Prenatal exposure to neonicotinoid insecticides and childhood allergic disease trajectories: A nationwide risk assessment from the JECS birth cohort.

BACKGROUND: Neonicotinoid insecticides are widely used globally, raising concerns about their impact on human health, particularly during the vulnerable prenatal period. However, long-term epidemiological evidence regarding their role in childhood allergic disease development remains unclear. This study evaluated the association between prenatal neonicotinoid exposure and longitudinal trajectories of atopic dermatitis (AD) and wheeze in early childhood to provide data for environmental risk assessment. METHODS: Using data from the Japan Environment and Children's Study (JECS), we analyzed a nationwide sub-cohort of approximately 8,900 mother-child pairs. Neonicotinoid concentrations were measured in maternal urine during early and mid-pregnancy. Disease trajectories (1-6 years) for AD and wheeze were identified using Latent Class Growth Analysis (LCGA). Multivariable logistic regression was used to estimate the association between exposure levels and trajectory phenotypes, focusing on the impact of background environmental exposure. RESULTS: Four distinct trajectories were identified for both AD and wheeze. In the multivariable analyses, several nominal associations were observed (e.g., ACE and late-onset AD: aOR 1.67, 95 % CI 1.09-2.54); however, none remained statistically significant after Benjamini-Hochberg correction. Overall, prenatal exposure to neonicotinoids at current environmental levels in Japan was not consistently associated with any specific trajectory of AD or wheeze. CONCLUSION: We found no robust and consistent evidence of an association between prenatal neonicotinoid exposure and childhood atopic dermatitis or wheeze trajectories in this Japanese cohort under relatively low background exposure conditions. Further studies in populations with different exposure profiles are warranted.