Abstract
Introduction. While epidemiologic studies suggest cardiorespiratory effects of particle-phase organics, health effects of volatile organic compounds (VOCs) have received less attention. The large number of VOCs detected also presents a challenge for estimating health risk. Methods. Daily ambient concentrations of 89 VOCs were measured at a central location in a southern US city during 1998-2008. We classified the VOCs into 10 groups based on their chemical structure: n-alkane, iso/anteiso-alkane, multi-branched alkane, cycloalkane, alkene, alkyne, aromatic hydrocarbon, aldehyde, ketone, and acid. Associations between VOC groups and daily counts of cardiorespiratory emergency department (ED) visits were estimated using Poisson regression in a time-series framework. We compared associations for a given VOC group among four estimation approaches, considering for each group an indicator VOC, the sum of VOCs, the joint effect of VOCs, and weighted average effect of VOCs. Single-group models and models controlling for other VOC groups were run. Results. Five hydrocarbon groups (iso/anteiso-alkane, multi-branched alkane, cycloalkane, alkene, and alkyne) were associated with respiratory and cardiovascular ED visits in single-group models, with consistent results across different estimation approaches. Associations with oxygenated groups (aldehyde, ketone, or acid) were null. Among hydrocarbons, only the alkyne effect remained upon control for other VOC groups, with rate ratios (95% confidence intervals) of 1.005 (1.000, 1.011) and 1.009 (1.002, 1.017) per interquartile range increase in 3-day moving average and lag 0 concentrations for respiratory and cardiovascular ED visits respectively. Discussion. VOC chemical structure influences toxicity and/or exposure pathways. The observed health associations with the alkyne group – containing acetylene, a stable tracer of automobile emissions - support a link between automobile sources and cardiorespiratory outcomes.
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