Respirable inorganic fibers dispersed in air and settled in human lung samples: Assessment of their nature, source, and concentration in a NW Italy large city

Our plain-English summary of Respirable inorganic fibers dispersed in air and settled in human lung samples: Assessment of their nature, source, and concentration in a NW Italy large city, by S. Capella, D. Bellis, E. Fioretti, et al (Environmental Pollution, 2020).

The study

• Authors: S. Capella, D. Bellis, E. Fioretti, R. Marinelli, E. Belluso
• Journal: Environmental Pollution
• Published: 2020;263(Pt B):114384
• Type of article: Review
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The present investigation represents a new approach useful to evaluate the general population risk correlated with environmental exposure to air dispersed inorganic fibers. The used method is based on the evaluation of the respirable inorganic fibers both air dispersed in a big city and contained in lungs of the general population following their respiration. Moreover, these data allow to identify the sources of dispersion (anthropogenic or natural) in air of the inorganic fibers and therefore to apply strategies to improve air quality. To describe this approach, we investigated air samples from a big city in NW Italy and lung inorganic burden of people here lived. This paper reports the data of the airborne inorganic fibers detected in two sampling campaign (2014 and 2016), in 24 districts of Torino (Piemonte - NW Italy), and in some autoptic lungs of general population lived here. The airborne fibers (collected on mixed-cellulose esters membrane) were characterized by SEMEDS. The identified inorganic fiber species were assigned to 5 classes, one of these including 2 types of asbestos. These last are grouped as tremolite/actinolite asbestos. They are dispersed from natural sources (i.e. certain kinds of rocks outcropping in the city surrounding areas). In no-one of the 24 districts of Torino their concentration highlighted a situation of asbestos pollution in place. A correlation with inorganic fibers (collected on mixed-cellulose esters membrane and characterized by SEM-EDS) detected in lung tissue samples of 10 subjects lived in Torino all their life and without professional exposure to asbestos were attempted. The only types of fibers identified as asbestos are tremolite/actinolite asbestos, and they match those detected in air sampling. The number of fibers per 1 g of tissue dry weight is lower than the quantities reported as indicative of significant asbestos exposure. We observed interesting gender differences.

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In plain English

This preliminary study in Torino (Turin), Italy, measured respirable inorganic fibers in outdoor air and in human lungs. Air was sampled once in each of 24 city districts between April and November in 2014 and in 2016. Fibers were identified by scanning electron microscopy with chemical analysis. Autopsy lung tissue from 10 lifelong Torino residents (5 women, 5 men) was also analysed; none had died from occupational asbestos exposure or had lung disease. The only asbestos identified in air was tremolite/actinolite asbestos, found in 41.7% of districts at no more than 0.1 fibers per liter. The authors attributed it to natural rocks around the city. Crocidolite, grunerite asbestos and anthophyllite asbestos were not detected. Chrysotile/asbestiform antigorite, which the method could not tell apart, was the most abundant fiber group. The authors found no asbestos pollution in any district. Lung asbestos counts were below the European Respiratory Society level indicating significant amphibole exposure, and women's samples held more fibers on average than men's. The authors concluded that mesothelioma risk from environmental exposure in Torino appears extremely low, though not quantifiable. They noted that only 10 lung samples were available.

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: Preliminary environmental study combining outdoor air monitoring with a retrospective analysis of autopsy lung tissue, both examined by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS)
• Who was studied: Outdoor air in 24 districts of Torino, NW Italy, sampled once per district in the morning between April and November in 2014 and 2016. Autopsy lung tissue from 10 people (5 women aged 67 to 76, 5 men aged 59 to 81) who lived in Torino all their life, did not die from occupational asbestos exposure, and did not have lung disease.
• Exposure: Environmental (non-occupational) exposure to airborne inorganic fibers of respirable size, including asbestos released from naturally occurring sources (rocks around the city) and from asbestos-containing materials such as roofs. Fibers were sorted into silicates (including tremolite/actinolite asbestos and chrysotile/asbestiform antigorite), oxides, carbonates, sulfates and synthetic fibers.
• Main results:
  • In air, the only fibers classified as asbestos were tremolite/actinolite asbestos.
  • Tremolite/actinolite asbestos was found in 41.7% of districts in both sampling campaigns. Its highest concentration was 0.1 fibers per liter, at SPOT 4 (Lingotto) in 2014 and SPOT 18 (Madonna di Campagna) in 2016.
  • Crocidolite, grunerite asbestos and anthophyllite asbestos, which the authors describe as commonly contained in asbestos-containing materials, were not detected in any district.
  • Fibers of the chrysotile/asbestiform antigorite group, which the method could not distinguish and which the authors call 'potentially classifiable as asbestos', were found in all districts in 2014 and in 75% of districts in 2016. They were the most abundant fiber type in both campaigns, and the authors attributed them to both natural and man-made sources.
  • Considering asbestos concentrations regardless of source, the authors found no situation of asbestos pollution in any district.
  • The types of asbestos and potentially asbestos fibers found in the 10 lung samples corresponded to those found in the air samples.
  • In lung tissue, the highest concentrations were 0.10 × 10^5 fibers per gram of dry tissue for tremolite/actinolite asbestos and 0.28 × 10^5 for chrysotile/asbestiform antigorite. The authors reported these as lower than the European Respiratory Society guideline level indicating significant asbestos exposure for amphiboles (1 × 10^5 fibers per gram dry weight).
  • The average number of fibers in women's lung samples was much greater than in men's. Chrysotile/asbestiform antigorite fibers were detected only in women's samples. Tremolite/actinolite asbestos was present in all five women's samples; the authors state it was found in 25% of men's samples, while their table lists it in one of the five men.
• The authors' conclusion: The authors concluded that the tremolite/actinolite asbestos in Torino's air comes not from asbestos-containing materials but from naturally occurring asbestos in rocks around the city, carried by the wind. They concluded that the risk of developing mesothelioma from environmental exposure in Torino would seem to be extremely low, even if not quantifiable. They left open whether a no-effect threshold exists and whether asbestos behaves differently in the body by gender.
• Limitations the authors state:
  • Only 10 lung samples could be obtained, because autopsies are limited to specific deaths; the authors state their data are not sufficient for statistical analysis.
  • The lung findings reflect exposure over each person's whole life, not a specific time period.
  • The method could not tell chrysotile from asbestiform antigorite, or tremolite asbestos from actinolite asbestos, so these were reported as combined groups.

Topics

Medical terms in this study, explained in our Lexicon: Environmental Exposure, Tremolite, Actinolite, Air Sampling, Asbestos Exposure.

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