Take longer shifts, add being new on the job and lacking a routine and - in mining - you get an increased risk of injuries relative to those occurring during the first eight hours, according to a study published recently in Occupational & Environmental Medicine. Furthermore, incidents occurring during long working hours were more likely to result in a death or involve multiple injured workers.

Researchers Lee S. Friedman, Kirsten S. Almberg and Robert A. Cohen used data from the US Mine Safety and Health Administration (MSHA) to take a look at occupational safety risk during longer working hours – which are increasingly becoming the norm. U.S. miners often work extended shifts and over 47 hours per week, unlike the general US workforce where average work hours have declined to 38.5 hours per week,

Another key finding of Injuries associated with long working hours among employees in the US mining industry: risk factors and adverse outcomes is that injuries reported by contract workers increased fourfold compared with those working directly for mine operators. They were also more likely to be injured during long working hours.

“Working for contractors is associated with working extended hours and irregular shifts, and the use of contract labour has been reported to be associated with inadequate training, lower compliance with occupational safety laws and higher injury rates.”

Previous studies have uncovered a relationship between long work hours, psychomotor impairments caused by fatigue and an increased risk of injury.

The numbers

A total of 52 206 injuries (9.6%) occurred during long working hours. The proportion of long working hour injuries increased from 5.5% of all injuries in 1983 to its peak in 2015 at 13.9% (p<0.001). Risk factors associated with long working hour injuries included irregular shift starts, being newly employed, employment by a contractor, metal/non-metal operations and mines with <100 employees. In two separate adjusted models, long working hour injuries were associated with a higher odds of death (adjusted OR [aOR]=1.32; 95% CI 1.18 to 1.48) and single incidents resulting in two or more workers injured (aOR=1.73; 95% CI 1.58 to 1.89).


The authors predict that injuries during long working hours will likely continue to grow as a problem in the mining industry, given the international shift towards using contract labor and extended workdays.

Lee S Friedman is with the School of Public Health, University of Illinois at Chicago, Chicago, Illinois.

Kirsten S Almberg is with the School of Public Health, Division of Environmental and Occupational Health Sciences, University of Illinois at Chicago, Chicago, Illinois.

Robert A Cohen is with the Environmental and Occupational Health Sciences, University of Illinois at Chicago, Chicago, Illinois, USA and Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois.