Current intelligence bulletin 62: asbestos fibers and other elongate mineral particles: state of the science and roadmap for research.

Abstract

This Roadmap is intended to outline the scientific and technical research issues that need to be addressed to ensure that workers are optimally protected from health risks posed by exposures to asbestos fibers and other EMPs. Achievement of the research goals framed in this Roadmap will require a significant investment of time, scientific talent, and resources by NIOSH and others. This investment, however, can result in a sound scientific basis for better occupational health protection policies for asbestos fibers and other EMPs.

Integration of Evidence on Community Cancer Risks from Elongate Mineral Particles in Silver Bay, Minnesota

“…MDH Method 852 defines a fiber for counting as a “parallel‐sided mineral particle having an aspect ratio of at least 3:1 and may or may not exhibit diffraction contrast” using transmission electron microscopy (TEM) (MDH, 1991a ). This definition of “fiber” also is consistent with the definition of EMP (any mineral particle with a minimum aspect ratio of 3:1) (National Institute of Occupational Safety and Health [NIOSH], 2011 ). This definition of “fiber” or EMP should not be confused, however, with definitions of “fiber” in various asbestos regulations, which specify counting certain mineral particles with lengths >5 μm and length‐to‐width (or aspect) ratios of ≥3:1 or ≥5:1.…”

“…Characteristics of EMPs known to affect their biological activity (and hazard potential) include physical dimensions, solubility, and biopersistence (NIOSH, 2011 ). Although certain investigators have argued that health effects associated with shorter mineral EMPs cannot be ruled out as causes or contributors to mesothelioma or lung cancer (Aust, Cook, & Dodson, 2011 ; Cook et al., 2016 ; Dodson, Atkinson, & Levin, 2003 ; Suzuki, Yuen, & Ashley, 2005 ), there is a general consensus that long and thin amphibole asbestos fibers are more potent for mesothelioma and lung cancer than shorter fibers (Barlow, Grespin, & Best, 2017 ; Berman & Crump, 2008 ; Mossman, 2008 , 2018 ; Roggli, 2015 ; Wylie, Bailey, Kelse, & Lee, 1993 , among others).…”

“…Although chrysotile is a phyllosilicate, its presence on the Iron Range has not been reported (McSwiggen & Morey, 2008 ; Zanko et al., 2008 ). Chrysotile is also widely recognized to be less potent than amphibole asbestos for mesothelioma (Berman & Crump, 2008 ; Hodgson & Darnton, 2000 ; NIOSH, 2011 ). Furthermore, lung cancer risks are not increased in taconite workers across the MIR (Allen et al., 2015a , 2015b ).…”

“…OSHA and MSHA exclude cleavage fragments and nonasbestiform minerals from asbestos regulations, while the National Institute of Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL) does not. For the REL, NIOSH ( 2011 ) defined a “countable EMP” as mineral particles meeting the length >5 μm and aspect ratio (AR) ≥3:1 using phase contrast microscopy (PCM) as specified in NIOSH Analytical Method 7400 (“A” Rules).…”