Health implications of atmospheric aerosols from asbestos-bearing road pavements traditionally used in Southern Brazil

Our plain-English summary of Health implications of atmospheric aerosols from asbestos-bearing road pavements traditionally used in Southern Brazil, by R.H.M. Godoi, S.J. Gonçalves, C. Sayama, et al (Environmental Science and Pollution Research International, 2016).

The study

• Authors: R.H.M. Godoi, S.J. Gonçalves, C. Sayama, G. Polezer, J.M. Reis Neto, B. Alföldy, R. Van Grieken, C.A. Riedi, C.I. Yamamoto, A.F.L. Godoi, L. Bencs
• Journal: Environmental Science and Pollution Research International
• Published: 2016;23(24):25180-25190
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Serpentine and amphibole asbestos occur naturally in certain geologic settings worldwide, most commonly in association with ultramafic rocks, along associated faults. Ultramafic rocks have been used in Piên County, Southern Brazil for decades for the purpose of road paving in rural and urban areas, but without the awareness of their adverse environmental and health impact. The aim of this study was the chemical characterization of aerosols re-suspended in two rural roads of Piên, paved with ultramafic rocks and to estimate the pulmonary deposition of asbestos aerosols. Bulk aerosol samples were analyzed by means of X-ray fluorescence spectrometry and X-ray diffraction analysis, in order to characterize elemental composition and crystallinity. Single-particle compositions of aerosols were analyzed by computer-controlled electron-probe microanalysis, indicating the presence of a few percentages of serpentine and amphibole. Given the chemical composition and size distribution of aerosol particles, the deposition efficiency of chrysotile, a sub-group of serpentine, in two principal segments of the human respiratory system was estimated using a lung deposition model. As an important finding, almost half of the inhaled particles were calculated to be deposited in the respiratory system. Asbestos depositions were significant (∼25 %) in the lower airways, even though the selected breathing conditions (rest situation, nose breathing) implied the lowest rate of respiratory deposition. Considering the fraction of inhalable suspended chrysotile near local roads, and the long-term exposure of humans to these aerosols, chrysotile may represent a hazard, regarding more frequent development of lung cancer in the population of the exposed region.

In plain English

This study sampled airborne dust beside two rural roads in Piên County, Paraná State, Southern Brazil, that had been paved with ultramafic and mafic rocks. Air was collected in January 2010 at Crispins' Meadow and Maias' Meadow, and more than 4200 single particles were analysed chemically. X-ray analysis showed lizardite, which the authors describe as a fibrous serpentine, in the samples. Some particles were classed by their chemistry as chrysotile, and others as amphiboles (tremolite, winchite, anthophyllite). Altogether, 96 fiber particles were counted. The authors then used a computer model of a healthy adult breathing through the nose at rest to estimate where such particles would settle. The model placed 44.5% of inhaled particles in the respiratory tract and 24.9% of the total in the lung, mainly the deep (pulmonary) region. No people were examined. The authors noted three limits: fiber dimensions were not measured, the chosen breathing setting gives the lowest deposition, and January is the region's wettest month. They concluded that health risks to the local population from these fibers cannot be negligible.

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: Environmental air sampling and particle analysis at two road sites, combined with a computer (stochastic) lung deposition model; no human subjects were studied
• Who was studied: Airborne particles at two rural road sites (Crispins' Meadow and Maias' Meadow) in Piên County, Paraná State, Southern Brazil, sampled in January 2010; the deposition model represented a healthy adult at rest
• Exposure: Dust re-suspended from roads paved with ultramafic and mafic rocks. The particles included serpentine (lizardite; particles chemically classed as chrysotile) and particles chemically classed as amphiboles (tremolite, winchite, anthophyllite).
• Main results:
  • X-ray powder diffraction found lizardite, described by the authors as a fibrous serpentine, in aerosol samples from both sites
  • More than 4200 single particles were analysed; Si- and Mg-rich particles were classed as chrysotile, and particles also containing Na, Fe and/or Ca were classed as amphiboles
  • 96 fiber particles were counted manually and used for the size distribution input to the lung model
  • In the model, 44.5% of inhaled particles deposited in the respiratory tract and 24.9% of the total deposited in the lung, mainly in the pulmonary region (55.5% were exhaled)
  • By region in the model: 19.6% deposited in the upper (extrathoracic) airways, 5.6% in the conductive airways and 19.3% in the pulmonary region
  • In the model, 4.1% of inhaled particles deposited by interception, a mechanism specific to elongated particles. Assuming longer fibers (aspect ratio 10 instead of 3) more than doubled this fraction.
• The authors' conclusion: The authors concluded that chrysotile occurs in airborne fine particles over secondary roads in Piên. They judged that the health risks to the local population from fibers from natural sources cannot be negligible, and that naturally occurring asbestos should be treated as a large-scale environmental health problem.
• Limitations the authors state:
  • No geometric measurements of the fibers were made, so fiber geometry for the model was missing. An aspect ratio of 3 was assumed instead.
  • Magnesium, a tracer for serpentine minerals, could not be measured by the bulk X-ray fluorescence method
  • The modelled breathing condition (nasal breathing at rest) corresponds to the lowest degree of deposition, so the results represent a minimum
  • Sampling took place in January, usually the wettest month; the authors suggest concentrations may be higher in the dry season

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Serpentine Group, Amphibole Asbestos, Ultramafic Rocks, Deposition, X-Ray Diffraction (XRD), Amphibole Group, Chrysotile, Lung Cancer.

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