BACKGROUND: Household air pollution from solid fuel burning is a leading contributor to disease burden globally. Fine particulate matter (PM) is thought to be responsible for many of these health impacts. A co-pollutant, carbon monoxide (CO) has been widely used as a surrogate measure of PM2.5 in studies of household air pollution. OBJECTIVE: The goal was to evaluate the validity of exposure to CO as a surrogate of exposure to PM2.5 in studies of household air pollution and the consistency of the PM2.5 –CO relationship across different study settings and conditions. METHODS: We conducted a systematic review of studies with exposure and/or cooking area PM2.5 and CO measurements and assembled 2,048 PM2.5 and CO measurements from a subset of studies (18 cooking area studies and 9 personal exposure studies) retained in the systematic review. We conducted pooled multivariate analyses of PM2.5 –CO associations, evaluating fuels, urbanicity, season, study, and CO methods as covariates and effect modifiers. RESULTS: We retained 61 of 70 studies for review, representing 27 countries. Reported PM2.5 –CO correlations (r) were lower for personal exposure (range: 0.22–0.97; median = 0:57) than for cooking areas (range: 0.10–0.96; median = 0:71). In the pooled analyses of personal exposure and cooking area concentrations, the variation in ln(CO) explained 13% and 48% of the variation in ln(PM2.5), respectively. CONCLUSIONS: Our results suggest that exposure to CO is not a consistently valid surrogate measure of exposure to PM2.5. Studies measuring CO exposure as a surrogate measure of PM exposure should conduct local validation studies for different stove/fuel types and seasons.
Bibliographical noteFunding Information:
We thank K. Ni, S. Pollard, O. Adetona, and M. Bechle for assistance with data compilation. This publication was made possible by U.S. EPA grant 83542201. Its contents are solely the responsibility of the grantee and do not necessarily represent the official views of the U.S. EPA. Further, the U.S. EPA does not endorse the purchase of any commercial products or services mentioned in the publication. J.B. was supported by Canadian Institutes of Health Research New Investigator Award 141959.
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