IARC assesses whether some nanomaterials and fibres cause cancer

As part of our ongoing surveillance of Canadians exposures to carcinogens, the CAREX team monitors evaluations by the International Agency for Research on Cancer (IARC). In October 2014, IARC gathered 21 experts from 10 countries to evaluate whether a selection of nanomaterials and fibers cause cancer.

The expert team looked specifically at fluoro-edenite, silicon carbide fibres and whiskers, and carbon nanotubes (including single-walled and multi-walled varieties). A summary of their conclusions for each nanomaterial is summarized below.

Silicon carbide:

  • Occupational exposures associated with manufacturing silicon carbide particles, called the Acheson process, were classified as carcinogenic (Group 1) based on sufficient evidence that they cause lung cancer in humans.
  • Fibrous silicon carbide was classified as possibly carcinogenic (Group 2B) based on limited evidence in humans that it causes lung cancer.
  • Silicon carbide whiskers were classified as probably carcinogenic to humans (Group 2A), rather than possibly carcinogenic to humans (Group 2B), because the physical properties of the whiskers resemble those of asbestos fibres, which are known carcinogens.

Virtually all the silicon carbide sold in the world is manufactured. This substance occurs in three forms: particles that are used in industry as an abrasive, fibres that are a by-product of particle manufacturing, and whiskers that are used as durable substitutes for asbestos.

Fluoro-edenite fibres:

  • These fibres were classified as carcinogenic (Group 1) based on sufficient evidence that human exposure causes mesothelioma.

Fluoro-edenite is a mineral that can take the form of fibres similar to asbestos. Quarry products from Biancavilla in Italy, used to make unpaved roads in the area since the 1950s, are a source for airborne fluoro-edenite fibres. Exposures have also occurred via indoor air, as a result of the quarry’s products being used in building materials.

Carbon nanotubes:

  • A specific nanotube, multi-walled carbon nanotube-7 was classified as possibly carcinogenic(Group 2B) based on evidence showing that they caused mesotheliomas in male and female rats.
  • All other multi-walled and single-walled carbon nanotubes were categorised as not classifiable as to their carcinogenicity to humans (Group 3) due to insufficient evidence.

Carbon nanotubes consist of either a single cylinder of carbon (single-walled), with an outer diameter of 1–3 nm, or of multiple carbon cylinders arranged in layers (multi-walled) with diameters of 10–200 nm. The characteristics of carbon nanotubes vary depending on how they’re produced. They can be used to improve the structural integrity of fabrics, plastics, rubbers, electronics (i.e. in transistors and solar cells), and structural materials, as well as in medicine (i.e. drug delivery and bone tissue engineering). More information can be found on our carbon nanotubes profile.

The full IARC Monograph Volume 111: Some Nanomaterials and Some Fibres is available here.

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CAREX Canada

Faculty of Health Sciences

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Harbour Centre Campus
2602 - 515 West Hastings St
Vancouver, BC  V6B 5K3
CANADA

© 2022 CAREX Canada

CAREX assesses Canadian veterinary workers’ exposures to radiation and cancer drugs

veterinarianCAREX team members performed the first national assessment of Canadian veterinary workers’ exposures to ionizing radiation and antineoplastic agents (drugs used to treat cancer). The results of this assessment are published in the November/December 2013 issue of the Canadian Journal of Public Health.

There are approximately 12,600 registered veterinarians in Canada, employed primarily in private practice, government, education, research, and industry. An additional 11,100 Canadians are trained to assist as “veterinary technicians”.

Ionizing radiation, a known carcinogen, is commonly used for X-ray scans in veterinary practice. CAREX estimates showed that <10% of all veterinarians and veterinary technicians were exposed to an annual ionizing radiation dose above 0.1 mSv (the minimum detectable level) in 2006, representing a total of between 536 and 1450 workers. Although none of these exposures was over regulatory limits, accumulated low levels of ionizing radiation may present a health hazard. Exposure estimates were calculated using a combination of Census statistics and data from the Radiation Protection Bureau of Health Canada’s National Dose Registry.

Although the National Dose Registry is intended to monitor all potentially exposed workers, CAREX found that not all are being captured by this program . Provincial monitoring proportions ranged from 12% to 94% of veterinarians and 9% to 80% of veterinary technicians. This variation can be partly (but not entirely) explained by differences in monitoring requirements across provinces.

For antineoplastic agents, used to treat cancer in dogs and cats, exposure was predicted in up to 23% (5,300) of all veterinary workers, with an estimated prevalence range of 22% to 24% of veterinarians and 20% to 21% of veterinary technicians. Estimates were developed using statistics on employment by practice type obtained from veterinary licensing bodies, and agent usage rates obtained from peer-reviewed literature.

CAREX’s investigation into exposures to antineoplastic agents revealed that little is known about how the agents are being used and who is being exposed in Canadian veterinary settings. This is likely due to their emerging – and increasing – use in veterinary medicine and a lack of regulatory surveillance.

Suggested next steps include increasing exposure surveillance and examining exactly how veterinarians are being exposed to these agents across practice areas, occupations, and tasks. This information will help to identify individuals at risk for exposure and disease, direct prevention efforts, and inform future research.

To learn more about ionizing radiation and antineoplastic agents, and how Canadians are exposed to these and many other agents at work, please visit our Profiles and Estimates page.

Subscribe to our newsletters

The CAREX Canada team offers two regular newsletters: the biannual e-Bulletin summarizing information on upcoming webinars, new publications, and updates to estimates and tools; and the monthly Carcinogens in the News, a digest of media articles, government reports, and academic literature related to the carcinogens we’ve classified as important for surveillance in Canada. Sign up for one or both of these newsletters below.

CAREX Canada

Faculty of Health Sciences

Simon Fraser University
Harbour Centre Campus
2602 - 515 West Hastings St
Vancouver, BC  V6B 5K3
CANADA

© 2022 CAREX Canada