Formaldehyde Exposure and Asthma in Children: A Systematic Review

OBJECTIVE: Despite multiple published studies regarding the association between formaldehyde exposure and childhood asthma, a consistent association has not been identified. Here we report the results of a systematic review of published literature in order to provide a more comprehensive picture of this relationship. DATA SOURCES: After a comprehensive literature search, we identified seven peer-reviewed studies providing quantitative results regarding the association between formaldehyde exposure and asthma in children. Studies were heterogeneous with respect to the definition of asthma (e.g., self-report, physician diagnosis). Most of the studies were cross-sectional. DATA EXTRACTION: For each study, an odds ratio (OR) and 95% confidence interval (CI) for asthma were either abstracted from published results or calculated based on the data provided. Characteristics regarding the study design and population were also abstracted. DATA SYNTHESIS: We used fixed- and random-effects models to calculate pooled ORs and 95% CIs; measures of heterogeneity were also calculated. A fixed-effects model produced an OR of 1.03 (95% CI, 1.02–1.04), and random effects model produced an OR of 1.17 (95% CI, 1.01–1.36), both reflecting an increase of 10 μg/m(3) of formaldehyde. Both the Q and I(2) statistics indicated a moderate amount of heterogeneity. CONCLUSIONS: Results indicate a significant positive association between formaldehyde exposure and childhood asthma. Given the largely cross-sectional nature of the studies underlying this meta-analysis, further well-designed prospective epidemiologic studies are needed.