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Replies to post #15000 on Chesapeake Energy Corp (CHK)
5.1.1 Investigate the impact of mixed exposures in the hydraulic fracturing and petroleum industries to
benzene, toluene, ethyl benzene, and xylene (BTEX), polycyclic aromatic hydrocarbons (PAHs), respirable
crystalline silica, and other agents on the respiratory health of workers, in particular airways disease and
cancer
The natural gas obtained by hydraulic fracturing (also called hydrofracturing or fracking) burns much
cleaner than coal, which means fewer air emissions. However, a recent review of emerging occupational
and environmental respiratory diseases highlighted concerns about the airborne exposures from
hydraulic fracturing (Moitra, Puri, Paul, & Huang, 2015). Investigations of exposures at fracking sites have
identified a variety of potential threats to the respiratory tracts of both workers and the general
population, including benzene, toluene, ethyl benzene, and xylene (BTEX), polycyclic aromatic
hydrocarbons (PAHs), respirable crystalline silica, hydrogen sulfide, diesel exhaust, and other airborne
agents (Carpenter, 2016; McCawley, 2015; McKenzie, Witter, Newman, & Adgate, 2012). These
exposures could pose a risk to the respiratory health of workers and others living close enough to the
fracking sites, and of particular concern is their contribution to airways disease and respiratory cancers.
Studies of human health effects have focused on community environmental exposures. For example, a
recent study reported that the exacerbation of asthma among people living near fracking well sites was
associated with phases of well development such as pad preparation, well drilling, actual hydraulic
fracturing, and production (Rasmussen et al., 2016). Additional studies are needed to investigate the
impact of these exposures on the respiratory health of workers at well sites.
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Objective 6: Advance the understanding of the impact of occupational chronic low-level
toxicant exposure on respiratory health, notably chronic low-level irritant exposure
Chronic exposure to inhaled irritants such as vapors, gases, dusts (organic and inorganic), and fumes
(VGDF) has been associated with development of chronic obstructive pulmonary disease (COPD). COPD
affects >5% of the population and is associated with high morbidity and mortality (NHLBI, 2012). An
official statement of the American Thoracic Society estimated that 15% of the population burden of
COPD is attributable to occupational exposures (Balmes et al., 2003). The population attributable
fraction for occupational exposure is higher among never smokers, with a recent estimate of 48% (Würtz
et al., 2015).
Chronic exposures to inhaled respiratory irritants at work have also been associated with worsening of
asthma, termed work-exacerbated asthma. The prevalence of work-exacerbated asthma has been
estimated at 21.5% for adults with asthma (Henneberger et al., 2011). Chronic moderate to low inhaled
irritant exposures have also been suggested, from epidemiologic studies, to increase new-onset irritantinduced asthma (Vandenplas et al., 2014). The prevalence of asthma is increased in occupations with
moderate to low irritant exposures, such as for cleaners, farmers, wood workers, aluminum smelter
workers, and previously radiology technicians exposed to “dark room” chemicals. However, for many of
these occupations there may be other mechanisms of new-onset asthma such as intermittent high level
irritant exposures and sensitizer exposures, so this has been classified in a diagnostic algorithm as
“possible irritant-induced asthma” (Vandenplas et al., 2014). In a previous evidence-based report, Baur
et al. found the best evidence for causation of asthma or COPD related to irritants from 17 types of
agents: benzene-1,2,4-tricarboxylicacid-1,2-anhydride, chlorine, platinum salt, isocyanates, cement
dust, grain dust, animal farming, secondhand tobacco smoke, welding fumes or construction work,
phthalic anhydride, glutaraldehyde, sulfur dioxide, cotton dust, cleaning agents, aluminum potrooms,
various other farming environments, and foundries (Baur, Bakehe, & Vellguth, 2012)
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