ObjectiveStudies have identified associations between household secondhand tobacco smoke (SHS) exposure and induction of childhood asthma. However, the true nature and strength of this association remains confounded in many studies, producing inconsistent evidence. To look for sources of potential bias and try to uncover consistent patterns of relative risk estimates (RRs), we conducted a meta-analysis of studies published between 1970 and 2005.Data sourcesThrough an extensive literature search, we identified 38 epidemiologic studies of SHS exposure and the development of childhood asthma (that also controlled for atopy history) from 300 potentially relevant articles.Data synthesisWe observed substantial heterogeneity within initial summary RRs of 1.48 [95% confidence interval (CI), 1.32–1.65], 1.25 (1.21–1.30), and 1.21 (1.08–1.36), for ever, current, and incident asthma, respectively. Lack of control for type of atopy history (familial or child) and child’s own smoking status within studies and age category altered summary RRs in separate meta-regressions. After adjusting for these confounding characteristics, consistent patterns of association emerged between SHS exposure and childhood asthma induction. Our summary RR of 1.33 (95% CI, 1.14–1.56) from studies of incident asthma among older children (6–18 years of age) is 1.27 times the estimate from studies of younger children and higher than estimates reported in earlier meta-analyses.ConclusionsThis new finding indicates that exposure duration may be a more important factor in the induction of asthma than previously understood, and suggests that SHS could be a more fundamental and widespread cause of childhood asthma than some previous meta-analyses have indicated.

June 2007] and is part of the scientific collaboaration between Cien Saude Colet and EHP. The authors gratefully acknowledge S. Kheradpir, who provided important technical support, and M. Lipsett and C. Steinmaus for their helpful comments on early drafts of this manuscript.

Background In 1990, Yale University, the Connecticut Departments of Health Services and of Transportation, the Connecticut Construction Industries Association, and the state's construction trade unions created the Connecticut Road Industry Surveillance Project (CRISP). Methods Data from 90 bridge projects from 1991 to 1995 and approximately 2,000 workers were evaluated. The distribution of peak lead concentrations in the blood for CRISP workers classified into five groups were compared to that from workers outside of Connecticut. Results This demonstration project was instrumental in lowering bridge worker blood lead levels. After 1992, only the painting contract employees experienced peak blood lead levels with ≤2% exceeding 50 μg/dl. Compared to similar workers in other states, Connecticut workers had significantly lower peak blood lead levels. Conclusions Two thousand workers and over 120 contractors benefited directly from CRISP. Two key features of the CRISP model differed from the 1993 OSHA standard: a contract‐specified lead health protection program and a centralized system of medical monitoring. These differences may account for the improved protection observed between the CRISP and non‐Connecticut cohorts. Am. J. Ind. Med. 39:243–253, 2001. © 2001 Wiley‐Liss, Inc.

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