Monitoring of daily integrated exposure of outdoor workers to respirable particulate matter in an urban region of India

It is more and more recognised that an estimation of the exposure of the po pulation to air pollutants is more relevant than the ambient air quality, s ince it gives a better indication of health risk. Outdoor workers in an urb an region are generally of low income status and are exposed to higher leve ls of both indoor and outdoor air pollution. Hence respondents from this po pulation subgroup have been selected for this study. Outdoor workers are di vided into two categories, viz. traffic constables and casual outdoor worke rs like watchmen, roadside shopkeepers etc. Most of the respondents are fro m the lower income group. Each respondent is monitored for a continuous 48- hour period. The sampling frequency is once a week. The study region is situated in the north-west part of the Greater Mumbai M unicipal Corporation. It can be classified as industrial cum residential ar ea. The daily integrated exposure of the outdoor workers consists of two ma jor micro-environments, viz. occupational and indoor residential. A personal air sampler was used along with a cyclone to measure levels of R espirable Particulate Matter (RPM). The cyclone has a 50% removal efficienc y for particle diameter of 5 mu m. Paired samples of PM10 (ambient) and RPM (personal) were collected to establish the correlation between them. The a verage 24-hour integrated exposure to RPM was 322 mu g/m(3) and exceeded th e corresponding PM10 level observed at the nearest Ambient Air Quality Moni toring Station by a factor of 2.25. The 90% confidence interval for this ex posure is 283-368 mu g/m(3). This study clearly demonstrates that the daily integrated exposure and therefore the health risk of outdoor workers in an urban area is significantly more serious than that indicated by ambient ai r quality data.