This study was conducted according to international guidelines for the protection of human subjects
and was approved by the ethics committee of the University of Brasilia. All participants read and
signed the free and informed Consent Term, which included the research objectives, procedures, and
privacy in data handling.
2.1. Population Studied
This was a cross-sectional epidemiologic study conducted between 2009 and 2011 with farmers from
two locations in the Midwestern region of Brazil: Goianápolis (162.38 km2, located 170 km from
Brasília, the capital of Brazil) and Taquara Rural Nucleus, in the city of Planaltina (351 km2, 90 km from
Brasília). All participants were 18 years of age or older. All farmers were directly involved with
pesticides, either in the preparation of the pesticide solution and/or its application in the field. The study
used a convenience sampling (non-probability sampling), through a systematic recruitment process.
In Goianápolis, 40% of its approximately 11,000 inhabitants are directly or indirectly involved in
tomato-growing activities [25]. At this location, the crop is cultivated year-round in about 30 planting
areas of 1–2 ha, in which 9–10 farmers work in a sharecropper regime under the management of the
owner or some other person. After harvesting, the workers migrate to another planting area, repeating
the cycle. The managers of 21 planting areas were contacted by telephone (numbers provided by the
local seed supplier) to obtain permission to visit the areas, and to recruit farmers to participate in the
study. Only two managers agreed to join the study, and we were able to recruit 18 farmers from two
planting areas in the region.
According to EMATER-DF, a local government agency that provides technical support to farmers,
there are 318 planting areas and 1,100 farmers in Taquara, mainly vegetable and fruit growers. In each
4–5 ha planting area, 5–13 individuals work in family farming settings or share-cropper regimes
growing multiple crops. After harvesting, a new planting cycle begins, usually with a different crop.
Our first contact with the farmers took place at two community events sponsored by EMATER, at
which 30 farmers agreed to participate in the study, answering a questionnaire and giving us their
contact information. We obtained the telephone contact information of an additional 112 farmers from
EMATER, 30 of whom were unreachable, 10 were no longer involved in agricultural activities, six did
not want to participate in the project, and two were no longer living in the area. A total of 94 farmers
from 38 Taquara planting areas participated in the study. In addition, 18 family members not directly
involved with pesticides (residents) agreed to participate in the study. For the control group, 64
individuals were recruited from the local hospital, school and EMATER office, in addition to rural
workers with no contact with pesticides. An interview was conducted with each potential control group
member to assure that none of them had any direct or indirect contact with pesticides over the last
year. In summary, the study involved 112 farmers, 18 residents, and 64 controls.