Agency for Toxic Substances and Disease Registry
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Learning Objectives |
Upon completion of this section, you will be able to
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Treatment and Management Overview |
This Case Study discusses the role environmental factors play in causing, triggering, and exacerbating asthma. It does not comprehensively review asthma treatment and management.The treatment and management of environmental asthma follow the guidelines set forth by the National Heart, Lung, and Blood Institute, with special emphasis on the management of the patient’s environment. Pharmaceutical intervention forms the basis of asthma treatment. Asthma medications are generally categorized as:
After confirming the asthma diagnosis and assessing the severity of disease, a stepwise approach is taken for the long-term management of asthma (NHLBI1997; NHLBI 2003; Spahn et al. 2002). Goals for the general management of a patient with asthma include
Management includes careful monitoring of the patient’s response to treatment and appropriate adjustments. It also includes educating the patient and family regarding primary and secondary preventive measures (NHLBI 1997; NHLBI 2003; AAP 1999; Lim 2002). |
Predisposing Factors |
Atopy, the genetic predisposition for the development of an IgE-mediated response to common airborne allergens, is the strongest identifiable predisposing factor for developing asthma (NHLBI 1997; NHLBI 2003; Busse and Rosenwasser 2003). Most children with asthma have allergic rhinitis, a major independent risk factor for asthma. Rhinitis and asthma can be viewed as manifestations of one syndrome—the chronic allergic respiratory syndrome—in different parts of the respiratory tract (Togias 2003). Certain immune system components, such as the T-helper phenotype, are determined in the first year of life by environmental exposure to respiratory infections or environmental allergens in genetically predisposed individuals (Robinson et al. 2004; Luft et al. 2004; Larche et al. 2003; Umetsu et al. 2003). |
Exposure to Allergens and Risk of Asthma |
Studies of exposure to allergens and risk of asthma have yielded paradoxical results. Exposure to some pets appears to increase the risk of asthma and wheezing in older children, yet lower the risk among young children (Apelberg et al. 2001). House dust mite and cockroach allergens appear to have a positive linear relationship, whereas cat allergens appear to act quite differently, with maximum sensitization developing at moderate exposure levels. Very low levels of cat allergen exposure are likely to induce no response; very high levels are likely to develop a form of tolerance (Murray et al. 2001). Decreased exposure to infections and allergens in early childhood has been linked to the increased incidence of asthma in industrialized countries (the “hygiene hypothesis”) (Liu and Murphy 2003). |
Hygiene Hypothesis |
The hygiene hypothesis of asthma states that naturally occurring infections and allergen exposures might essentially immunize against the development of asthma and allergic and autoimmune diseases. The modern emphasis on cleanliness or “sanitizing the environment” may have reduced this natural immunotherapy over the past century and might be a factor in the global increase of these conditions (Liu and Murphy 2003). The differences in health outcomes from exposure are due to important moderating variables, such as:
Growing up on a farm may protect against developing asthma and allergic rhinoconjunctivitis (Von Essen 2001). A recent study showed that exposure of young children to older children at home or to other children in childcare settings protects against the development of asthma and frequent wheezing later in childhood (Ball et al. 2000). |
Primary Prevention Strategies in Children |
Well-documented primary prevention strategies for asthma include the following.
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Primary Prevention in Adults |
In adult-onset asthma, primary prevention relies mainly on smoking cessation and control of workplace exposures. Studies of factory workforces in the past decade have provided consistent evidence of exposure-response relationships for both sensitization (IgE production) and asthma (Taylor 2001; Jeebhay et al. 2001). New-onset occupational asthma may be immunological or nonimmunological in origin. The immunologic variants are usually caused by high molecular-weight allergens such as grain dust and animal or fish protein. Symptoms may take months or years to develop. Nonimmunologic occupational asthma can be precipitated by a brief, high-level exposure to a strong irritant. Symptoms occur immediately or within a few hours of the exposure. Multiple lower level exposures to an irritant can also cause asthma. Whether immunologic or nonimmunologic in origin, once the diagnosis of occupational asthma is established, the worker should be removed from further exposure. Continued exposure to sensitizers or irritants following sensitization may cause persistent problems that can lead to permanent impairment. In addition, once sensitized, individuals may have a substantial response to extremely low levels of sensitizers or irritants. If the diagnosis is made in a timely fashion and steps are taken to stop exposure, most workers experience improvement. Prevention is the best therapeutic intervention (Bardana 2003). Avoidance of exposure to occupational irritants and allergens is the mainstay of primary prevention. Jobs that use diisocyanates, enzymes, or latex are especially notorious for producing occupational asthma. Prospective surveillance can detect the development of specific IgE antibody before the onset of allergic symptoms. This allows for continuing interventions to reduce exposures and minimize or eliminate those associated with symptoms. Workers with IgE to specific allergens can continue to work in the industry symptom-free for their entire careers. This indicates that exposures needed to induce sensitization are different and probably lower than exposures needed to elicit allergic symptoms (Wisnewski 2006; Sarlo and Kirchner 2002). |
Secondary Prevention in Children and Adults |
Patients can take a number of steps to reduce or avoid exposure to pollutants, irritants, and allergens that may trigger or exacerbate asthma episodes (Williams et al. 2003; AAPCEH 2003). The National Environmental Education and Training Foundation outlines possible preventive measures in Environmental Management of Pediatric Asthma: Guidelines for Health Care Providers. Those environmental intervention guidelines are summarized below (NEETF 2005). |
Dust Mites |
No matter how clean a home is, dust mites cannot be totally eliminated. However, household interventions can decrease exposure to dust mites and possibly reduce asthma exacerbations (Ehnert et al. 1992; Murray and Ferguson 1983). Cleaning with a high-efficiency particulate air (HEPA) filter vacuum is particularly effective in removing allergens and thus decreasing asthma symptoms (McDonald et al. 2002; Platts-Mills et al. 2001). The following steps are recommended to reduce dust mites in the home (NEETF 2005).
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Animal Allergens |
Modifications to the home environment can significantly reduce animal allergens and the frequency of asthma episodes (Williams et al. 2003). The following steps can reduce exposure to animal allergens.
If those options are not possible, the following steps may help reduce exposure.
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Cockroach Allergens |
The first step in limiting cockroach allergens is to keep the house clean and in good shape (O’Connor and Gold 1999). In general, use the least hazardous methods of roach control first. Food
Hygiene and maintenance
Pest management
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Mold and Mildew |
Mold spores are allergens that can be found indoors and outdoors. Outdoor molds are present year-round throughout the West (lower altitudes) and South, and in the North during the fall. Outdoor molds in the North generally peak in late summer. There is no definite seasonal pattern to molds that grow indoors. Moisture control is the key step in limiting indoor mold growth (Krieger and Higgins 2002). Tips to help keep exposure to mold spores as low as possible.
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Environmental Tobacco Smoke |
Cigarette smoke contains many toxic chemicals and irritants. Approximately 42% of children 2 months to 11 years of age live in a home with at least one smoker (Pirkle et al. 1996). Children exposed to tobacco smoke have increased asthma exacerbations. Studies suggest that asthma symptoms may be less severe for asthmatic children if parents expose them to less cigarette smoke (Murray and Morrison 1993). Simply “smoking outside” is not enough to limit the harm to children from tobacco smoke (CDC 2000). Complete cessation of indoor smoking in the homes of children with asthma may be needed to achieve significant health improvement (Lodrup and Carlsen 2001). The following are the most important preventive strategies to reduce exposure to environmental tobacco smoke.
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Indoor Air Pollution |
For indoor air pollution, the two best approaches to reducing indoor air pollution are source control and ventilation. Listed below are specific steps for improving indoor air quality.
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Outdoor Air Pollution |
Outdoor air pollution, especially ozone and particulate matter, can increase asthma symptoms. Ways to limit exposure to outdoor air pollution.
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Desensitization |
For some cases, consider desensitization—especially if environmental control fails to decrease asthma exacerbations. Specific immunotherapy involves the administration of allergen extracts to achieve clinical tolerance of the allergens that cause symptoms in patients with allergic conditions. Immunotherapy can be effective in patients with mild forms of allergic disease, and in those who do not respond well to standard drug therapy. Effects of specific immunotherapy take longer to manifest, but once established, specific immunotherapy may give long-lasting relief of allergic symptoms, whereas the benefits of drugs only last as long as they are continued (Frew 2003b; Nelson 2003). |
Key Points | Every practitioner who treats asthma patients should have general goals for management. Environmental triggers can cause or exacerbate asthma. Patients can take a number of steps to reduce or avoid exposure to the pollutants, irritants, and allergens that may trigger or exacerbate asthma episodes. |
Progress Check |