Geospatial analysis of cancer incidence and its association to estimated
pesticide usage in the U.S. west
Abstract
This study’s objective was to evaluate the potential geospatial
relationship between agricultural pesticide use and cancer incidences by
using the concept of consolidated environmental burden indices. We
conducted two sets of experiments, using pesticide data collected from
the U.S. Geological Survey Pesticide National Synthesis Project database
and using cancer data collected from the National Cancer Institute State
Cancer Profiles and Cancer Data Registry of Idaho. In the first
experiment, we analyzed the associations between several potentially
carcinogenic pesticides and metals to the pediatric cancer incidence
among the counties of Idaho. Principal component analysis was adopted to
consolidate the environmental variables. This study identified that the
principal components (PCs) were significantly associated with pediatric
cancer at P-value < 0.01 and a t-statistic > 3.
The PC’s improved model performance substantially, from NSE = 0.22 for
the control case to NSE = 0.52 for the treatment case. In the second
experiment, we evaluated the associations of pesticides to two cancer
metrics (pediatric cancer incidence and total cancer incidence) across
each of the 11 contiguous states in the Western U.S. at the state and
county spatial scales. A multi-level model was developed using fumigant
mass, fumigant mass tertiles as well as county and state boundaries,
which strongly predicted total cancer incidence (R-squared = 0.95, NSE =
0.91, and SSR = 8.22). Further, this study also identified significant
associations between total fumigant mass, total pesticide mass, medium
and high fumigant class (tertiles > 0.33), and high
pesticide class (tertile > 0.66), relative to total cancer
incidence (P-value < 0.01) in the U.S. west. Fumigant
application rate was shown to be significantly related to the incidence
of total cancers and pediatric cancer. Moreover, this relationship was
maintained regardless of the spatial resolution used in the analysis
(county or state). Both studies reinforce inferences from previous
studies that pesticides are related to an elevated risk for pediatric
cancer. Similarly, among the pesticides, fumigants such as metam were
shown to be important relative to the cancer incidences for both
experiments, highlighting the significance of further analysis.