The pulmonary toxicity of talc and granite dust as estimated from an in vivo hamster bioassay

Our plain-English summary of The pulmonary toxicity of talc and granite dust as estimated from an in vivo hamster bioassay, by B.D. Beck, H.A. Feldman, J.D. Brain, et al (Toxicology and Applied Pharmacology, 1987).

The study

• Authors: B.D. Beck, H.A. Feldman, J.D. Brain, T.J. Smith, M. Hallock, B. Gerson
• Journal: Toxicology and Applied Pharmacology
• Published: 1987;87(2):222-34
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A short-term animal bioassay was used to assess the toxicity of occupational dusts. We quantified pulmonary responses in hamsters exposed to granite (12% quartz) and talc (quartz and asbestos-free) dust collected from worksites. Personal samples collected on workers showed similar quartz content and particle-size distributions to the high-volume samples collected for bioassays, thus demonstrating that the particulates were representative of worker exposure. We measured biochemical and cellular indicators of injury in bronchoalveolar lavage fluid (BAL) of animals exposed to dust suspensions by intra-tracheal instillation. The assays measured release of cytoplasmic and lysosomal enzymes into the cell-free supernatant of BAL; levels of albumin and red blood cells; changes in macrophage and polymorphonuclear neutrophil cell numbers; and in situ macrophage phagocytosis. Dose-response (0.15, 0.75, and 3.75 mg/100 g body wt) and time-course (1-14 days postexposure) studies were performed. One day after exposure, both talc and granite dust resulted in elevated enzyme levels, pulmonary edema, and increased cell numbers in BAL. Macrophage phagocytosis was also inhibited. Based on earlier studies, response levels were either intermediate between nontoxic iron oxide and toxic alpha-quartz or comparable with alpha-quartz. The response to granite dust diminished fairly rapidly over time. By contrast, after talc exposure, there was a more persistent elevation in enzyme levels, and macrophage phagocytosis remained depressed. These results indicate that, when a similar mass was deposited in the lungs, talc caused more lung injury than did granite. Better estimates of exposure-dose relationships in talc and granite workers as well as longer-term animal studies are required to evaluate the harmfulness of these work environments at present-day exposure levels.

In plain English

This animal experiment compared two Vermont workplace dusts: granite dust from a monument-carving shed and talc dust from a talc mill. The authors described the talc as quartz- and asbestos-free. The granite dust contained 12% quartz and the talc less than 1%. Hamsters had dust suspensions placed directly into their windpipes at 0.15, 0.75 or 3.75 mg per 100 g of body weight. Their lungs were then washed and tested for signs of injury over 1 to 14 days. One day after exposure, both dusts caused similar responses: raised enzyme levels, more inflammatory cells and reduced particle uptake by lung scavenger cells. Over time, granite responses faded faster, while talc caused longer-lasting enzyme rises and longer-lasting reduced scavenger-cell function. The authors concluded that both dusts have moderate-to-high lung toxicity, based on the early responses. They noted the results were unexpected and that a single dose to hamsters may not predict long-term human effects. They also noted that talc particles were much larger, so breathing equal airborne amounts would not give equal deep-lung doses; at the same respirable-dust level, granite would deliver much more.

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: Animal experiment: short-term in vivo hamster bioassay using intratracheal instillation, with dose-response and time-course studies
• Who was studied: Hamsters. At least six animals per exposure group and in the control group for the dose-response experiments. At least four per exposure group and at least three per control group for the time-course experiments. The dust was collected at a granite shed in Barre, Vermont, and a talc mill in central Vermont.
• Exposure: Respirable worksite dusts: granite dust containing 12% quartz, and talc dust containing less than 1% quartz, described as quartz- and asbestos-free. Single doses of 0.15, 0.75 and 3.75 mg per 100 g body weight. Controls received saline and surface active material alone.
• Main results:
  • One day after exposure, the cellular and biochemical indicators in lung wash fluid differed little between talc-exposed and granite-exposed hamsters.
  • Both dusts raised neutrophil (PMN) numbers one day after exposure. Granite caused a greater rise at the high dose.
  • One day after exposure, macrophage uptake of gold particles (lambda) was reduced to the same extent by talc and by granite.
  • For some indicators, such as LD levels, responses to talc and granite at 3.75 mg per 100 g one day after exposure were similar to the responses to alpha-quartz reported in the authors' earlier study.
  • In the time-course study at 3.75 mg per 100 g, granite raised macrophage numbers about twofold over control at 4 to 14 days. Talc caused a more moderate rise.
  • Lactate dehydrogenase (LD) levels fell more quickly after granite than after talc exposure.
  • Talc caused a persistent depression of macrophage particle uptake (lambda). After granite, lambda values were at or above control values.
  • The dusts differed in particle size: 92% of the talc mass was in particles larger than 4 micrometers, compared with 7% of the granite mass.
• The authors' conclusion: The authors concluded that, based on the acute responses, both talc and granite dust have moderate-to-high pulmonary toxicity. They interpreted the time-course results as showing more persistent macrophage injury from talc.
• Limitations the authors state:
  • Species differences between humans and hamsters may lead to different responses to the two dusts.
  • A single large dose given to hamsters may not predict the long-term changes caused by low-level chronic exposure in humans.
  • The bioassay may not be sensitive enough to tell apart dusts that are closer in toxicity than quartz and volcanic ash.
  • Because the talc particles were much larger, instilling equal masses of talc and granite does not represent equal deep-lung doses from breathing the dusts. At the same respirable-dust level, the granite inhalation dose would be much higher. The authors thought this was likely a factor in their unexpected results, having expected granite to be more toxic.

Topics

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

Medical terms in this study, explained in our Lexicon: Talc, Personal Breathing Zone Sample, Bronchoalveolar Lavage (BAL), Macrophage, Phagocytosis, Dose-response relationship.

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