Abstract

Background: Formaldehyde, an indoor air pollutant, is known to be an irritant and an etiologic factor in occupational asthma. An epidemiologic study suggests that it may also increase the risk of childhood asthma for concentrations above 60 µg/m3.

Aim: To evaluate the influence of pre-exposure to low-dose formaldehyde (100 µg/m3 in 30 min according to the World Health Organization's recommended maximum value for indoor environments) on bronchial response to Dermatophagoides pteronyssinus.

Method: Nineteen asthmatic subjects were included. Each subject underwent a mite allergen bronchial challenge test immediately after a standardized exposure in a chamber to formaldehyde or air (random order). Induced sputum were collected 24 h before and after mite challenge.

Results: After formaldehyde inhalation, patients developed an immediate bronchial response at a significantly lower dose of mite allergen than after air exposure (the geometric mean PD20 for Der p 1 was 34.3 ng after formaldehyde and 45.4 ng after placebo, P = 0.05). The late-phase reaction, expressed as the maximum fall in forced expiratory volume in 1 s (FEV1) from baseline, was significantly higher after formaldehyde (15%vs 11%, P = 0.046).

Conclusion: Our study demonstrated that exposure to low levels of formaldehyde significantly enhanced bronchial responsiveness to mite allergen in mite-sensitized subjects with asthma.

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Comments

Exposure to formaldehyde at levels about 100 ug/m3 (the upper level recommended by WHO for indoor air) decreased the threshold for reactions to Dermatophagoides pteronyssinus antigen in sensitised patients, and increased the late phase reaction. The changes were statistically signisicant but relatively modest (about 15%), but are a good example of a combination of (supposed) irritant and allergen.

4/18/2008