Academic journal article Environmental Health Perspectives

Effect of Formaldehyde on Asthmatic Response to Inhaled Allergen Challenge

Academic journal article Environmental Health Perspectives

Effect of Formaldehyde on Asthmatic Response to Inhaled Allergen Challenge

Article excerpt

BACKGROUND: Exposure to formaldehyde may lead to exacerbation of asthma.

OBJECTIVES: Our aim in this study was to investigate whether exposure to a low level (500 [micro]g/[m.sup.3]) of formaldehyde enhances inhaled allergen responses.

METHODS: Twelve subjects with intermittent asthma and allergy to pollen were exposed, at rest, in a double-blind crossover study to either formaldehyde or purified air for 60 min. The order of exposure to formaldehyde and air-only was randomized, and exposures were separated by 2 weeks. We also performed an allergen inhalation challenge after each exposure. Airway responsiveness to methacholine and lower airway inflammation (induced sputum) were assessed 8 hr after allergen challenge.

RESULTS: The median dose of allergen producing a 15% decrease in forced expiratory volume in 1 sec (P[D.sub.15]FE[V.sub.1]) was 0.80 IR (index of reactivity) after formaldehyde exposure compared with 0.25 IR after air-only exposure (p = 0.06). Formaldehyde exposure did not affect allergen-induced increase in responsiveness to methacholine (p = 0.42). We found no formaldehyde-associated effect on the airway inflammatory response, in particular the eosinophilic inflammatory response, induced by the allergen challenge 8 hr before.

CONCLUSION: In this study, exposure to 500 [micro]g/[m.sup.3] formaldehyde had no significant deleterious effect on airway allergen responsiveness of patients with intermittent asthma; we found a trend toward a protective effect.

KEY WORDS: allergen, asthma, formaldehyde, human exposure study. Environ Health Perspect 115: 210-214 (2007). doi:10.1289/ehp.9414 available via http://dx.doi.org/ [Online 7 November 2006]

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Formaldehyde is a well-known airborne contaminant causing eye, nose, and throat irritation as well as airway irritation and slight neuropsychologic changes (Hester and Harrison 1998; Samet et al. 1988).

The major indoor sources of formaldehyde are off-gassing from urea-formaldehyde foam insulation, particle board, paneling, plywood, some carpets and furniture, and, to a lesser extent, tobacco smoke and indoor combustion sources. Indoor concentrations of formaldehyde can vary between different countries (Sakai et al. 2004). In a Japanese study, formaldehyde concentrations ranged between 91.25 and 290 [micro]g/[m.sup.3] (Minami et al. 2002), whereas in the United Kingdom, the highest level measured in 876 homes was much lower (median = 24 [micro]g/[m.sup.3]) (Brown et al. 2002). Indoor formaldehyde concentrations measured in mobile homes in the United States ranged from nondetectable values to 575 [micro]g/[m.sup.3] (Liu et al. 1991).

Indoor concentrations generally exceed those outdoors, and studies on formaldehyde levels in homes have demonstrated higher formaldehyde concentrations in newer compared with older dwellings, with higher levels in buildings built after 1970 (Gilbert et al. 2005).

Formaldehyde is an etiologic factor in occupational asthma. However, although formaldehyde may cause asthma in some individuals, this occurs relatively rarely (Nordman et al. 1985; Paustenbach et al. 1997).

Whether nonoccupational exposure to formaldehyde is related to asthma is still subject to discussion (Delfino 2002; Institute of Medicine 2000). In murine models, formaldehyde exposure has been shown to enhance the allergic eosinophilic airway inflammation in sensitized mice (Sadakane et al. 2002). In a part of the European Community Respiratory Health Survey, asthma prevalence was greater for newly painted homes, consistent with greater differences in formaldehyde exposure (Wieslander et al. 1997). A relationship between physician-diagnosed asthma and indoor concentration of formaldehyde was reported even at low levels of exposure in children (Rumchev et al. 2002). Franklin et al. (2000) reported that exposure to formaldehyde in homes could produce a subclinical inflammatory response in the airways of healthy children. …

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