Overnight Shift Work Identified as "Probable Carcinogen"

The International Agency for Research on Cancer (IARC), a part of the World Health Organization has evaluated more than 900 agents since 1973, of which approximately 400 have been identified as carcinogenic or potentially carcinogenic to humans. After a thorough review of scientic evidence and expert working group with IARC has concluded that shiftwork that involves circadian disruption is probably carcinogenic to humans.


Medical research studies have found that long-term night workers have a higher risk of breast cancer than women who do not work at night. The studies show that constant light, dim light at night or simulated chronic jet lag can substantially increase tumour development. Other studies show that reducing melatonin levels at night increases the incidence or growth of tumours.


The agency noted that these study results may be explained by the disruption of the circadian system that is caused by exposure to light at night. This can alter sleep-activity patterns, suppress melatonin production and disregulate genes involved in tumour development. The noted that the most disruptive shiftwork is nightwork.


This classification will be of importance to healthcare and automotive workers among others who work midnights in our city and province.



The IARC website is an extremely useful website when it comes to identifying cancer causing agents and can be found at http://www.iarc.fr/ENG/Databases/index.php.