The International Agency for Research on Cancer (IARC), which is the cancer agency of the World Health Organization (WHO), has evaluated the carcinogenicity of talc and acrylonitrile and issued a statement saying that the expert working group has classified talc as probably carcinogenic to humans (Group 2A) “based on a combination of limited evidence of cancer in humans (for ovarian cancer), sufficient evidence of cancer in experimental animals and strong mechanistic evidence that talc exhibits key characteristics of a carcinogen in human primary cells and experimental systems.”
Acrylonitrile is a chemical used in the manufacture of clothing fibres, carpets and other textiles, synthetic rubber and plastics, and has been classified by the agency as “carcinogenic to humans” (Group 1). These findings are based on an exhaustive review of the available scientific literature and are included in an article published in The Lancet Oncology.
How exposure to talc and acrylonitrile occurs
Occupational exposure to acrylonitrile can occur during its production or use in making polymers, but it is also found in cigarette smoke, so inhaling this smoke, even secondhand, is the main source of exposure for the general population, apart from air pollution, the IARC report explains.
Talc is a mineral and people who work in its extraction and processing or in the manufacture of products containing it have occupational exposure, while the general population is exposed through the use of cosmetics and body powders that contain it, such as makeup or deodorants, although exposure through food and other consumer products is also possible, according to experts.
Cancers associated with exposure to these substances
The Working Group of 29 international experts classified talc as probably carcinogenic to humans (Group 2A) based on a combination of limited evidence of cancer in humans (for ovarian cancer), sufficient evidence of cancer in experimental animals, and strong mechanistic evidence that talc exhibits key characteristics of carcinogens in human primary cells and experimental systems.
Classification in Group 2A is the second highest level of certainty that a substance may cause cancer. Numerous studies consistently showed an increased incidence of ovarian cancer in women who reported using body powder in the perineal region. Although the evaluation focused on talc that does not contain asbestos, contamination of talc with asbestos could not be excluded in most studies in exposed humans.
An increased rate of ovarian cancer was also observed in studies examining occupational exposure of women exposed to talc in the pulp and paper industry. However, confounding by co-exposure to asbestos could not be excluded, and the increased rate was based on a small number of ovarian cancer cases in these occupational studies.
In experimental animals, treatment with talc caused an increase in the incidence of malignant neoplasms in females (adrenal medulla and lung) and a combination of benign and malignant neoplasms in males (adrenal medulla) of a single species (rat).
The classification of acrylonitrile as a human carcinogen (Group 1) was based on sufficient evidence of lung cancer in humans. There was also limited evidence of bladder cancer in humans, mainly from studies of workers producing or using acrylonitrile. In addition, there was sufficient evidence of cancer in experimental animals. Classification in Group 1 indicates the highest level of certainty that a substance may cause cancer.
Numerous studies consistently showed an increased incidence of ovarian cancer in women who reported using body powder in the perineal region.
The strongest evidence came from a large cohort study of workers in different industries producing or using acrylonitrile, where those with higher exposure had a higher mortality rate from lung cancer compared to workers with lower exposure. In experimental animals, administration of acrylonitrile caused an increase in the incidence of malignant neoplasms in both sexes of two species in multiple studies.
Alejandro Pérez Fidalgo, an associate physician at the Oncology Department of the Hospital Clínico de Valencia and a researcher at INCLIVA, has sent a reassuring message in his statements to SMC Spain, highlighting that, although the IARC has classified talc as a “probably carcinogenic” agent, “that does not mean that just because someone has used talc once, or even that they use it regularly, they are clearly at risk, since the risk of developing cancer will depend on the dose of exposure, time and form of contact with the talc.”
According to this expert, “the studies that support this classification have many biases, that is, certain confounding factors that prevent us from fully appreciating or predicting the relationship between the use of talc or exposure to it and cancer,” and he adds that in animals it has been seen that talc has properties of producing malignant tumors, but this exposure to animals is experimental and does not always reproduce what occurs in people. However, it proves the capacity of talc to induce tumors in laboratory environments.”
For all these reasons, she concludes that “it would be advisable to avoid genital use of talcum powder, particularly in women, as far as possible. However, this does not mean that previous use of talcum powder will cause cancer or that previous exposure to this agent will clearly be responsible for the appearance of a tumor.”
According to Andrew Watterson, a public health researcher at the Faculty of Health Sciences at the University of Stirling in Scotland (United Kingdom), and as stated to the same media, “both decisions taken by IARC on acrylonitrile (ACN) and talc are based on a careful examination of the evidence and both are therefore evidence-based decisions that should inform policies and controls in the workplace. Consumers and workers should have access to IARC information to help them make their own decisions about what to use when options are available.”
Regarding acrylonitrile, “its use in plastics is now even more questionable when, globally and within Europe, policies advocate deep cuts in plastics use linked to increased environmental and health risks. Suggestions that there are no alternatives to acrylonitrile do not stand up to scrutiny in many cases. Worker protection should be improved with even stricter ACN exposure standards and the risks of ACN for smokers should be highlighted again.”
