Dust and Human Health - Mineral Dust: A Key Player in the Earth System - page 390

change over such a short time period (Hartert and Peebles 2000 ; Subbarao et al.
2009 ;Zervasetal. 2012 ). Until recently, few studies have sought to link MD
and respiratory disease such as asthma though several studies have demonstrated
an association between PM exposure and increased risk for respiratory disease
exacerbation.
Few population health studies for regionally produced dust exist, particularly for
dusts differentiated as MD and not as PM. Those that do support an association
between exposure to MD and asthma. For example, Chimonas and Gessner ( 2007 )
reported a 9.3 % increase in the rate of outpatient visits for asthma and an 18 %
increase in quick relief medication prescriptions (for asthma) following exposures
to PM10 levels of 22-33 g/m 3 , which is substantially lower than the National
Ambient Air Quality Standards (NAAQS) level of 150 g/m 3 . Their study examined
PM exposures that the authors describe as being derived primarily from geological
sources in Alaska. In El Paso, Texas, where dust events are common, Grineski et al.
( 2011 ) found that hospitalizations for asthma and acute bronchitis increased in all
age groups (children, adults, and elderly) following dust events caused by relatively
low winds. Study participants from the Cheyenne River Reservation in South Dakota
identified dust as one of the top four asthma triggers (other top triggers were cold
air, smoke, and exercise) for all seasons (O'Leary and Wallace 2012 ). Describing the
composition of dusts in regional storms as particulates from nonindustrial sources,
Hefflin et al. ( 1994 ) found an increase in daily emergency room visits for bronchitis
for each 100 g/m 3 increase in PM10 during a study of the effects of dust storms in
Washington State. The authors relate that the dusts in these regional seasonal storms
are volcanic in origin (Hefflin et al. 1994 ).
International studies demonstrate similar findings. Rutherford et al. ( 1999 )
analyzed rural dust events in Australia and observed that in spite of study design
limitations, the potential for adverse health effects in predisposed individuals such
as asthmatics was evident. A study in the United Arab Emirates indicates sudden
heavy exposures to dust and sand storms may precipitate acute severe asthma in
uncontrolled asthmatics and result in emergency room visits and hospitalizations
(Mahboub et al. 2012 ). In Japan, using light detection and ranging (LIDAR) to
distinguish between mineral dust particles (“nonspherical”) and nonmineral dust
particles (“spherical”), Kanatani et al. ( 2010 ) found mineral dust events originating
in Asia were associated with increased risk of hospitalizations for asthma in
pediatric patients. In Barbados, however, Prospero et al. ( 2008 ) found no substantial
changes in clinic attendance for pediatric asthma cases related to short-term
increases in dust concentrations that were transported substantial distances from
Africa. Their study reports that although these dusts had not been extensively
studied in terms of composition, the presence of commonly suspected pollutants,
concentrations of major pollutant aerosol species, ozone and organic matter are low
when compared to urban dusts (Prospero et al. 2008 ). Measurements of dust in the
trade winds at Barbados and in the southeastern United States (Prospero et al. 2008 )
indicate that one third to one half of the transported African dust mass was below
2.5 m, a fraction which is generally deemed respirable.