Indoor environment of residential homes in Hong Kong — relevance to asthma and allergic disease

Background The prevalence of asthma and allergic disease has been increasing in Hong Kong and environmental factors are thought to play a major role. Aim To define the distribution of common inhaled allergens and air pollutants inside residential homes in Hong Kong. Methods Forty randomly selected residential homes were visited and surveyed. Dust samples were collected from mattress, bedroom floor, lounge room floor and kitchen floor for assays of Der p 1, Fel d 1, and Bla g 2. Nitrogen dioxide (NO2) levels were measured by stationary samplers left in the bedroom, lounge room and kitchen over a 1-week period. Result All 40 homes were apartments in high-rise buildings and the mean age of the homes was 7.6 ± 4.8 years. Visible dampness and mould patches were present in 27.5% of homes and the main fuel for cooking was gas (97.5%). Der p 1, Fel d 1 and Bla g 2 were detectable in at least 1 niche in over 85% of homes. In particular, all dust samples from mattress and bedroom floor contained Der p 1, and over 50% had levels ≥ 2 μg/g. The (geometric) mean Der p 1 level in mattress dust was 8.8 (0.3–157.8) μg/g. Fel d 1 and Bla g 2 were present in low levels throughout the homes with respective (geometric) means of 0.3 (0–3.7) μg/g and 0.1 (0–1.1) Unit/g in mattress dust. NO2 was readily detected in all niches but the highest level was in the kitchen with mean exposure of 48.7 ppb which was 1.5 times higher than that in the bedroom and lounge room. Conclusion Major allergens of mite, cat and cockroach, and NO2 are present in varying quantities in residential homes in Hong Kong. Exposure to these environmental factors could be important in the development of asthma and allergic diseases in susceptible individuals.