Injury incidence rates in a paint company on rotating production shifts

Reports of work accidents and increased absence due to sickness among shift workers have suggested that their work performance and health are adversely affected by interference with the body's normal circadian or biological rhythm. Since the rotating shift is the most disruptive of the work regimens, an investigation was undertaken of the reportable occupational injuries of 1700 paint production and associated employees of one company working only on rotating shift. Their annual accident incidence rates averaged over 10 years were compared to the average annual rate reported by the Department of Labor for the entire United States paint manufacturing industry representing predominately day and non-rotating shift workers. The significance of the hour of the accident incidence rates was tested by chi-square statistics using loglinear models appropriate for null hypotheses that assume no effect due to shift work. The incidence rates of the company studied were lower than those of the U.S. paint industry, suggesting work safety practices uniquely related to the company studied may have predominated. Within the company, however, some time-of-day and circadian effects were indicated by an increased rate of accidents on the night shift, particularly during the last 3 h of the shift.