Exploring the Joint Association Between Agrichemical Mixtures and
Pediatric Cancer
Abstract
Nebraska’s age-adjusted incidence rates for childhood cancers are among
the highest in the US. Previous studies indicated associations between
agrichemical exposures (atrazine and nitrates) and pediatric cancer
rate, assuming single pollutant exposure. We evaluated the joint
association between the agricultural mixture and pediatric cancer.
Agrichemical exposures at a county scale were quantified using the USGS
Pesticide National Synthesis Project for frequently applied pesticides
from 1992 to 2014 in 93 Nebraska counties. Outcomes were quantified
using pediatric cancer diagnosed among children < 20 years of
age (1992-2014) from the Nebraska cancer registry. We adjusted for
social vulnerability factors such as race, income, employment, and
access to care. The associations between 32 agrichemicals and cancer
subtypes were assessed using the Generalized Weighted Quantile Sum
Regression (gWQS) model. The model was fit assuming a Poisson
distribution and using the pediatric population as an offset-term and
social vulnerability factors as covariates. We observed a statistically
significant positive association between the 32 agrichemicals and
overall pediatric cancer and subtypes. The strength of associations was
slightly stronger among brain and CNS cancers (β=0.36, CI = 0.14, 0.57)
compared to overall cancer (β=0.30, CI = 0.16, 0.44) and leukemia
(β=0.23, CI =0.09, 0.38). Dicamba, glyphosate, paraquat, quizalofop,
triasulfuron, and tefluthrin largely contributed to the joint
association. These findings may explain the joint associations of the
agrichemical mixture on childhood cancer. Alternative biomarker-based
approaches to measuring human exposure are worth investigating for
chemicals of concern, particularly in counties with high agrichemical
and cancer rates.