Dust and Human Health - Mineral Dust: A Key Player in the Earth System - page 389

Fig. 15.2 ( a ) Shows the position of the lungs. ( b ) Depicts a cross section of a normal airway. ( c )
Shows a cross section of an airway during asthma symptoms (Source: National Heart, Lung, and
Blood Institute; National Institutes of Health; U.S. Department of Health and Human Services.
National Institutes of Health)
Europe average 21 billion dollars annually (Braman 2006 ). In 2007, costs related to
asthma in the United States were 56 billion dollars (CDC 2011 ).
Asthma has been described as a complex inflammatory disease, characterized by
episodes of wheezing, coughing, and shortness of breath secondary to reversible
airflow limitations (Zervas et al. 2012 ;Fig. 15.2 ). Studies have demonstrated that
childhood asthma actually begins in infancy (Hartert and Peebles 2000 ). Evidence
suggests reduced lung function in children and adults, as well as adult lung disease,
may be linked to events that occur during fetal development and postnatal (after birth
to about 6 weeks) life (Soto-Martinez and Sly 2010 ). The importance of genetic
factors in the development of asthma has also been established (Zervas et al. 2012 ).
Epidemiological and genome-wide linkage studies have identified more than 100
genes associated with allergy and asthma in eleven different populations (Subbarao
et al. 2009 ). Risk factors for childhood asthma include genetic predisposition,
exposure to tobacco smoke or animals, and respiratory infections. Adult-onset
asthma may occur as a relapse of childhood asthma or have environmental or
occupational causes (Subbarao et al. 2009 ).
Environmental exposures are acknowledged as a factor in the exacerbation of
existing asthma and to a lesser degree the development of asthma (Zervas et al.
2012 ). Gene-environment interactions support the observed increase of asthma cases
over the last 50 years as genetic susceptibility factors within a population cannot