Professionally and non-professionally applied household insecticides during pregnancy and early life and their associations with autism spectrum disorder and developmental delay in the CHARGE case-control study.

BACKGROUND

Autism Spectrum Disorder (ASD) is an increasing concern globally, with risks attributed to both genetic and environmental factors, including pesticide exposures. The CHARGE case-control study collected data to examine the relationship between household insecticide use and ASD or developmental delay (DD).

METHODS

Participants (n = 1526) aged 2-5 years from the CHARGE study encompassed children with clinically confirmed ASD (n = 810), DD (n = 186), and typically developing controls (n = 530) frequency matched to ASD children by age, sex, and geographic region. Household insecticide use was determined from parent interviews, as were the timing, frequency, and type of applications (professionally or non-professionally applied; indoor, outdoor, and flea applications) from three months pre-conception to the child's second birthday. Logistic regression models were adjusted for confounders to estimate odds ratios (OR) for ASD or DD associated with insecticide exposure.

RESULTS

Professionally applied indoor insecticides were associated with greater than two-fold increased odds of ASD for all time periods (OR: pre-pregnancy, 2.62 (1.26, 5.44); pregnancy, 2.52 (1.41, 4.48); year 1, 2.20 (1.33, 3.64); year 2, 2.13 (1.29, 3.49)). Odds were also elevated for any outdoor application during years 1 and 2 (OR: 1.37 (1.05, 1.79) and 1.34 (1.03, 1.74), respectively), however, significance did not hold after false discovery rate correction. Higher exposure frequency was associated with greater odds of ASD for nearly all application types and time periods. Non-professional indoor insecticide use was associated with increased odds of DD in trimester 3 and the pregnancy period (OR: 1.72 (1.03, 2.89) and 1.58 (1.03, 2.40), respectively).

CONCLUSION

Professionally applied indoor insecticides were consistently associated with ASD. The strong trend of increased odds with more frequent exposures, additional evidence for DD, and widespread use of household insecticides support increased regulatory scrutiny and public health interventions to minimize exposure during critical developmental windows.