Personal Exposure of Adults with Cardiorespiratory Disease to Particulate Acid and Sulfate in Saint John, New Brunswick, Canada

Abstract

Saint John is the site of an ongoing study of the relationship between cardiorespiratory emergency department visits and airborne particles, including particulate acid and sulfate. The purpose of the present study was to assess the extent to which fixed site monitors reflect average personal exposure to fine particle sulfate and acidity among adults visiting the emergency department with cardiorespiratory disease. Study participants had made an emergency department visit for cardiorespiratory disease in the previous 12 months and resided within approximately 5 km of the fixed site monitor which records the highest sulfate and acid concentrations in Saint John. Twenty-one volunteers wore personal annular denuders during the period from 7 a.m. to 6 p.m. (mean duration 7.6 hours) for up to four separate days between July 6 and August 11, 1995, and completed a time-activity diary for each sampling period. Subjects ranging from 49 to 85 years of age completed a total of 62 sampling periods. The mean percent of time spent indoors, outdoors, and in vehicles was, respectively, 81.8, 7.6, and 10.5. Mean personal sulfate (29.8 nmol/m³) and acid concentrations (17.5 nmol/m³) were lower than measurements at fixed site monitors (mean sulfate 49.1 nmol/m³; mean acid 39.2 nmol/m³). The correlation (R-square) between mean personal and fixed site sulfate was 0.90 (p < 0.0001), and high daily concentrations measured at the fixed site were reflected in high mean personal concentrations. There was little correlation between mean personal and fixed site acid measurements (R-square = 0.13; p = 0.11), although some high personal measurements corresponded to high fixed site concentrations. In this population of adults visiting an emergency department with cardiorespiratory disease, fixed site sulfate monitors appear to accurately reflect daily variability in average personal exposures to particulate sulfate. Personal exposure to particulate acid does not appear to be well represented by fixed site monitors.