Occupational styrene exposure and acquired dyschromatopsia: A systematic review and meta-analysis

Background: Styrene is a chemical used in the manufacture of plastic-based products worldwide. We systematically reviewed eligible studies of occupational styreneinduced dyschromatopsia, qualitatively synthesizing their findings and estimating the exposure effect through meta-analysis. Methods: PubMed, EMBASE, and Web of Science databases were queried for eligible studies. Using a random effects model, we compared measures of dyschromatopsia between exposed and non-exposed workers to calculate the standardized mean difference (Hedges'g). We also assessed between-study heterogeneity and publication bias. Results: Styrene-exposed subjects demonstrated poorer color vision than did the non-exposed (Hedges' g = 0.56; 95% CI: 0.37, 0.76; P < 0.0001). A non-significant Cochran's Q test result (Q = 23.2; P = 0.171) and an I-2 of 32.2% (0.0%, 69.9%) indicated low-to-moderate between-study heterogeneity. Funnel plot and trim-and-fill analyses suggested publication bias. Conclusions: This review confirms the hypothesis of occupational styrene-induced dyschromatopsia, suggesting a modest effect size with mild heterogeneity between studies.