Residential radon and birth defects: A population-based assessment.

BACKGROUND Associations have been reported between maternal radiation exposure and birth defects. No such studies were found on radon. Our objective was to determine if there is an association between living in areas with higher radon levels and birth defects. METHODS The Texas Birth Defects Registry provided data on all birth defects from 1999 to 2009 from the entire state. Mean radon levels by geologic region came from the Texas Indoor Radon Survey. The association between radon and birth defects was estimated using multilevel mixed effect Poisson regression. RESULTS Birth defects overall were not associated with residential radon levels. Of the 100 other birth defect groups with at least 500 cases, 14 were significantly elevated in areas with high mean radon level in crude analyses, and 9 after adjustment for confounders. Cleft lip with/without cleft palate had an adjusted prevalence ratio of 1.16 per 1 picoCurie/liter (pCi/L) increase in exposure to region mean radon, 95% confidence interval, 1.08-1.26. Cystic hygroma / lymphangioma had an adjusted prevalence ratio of 1.22 per 1 pCi/L increase, 95% confidence interval, 1.02-1.46. Other associations were suggested but not as consistent: three skeletal defects, Down syndrome, other specified anomalies of the brain, and other specified anomalies of the bladder and urethra. CONCLUSION In the first study of residential radon and birth defects, we found associations with cleft lip w/wo cleft palate and cystic hygroma / lymphangioma. Other associations were suggested. The ecological nature of this study and multiple comparisons suggest that our results be interpreted with caution.