Assessing occupational erionite and respirable crystalline silica exposure among outdoor workers in Wyoming, South Dakota, and Montana

Our plain-English summary of Assessing occupational erionite and respirable crystalline silica exposure among outdoor workers in Wyoming, South Dakota, and Montana, by C. Beaucham, B. King, K. Feldmann, et al (Journal of Occupational and Environmental Hygiene, 2018).

The study

• Authors: C. Beaucham, B. King, K. Feldmann, M. Harper, A. Dozier
• Journal: Journal of Occupational and Environmental Hygiene
• Published: 2018;15(6):455-465
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Erionite is a naturally occurring fibrous mineral found in many parts of the world, including the western United States. Inhalational exposure to erionite fibers in some localities is associated with health effects similar to those caused by asbestos exposure, including malignant mesothelioma. Therefore, there is concern regarding occupational exposures in the western United States. Currently, there are no standard sampling and analytical methods for airborne erionite fibers, as well as no established occupational exposure limits. Due to the potential adverse health effects, characterizing and minimizing exposures is prudent. Crystalline silica also occurs naturally in areas where erionite is found, principally as the mineral quartz. Work activities involving rocks containing quartz and soils derived from those rocks can lead to exposure to respirable crystalline silica (RCS). The typically dry and dusty environment of the western United States can increase the likelihood of exposures to aerosolized rocks and soils, but inhalation exposure is also possible in more humid conditions. In this case study, we describe several outdoor occupational environments with potential exposures to erionite and RCS. We describe our method for evaluating those exposures and demonstrate: (1) the occurrence of occupational exposures to airborne erionite and RCS, (2) that the chemical make-up of the erionite mineral can be determined, and (3) that effective dust control practices are needed to reduce employee exposures to these minerals.

In plain English

In this case study, the authors measured exposure to erionite, a naturally occurring fibrous mineral, and to respirable crystalline silica (quartz) among outdoor workers of two U.S. federal agencies. During four site visits from October 2012 to September 2014, they sampled air while employees did dirt road maintenance and forestry tasks in Wyoming and in the Custer-Gallatin National Forest, and they tested rock and soil. In Wyoming, no erionite was found in the air or rock samples. One backhoe operator there had a respirable quartz level of 0.11 mg/m3, which exceeded the OSHA, NIOSH and ACGIH limits. In the national forest, erionite was found in rock, soil and air. Air levels ranged from not detected to 0.36 fibers per cubic centimeter, and the highest level was for a masticator operator. Silica in the forest was generally low or not detected. Repeat sampling in 2014 took place in rain and snow, which likely reduced dust. The study measured exposures, not workers' health. The authors concluded that several tasks stirred up dust containing erionite. They noted the small number of workers and site visits.

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: Case study (occupational exposure assessment done in response to health hazard evaluation requests), using personal air sampling plus bulk rock and soil sampling
• Who was studied: Outdoor employees of two U.S. federal agencies, studied over four site visits (October 2012, July 2013, August 2013, September 2014) near Lander, Worland and Cody, Wyoming, and in the Custer-Gallatin National Forest (CGNF). The total number of workers is not stated; for example, 36 personal silica air samples were taken in July 2013 and 14 full-shift samples in September 2014 in the CGNF.
• Exposure: Airborne erionite (a fibrous zeolite mineral, for which there is no established occupational exposure limit) and respirable crystalline silica (quartz). Exposure occurred during dirt road maintenance (road grading/blading, culvert and ditch work with backhoes, cattle guard replacement, spreading aggregate) and forestry tasks (chainsaw felling and bucking, mastication, mowing, digging fireline, push pit reclamation, terrain vehicle operation), and during rock grinding in a minerals lab.
• Main results:
  • Wyoming (October 2012 and August 2013): no erionite fibers were found in the personal air samples, and none of the bulk rock samples near work locations contained erionite.
  • CGNF (July 2013 and September 2014): erionite was found in personal air samples, at concentrations ranging from not detected to 0.36 fibers per cubic centimeter.
  • The highest July 2013 erionite levels were 0.36 f/cc for operating the masticator in East Short Pines, 0.26 f/cc for mowing at the Slim Buttes/Reva Gap campground, 0.11 f/cc for digging fireline with a Pulaski axe, and 0.11 f/cc for chainsaw operation.
  • In the September 2014 re-evaluation of the highest-exposure tasks, the text reports erionite levels of 0.009 to 0.096 f/cc. That sampling took place in rain and snow.
  • Wyoming, October 2012: a backhoe operator clearing ditches had a respirable quartz concentration of 0.11 mg/m3, above the OSHA PEL, the NIOSH REL and the ACGIH TLV.
  • Wyoming, October 2012: a backhoe operator replacing culverts had a respirable quartz exposure of 0.04 mg/m3, which exceeded the ACGIH TLV. This operator kept the cab door open most of the time.
  • CGNF, July 2013: respirable crystalline silica was present but below the minimum quantifiable concentration in 30 of the 36 personal air samples.
  • CGNF, September 2014: respirable crystalline silica was not detected in any of the 14 full-shift air samples.
  • CGNF bulk rock (July 2013): by visual area estimate the samples contained a large percentage of erionite, but converted to weight this was only around 1%.
  • CGNF soil (September 2014): erionite measured by PLM ranged from not detectable to approximately 5%. East Short Pines soils had the highest percentage.
• The authors' conclusion: The authors concluded that erionite was present in rock formations and soils where CGNF employees worked, and that several job tasks there aerosolized dust containing erionite, with generally low or non-detectable respirable crystalline silica. They also stated that a validated sampling and analytical method for airborne erionite is needed.
• Limitations the authors state:
  • The authors state that the study had a small number of workers, a limited number of site visits, and no standardized sampling and analytical methods for erionite.
  • The September 2014 samples were taken in rain and snow, which likely reduced dust. Exposures could be higher in dry weather.
  • The Wyoming silica samples did not cover the 1.5-hour drive on dirt roads, so silica exposures could be higher at times.
  • The August 2013 Wyoming silica samples measured the wrong dust fraction and were not reported.
  • The authors state that the published Dogan and Dogan criteria for confirming erionite may not be accurate enough for the sedimentary erionite found in these areas.

Topics

Medical terms in this study, explained in our Lexicon: erionite, Crystalline, Asbestos Exposure, Malignant Mesothelioma, Occupational Exposure, Dust Control.

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