New insights on 'old' toxicants in occupational toxicology (Review)

Our plain-English summary of New insights on 'old' toxicants in occupational toxicology (Review), by C. Costa, E. Miozzi, M. Teodoro, et al (Molecular Medicine Reports, 2017).

The study

• Authors: C. Costa, E. Miozzi, M. Teodoro, G. Briguglio, V. Rapisarda, C. Fenga
• Journal: Molecular Medicine Reports
• Published: 2017;15(5):3317-3322
• Type of article: Review
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In order to deliver the best possible working environment, it is essential to identify professional conditions that could be harmful for worker's health and prevent (or limit) the occurrence of such conditions. The appropriate use of personal protective equipment and the development of appropriate regulations allowed to reduce the prevalence of 'classic' occupational diseases, such as occupational hearing loss or asbestosis, just to name a few. Nowadays, environmental pollution seems to be one of the most relevant concerns for human and animal health, and toxicology is becoming one of the most prominent fields of interest in occupational settings. An increasing number of studies demonstrate that the presence of toxicants in the workplace could be responsible for the development of chronic diseases, even at doses that were considered 'safe'. The present review summarizes some of the most recent advancements in occupational toxicology, focusing on topics that have long been debated in the past and that have recently returned to the fore.

In plain English

This article was a review. The authors searched PubMed up to November 2016 for recent findings on asbestos-like fibers such as carbon nanotubes (CNTs), on pesticides, and on benzene. The review reported that in 2014 the International Agency for Research on Cancer classified fluoro-edenite fibrous amphibole as carcinogenic to humans (Group 1), and multi-walled CNT-7 and fibrous silicon carbide as possible human carcinogens (Group 2b). It described animal studies by other researchers. One reported a high incidence of mesothelioma in mice after multi-walled CNTs were injected into the abdomen. In another, only crocidolite, not the nanotubes tested, induced mesothelioma, which that study's authors attributed to the nanotubes' short length. The review stated there was no conclusive data on CNT toxicity in humans. It noted NIOSH advice not to exceed 1 µg/m3 of respirable elemental carbon over 8 hours. It also summarized studies on pesticides and benzene. The authors concluded that CNT exposure recalls what happened with asbestos some decades ago, while acknowledging that the comparison may sound exaggerated.

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 based on a computerized PubMed search up to November 2016, plus review of references in reports
• Who was studied: Published studies on carbon nanotubes, pesticides and benzene (number of studies not given); in vivo studies were generally preferred to in vitro studies
• Exposure: Asbestos-like fibers (carbon nanotubes, fluoro-edenite, silicon carbide fibers), pesticides, and benzene; asbestos itself is discussed only as a point of comparison
• Main results:
  • The review reported that the International Agency for Research on Cancer in 2014 classified fluoro-edenite fibrous amphibole as carcinogenic to humans (Group 1). It also classified occupational exposure associated with the Acheson process as Group 1.
  • Per the same IARC evaluation as reported in the review: fibrous silicon carbide and multi-walled CNT-7 were classified as possible carcinogens to humans (Group 2b). Single-walled CNTs and other forms of multi-walled CNTs were not classifiable (Group 3).
  • A 2008 study cited by the review reported a high incidence of mesothelioma after intraperitoneal injection of multi-walled CNTs in mice. In that study, the CNT injection produced the highest mortality compared to fullerene and crocidolite.
  • In another cited experiment comparing multi-walled CNTs with and without structural defects to a similar dose of crocidolite, only crocidolite induced mesothelioma.
  • The authors of that experiment attributed the negative results to the short length of the nanotubes used. The review stated that later studies confirmed length is a key parameter.
  • The review reported that NIOSH advises not exceeding 1 µg/m3 of respirable elemental carbon as an 8-hour time-weighted average for CNTs and carbon nanofilaments.
  • On pesticides, a cited review of studies from 2000 to 2011 found that 13 case-control studies reported a significant association between pesticide exposure and Parkinson's disease.
  • On benzene, the authors' own group's earlier study, as described in the review, compared 91 male gas station attendants with 63 male office workers. It examined the effects of low-dose chronic benzene exposure on oxidative stress-related signaling pathways.
• The authors' conclusion: The authors concluded that occupational and environmental exposure to CNTs and nanoparticles reminds them of what happened with asbestos some decades ago, although they acknowledged the comparison may sound exaggerated. They noted that exposure continues even though the possible consequences are not yet fully clear.
• Limitations the authors state:
  • The authors stated that there is no conclusive data on the toxicity of CNTs in humans.
  • The authors stated that animal models can only partially indicate the potential toxicity of CNTs and nanofilaments, because many variants are produced.
  • The authors stated that proper assessment of occupational pesticide exposure is very difficult to obtain, which affects the reliability of many epidemiological and retrospective studies.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Disease.

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