Using geographic information systems to estimate potential pesticide exposure at the population level in Canada

Residents in close proximity to agricultural land are at risk of higher pesticide exposures. The purpose of this study was to generate national population-level exposure estimates for Canada for three commonly applied pesticides that are suspected carcinogens (2,4-dichlorophenoxyacetic acid (2,4-D), glyphosate and chlorothalonil). Using geographic information systems, pesticide exposure was estimated for every - census subdivision (CSD) in Canada (n = 5054) by combining raster-based surfaces for the distribution of crops with average crop-specific pesticide application rates data. Analyses examined all identified crops in combination with different pesticide application rates to obtain a cumulative potential total exposure. Specifically, the number of acres of particular crops were calculated for each CSD and then multiplied by the average pesticide application rates data, summed across crops, and combined with population data by CSD to provide a potential pesticide exposure estimate for each CSD. Results demonstrate that the population exposure varies greatly depending on agricultural production by CSD region. For example, in Ontario, the 2,4-D application rate was an average of 361 kg/km², while in Saskatchewan, which primarily grows field/cereal crops, 2,4-D application rates were much higher (3810 kg/km²). The highest potential exposures to all three pesticides were in the prairie provinces (Alberta, Saskatchewan, Manitoba) along with Prince Edward Island, Southern Quebec and British Columbia. This work can be used in conjunction with other exposure assessment approaches to better understand overall pesticide exposure among Canada's general population.