Environmental asbestos pollution related to use of quarried serpentine rock

Our plain-English summary of Environmental asbestos pollution related to use of quarried serpentine rock, by A.N. Rohl, A.M. Langer, I.J. Selikoff (Science, 1977).

The study

• Authors: A.N. Rohl, A.M. Langer, I.J. Selikoff
• Journal: Science
• Published: 1977;196(4296):1319-22
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004995).

Abstract

Crushed serpentinite quarried in Montgomery County, Maryland, has been extensively used for paving roads and other surfaces. The mineral assemblage includes antigorite or lizardite as well as chrysotile and tremolite. Air samples taken in the vicinity of serpentine-paved roads show that chrysotile concentrations are about 10(3) times greater than those typically found in urban ambient air in the United States.

In plain English

This 1977 report examined whether crushed serpentine rock from a quarry near Rockville, Maryland, put asbestos into community air. The rock was used to pave roads, parking lots and driveways. The authors analyzed quarry rock, crushed stone and dust on roadside plants. They took five air samples near serpentinite-paved roads, including a school parking lot and a residential area. The rock was mostly platy serpentine (antigorite or lizardite or both). Chrysotile was present throughout it, possibly at several percent or more. Tremolite was found in quarry and settled-dust samples; anthophyllite was not found in these samples. Chrysotile in the five air samples ranged from 500 nanograms per cubic meter near a road with light traffic to 4700 near an intersection with moderate traffic. The authors reported the average was about 1000 times the average values found in 49 United States cities. The standard optical workplace method recorded few fibers; the authors said it cannot determine actual asbestos exposure. They noted these were only five single measurements. The authors concluded the results suggest a possible public health hazard from using this rock.

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 sampling study: mineral analysis of quarry rock, crushed stone and settled roadside dust, plus five air samples analyzed by electron and optical microscopy
• Who was studied: Five air sampling locations near Rockville, Maryland (residential and school areas and sites near serpentinite-paved roads), plus samples of quarry rock, stockpiled crushed stone and dust on roadside vegetation
• Exposure: Crushed serpentinite from a quarry near Rockville, Maryland, used for road surfacing and other paving. It was mainly platy serpentine (antigorite or lizardite or both) and contained chrysotile and tremolite.
• Main results:
  • In the quarry rock, chrysotile was found throughout the rock mass, not only in veins. The authors estimated it may make up several percent or more of the rock.
  • Tremolite was identified in quarry samples and settled dust samples. Anthophyllite was not found in these samples, although an earlier report had listed it among minerals in the serpentinite.
  • Electron microscopy confirmed chrysotile in dust settled on roadside vegetation
  • Air sample taken 10 m from a road intersection with light traffic: 500 ng/m3 chrysotile
  • Air sample taken 10 m from a road intersection with moderate traffic: 4700 ng/m3 chrysotile by electron microscopy, and 0.05 fibers per milliliter by optical microscopy
  • School parking lot 100 m from the intersection: 1000 ng/m3 chrysotile
  • Residential area 70 m from the intersection: 2000 ng/m3 chrysotile
  • 10 m from a roadside next to the National Bureau of Standards, moderate traffic: 3600 ng/m3 chrysotile
  • The average chrysotile concentration in the five Rockville samples was approximately 1000 times greater than the average values found in 49 United States cities
  • Comparing electron and optical microscopy results, the authors stated that the NIOSH optical workplace method cannot determine actual asbestos exposure levels
  • A second sample preparation method (direct transfer) gave results similar to the rub-out method
• The authors' conclusion: The authors concluded that their limited data suggest a possible public health hazard from distributing and using quarried asbestos-containing serpentinite
• Limitations the authors state:
  • The air data consist of only five single measurements
  • A precise measurement of the chrysotile content of the rock body was difficult
  • Airborne mass concentrations counted only free chrysotile fibers. Chrysotile intergrown with platy minerals was not measured.
  • Judging the health hazard requires information not yet known. This includes the biological activity of short chrysotile fiber and whether any safe exposure level exists for human cancers.

Topics

Medical terms in this study, explained in our Lexicon: Serpentine Group, Serpentinite, Antigorite, Lizardite, Chrysotile, Tremolite.

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