Dust and Human Health - Mineral Dust: A Key Player in the Earth System - page 396

In the past, these diseases were largely thought to result from occupational
exposures to high levels of the dusts, with lesser but still measureable impacts
from lower-level environmental exposures to dusts from commercial asbestos.
However, concerns have increased over the last several decades about potential
health risks resulting from environmental and occupational exposures to dusts
of these minerals that are liberated from their source rocks by natural processes
(e.g., weathering, erosion, landslides) or anthropogenic activities (e.g., road building
or excavation). For example, unusually high rates of malignant mesothelioma were
linked to environmental exposures to erionite dusts released from tuffaceous lake
sediments in three Turkish villages (Carbone et al. 2011 ; Baris et al. 1978 ). Concerns
about the potential for similar environmental exposures to erionite in the western
United States are increasing, such as in parts of North Dakota where erionite-
bearing gravels were used to gravel hundreds of miles of dirt roads (Weissman and
Keifer 2011 ; Carbone et al. 2011 ). A California study linked residential proximity
to ultramafic rock units containing natural occurrences of asbestos (NOA) to an
increased risk for mesothelioma (Pan et al. 2005 ); however, the study was unable
to exclude with certainty other possible causes, such as the retirement of asbestos-
exposed shipyard workers to areas with geologically elevated NOA. Baumann et al.
( 2011 ) linked high incidences of malignant mesothelioma in New Caledonia to
environmental asbestos exposures, particularly to dusts from gravel roads.
More research is needed to understand the potential health risks posed by
exposures to dusts from natural occurrences of asbestos, erionite, and other REMPs.
One key step is to understand the spatial distribution of geological favorable
host rocks from which dusts containing these minerals may be released. The US
Geological Survey has completed a systematic inventory of known geological
occurrences of asbestos, fibrous amphiboles, and erionite across the United States
(Van Gosen et al. 2013 ; Van Gosen and Clinkenbeard 2011 ). These compilations
provide public health and other local agencies (e.g., environment, land use and
development) with important information that can be used for future planning,
exposure mitigation, and reducing risks of disease (Van Gosen et al. 2013 ; Meeker
and Miller 2012 ;VanGosen 2007 ).

15.6 Conclusion

The National Research Council recently identified ten research priorities for
airborne particulate matter. Two of these were the characterization of emission
sources and the assessment of hazardous particulate matter components. The
research summarized in this chapter indicates that MD exposures may play a
role in human morbidity and mortality although in some cases the association
is tentative and the biological mechanisms and components responsible remain
unclear. It is apparent that additional research is needed to identify contributions
made by MD and the resulting risks posed to human health. Several studies indicate
an increase in exposure and/or particle concentration related to dust events may