The Canadian Cancer Society estimates that thyroid cancer will be the seventh most commonly diagnosed cancer overall in Canada in 2020, and the fifth most commonly diagnosed in females [1]. It is most commonly diagnosed among people aged 20 to 55.
Little is known about occupational risk factors for thyroid cancer. Exposure to ionizing radiation (from radiation therapy, diagnostic imaging or nuclear fallout) during childhood and adolescence is the strongest known risk factor for thyroid cancer. In the workplace, the most consistent associations have been seen for radiation-exposed workers and health care occupations, while some other studies have seen an increased risk in pesticide-exposed workers and agricultural occupations [2].
Known occupational risk factors
Possible occupational risk factors
Some previous studies have found increased risk of thyroid cancer among workers in agricultural workers, who may be exposed to pesticides. However, no increased risks were seen among these groups in the ODSS.
Medical workers may be exposed to low-dose ionizing radiation when they administer radiation therapy or perform diagnostic imaging. Exposure to ionizing radiation during adulthood is a possible risk factor for thyroid cancer.
*This industry includes laboratories (dental, medical, x-ray, etc.) providing analysis, diagnosis or treatment service to the medical or dental professions or to patients on prescription of a physician or dentist, and organizations such as the Victorian Order of Nurses, Red Cross Blood Transfusion Service, and St. John Ambulance.
Figure 1. Risk of thyroid cancer diagnosis among workers employed in each industry group relative to all others, Occupational Disease Surveillance System (ODSS), 1983-2016
The hazard ratio is an estimate of the average time to diagnosis among workers in each industry/occupation group divided by that in all others during the study period. Hazard ratios above 1.00 indicate a greater risk of disease in a given group compared to all others. Estimates are adjusted for birth year and sex. The width of the 95% Confidence Interval (CI) is based on the number of cases in each group (more cases narrows the interval).
Figure 2. Risk of thyroid cancer diagnosis among workers employed in each occupation group relative to all others, Occupational Disease Surveillance System (ODSS), 1983-2016
