It has been proposed that formaldehyde may influence the risk or severity of asthma through irritant effects by stimulating allergic responses (when linked with endogenous proteins) or by inhibiting bronchodilation, but findings of observational studies of childhood asthma and formaldehyde have been inconsistent. McGwin et al. conducted a systematic review and quantitative meta-analysis of seven peer-reviewed studies that included children with and without asthma and reported formaldehyde exposure levels and estimates of association. Pooled odds ratios (ORs) from both fixed-effects and random-effects models (that account for heterogeneity among studies) indicated positive associations for all studies combined [for a 10-