Annually from late July through early September, thousands of seasonal workers harvest wild blueberries in Maine and the eastern Provinces of Canada. Maine's crop in 1993 was approximately 65 million pounds. The harvesting is mostly done by manual raking through the low lying bush (height < 10 inches). In response to reports of tendinitis among blueberry rakers, we conducted a survey in August, 1993, consisting of a symptom questionnaire, physical examinations of the hands and wrists, and an ergonomic assessment of raking.
The participants were 134 rakers who volunteered on-site; 73% were males, compared to 74% among the total 1300 rakers hired by this company. The median age of our participants was 30, compared to 28 for all rakers. Children (age 12 to 18) were 10% among the participants and 16% among all rakers.
Participants reported moderate to severe pain in the back (13.5%), in the hand/wrist (12.0%), and in the elbow (7.5%). On screening physical examinations, 9.8% had some hand/wrist pain accompanied by a positive Phalen's or Tinel's test (suggesting carpal tunnel syndrome), or a positive Finkelstein's test (suggesting de Quervain's disease - tenosynovitis of the abductor pollicis longus and the extensor pollicis brevis). Since the survey was conducted in late August, some rakers might have left work because of pain.
Ergonomic analysis of raking revealed that rakers worked mostly in stooped posture and frequently carried loaded buckets (up to 28 pounds each). The metal rakes, shaped like a deep dustpan with the handle attached inward, varied in size (14 to 24 inches wide) and weight (2.6 to 4.6 pounds). The typical raking motion involved constant firm grip on the handle, ulnar deviation of the wrist initially to insert the tines into the bush, followed by radial deviation and lifting of the rake to separate berries. The force of this lifting was estimated to he 87 ñ 17.5 newtons, and the motion was repeated 32 ñ 13 times/min.
These forceful and repetitive motions would cause friction on the tenosynovium and explain a high incidence of tendinitis. Many seasonal workers depend on income from this work, which nonetheless needs to be performed without adverse health effects. Ergonomic recommendations such as keeping the wrist in a neutral position (to avoid deviations) and an initial period of slow raking (work hardening) might reduce the incidence of tendinitis. Some efforts are underway to improve the design of the rake.
This research abstract was extracted from a portion of the proceedings of "Agricultural Safety and Health: Detection, Prevention and Intervention," a conference presented by the Ohio State University and the Ohio Department of Health, sponsored by the Centers for Disease Control/National Institute for Occupational Safety and Health.
The authors noted above are from: NIOSH, Cincinnati, OH; NIOSH, Cincinnati, OH; Maine Dept. of Human Services, Augusta, ME; and Maine Dept. of Human Services, Augusta, ME respectively.
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