Study explores link between farm machinery vibration and workers’ back pain

Iowa City, IA — A NIOSH-funded study of farm machinery found that the machine operators experienced whole-body vibration at levels that reached the European Union’s “action level” for exposure limit within two hours of operation on nearly 30 percent of the equipment tested.

Examining vibrations levels on 112 pieces of machinery – including tractors, combines, forklifts, skid loaders and all-terrain vehicles – used by 55 farm workers, researchers from the University of Iowa attached sensors to the seats and floors. The floor sensors allowed the researchers to monitor how effectively the seats reduced vibration levels. The group also measured the participants’ posture aboard the machinery.

More than half of the machines (56 percent) met the EU’s action level – defined as that above which the risk of health effects increase – within eight hours of use. The EU’s whole-body vibration exposure limits are similar to recommendations made by the American Conference of Governmental Industrial Hygienists. OSHA does not enforce any such standard.

“Exposure to whole-body vibration is a key occupational risk factor for back pain, which is common among agricultural workers,” study author Nathan Fethke, associate professor of occupational and environmental health at the school’s College of Public Health, said in an Oct. 2 press release. “Spending many hours operating machinery can increase the frequency of back pain episodes and, if the pain is severe or becomes chronic, medical costs can be quite high.”

Among the equipment, the combines had the lowest average vibration exposure level, while tractors and heavy utility vehicles showed measurements that were about twice that of the combines. The researchers credit the combines’ mass and high-quality seat suspension systems for the lower levels. In fact, combine seats reduced by up to half the vibration levels measured by the floor sensors.

Researchers recommend farm workers regularly check seat suspension systems to ensure they are greased, working properly and adjusted for the operator’s body weight. If a seat tends to “bottom out” despite regular maintenance and body-weight adjustments, the researchers advise replacing it.

Body posture in the driver’s seat also plays a role in back pain and discomfort. Compared with the other equipment tested, combines exhibited the best trunk postures among the workers.

The study was published online Sept. 20 in the Annals of Work Exposures and Health.