Assessing Exposure to Household Air Pollution: A Systematic Review and Pooled Analysis of Carbon Monoxide as a Surrogate Measure of Particulate Matter

BACKGROUND: Household air pollution from solid fuel burning is a leading contributor to disease burden globally. Fine particulate matter ([Formula: see text]) 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 [Formula: see text] in studies of household air pollution. OBJECTIVE: The goal was to evaluate the validity of exposure to CO as a surrogate of exposure to [Formula: see text] in studies of household air pollution and the consistency of the [Formula: see text] relationship across different study settings and conditions. METHODS: We conducted a systematic review of studies with exposure and/or cooking area [Formula: see text] and CO measurements and assembled 2,048 [Formula: see text] 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 [Formula: see text] 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 [Formula: see text] correlations (r) were lower for personal exposure (range: 0.22–0.97; [Formula: see text]) than for cooking areas (range: 0.10–0.96; [Formula: see text]). 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([Formula: see text]), respectively. CONCLUSIONS: Our results suggest that exposure to CO is not a consistently valid surrogate measure of exposure to [Formula: see text]. Studies measuring CO exposure as a surrogate measure of PM exposure should conduct local validation studies for different stove/fuel types and seasons. https://doi.org/10.1289/EHP767