First we combined the PUR data, land use maps, and geocoded address information and
created 500 meter buffers around addresses in our GIS for each year in the 26-year period from 1974
to 1999. Then we calculated annual ambient exposures to the individual pesticides, maneb, ziram, and
paraquat, for each participant by summing the pounds of pesticides applied in each buffer and
weighting the total poundage by the proportion of the acreage treated. For each of the three
pesticides examined in this study, we summed the annual pounds applied per acre to obtain 26 annual
exposure values for each pesticide separately for occupational and residential addresses.
Average pesticide exposures were then calculated for the following exposure time
windows: (1) 1974–1999, (2) 1974–1989, (3) 1990–1999 to address a possible
extended induction period for PD and assess the influence of age at exposure. A participant was
considered exposed to a particular pesticide when the pounds per acre measured was greater than zero
during the time window. We created exposure measures for single and combined pesticides by creating
categories of co-exposures to different pesticides. Participants who did not work or live in the
tri-county area between 1974 and 1999 could not be assigned an exposure estimate and were considered
unexposed.
In the same manner, we also created exposure estimates for organophosphates and
organochlorines, two pesticide classes that also contribute to neurodegeneration [34 (link), 35 (link)]. Participants were
considered exposed if they had any exposure to at least one organophosphate or organochlorine
pesticide.
created 500 meter buffers around addresses in our GIS for each year in the 26-year period from 1974
to 1999. Then we calculated annual ambient exposures to the individual pesticides, maneb, ziram, and
paraquat, for each participant by summing the pounds of pesticides applied in each buffer and
weighting the total poundage by the proportion of the acreage treated. For each of the three
pesticides examined in this study, we summed the annual pounds applied per acre to obtain 26 annual
exposure values for each pesticide separately for occupational and residential addresses.
Average pesticide exposures were then calculated for the following exposure time
windows: (1) 1974–1999, (2) 1974–1989, (3) 1990–1999 to address a possible
extended induction period for PD and assess the influence of age at exposure. A participant was
considered exposed to a particular pesticide when the pounds per acre measured was greater than zero
during the time window. We created exposure measures for single and combined pesticides by creating
categories of co-exposures to different pesticides. Participants who did not work or live in the
tri-county area between 1974 and 1999 could not be assigned an exposure estimate and were considered
unexposed.
In the same manner, we also created exposure estimates for organophosphates and
organochlorines, two pesticide classes that also contribute to neurodegeneration [34 (link), 35 (link)]. Participants were
considered exposed if they had any exposure to at least one organophosphate or organochlorine
pesticide.
