Foetal exposure to heavy metals and risk of atopic diseases in early childhood

Background: Accumulating evidence suggests that in utero exposures can influence the development of the immune system and thus contribute to disease development. Studies investigating the association between prenatal exposures to heavy metals and atopic diseases, however, are scarce.Methods: Children from the EDEN birth cohort were prospectively followed up using parental questionnaires with validated questions on asthma, allergic rhinitis, eczema, and food allergy symptoms. The questionnaires were administered every 4 months during the children's first year, and then every year until the age of 5, with a final survey at the age of 8. Serum concentrations of lead (Pb), cadmium (Cd), and manganese (Mn) were assessed in maternal blood samples collected during mid-pregnancy and in cord blood of 651 mother-children pairs. Hazard ratios (HR) for the incidence of each atopic disease in relation to the exposure to metals were calculated using Cox proportional hazard models.Results: Levels of Cd in cord blood were associated with greater risk of asthma (hazard ratio [95% confidence interval] for upper vs lower quartile: 1.81 [1.00-3.29]), eczema (1.60 [1.09-2.35]), and food allergy (3.17 [1.36-7.38]), while Mn levels in maternal serum were associated with eczema (1.55 [1.05-2.28]). These associations were similar in males and females and were confirmed using log concentrations of metals as exposures.Conclusions: Our results support the hypothesis that fetal exposure to heavy metals may affect the development of asthma, eczema, and food allergy in childhood and suggest that timing of exposure in utero may have a role in these associations.