Are rubber and plastics workers at risk for salivary gland cancer?

Background

Salivary gland cancer

The salivary glands produce saliva and are part of the head and neck [1]. Salivary gland cancer is rare, with 2.1 cases diagnosed per 100,000 people in Ontario [2]. This represents 0.3% of all cancers diagnosed in Ontario, although the rate of new cases has been increasing since 1981.

Not much is known about what causes salivary gland cancer, which is often grouped with other head and neck cancers. The only known causes are exposure to acetaldehyde from consumption of alcoholic beverages [3], and exposure to ionizing radiation, especially during radiation therapy or x-rays to the head and neck [4]. There is limited evidence that exposure to radioiodines, primarily iodine-131 when use to treat thyroid cancer, may also increase the risk of salivary gland cancer [4].

The role of workplace exposure in the development of salivary gland cancer is not fully understood. Studies have investigated possible associations with a range of occupational risk factors, though more research is necessary to understand whether workplace exposures contribute to the development of salivary gland cancer [5-13].


Rubber and plastics workers

A few previous studies have found an increased risk of salivary gland cancer among workers in plastic and rubber product manufacturing [10-13]. However, these studies were based on few cases of salivary gland cancer making it challenging to interpret the findings. Rubber and plastics workers may be exposed to a wide range of chemicals when fabricating rubber and plastic products, including dusts and fumes, solvents (e.g., benzene, styrene), formaldehyde, N-nitrosamines, diisocyanates, phthalates, and polycyclic aromatic hydrocarbons (PAHs) [14-16]. More research is needed to understand whether these exposures may contribute to risk of salivary gland cancer.

Salivary gland cancer risks in the ODSS

The following results show the percent increase in risk among rubber and plastics workers by industry or occupation compared to all other workers in the ODSS. This analysis looked at 55,232 rubber and plastics workers in the ODSS, under the age of 85.

Elevated risks of salivary gland cancer were identified in rubber and plastic products industry workers, and specifically among plastics fabricating workers. A stronger association was identified for male workers in plastics fabricating. There were not enough cases among female workers to assess their risk separately. These results demonstrate the challenge that lies with identifying a rare cancer across specific occupation and industry groups.

Industry or Occupation Increased risk †
All workers Male workers 
Rubber and Plastics Products Industries 34% 45%

Plastics Fabricating Industry

44% 73%*
Chemicals, Petroleum, Rubber, Plastic and Related Materials Processing Occupations 27% 57%
Compared to all other workers in the ODSS
*Statistically significant (α=0.05)

 

Other groups of workers in the ODSS that have shown elevated risks of salivary gland cancer are discussed in the salivary gland cancer disease page. More information on risks among plastics and rubber workers in the ODSS is available in a scientific publication: Cancer surveillance among workers in plastics and rubber manufacturing in Ontario, Canada (Occup Environ Med, 2020;77(12):847-856).

Risk recognition and prevention

Given that so little is known about what causes salivary gland cancer, and how rare it is, prevention strategies are limited. Implementing control strategies to reduce occupational exposures may help reduce the risk of salivary gland cancer, as well as reducing the risk of many other workplace diseases. According to the hierarchy of controls, strategies that eliminate the hazard, substitute a less hazardous exposure, or isolate the exposure from the workers (engineering controls) are the most effective [17]. Although the findings for rubber and plastics workers in the ODSS were limited, this may be due in part to the rarity of salivary gland cancer and there should be continued work to explore the risk among working populations.

Reducing alcohol consumption and following medical advice when receiving treatments or tests involving ionizing radiation or radioiodines may also help decrease the risk of salivary gland cancer. As with any cancer, early detection is key to more treatment options and better odds of survival. Symptoms of salivary gland cancer include: a usually painless lump in the ear, cheek, jaw or lip area or inside the mouth; fluid draining from the ear; trouble swallowing or opening the mouth widely; and numbness, weakness or pain in the face [1].

References
  1. Canadian Cancer Society. Salivary gland cancer. (Accessed Nov 2022).
  2. Ontario Health (Cancer Care Ontario). Ontario Cancer Statistics 2020. Toronto: Ontario Health (Cancer Care Ontario); 2020.
  3. International Agency for Research on Cancer. Personal Habits and Indoor Combustions. IARC Monogr Eval Carcinog Risks to Humans Vol. 100E (2012).
  4. International Agency for Research on Cancer. Radiation. IARC Monogr Eval Carcinog Risks to Humans Vol. 100D (2012).
  5. Wilson RT, Moore LE, Dosemeci M. Occupational Exposures and Salivary Gland Cancer Mortality among African American and White Workers in the United States. J Occup Environ Med. 2004;46(3):287–97.
  6. Swanson GM, Belle SH. Cancer morbidity among woodworkers in the U.S. automotive industry. J Occup Med.1982;24(4):315–9.
  7. Swanson GM, Burns PB. Cancers of the salivary gland: workplace risks among women and men. Ann Epidemiol.1997;7(6):369–74.
  8. Milham S. Cancer mortality patterns associated with exposure to metals. Ann NY Acad Sci. 1976;271:243–9.
  9. Pan SY, de Groh M, Morrison H. A Case-Control Study of Risk Factors for Salivary Gland Cancer in Canada. J Cancer Epidemiol. 2017;2017:4909214.
  10. Mancuso T, Brennan M. Epidemiological considerations of cancer of the gallbladder, bile ducts and salivary glands in the rubber industry. J Occup Med. 1970;12(9):334–41.
  11. Kolstad HA, Juel K, Olsen J, Lynge E. Exposure to styrene and chronic health effects: mortality and incidence of solid cancers in the Danish reinforced plastics industry. Occup Environ Med. 1995;52(5):320–7.
  12. Horn-Ross PL, Ljung B-M, Morrow M. Environmental factors and the risk of salivary gland cancer. Epidemiology.1997;8(4):414–9.
  13. Straif K, Weiland SK, Bungers M, Holthenrich D, Keil U. Exposure to nitrosamines and mortality from salivary gland cancer among rubber workers (Letter). Epidemiology. 1999 Nov;10(6):786-7.
  14. American Industrial Hygiene Association. IH/OEHS Exposure Profiles in Rubber and Plastic Products. (Accessed Nov 2022).
  15. CAREX Canada. Data outputs from eWork Online Tool. (Accessed Nov 2022).
  16. International Agency for Research on Cancer. Chemical agents and related occupations. IARC Monogr Eval Carcinog Risks to Humans Vol. 100F (2012).
  17. National Institute for Occupational Safety and Health. Hierarchy of Controls. (Accessed Nov 2022).

The Occupational Disease Surveillance System (ODSS) Surveillance Alerts provide brief summaries of occupational exposures and disease risks across different industries and occupational groups. The aim of these alerts is to highlight new or emerging issues detected through occupational disease surveillance. At this time the ODSS includes workers from 1983-2014 and follows their health outcomes until 2016. This alert reflects only the diseases currently tracked within the ODSS. The system is updated and expanded on an ongoing basis. 

More information about the ODSS including data sources, methods and the most recent results can be found at ODSP-OCRC.ca and OccDiseaseStats.ca.