Associations between prenatal metal mixtures and allergic symptoms in childhood

Previous work has linked exposure to individual metals in pregnancy to allergic outcomes postnatally but few studies have examined metals exposure as a mixture. Analysis included 542 mother-child dyads enrolled in the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) birth cohort in Mexico City. Levels of arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), manganese (Mn), nickel (Ni) and lead (Pb) were analyzed in blood collected during the 2^nd and 3^rd trimesters. Atopic dermatitis and allergic rhinitis symptoms were assessed via questionnaire at 4-6 years and 6-8 years of age. Mixture associations were modeled using repeated holdout WQS regression with adjustment for relevant covariates. We found evidence of a 2^nd trimester metal mixture association with an increased risk of ever allergic rhinitis symptoms at 6-8 years (OR = 1.16, 95 % CI: 1.05, 1.28). Mn contributed the most to the mixture effect, followed by Cu, and Pb. We also found evidence of a 2^nd trimester metal mixture association with an increased risk of current allergic rhinitis symptoms at 6-8 years (OR = 1.13 95 % CI: 1.02, 1.26) in which Mn, Cu and Pb were again the main contributors. Lastly, we saw evidence of a 3^rd trimester metal mixture association with an increased risk of current allergic rhinitis symptoms at 6-8 years (OR = 1.17 95 % CI: 1.03, 1.32). As and Mn were the top contributors to the mixture association followed by Cu and Ni. Our results suggest that prenatal exposure to metals is related to childhood allergic symptoms.