HOUSE-DUST MITE ALLERGEN LEVELS IN 2 CITIES IN CANADA - EFFECTS OF SEASON, HUMIDITY, CITY AND HOME CHARACTERISTICS

The homes of 120 patients with asthma, 57 in Vancouver and 63 in Winni peg, were studied. The characteristics of the homes were assessed by a questionnaire. Dust samples were collected and the indoor relative hu midity was measured four times during the year covering all four seaso ns in both cities. Mite allergen levels were determined using monoclon al antibodies against Der p I and Der f I by the ELISA method. The mea n levels of both mite allergens in mattress and floor samples in the h omes in Vancouver and in Winnipeg were relatively low for all seasons. Mite allergen levels were found to be associated with city, season an d individual home differences. They were significantly higher in Vanco uver than in Winnipeg. Der p I and Der f I in mattress samples in both cities and Der f I in floor samples in Vancouver, varied by season. T he indoor relative humidity level in the homes in Vancouver were also significantly higher than those in Winnipeg. There was, however, no si gnificant association between the levels of indoor relative humidity a nd the levels of mite allergens after adjusting for variations in city , season and individual home. Although individual home differences wer e highly associated with mite allergen levels, only a few home charact eristics were found to be related to mite allergen levels such as the type and the age of the home, the type of heating, the use of feather pillows and the number of occupants in the homes. Whether low levels o f mite allergens are partially responsible for the relatively low prev alence of childhood asthma in Canada remains to be investigated.