Residential pesticide exposures

All participants were asked to provide a residential history that included the residence they lived in for the longest period of time prior to age 14. Details obtained included calendar years of residence; whether the property was urban, suburban, small town or rural; if the residence was ever used as a farm or orchard; if the residence was treated regularly for pest control and if so, how frequently and by whom; and proximity (“within seeing, smelling, or hearing distance”) of several land use types including orchards, golf courses, nurseries or commercial greenhouses.

Among women who reported ever living on a farm for ≥12 months or that their longest residence before age 14 was a farm, additional farm exposure information was collected. Living on a farm was defined as a residence where crops are grown or livestock is raised, not including small personal gardens. Women were asked to recall characteristics of the farm they lived on longest from birth to age 18. Farm characteristics included types of crops or livestock, whether pesticides were ever used on the farm, whether participants were ever present in fields on the same day as pesticides were applied, whether participants personally mixed, loaded, or applied pesticides, cleaned or help clean pesticide mixing or application equipment, or ever got an unusually high amount of pesticides on skin or clothing during these activities.

Women were also asked to report whether they were ever, “in the fog or spray of chemicals, or as a child, did you ever chase after the fogger trucks or airplanes that sprayed for mosquitos or other pests?” and, if so, whether this occurred before and/or after 1975. Study participants’ ages in 1975 were calculated by subtracting their year of birth. Based on peak use of DDT in fogger trucks and planes in 1959, we performed sensitivity analyses to examine breast cancer associations specifically among women born in 1941–1958 (who would have been ages 0–18 in 1959), and women born during 1944–1949 (who would have been pubertal during peak years of DDT use).