Workers Health & Safety Centre

Shift Work: Disrupting Workers' Health and Lives

Shift Work: Disrupting Workers' Health and Lives
Though shift work has long been considered an occupational hazard, its widespread and serious impact on worker health is becoming increasingly clear. Citing a number of health concerns for workers, editors of the globally recognized Scandinavian Journal of Work and Environmental Health (SJWEH) concluded in March 2010, “…shift work is definitely among one of the most serious occupational health problems of our time. …we cannot continue to delay taking preventive and curative public health actions in anticipation of further data.”
Later the same year (October, 2010), the same journal published online a Canadian study entitled, Shift Work Trends and Risk of Work Injury Among Canadian Workers,  which associated nine per cent of all workplace injuries with shift work exposure.
The SJWEH is not alone in their concern. An expert working group convened by the International Agency for Research on Cancer (IARC) in December 2007 designated shift work involving circadian rhythm disruption as “probably carcinogenic to humans” (Group 2A).
The human body functions according to a natural sleep-wake/day-night cycle referred to as a circadian rhythm. This rhythm, guided by environmental cues such as darkness and light, helps to control sleep and the maintenance of biological functions including body temperature and hormone levels. Shift work, particularly involving work at night, disrupts this rhythm and can lead to a range of adverse health effects.
Sari Sairanen, director health, safety and environment for the Canadian Auto Workers Union (CAW) agrees with the SJWEH editorial and the findings of IARC’s expert working group – for the most part. “I think however it’s safe to say we can remove the term “probably”. When we consider the experiences of workers and the mounting body of evidence, we know for certain shift work is damaging their health and well-being.”
In designating shift work a Group 2A carcinogen, IARC cited studies where breast cancer incidence was found to be higher in female flight attendants who frequently cross time zones. They also cited studies of nurses employed long-term and working at night who showed increased risk of developing breast cancer.
 “This is an obvious concern for our members,” explains Nancy Johnson, health and safety representative, Ontario Nurses’ Association (ONA). “Shift work is an essential part of the job for many nurses. So our efforts of necessity will focus on ways to eliminate or mitigate the risks to health.”
In April 2010, Ontario’s Institute for Work and Health (IWH) published the results of an extensive literature review titled Shift Work and Health citing research linking exposure with breast, colorectal and prostate cancer. They also reported links with reproductive health issues, gastrointestinal disorders, cardiovascular disease, diabetes, fatigue, sleep disorders as well as excess risk for workplace incidents/injuries. Stress, work/life conflict and other mental health issues were also identified.
 “Though we have obvious concerns with cancer and other risks to health, we are equally worried with the enormous strain placed on lives beyond work,” says Andy King, national health, safety and environment department leader, United Steelworkers Union (USW). “This work/life conflict can have serious consequences in terms of damaged or severed relationships and the ability of these workers to participate in their communities. This conflict can also lead to debilitating mental health issues for affected workers.”
Unions are increasingly engaging their members and employers to both increase awareness about shift work as an occupational hazard, but also to explore solutions to reduce the health impacts of shift work or eliminate the risk altogether.
Dr. Robert Casper, a researcher at the Samuel Lunenfeld Research Institute at Toronto’s Mount Sinai Hospital, has developed an optical lens that could be worn by shift workers or installed on light covers to reduce the health risks associated with light at night. In clinical trials researchers have shown it’s possible to prevent circadian rhythm disruptions. “Not only could these lenses help improve the overall health of shift workers, they could also help people with other sleep disorders,” said Dr. Casper.
The Canadian Auto Workers Union is currently working with General Motors of Canada to establish a pilot project to test the effectiveness of glasses fitted with these lenses for shift workers. 
To date though, most efforts to mitigate or prevent the health or safety effects related to shift work have focused on shift scheduling and shift rotation, including choosing only forward shift rotations (day to afternoon to night) and ensuring adequate rest between each shift and between shift changes.
Many unions, including the United Steelworkers Union and the Communications, Energy and Paperworkers Union of Canada (CEP), have developed resources to help raise awareness about the serious risk to health shift work poses, as well as control strategies to consider at the workplace level.  
According to CEP’s Shiftwork fact sheet, workers should be scheduled for no more than five consecutive eight hour night shifts, four consecutive 10 hour shifts or three consecutive 12 hour shifts. A concern raised by CEP is the fact “Most shift schedules have been borrowed or inherited rather than thought out.”
Research supports a more participatory approach to developing shift schedules. “Engagement from workers, unions, supervisors, etc.,” was a key message in IWH’s Shift Work and Health literature review. This approach is also supported by the European Union (EU) Survey on Working which found the impacts of non-standard working hours on health may be lessened if workers can participate in designing and implementing their shift schedules. 
Andy King of the USW concurs. “In most cases, shift scheduling has been done with little regard for safety, health or the social needs of workers and with very little if any input from workers. And if we’ve learned one thing time and again, it’s that worker and worker representative involvement throughout any hazard prevention process is essential.”
Editor’s Note
The WHSC offers training and other information resources to address this serious occupational hazard. Be sure to talk to a WHSC Training Services rep near you or visit us online at There you will find a recently published edition of Resource Lines entitled, Shift work: Disrupting Worker Health and Lives.

What is shift work and who’s working it?

A standard work day consists of a shift scheduled between 7:00 am and 6:00 pm. Shift work can be defined as work scheduled outside of these “normal” hours. Examples include: regular evening schedule (begin after 3:00 pm and end before midnight); regular night schedule (begin after 11:00 pm and end before 11:00 am), rotating shift schedule (day, afternoon/evening, night), split shifts (two scheduled periods of work each day), on call, and irregular schedule.
Overall, 25 per cent of the working population work shifts here in Canada. Twenty per cent are engaged in shift work involving the night shift. Some sectors rely on shift work more than others. A 2005 Statistics Canada survey reported almost half of those employed full-time in health-related occupations and two-thirds of police, security and others in protective services worked shifts. Shift work is also common in accommodation and food industries, transportation and warehousing, sales and service, primary industries (ie. forestry, mining and agriculture) and manufacturing.