Clearing the Air Asthma and Indoor Air Exposures (2000) / Chapter Skim
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6 Indoor Chemical Exposures
6 Indoor Chemical Exposures
Pages 223-262
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From page 223... ...
The committee was also tasked with examining possible means of mitigating or preventing exposure to these agents. In this chapter the committee evaluates indoor exposure to chemical agents, addressing the following to the extent permitted by available research: 1.
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From page 224... ...
Indoor sources include gas stoves and space heaters, kerosene space heaters, and poorly vented furnaces and fireplaces. In homes with indoor combustion sources, personal NO2 exposures are usually driven by indoor concentration in the home, even in urban areas with elevated outdoor levels.
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From page 225... ...
On average, about half of U.S. homes have gas stoves or ovens, and much higher percentages of gas appliances exist in some urban areas (Samet et al., 1987~.
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From page 226... ...
Evidence Regarding Asthma Exacerbation and Development Numerous epidemiologic studies have examined whether respiratory health effects are associated with exposures to typical indoor NO2 concentrations. Most such studies have addressed respiratory symptoms and/or Jung function variables as the primary outcomes, both of which include measures (i.e., wheeze or decline in FEF25 75)
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From page 227... ...
, and found significant associations between incident asthma and several factors other than gas appliances, including heavy maternal smoking, childhood atopy, and others. A subset of 140 subjects provided a 24-hour personal NO2 sample.
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From page 228... ...
The cross-sectional associations found in these two surveys suggest the possibility of small impacts of NO2 on asthma risk; however, prospective cohort studies would be needed to rigorously test this hypothesis. Respiratory symptoms that are associated with asthma, such as coughing, wheezing, and shortness of breath, have been studied in relation to gas stove usage and/or NO2 measurements in a large number of cross-sectional surveys, longitudinal pane]
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From page 229... ...
Other cross-sectional survey studies have reported no associations between respiratory symptoms and gas appliances (Braun-Fahriander et al., 1992; Dekker et al., 1991; Dijkstra et al., 1990; Hosein et al., 1989~. There are no obvious differences between the two groups of studies that would explain the differences in results.
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From page 230... ...
Chamber studies involving one- to threehour exposures to 50-1,500 ppb NO2 did not detect effects on respiratory symptoms among normal or asthmatic subjects (Salome et al., 1996; Utell et al., 1991~. In a pane!
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From page 231... ...
Because of the importance of acute respiratory infections as triggers of asthma symptoms, an effect of NO2 exposure on increased risk of respiratory infections might represent an indirect mechanism linking NO2 with asthma exacerbations. In the late 1970s, Melia and colleagues reported an increased risk of respiratory infections among children living in homes with gas stoves in a large British cross-sectional survey (Melia et al., 1977, 1985~.
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From page 232... ...
that may occur only in poorly ventilated kitchens with gas appliances in use. · There is limited or suggestive evidence of an association between the use of gas appliances and increased risk of respiratory symptoms, increased risk of respiratory infections, and to a lesser extent, decreased lung function.
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From page 233... ...
For example, that study recommended that "unvented combustion space heaters should not be used, particularly in cold climates where they may be on for prolonged periods." On the other hand, while removal of gas stoves would in theory represent an effective exposure reduction strategy, it may not be practical or economically feasible in most cases. Continuous pilot lights add between 10 and 20 ppb of NO2 to background indoor levels and should be turned off or eliminated (Samet, 1990~.
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From page 234... ...
Residential pesticides represent a broad class of chemicals and applications aimed at controlling flies, ants, moths, cockroaches, fleas, ticks, infectious organisms, fungi, plants and other unwanted species in and around the residential environment. Pesticides that have been measured in residential indoor air include chiordane, heptachior, aldrin, dieldrin, diazinon, propoxur, dichiorvos, naphthalene, p-dichiorobenzene, pentachiorophenol, chiorpyrifos, malathion, and carbary!
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From page 235... ...
EPA, 1983~. Evidence Regarding Asthma Exacerbation and Development Although there is a great deal of interest in the possibility of an association between pesticide exposure and asthma, relatively little research has been done on the topic to date.
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note that acute asthma has been described in farm workers who use organophosphate insecticides, which act as an anticholinesterase and probably precipitate airflow obstruction on a pharmacologic basis without the requirement of an underlying predisposition to asthma. Conclusions: Asthma Exacerbation and Development · There is inadequate or insufficient evidence to determine whether or not an association exists between pesticide exposures at the levels typically encountered in nonoccupational or residen
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From page 237... ...
VOLATILE ORGANIC COMPOUNDS Definition of Agent and Means of Exposure Volatile organic compounds are any of a large number of organic molecules that exist either as free vapors or adsorbed onto particles in air. More than 300 VOCs have been measured in indoor air (Wallace, 1987~.
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From page 238... ...
Factors Influencing Exposure Most available data suggest that personal exposures to VOCs are dominated by indoor exposures, even for persons living in urban areas near major outdoor VOC sources such as the petrochemical industry (Wallace, 1991; Wallace et al., 1987~. Numerous VOC sources exist indoors, including cigarette smoking, combustion appliances, solvents, printed materials, photocopying machines, chlorinated water, dry-cleaned clothes, pesticides, silicone caulk, floor adhesive, particleboard, moth crystals, floor wax, wood stain, paint, furniture polish, floor finish, carpet shampoo, room deodorizer, and viny]
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From page 239... ...
reported data on simultaneous personal and outdoor VOC measurements in randomly selected groups of subjects living in two urban areas of New Jersey, in a moderately sized city in North Carolina, and in a small town in North Dakota. Personal exposures were consistently higher than simultaneous outdoor measurements in all three populations, presumably due to the dominant influence of indoor exposures.
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From page 240... ...
cific indoor source materials, exposure mitigation can be directed at reducing contact with specific sources. Evidence Regarding Asthma Exacerbation and Development A series of studies examined associations between asthma or asthma-related symptoms and indoor environmental factors in
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From page 241... ...
In a separate cross-sectional survey of 627 school children age 13-14 years, associations were observed between current asthma and school VOC concentrations in a logistic regression analysis that controlled for atopy, food allergies, and day care histories (Smoke et al., 1997~. Many other environmental factors besides VOCs were associated with asthma, including school size, the presence of open shelves in classrooms, lower room temperature, higher relative humidity, and formaldehyde concentrations.
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From page 242... ...
Conclusions: Asthma Exacerbation and Development There is inadequate or insufficient evidence to determine whether or not an association exists between indoor residential VOC exposures and the development or the exacerbation of asthma, although elevated indoor concentrations of VOC mixtures are suspected to play a role in the constellation of symptoms known as sick building syndrome (e.g., headaches, fatigue, eye and upper respiratory irritation)
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From page 243... ...
Potential indoor sources include ureaformaldehyde foam insulation (UFFI) ; glues used in plywood and pressed-board products; paper products including tissues, tow
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From page 244... ...
Because mobile homes often contain a high percentage of such materials, as well as being relatively airtight, such structures will often contain higher formaldehyde concentrations than other types of residences. Indoor residential formaldehyde concentrations in large numbers of conventional and mobile homes have been reported from several studies (Dally et al., 1981; Hanrahan et al., 1984; Ritchie and Lehnen, 1985; Sexton et al., 1986; Stock and Mendez, 1985)
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From page 245... ...
With respect to occupational asthma, it remains unclear to what extent formaldehyde acts through immunologic mechanisms involving specific sensitization as opposed to irritant mechanisms (Nordman et al., 1985~. Although several surveys have reported high rates of upperrespiratory symptoms among residents of mobile homes and/or homes containing UFFI (Breysse, 1980; Dally et al., 1981; Norsted et al., 1985; Sardinas et al., 1979)
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From page 246... ...
However, they do demonstrate the strong associations that may be found between a variety of measures of indoor air quality and health outcomes related to asthma. Conclusions: Asthma Exacerbation and Development · There is limited or suggestive evidence of an association between formaldehyde exposure and wheezing and other respiratory symptoms.
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From page 247... ...
Conclusions Regarding Means of Source Mitigation or Prevention Although strategies exist that may be effective in reducing indoor formaldehyde concentrations, there is inadequate or insufficient evidence to determine whether or not an association exists between the implementation of these strategies and a decrease in asthma development or exacerbation. Research Needs No specific research is recommended.
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From page 248... ...
found that breathing through a carbon filter had no protective effect for nine patients with respiratory symptoms (but without immunogIobulin E [IgE] mediated allergy)
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From page 249... ...
In summary: · There is limited or suggestive evidence of an association between exposure to certain fragrances and the manifestation of respiratory symptoms in asthmatics sensitive to such exposures. · There is inadequate or insufficient evidence to determine whether or not an association exists between exposure to fragrances and asthma development.
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Evidence Regarding Asthma Exacerbation and Development There is a small literature addressing the possible connection between plasticizer exposure and asthma. Di(2-ethy~hexyI)
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From page 251... ...
The following section addresses three of these pollutants: ozone, non-biologic particulate matter with sources other than tobacco smoke, and sulfur dioxide. Since the committee's mandate was to address indoor air polJutants, the discussion of these is less detailed than others in the chapter and no conclusions are drawn concerning indoor exposures and asthma outcomes.
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From page 252... ...
Xerographic copying machines found in offices, schools, and some other indoor environments also produce ozone. Time-series epidemiologic studies have demonstrated significant associations between daily asthma hospitalizations and/or emergency room visits and daily outdoor ozone concentrations (U.S.
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For spaces without significant sources, indoors is a protective environment. Studies consistently report an association between exposure to high outdoor levels of air pollutants, including PM, and adverse respiratory health effects (Koren, 1995~.
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Official Conference Report. American Journal of Respiratory and Critical Care Medicine 158~5 Pt 2~:S1-S76.
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and the risk of virus related asthma morbidity in children. American Journal of Respiratory and Critical Care Medicine 159:A699.
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1998. Respiratory symptoms in children and indoor exposure to nitrogen dioxide and gas stoves.
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1996. Association of respiratory symptoms and lung function in young adults with use of domestic gas appliances.
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1991. Association of indoor nitrogen dioxide with respiratory symptoms and pulmonary function in children.
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1993. Effect of ambient winter air pollution on respiratory health of children with chronic respiratory symptoms.
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American Review of Respiratory Disease 121~1~:3-10.
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1991. Effects of home environment on respiratory symptoms and lung function in a general population sample in north Italy.
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American Review of Respiratory Disease 129~3~:366-374. Wax PM, Hoffman RS.
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