Ozone and Other Air Pollutants and the Risk of Oral Clefts

BACKGROUND: Air pollution influences the development of oral clefts in animals. There are few epidemiologic data on the relation of prenatal air pollution exposure and the risk of oral clefts. OBJECTIVES: Our goal in this study was to assess the relations between exposure to ambient air pollution and the risk of cleft lip with or without cleft palate (CL/P). METHODS: We conducted a population-based case–control study of all 653 cases of CL/P and a random sample of 6,530 control subjects from 721,289 Taiwanese newborns in 2001–2003. We used geographic information systems to form exposure parameters for sulfur dioxide, nitrogen oxides, ozone, carbon monoxide, and particulate matter with an aerodynamic diameter ≤ 10 μm (PM(10)) during the first 3 months of pregnancy using inverse distance weighting method. We present the effect estimates as odds ratios (ORs) per 10-ppb change for SO(2), NO(x), and O(3), 100-ppb change for CO, and 10-μg/m(3) change for PM(10). RESULTS: The risk of CL/P was increased in relation to O(3) levels in the first gestational month [adjusted OR = 1.20; 95% confidence interval (CI), 1.02–1.39] and second gestational month (adjusted OR = 1.25; 95% CI, 1.03–1.52) in the range from 16.7 ppb to 45.1 ppb, but was not related to CO, NO(x), SO(2), or PM(10). CONCLUSIONS: The study provides new evidence that exposure to outdoor air O(3) during the first and second month of pregnancy may increase the risk of CL/P. Similar levels of O(3) are encountered globally by large numbers of pregnant women.