Immunotoxic effects of chemicals: A matrix for occupational and environmental epidemiological studies

Our plain-English summary of Immunotoxic effects of chemicals: A matrix for occupational and environmental epidemiological studies, by A. Veraldi, A.S. Costantini, V. Bolejack, et al (American Journal of Industrial Medicine, 2006).

The study

• Authors: A. Veraldi, A.S. Costantini, V. Bolejack, L. Miligi, P. Vineis, H. van Loveren
• Journal: American Journal of Industrial Medicine
• Published: 2006;49(12):1046-55
• Cited by: 45 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Many biological and chemical agents have the capacity to alter the way the immune system functions in human and animals. This study evaluates the immunotoxicity of 20 substances used widely in work environments.

Methods: A systematic literature search on the immunotoxicity of 20 chemicals was performed. The first step was to review literature on immunotoxicity testing and testing schemes adopted for establishing immunotoxicity in humans. The second step consisted of providing a documentation on immunotoxicity of substances that are widely used in work environment, by building tables for each chemical of interest (benzene, trichloroethylene, PAHs, crystalline silica, diesel exhausts, welding fumes, asbestos, styrene, formaldehyde, toluene, vinyl chloride monomer, tetrachloroethylene, chlorophenols, 1,3-butadiene, mineral oils, P-dichlorobenzene, dichloromethane, xylene, 1,1,1-trichloroethane, ethylene oxide). The third step was the classification of substances; an index (strong, intermediate, weak, nil) was assigned on the basis of the evidence of toxicity and type of immunotoxic effects (immunosuppression, autoimmunity, hypersensitivity) on the basis of the immune responses. Finally substances were assigned a score of immunotoxic power.

Results: Tables have been produced that include information for the 20 substances of interest, based on 227 animal studies and 94 human studies. Each substance was assigned an index of immunotoxic evidence, a score of immunotoxic power and type of immunotoxic effect.

Conclusions: This matrix can represent a tool to identify chemicals with similar properties concerning the toxicity for the immune system, and to interpret epidemiological studies on immune-related diseases.

In plain English

This article was a literature review, not a new study of exposed people. The authors reviewed published research on the immune effects of 20 chemicals widely used at work, including asbestos. These were the chemicals most often reported in work histories in an Italian case-control study of blood and lymphatic cancers. In total, 321 studies were reviewed: 227 in animals and 94 in humans. The human studies related mainly to crystalline silica and asbestos. Fifteen substances were ranked strong, intermediate or weak by which immune tests showed effects and how predictive they were; five had inadequate data and none was ranked nil. Ranked substances were also scored within their rank by dose, route of exposure and species, and labeled by type of effect. Asbestos was ranked intermediate, scored 3, with effects listed as suppression and enhancement in humans and animals. The article did not name asbestos fiber types. The authors concluded that the matrix could help identify chemicals with similar immune effects. They noted that results varied between laboratories and that different chemicals had been tested differently.

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: Systematic literature review used to build a classification matrix of the immune-system effects (immunotoxicity) of 20 workplace chemicals. Substances were classified by which tests showed effects, weighted by how well those tests predict immunotoxicity.
• Who was studied: Published studies on 20 substances: 321 studies in total, 227 in animals and 94 in humans. The human studies related mainly to crystalline silica and asbestos.
• Exposure: 20 chemicals, including asbestos (no fiber type specified). They were chosen as the chemicals most often reported in the work histories of cases and controls in the Italian multicenter case-control study on hematolymphopoietic malignancies.
• Main results:
  • Human studies in the review related mainly to crystalline silica and asbestos
  • In Table IV, 15 substances were given an index of strong (4), intermediate (4) or weak (7). Five substances (p-dichlorobenzene, dichloromethane, xylene, 1,1,1-trichloroethane, ethylene oxide) were listed as having inadequate data, with no score or effect label. None was listed as nil.
  • Within each index, substances were scored for potency, defined by dose, route of exposure and species
  • Asbestos was given an 'intermediate' index of immunotoxic evidence and a score of 3 within that index. Its main effects on the immune system were listed as suppression and enhancement, with evidence from both human and animal studies.
  • Asbestos was among the six substances classed as having immunosuppressive effects with a 'strong' or 'intermediate' index, together with benzene, trichloroethylene, PAHs, welding fumes and styrene
• The authors' conclusion: The authors concluded that the matrix can be a tool to identify chemicals with similar immunotoxic properties and to improve risk estimates for immune-related diseases. They intend to use it in the Italian case-control study and to make it available to other studies once it has been validated.
• Limitations the authors state:
  • Some results may reflect differences between laboratories and experimental systems rather than real biological differences
  • The weight of evidence partly depends on chance, because some substances have been studied less than others
  • Different tests were performed for different chemicals, which made comparison between substances difficult
  • Results for the same substance conflicted depending on dose, route of exposure and species
  • Toxic agents may affect mouse and human immune systems differently

Topics

Medical terms in this study, explained in our Lexicon: Crystalline.

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