乌鸦传媒

The risk of parkinsonism doubled with increased occupational exposure to pesticides, including eight agents associated with experimental parkinsonism, according to data from patients at North American movement disorder centers.

Any exposure to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) almost tripled the risk of parkinsonism compared with individuals who reported no exposure to the agent, according to a report in the September Archives of Neurology.

Developed in 1946, 2,4-D was the first successful selective herbicide and is now the most widely used weed killer in the world.

"Occupational pesticide exposure emerges as the most consistent etiologic association with parkinsonism", Caroline M. Tanner, MD, PhD, of the Parkinson's Institute in Sunnyvale, Calif., and colleagues concluded in their report.

"This convergence of epidemiologic and laboratory data from experimental models of Parkinson's disease lends credence to a causative role of certain pesticides in the neurodegenerative process," they added.

"Other pesticide exposures such as hobby gardening, residential exposure, wearing treated garments, or dietary intake were not assessed. Because these exposures may affect many more subjects, future attention is warranted."

While researchers had suspected occupational chemical exposure as an etiologic factor in Parkinson's disease, previous studies yielded inconsistent findings. Few studies evaluated a possible direct relationship between occupational chemical exposure and Parkinson's disease, the authors said.

Some evidence had suggested that toxicant-induced parkinsonism has atypical features, but that issue also had not been systematically investigated.

To address limitations of current data, Tanner and colleagues enrolled patients at eight North American movement disorder centers in a case-control study of parkinsonism risk associated with occupations and exposure to toxicants.

The investigation focused on five occupations previously suggested as posing an increased risk of parkinsonism: agriculture, education, healthcare, welding, and mining. Examination of toxicant exposures included solvents and pesticides putatively associated with parkinsonism.

To reduce the potential for excluding toxicant-induced cases, investigators enrolled patients with typical and atypical features. Occupation was determined in accordance with the 2000 Standard Occupational Classification manual. Toxicant exposure was assessed from detailed information about patients' job tasks.

The study included 519 patients with parkinsonism and 511 age- and sex-matched controls. The authors found no association between parkinsonism and work in agriculture, education, healthcare, or welding.

Any history of work in business and finance, legal occupations, construction and extraction, or transportation and material moving was associated with an increased risk of postural instability and the gait-difficulty subtype of parkinsonism.

The adjusted odds ratio for parkinsonism increased with pesticide use (OR 1.90, 95% CI 1.12 to 3.21), use of any of eight agents linked to experimental parkinsonism (OR 2.20, 95% CI 1.02 to 4.75), and exposure to 2,4-D (OR 2.59, 95% CI 1.03 to 6.48).

Specific occupation, job tasks, or task-related exposures were not associated with diagnosis of parkinsonism at a younger age.

Limitations of the study included use of a referral population, exclusion of patients with dementia, and a largely Caucasian group, all of which may limit generalization of the findings to other groups.

Other limitations include the absence of pesticide exposure measurements, as opposed to patient recall, inclusion of multiple association data, and inability to determine causality from case-control studies.

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