Back injuries and related musculoskeletal disorders are the most common and costly work-related injuries in agriculture. The risk is especially high among workers who hand-harvest grapes; they are constantly turning, twisting and leaning forward to remove grapes from the vine, while routinely carrying loads of up to 80 pounds and lifting to dump the grapes into gondolas.

In a peer-reviewed study published in the January-March 2006 issue of the University of California's California Agriculture research journal, scientists showed that a simple engineering solution — giving workers smaller bins to fill with grapes — significantly reduced the risk of back injury among grape harvesters, without affecting productivity. The full article is posted online at http://californiaagriculture.ucop.edu.

“It may seem obvious that lightening the load would reduce back injury risk, but the problem is more complicated in that workers handle heavy loads differently than lighter loads,” explains James M. Meyers, specialist in the UC Berkeley School of Public Health. “Compared with heavier loads, lighter loads may be moved with more bending, velocity and twisting. Workers may expose themselves to other risk factors and experience less recovery time.”

Training not answer

Meyers and colleagues with the UC Agricultural Ergonomics Research Center (UC AERC) conducted a 3-year intervention study among grape harvesters in Napa and Sonoma counties. Since 1994, the center has studied common agricultural injuries and developed and tested cost-effective interventions. Meyers notes that contrary to general belief and industry practice, training is regarded by safety professionals as the least effective way to reduce workplace injuries. Rather, studies have shown that engineering interventions — which eliminate or reduce the hazards themselves — actually do reduce injury rates.

The UC AERC scientists provided the workers with a commercially available tub that is 13 percent smaller in volume than the standard tubs used in grape harvesting, which reduced the average load carried from 57 to 46 pounds (19 percent). Before and after each harvest, the workers completed a comprehensive survey of their musculoskeletal symptoms. Productivity was assessed by monitoring the tons of grapes picked by participating crews on a daily basis.

During the first (control) year of the harvest, workers used the larger standard tub only; of 95 workers who reported no musculoskeletal symptoms prior to the harvest, 66 (70 percent) reported symptoms when the harvest ended. In the second year of the study, workers used the smaller tub; of 90 workers who had no symptoms preharvest, only 26 (29 percent) reported symptoms postharvest. (Results in the third year were similar.)

With the smaller tub there was a small, nonsignificant reduction in the pounds of grapes delivered (an average of 168 pounds less than the 7,000 pounds carried by the average worker during an 8-hour shift), but neither workers nor their managers appeared to mind. “Because workers are paid on an incentive rate per ton rather than time, this decrease was of minor importance to managers,” Meyers says. “Furthermore, the workers in our study preferred the smaller tub because it was easier to manage.” Indeed, all of the companies participating in the study subsequently adopted the smaller tub for their workers.