Inhalation Toxicity of Talc

Our plain-English summary of Inhalation Toxicity of Talc, by N.F. Johnson (Journal of Aerosol Medicine and Pulmonary Drug Delivery, 2021).

The study

• Author: N.F. Johnson
• Journal: Journal of Aerosol Medicine and Pulmonary Drug Delivery
• Published: 2021;34(2):79-107
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Respirable talc powder (RTP) is a complex mineral mixture of talc along with accessory minerals, including tremolite, anthophyllite, quartz, magnesite, dolomite, antigorite, lizardite, and chlorite. The industrial mining, milling, and processing of talc ore is associated with elevated incidences of fibrotic and neoplastic diseases, which are also seen among workers exposed to RTP in secondary industries and individuals using processed cosmetic talc for personal use. There is controversial evidence of a link between the talc-induced lung diseases and a potential contamination with asbestos fibers. This controversy is fueled by inadequate exposure data and the complex mineralogy and terminology of the accessory minerals. Talc aerosols exhibit a wide range of mineral habits, including particulates and fibrous structures that have dimensional and compositional characteristics related to the development of asbestos-related lung disease. The inhalation toxicology of RTP is based on the analysis of occupational hygiene and animal inhalation studies conducted between the 1940s and the 1990s and more recent mechanistic studies conducted both in vivo and in vitro. The review of talc toxicity studies reveals that the occupational studies provide only equivocal links between any of the components of the aerosols and the development of pulmonary cancer; however, there is substantial evidence of an association between the aerosols and pleural and pulmonary fibrosis and the development of nonmalignant respiratory disease. The animal inhalation and implantation studies appear to be less than optimal, which also appears to be true for the in vivo and in vitro studies. The mechanistic studies have identified the key pathogenic characteristics of asbestos to be long and thin fibers that are durable in lung tissues and fluids. Talc toxicity studies show that talc particles and fibers are durable and can remain in the lung for up to 40 years after the end of exposure. This extended tissue residence is considered to constitute a continuing tissue exposure that is capable of inducing the documented inflammatory and proliferative response. There is less consensus as to whether there is a threshold fiber length effect, as long, thin fibers (>5 μm) form only a small fraction of talc aerosols and the possible role of fibers >5 μm in the translocation from the lung to the pleura and their association with pleural fibrotic and carcinogenic lesions. Long, thin fibers are preferentially deposited in hot spots in the lung, such as airway bifurcations, areas typically associated with the development of lung cancer. The platy structures typical of talc can form oblate structures behaving more as fibers in the air stream, and these have also been shown to deposit preferentially in such locations. The review of the inhalation toxicity of talc provides a plausible explanation for the carcinogenic potential of RTP.

In plain English

This article is a single-author review of research on breathing in respirable talc powder, which the author describes as a mixture of talc and accessory minerals such as tremolite, anthophyllite and quartz. It covered occupational hygiene and animal inhalation studies from the 1940s to the 1990s, later mechanistic studies in animals and cells, and studies simulating cosmetic talc use. The author judged that the occupational studies gave only equivocal links to lung cancer but substantial evidence of an association with pleural and pulmonary fibrosis and nonmalignant respiratory disease. None of the three long-term animal inhalation studies showed mesothelioma. The author concluded that respirable talc, cosmetic and industrial, contains regulated asbestos fibers in variable amounts, and that the carcinogenic risk of inhaling it is ill defined. The author also found insufficient evidence for a fiber length or diameter threshold below which fibers can be considered safe. The author noted that occupational data from many small cohorts were poor and that the animal studies all had flaws. The author concluded that the review offers a plausible explanation for the carcinogenic potential of respirable talc.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Narrative review (labeled an unsolicited review) of earlier occupational, animal and laboratory studies of inhaled talc
• Who was studied: Published and internal studies: occupational hygiene and animal inhalation studies from the 1940s to the 1990s, plus more recent mechanistic studies in animals and in cell cultures; also simulation studies of cosmetic talc use
• Exposure: Respirable talc powder (cosmetic and industrial grades), described as talc plus accessory minerals including tremolite, anthophyllite, quartz, magnesite, dolomite, antigorite, lizardite and chlorite
• Main results:
  • The author judged that the occupational studies gave only equivocal links to lung cancer, but substantial evidence of an association with pleural and pulmonary fibrosis
  • None of the three long-term animal inhalation studies reviewed showed mesothelioma
  • The author reported that talc particles and fibers are durable and can remain in the lung for up to 40 years after exposure ends
  • The author judged the evidence sufficient to conclude that respirable talc, both cosmetic and industrial grades, contains regulated asbestos fibers in variable amounts
  • The author judged that prolonged industrial and personal exposure to respirable talc is associated with impaired respiratory function and pulmonary fibrosis, but that its carcinogenic risk is ill defined
  • The author found insufficient evidence of a fiber length or diameter threshold below which fibers can be considered safe
  • The author's own dose estimates, based on the upper limits of the simulation studies, indicated that newborns receive a higher daily dose than older children and adults using personal care products
• The authors' conclusion: The author concluded that the review provides a plausible explanation for the carcinogenic potential of respirable talc powder
• Limitations the authors state:
  • The author stated that the individual chronic animal studies all have flaws, which makes their overall interpretation difficult
  • The author stated that extrapolating from animals to humans is difficult
  • The author stated that the occupational data from many small cohorts are poor
  • The author stated that the exposure and lung dose data needed to reliably quantify carcinogenic risk do not currently exist

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: Talc, Accessory Mineral, Tremolite, Anthophyllite, Dolomite, Antigorite, Lizardite, Chlorite.

Related studies

• Massive pulmonary fibrosis from the inhalation of talc — A.C. Hunt (1956)
• The pulmonary toxicity of talc and granite dust as estimated from an in vivo hamster bioassay — B.D. Beck, H.A. Feldman, et al. (1987)
• Talc deposition and effects after 20 days of repeated inhalation exposure of rats and mice to talc — J.A. Pickrell, M.B. Snipes, et al. (1989)
• Respiratory distress after talc inhalation — S.R. Gould, D.E. Barnardo (1972)
• Re: Brent L. Finley, Stacey M. Benson & Gary M. Marsh (2017): Cosmetic talc as a risk factor for pleural mesothelioma: a weight of evidence evaluation of the epidemiology, Inhalation Toxicology, DOI: 10.1080/08958378.2017.1336187 — M.M. Finkelstein (2017)
• Inhalation toxicity of mineral particles: critical appraisal of endpoints and study design — H. Muhle, I. Mangelsdorf (2003)

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