Dust and Human Health - Mineral Dust: A Key Player in the Earth System - page 388

by processing dusts, ingestion of dusts cleared from the respiratory tract was also
a likely but subordinate exposure pathway. In contrast, direct uptake of lead from
the respiratory tract was likely negligible due to the generally low solubility of the
respired lead minerals in the respiratory tract fluids and the likely reprecipitation of
any solubilized lead as insoluble lead phosphates (Plumlee et al. 2013b ).
A recent review by Sacks et al. ( 2011 ) identified population attributes that may
increase health risk from PM exposures. In addition to individuals with preexisting
disease (i.e., cardiovascular and respiratory), they identified life stage (i.e., children,
older adults), genetic polymorphisms, low socioeconomic status, and obesity as
additional factors. By reviewing epidemiological studies that presented stratified
results (e.g., males vs. females or <65 vs. >65 years of age), their study was able to
compare populations exposed to similar PM concentrations, thus providing a basis
for characterizing susceptible populations.

15.5 Ailments Associated with Airborne Dusts

Chronic or repeated acute exposures such as those that might be encountered by
communities in or near dryland areas where dust storms prevail have not received
much scrutiny prior to the last decade. Few population health studies related to
regionally produced dust exist, particularly for dusts differentiated as inorganic
minerals dusts and not PM (e.g., a size fraction such as PM2.5). The consistent
observation in the few studies that have been done is an increased incidence of
some form of respiratory disease. Interestingly, a lag period has been identified
in several studies, generally 2-3 days from exposure to illness, but the reason is
unclear. In China, in addition to an increased relative risk (1.14 %) of hospitalization
for respiratory and cardiovascular disease associated with dust events, a 3-day lag
period between exposure and hospitalization was observed (Meng and Lu 2007 ).
Other studies, particularly of respiratory disease associated with dust events, have
observed a similar lag period (Lopez-Villarrubia et al. 2010 ;Grineskietal. 2011 ;
Johnston et al. 2011 ).

15.5.1 Asthma

One common chronic disease associated with exposure to airborne MD is asthma.
Asthma is characterized by airway inflammation, variable lung function, and airway
responsiveness. However, epidemiological studies have been hampered because no
clear definition of asthma or clinically acceptable method for measuring inflam-
mation exists (Hartert and Peebles 2000 ). About 235 million people worldwide
have asthma (WHO 2011 ), and estimates suggest that asthma prevalence increases
globally by 50 % every decade with the highest increases seen among children
(Braman 2006 ). Direct medical and indirect economic costs related to asthma in