RESPIRATORY HOSPITAL ADMISSIONS AND SUMMERTIME HAZE AIR-POLLUTION IN TORONTO, ONTARIO - CONSIDERATION OF THE ROLE OF ACID AEROSOLS

A study of air pollution and daily hospital admissions for respiratory causes was conducted in Toronto, Ontario. Fine aerosol (d(a) < 2.5 mu m) samples were collected daily at a central city site during July an d August 1986, 1987, and 1988 and were subsequently extracted and anal yzed for daily particulate phase aerosol strong acidity (H+) and sulfa tes (SO4=). Daily counts of respiratory admissions to 22 acute care ho spitals and daily meteorological and environmental data (e.g. ozone [O -3], total suspended particulate matter [TSP], and thoracic particle m ass [PM10] were also obtained. Regression analyses indicated that only the O-3, H+, and SO4= associations with respiratory and asthma admiss ions remained consistently significant after controlling for temperatu re. Even after excluding days with maximum 1-hr O-3 > 120 ppb, O-3 was still strongly significant. In the various model specifications consi dered, the relative particle metric strengths of association with admi ssions were generally H+ > SO4= > FP > PM10 > TSP, indicating that par ticle size and composition are of central importance in defining the a dverse human health effects of particulate matter. On average, summert ime haze air pollution was associated with 24% of all respiratory admi ssions (21% with O-3, 3% with H+). On peak pollution days, however, ae rosol acidity yielded the highest relative risk estimates (e.g., RR = 1.5 at 391 nmole/m(3) H+), and summertime haze was associated with rou ghly half of all respiratory admissions. (C) 1994 Academic Press, Inc.