Public health impact of urban asthma

Public Health Significance of Urban Pests Allergic asthma 15 14 Conversely, it is debatable whether increased cleanliness resulted in the post-1950s increase in asthma. To correspond with the increase in asthma, the proposed change to cleaner living would have to have occurred within one generation. While it seems doubt- ful that parents of today’s asthmatic children grew up in much dirtier environments than those of their offspring, Matricardi, Bouygue Tripodi 2002 have proposed a theory whereby the increase in inner-city asthma is associated with increased hygiene, brought on by delayed class-driven urbanization in urban poor communities. Although many of the recent studies are compelling, the relevance of the hygiene hypothesis to the asthma epidemic is still not well established scientifically. Recently the trends towards a more sedentary lifestyle in industrialized countries have been scrutinized as a possible cause of the increase in asthma Crater Platts-Mills, 1998. Technological advances in indoor entertainment, such as television, became common in households in developed countries in the 1960s, which along with today’s cable televi- sion, video games, computers and video players, have resulted in children today spen- ding a larger proportion of their time in sedentary activities than did prior generations. A study of asthmatic children in inner-city Atlanta, Georgia, found that 82 of the chil- dren had a television in their bedroom Carter et al., 2001. Sedentary entertainment could have the additive effect of both lack of exercise and longer exposure to indoor allergens from sources such as dust mites, cockroaches, cats and dogs, which are known to be stron- gly associated with asthma Crater Platts-Mills, 1998. It is likely that causes for the increase in asthma include multifactorial features of wes- ternized countries, with some contributing more than others in different communities. What is clear is that there must be some commonality in the causes of the increase obs- erved in different communities, given the similar time frames of the increases Evans et al., 1987; Sears Beaglehole, 1987; Aberg, 1989; Haahtela et al., 1990; Crater Platts- Mills, 1998; ISAAC, 1998.

1.1.3. Public health impact of urban asthma

The public health impact of asthma in the urban environment is substantial, with the prevalence in some communities estimated at close to one in three children Peat et al., 1995; Nicholas et al., 2005. While mortality from asthma is low, the day-to-day burden for those with asthma is substantial, and the economic costs to society are high. As more countries develop urban centres and adopt western lifestyles and methods of building residential environments, the importance of understanding the effect of these changes on urban pests and how they relate to health will only increase. Findings from several studies show that the prevalence of childhood asthma in an urban population could range from 8 to 22 and that the prevalence of allergy among asth- matic children varies by community 50–80 Martinez et al., 1995; Kattan et al., 1997; Ronmark et al., 1999; Lau et al., 2000; Carter et al., 2001. Among these atopic children in an urban environment, many are allergic to urban pest allergens that can exacerbate symptoms Rosenstreich et al., 1997. Therefore, exposure to urban pests could affect 4–17 for example, from 50 of 8 to 77 of 22 of children living in an urban envi- ronment. One study in North America found that for every United States dollar spent, asthma disease management has been shown to save US 3–4, by decreasing visits to emergency departments Rossiter et al., 2000. Overall, the long-term economic and qua- lity-of-life benefits of decreasing the number of missed school and work days are diffi- cult to assess, but they are surely positive. 1.2. Assessing allergen exposure 1.2.1. Questionnaire assessment Several investigators have examined worldwide associations between home characteris- tics, reported by residents, and dust mite allergen levels Chan-Yeung et al., 1995; Munir et al., 1995; Platts-Mills et al., 1997; Tobias et al., 2004. In warm and humid environ- ments, the concentration of dust mite allergens is expected to be high in soft furnishings throughout the year Zhang et al., 1997. In more temperate climates, a seasonal variation has been observed Platts-Mills et al., 1987; Miyazawa et al., 1996; Chew et al., 1999a, and several characteristics have been associated with exposure to dust mite allergens: alti- tude, type of building, and presence and type of carpeting Wickman et al., 1991; Arlian, 1992; Harving, Korsgaard Dahl, 1993; van Strien et al., 1994, 2002; Chew et al., 1998; Wickens et al., 2001; Basagana et al., 2002; Mihrshahi et al., 2002; Matheson et al., 2003. In general, factors that lead to large dust mite populations will lead to high concentrations of the allergen. However, some evidence exists for the passive transfer of dust mite aller- gens from dust-mite-hospitable environments to inhospitable environments, such as auto- mobiles Neal, Arlian Morgan, 2002. In homes, a visual assessment is possible for cockroaches and mice, but not for micro- scopic dust mites. A resident, a trained inspector, or both can make visual assessments for cockroaches or mice. In the NCICAS, 937 homes were evaluated for cockroach and rodent infestation by residents and trained evaluators Crain et al., 2002. The percen- tage of residents that reported problems with mice or rats in the past 12 months was higher than that observed by the inspector 40 versus 9, and the percentage of resi- dents that reported problems with cockroaches in the past 12 months was higher than that observed by the inspector 58 versus 15. In another study, mouse allergen 1.6 µgg had a significant association with resident reports of rodent infestation odds ratio OR = 3.38, P 0.05, but not with inspector observations Cohn et al., 2004. In a study of inner-city children in Baltimore, 41 of homes had substantial amounts of a major cockroach allergen, Bla g 1 1 unitg, but only 18 had a cockroach infestation iden- tified by a home inspector Matsui et al., 2003. Although residents might not accurately report cockroaches or rodents in their homes for a variety of reasons, the studies above suggest that residents might be better informed than trained inspectors with regard to previous infestations that could lead to high levels of allergen in the dust. Because of the range of housing stock across the world, some home characteristics are not consistently associated with mouse or cockroach allergens Phipatanakul et al., 2000b;