Neurobehavioral performance and work experience in Florida farmworkers - Environmental Medicine

Environmental Health Perspectives, Nov, 2003 by Freya Kamel, Andrew S. Rowland, Lawrence P. Park, W. Kent Anger, Donna D. Baird, Beth C. Gladen, Tirso Moreno, Lillian Stallone, Dale P. Sandler

Farmworkers experience many work-related hazards, including exposure to neurotoxicants. We compared neurobehavioral performance of 288 farmworkers in central Florida who had done farm work for at least 1 month with 51 controls who had not. Most of the farmworkers had worked in one or more of three types of agriculture: ornamental ferns, nurseries, or citrus fruit. We collected information on farm work history in a structured interview and evaluated neurobehavioral performance using a battery of eight tests. Analyses were adjusted for established confounders including age, sex, education, and acculturation. Ever having done farm work was associated with poor performance on four tests--digit span [odds ratio (OR) = 1.90; 95% confidence interval (CI), 1.02-3.53], tapping (coefficient = 4.13; 95% CI, 0.00-8.27), Santa Ana test (coefficient = 1.34; 95% CI, 0.29-2.39), and postural sway (coefficient = 4.74; 95% CI, -2.20 to 11.7)--but had little effect on four others: symbol digit latency, vibrotactile threshold, visual contrast sensitivity, and grip strength. Associations with farm work were similar in magnitude to associations with personal characteristics such as age and sex. Longer duration of farm work was associated with worse performance. Associations with fern work were more consistent than associations with nursery or citrus work. Deficits related to the duration of work experience were seen in former as well as current farmworkers, and decreased performance was related to chronic exposure even in the absence of a history of pesticide poisoning. We conclude that long-term experience of farm work is associated with measurable deficits in cognitive and psychomotor function. Key words: citrus fruit, cognitive function, farm work, neurobehavioral performance, nurseries, ornamental ferns, psychomotor function. Environ Health Perspect 111:1765-1772 (2003). doi: 10.1289/ehp.6341 available via http://dx.doLorg/[Online 23 July 2003]

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Farmworkers are exposed to numerous hazards in the course of their work, including injury and exposure to pesticides and other toxicants (Moses et al. 1993; Villarejo and Baron 1999). Farmworkers are a vulnerable occupational group: They are often foreign-born and may not speak English; they may lack formal education; and they and their families often live in poverty. The agricultural industry is exempt from many federal regulations governing the workplace, and farmworkers are rarely represented by labor unions. Potential adverse health effects of farm work include traumatic injury, musculoskeletal disorders, respiratory conditions, dermatitis, cancer, and neurologic disorders. Some of these conditions may be related to pesticide exposure (Das et al. 2001; Keifer and Mahurin 1997; Moses et al. 1993). The health effects of farm work are compounded by the relative lack of access of this group to medical information and care.

Farmworkers in several settings have been reported to experience elevated rates of neurologic dysfunction. For example, they had increased frequency of neurologic symptoms (Ciesielski et al. 1994; Gomes et al. 1999) and decreased performance on some neurobehavioral tests (Bazylewicz-Walczak et al. 1999; Gomes et al. 1999; Rohlman et al. 2001) compared with unexposed workers. Farmworkers with a history of pesticide poisoning experienced more symptoms and had impaired neurobehavioral performance relative to nonpoisoned controls (McConnell et al. 1994; Rosenstock et al. 1991; Wesseling et al. 2002).

We report here the results of a large, population-based study of farmworkers in central Florida. The focus of the study was the relationship of long-term experience of farm work to neurobehavioral performance and potential differences related to type of farm work. We took into account important confounders, including education and acculturation.

Materials and Methods

Population. We conducted a cross-sectional study in central Florida in 1996-1997. Study participants were recruited in collaboration with the Farmworkers Association of Florida, a farmworker advocacy group (Kamel et al. 2001). Our target population was members of the Community Trust Federal Credit Union and their spouses. The Credit Union is a small savings institution with branches in several Florida communities. It is affiliated with several community organizations, including the Farmworkers Association; many but not all of its members are farmworkers. Credit Union members were typical members of the local communities (Kamel et al. 2001).

We randomly selected names from the membership lists of the Credit Union in two communities, Apopka and Pierson. Most farmworkers in these communities had worked in one of three types of agriculture: growing and harvesting ornamental ferns, working in nurseries, or picking citrus fruit. Bilingual recruiters chosen by the Farmworkers Association located the selected individuals and administered a screening interview to determine eligibility and to identify spouses of credit union members, who were then also screened. To reduce variability in neurobehavioral performance, we restricted the age range to 28-55 years of age and excluded individuals with diabetes, epilepsy, or stroke. We recruited men and women of any race or ethnicity who were fluent in Spanish or English. We screened 80% of selected individuals, and 81% of those eligible participated in the study (Kamel et al. 2001).