Erionite: An Emerging North American Hazard

Posted November 22, 2011

What to know

Summary: Evidence has slowly accumulated linking exposure to erionite with serious adverse health effects in North America, and suggesting that some workers may have a greater potential for exposure than previously recognized.
By: David Weissman, MD, and Max Kiefer, MS, CIH

Summary

Erionite is a naturally occurring mineral that belongs to a group of silicate minerals called zeolites. It is usually found in volcanic ash that has been altered by weathering and ground water. Like naturally occurring asbestos, deposits are present in many Western states (see map).1 Erionite can occur in a fibrous form. Disturbance of this material can generate airborne fibers with physical properties and health effects similar to asbestos. For example, it has long been known that residents of some Turkish villages where erionite-containing rock was used to construct homes have a remarkably high risk for development of malignant mesothelioma.2

Occurrences of erionite in sedimentary rocks of the western US. From Sheppard (USGS), 1996. Click the image for a list of the identified locations.
Occurrences of erionite in sedimentary rocks of the western US. From Sheppard (USGS), 1996. Click the image for a list of the identified locations.

Until recently, erionite was not generally considered to be a potential hazard in North America, in part because relatively little risk for exposure was seen. However, evidence has slowly accumulated linking exposure to erionite with serious adverse health effects in North America, and suggesting that some workers may have a greater potential for exposure than previously recognized. The first North American with erionite-related lung disease was recognized in Utah and reported in 1981.3 He was a road construction worker who lived in an area rich in zeolite deposits. He had extensive parenchymal and pleural fibrosis and had a lung biopsy revealing the presence of both fibrous and nonfibrous particles which had compositions determined by energy-dispersive X-ray analysis to be consistent with erionite. In 2008, a mesothelioma cluster was described in the vicinity of a small village in a zeolite-rich region of central Mexico.4 The same year, 2 additional cases were reported from a neighboring Mexican state.5 One of them underwent lung biopsy and examination of tissue showed a high burden of erionite. In 2009, a mesothelioma case associated with pulmonary interstitial fibrosis, pleural plaque formation and substantial lung burden of erionite was documented in a man who had lived in Mexico and the United States.6 In 2011, the results of a study conducted in southwestern North Dakota were reported.7 The study was motivated by the realization that, since the 1980s, gravel pits had been excavated in areas containing erionite deposits and the gravel used to surface local roads and other areas. Ambient and activity-based sampling was performed and demonstrated the potential for airborne fiber exposures. Individuals with potentially high exposures were identified and underwent careful clinical evaluation. Two with histories of road maintenance work (one had also worked in a local gravel pit) were found with mild bilateral localized pleural changes with calcification and minimal unilateral and bilateral lower lobe interstitial changes that could only be seen by CT scan. Other than erionite, neither reported potentially causative exposures.

There are no regulatory or consensus standards or occupational exposure limits (OEL) for airborne erionite fibers. Development of a quantitative OEL awaits development of a standardized, validated exposure assessment method and quantitative evaluation of risks associated with given exposures. Still, The National Toxicology Program has designated erionite to be a known human carcinogen and a study by the U.S. Geological Survey found that erionite fibers from the Cappadocian region of Turkey, North Dakota, and Oregon were chemically and morphologically similar.89 Little is known about exposures currently experienced by US workers. However, erionite-related disease has most often been reported in road construction and maintenance workers with potential occupational exposures to erionite-containing gravel used in road surfacing. Also, one case had worked in an erionite-containing gravel pit (but had also been a road worker). Although it is reasonable to be concerned, erionite-related clinical disease has not yet been reported in other US workers engaged in activities that might crush erionite-containing rock or stir up dust in soils/gravel that contain erionite.

Erionite fibers only pose a hazard if they are disturbed and become airborne, and control recommendations should focus on reducing the potential for exposure to airborne erionite fibers. Activity-based breathing zone air sampling has confirmed that when gravels containing erionite are disturbed, erionite fibers can become airborne.10 Intensity of these exposures may vary due to a number of factors, including the weather conditions (damp vs. dry, windy vs. calm), the intensity with which erionite-containing materials are disturbed and the concentration of erionite in the gravels being disturbed. However, bulk gravel erionite concentrations alone are not a reliable predictor of air concentrations, as disturbance of gravels containing erionite in "trace" amounts (< 0.2%) can sometimes result in relatively high airborne fiber concentrations.

These data support the need to implement precautions to protect workers by limiting the generation and inhalation of dust known or thought to be contaminated with erionite. A reasonable approach based on current information would be to take precautions such as those described in existing guidance for working with asbestos (Occupational Safety and Health Administration [OSHA] 29 CFR 1910.1001). Existing recommendations for working in areas with naturally occurring asbestos may be particularly relevant to reducing outdoor occupational erionite exposures.11

Risk reduction recommendations to limit erionite exposures of workers who engage in activities that disturb erionite-containing gravel/soil or crush rocks that contain erionite can include:

  • Training workers about the potential hazards of erionite and control methods for reducing the potential for exposure
  • Knowing where erionite containing material is present and will be encountered prior to beginning any work
  • Avoiding the use of erionite containing aggregate whenever possible
  • Using wet methods to reduce dust generation for road and other work such as in quarries where erionite is present (e.g., when drilling rock, apply water through the drill stem to reduce airborne dust, or use a drill with a dust collection system)
  • Limiting the number of workers who will be engaged in work with erionite
  • Establishing decontamination protocols including change of clothing, showering before leaving the worksite, and appropriate cleaning/disposal of personal protective equipment
  • Ensuring work clothing is not washed at home to prevent erionite fibers from being brought home on work clothes and boots
  • Prohibiting dry sweeping, the use of leaf blowers, or the use of compressed air for cleaning
  • Protecting employees with personal protective equipment, including respiratory protection. Note: An occupational safety and health professional should be consulted for specific guidance about the most appropriate personal protective equipment that should be used for the work being conducted.
  • Prohibiting eating, drinking, or smoking in dusty work areas where erionite fibers may be airborne. Workers should move away from the work area for breaks and wash their hands and face before eating, drinking, or smoking.
  • Establishing protocols for vehicle use on erionite containing roads (drive slowly, vents closed, windows up)
  • Wet washing equipment and vehicle exteriors, and wet cleaning/High Efficiency Particulate Air (HEPA) filter vacuuming of vehicle interiors.
  • Following Environmental Protection Agency (EPA) procedures for proper dispose of waste and debris that contains erionite.
  • Limiting bystander exposure by preventing visitors and coworkers from standing in work areas where erionite fibers may become airborne.

Although much remains to be learned about erionite in the US, airborne occupational erionite fiber exposures should be considered at least as hazardous as asbestos fiber exposures and similar preventive measures used. We look forward to working with our scientific colleagues to stay informed about further occupational health data relating to erionite as more studies become available, and we invite you to consider what scientific and technical questions you would have about this emerging occupational health issue.

Author information

Dr. Weissman is Director of the NIOSH Division of Respiratory Disease Studies.

Mr. Kiefer is Director of the NIOSH Western States Office.

Map: Occurrences of Erionite

From Sheppard R. Occurrences of erionite in sedimentary rocks of the western United States. Denver, CO: US Department of the Interior, US Geological Survey; 1996. Open File Report 96–018.

Arizona

1. Along the San Simon River, north of Bowie, Graham and Cochise Counties (NW1/4SE1/4 sec. 27, T. 11 N., R. 29 E.)

2. Near Bear Springs, Graham County (NW1/4SE1/4 sec. 4, T. 7 S., R. 23 E.)

3. Along Dripping Spring Wash, north of Christmas, Gila County (NWl/4sec. 1,T. 4 S., R. 15 E.)

4. Near Kearny, Pinal County (NW1/4NW1/4 sec. 11,T. 5S., R. 14 E.)

5. Horseshoe Reservoir, Maricopa County (Unsurveyed, about 1 km west of the Horseshoe Dam)

6. Near Kirkland Junction, Yavapai County (NE1/4SW1/4 sec. 5, T. 11 N., R. 4 W.)

7. Near Wikieup, Mohave County (NE1/4SE1/4 sec. 7, T. 15 N., R. 12 W.)

California

8. Drill hole (Hector 3, about 4.7-5.4 m and 10.7 m depths) near the Hector hectorite mine, San Bernardino County (NWl/4SWl/4sec. 25, T. 8 R, R. 5 E.)

9. Southern flank of the Cady Mountains, San Bernardino County (NWl/4SWl/4sec. 6, T. 8 N., R. 5 E.)

10. Near Mule Canyon, Calico Mountains, San Bernardino County (NE1/4SW1/4 sec. 24, T. 10 N., R. 1 E.)

11. Near Coon Canyon, Mud Hills, San Bernardino County (NW1/4NE1/4 sec. 23, T. 11 N., R. 2 W.)

12. Kramerborate mine at Boron, Kern County

13. Drill hole at China Lake, San Bernardino County

14. Near Shoshone, Inyo County (NE1/4 sec. 12, T. 21 N., R. 6 E.)

15. Drill hole at Owens Lake, Inyo County

Colorado

16. Near the Rio Grande, south of Creede, Mineral County

Idaho

17. Along Browns Creek, south of Oreana, Owyhee County (NE1/4NE1/4 sec. 24, T. 5 S., R. 1 W.)

Montana

18. Hepburn's Mesa in Yellowstone Valley, Park County

Nevada

19. Near Beatty, Nye County

20. Drill holes (UE-25a#l, about 395.1 m depth; J-12, about 189.0-192.0m depth; USW G-4, about 400.5 m depth; USW GU-3, about 362.5 m depth) at Yucca Mountain, Nye County

21. Gabbs Valley, northwest of Gabbs, Nye County

22. Southern Desatoya Mountains, Churchill County

23. Near Eastgate, Churchill County (sec. 28, T. 17 N., R. 36 E.)

24. Trinity Range, Churchill County (northeast part of T. 24 N., R. 28 E.)

25. Near Hungary Valley, Washoe County (SW1/4NW1/4 sec. 22, T. 22 N., R. 20 E.)

26. Near Windy Basin, east of Gerlach, Pershing County

27. Jersey Valley, Pershing County (sec. 8, T. 27 N., R. 40 E.)

28. Near Fish Creek, Lander County (NW1/4NW1/4 sec. 10, T. 27 N., R. 41 E.)

29. Near Reese River, Lander County (sec. 26 and 35, T. 24 N., R. 43 E.)

30. Pine Valley, Eureka County (NW1/4 sec. 20 T. 28 N., R. 52 E.)

31. Along Spring Creek, Humboldt County (NW1/4NE1/4 sec. 21, T. 41 N., R. 41 E.)

32. Eastern fork of Chimney Reservoir, Humboldt County (NWl/4SEl/4sec. 17, T. 41 N., R. 43 E.)

33. Along South Fork Little Humboldt River, Elko County (NW1/4NE1/4 sec. 1, T. 41 N., R. 44 E.)

34. Near Susie Creek, Elko County (sec. 6, T. 35 N., R. 54 E.)

New Mexico

35. Near Buckhorn, Grant County (NE1/4SW1/4 sec. 10, T. 15 S., R. 18 W.)

36. Drill hole (Oberlin No. 2, about 445-564 m depth) in the Plains of San Augustin, Catron County (center of sec. 28, T. 5 S., R. 13 W.)

North Dakota

37. Little Badlands of western Stark County (sec. 7, T. 137 N., R. 97 W.)

Oregon

38. Near the Bretz mine, along the northern rim of the McDermitt caldera, Malheur County

39. Near Rome, Malheur County (NW1/4NE1/4 sec. 22 T. 31 S., R. 41 E.)

40. Along Ryegrass Creek, Malheur County (SW1/4 sec. 23, T. 29 S., R. 40 E.)

41. Near Round Mountains, Malheur County (sec. 8 and 17, T. 25 S., R. 46 E.)

42. Near Harney Lake, Harney County (NW1/4 sec. 18, T. 28 S., R. 31 E.)

43. Wrights Point, Harney County (SW1/4SE1/4 sec. 34, T. 24 S., R. 31 E.)

44. Near Durkee, Baker County (SW1/4SW1/4 sec. 36, T. 11 S., R. 43 E.)

South Dakota

45. Sheep Mountain Table, Shannon County (NE1/4 sec. 32, T. 4 S., R. 44 W.)

Utah

46. Drill hole (Phillips Sunnyside No. 2) near Sunnyside, Carbon County (sec. 15, T. 13 S., R. 14 E.)

Wyoming

47. Near Fort LaClede, Sweetwater County (SE1/4SE1/4 sec. 1, T. 16N., R. 98 W.)

48. Beaver Rim (northeastward from the SW1/4 sec. 3, T. 30 N., R. 96 W. to the NEl/4 sec. 34, T. 32 N., R. 95 W.), Fremont County

49. Near Moonstone, Natrona County (NE1/4 sec. 17, T. 30 N., R. 89 W.)

50. Near Hawks Butte, Hot Springs County (NW1/4 sec. 36, T. 42 N., R. 90 W.)

51. Several drill holes in Lower and Upper Geyser Basins, Yellowstone National Park

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Content Source:
National Institute for Occupational Safety and Health
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