-size-fractionated airborne lead to blood lead during National Health and Nutrition Examination Survey, 1999-2008
Epidemiologic studies have demonstrated associations between blood Pb (PbB) and a broad range of adverse health effects. The national ambient air quality standard (NAAQS) for Pb is set for air Pb (PbA) not PbB, to protect public health. Therefore, assessment of the association between PbA and PbB is critically important to understand the impact of PbA on PbB and the associated adverse health effects. However, the PbB-PbA relationship has not been characterized for the U.S. on a national scale since tetramethyl Pb and tetraethyl Pb were completely phased out as antiknock agents in gasoline in the U.S. The objective of this work is to examine the association between PbB and PbA for PbA in particulate matter (PM) measured at different size cuts. PbB concentrations were obtained from the NHANES 1999-2008 surveys. PbA concentrations were obtained from the U.S. EPA Air Quality System (AQS). This work utilized data for particle-bound PbA with different PM size fractions (TSP, PM10 and PM2.5) and different averaging times (current and past 90 d average). A multi-level linear mixed effect model was used to characterize the PbB-PbA relationship. Covariates considered in the analysis included demographic information, socioeconomic status, exposure history, and exposures from other Pb sources. A total of 155 PM10, 548 PM2.5, and 456 TSP air monitors reported PbA concentrations to the AQS from 1999-2008. PbB was measured for a total of 41,961 subjects in NHANES from 1999-2008. PbA in PM10 was statistically significantly associated with PbB. At the current level of the NAAQS for Pb (0.15 µg/m3), a unit decrease in PbA in PM10 was associated with a decrease of PbB ranging from 0.3 -2.2 µg/dL for different age groups and averaging times. For PbA in PM2.5 and TSP, slopes were generally positive but not statistically significant. PbB levels were more sensitive to the change in PbA concentrations for children (aged 1-5 y and 6-11 y) and older adults (aged 60 y and above) than teenagers (aged 12-19 y) and younger adults (aged 20-59 y). For the years following the phase out of Pb as a gasoline additive and a resulting upward shift in the PbA particle size distribution, PbA in PM10 is a statistically significant predictor of PbB level. The results also suggest that age could significantly affect the PbB-PbA association. PbB for children is more sensitive than PbB for adults to the change in PbA.
Meng, Q., J. Richmond-Bryant, Allen Davis, J. Cohen, D. Svendsgaard, J. Brown, L. Tuttle, H. Hubbard, J. Rice, L. Vinikoor-Imler, J. Sacks, E. Kirrane, D. Kotchmar, E. P. HINES, AND M. Ross. Contribution of particle-size-fractionated airborne lead to blood lead during National Health and Nutrition Examination Survey, 1999-2008. ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 48(2):1263-1270, (2013).