A Case Study of Personal Exposure to Nitrogen Dioxide Using a New High Sensitive Diffusive Sampler

Abstract

P-552 Abstract: Exposure is a key element in the knowledge about health effects of air pollution. For many pollutants, its evaluation remains associated with large uncertainties because of a lack of suitable means for measuring personal exposure. Recent advancements in the field of passive sampling have led to the development of new high sensitive diffusive samplers which can allow a monitoring of exposure based on sequential short-time measurements. By this approach, information on personal exposure is more complete since a distinction can be made between the exposure levels found in different microenvironments. This study was designed to investigate the NO2 personal exposure of 45 volunteers living in Lille, a large city in northern France. Sequential measurements of personal exposure in four microenvironments were carried out using a new diffusive sampler having a high uptake rate estimated to 1 cm3.s−1 and a detection limit of 11 μg.m−3 for a one-hour measurement. This measurement campaign comprised four 24-h periods: two during the working days (from Thurday 12:00 to Friday 12:00) and two during the weekends (from Saturday 12:00 to Sunday 12:00). For each 24-h period, the participants received a diffusive sampler and four sampling cartridges: one cartridge for each of the following microenvironments: homes, other indoor places (including workplace, shops, restaurants…), transports (car, bus, train…) and outdoors. The participants carried the diffusive sampler all sampling period long, changed the cartridge each time they changed microenvironment and noted the corresponding time on a time-activity-diary. Thus, the personal exposure was divided into four parts corresponding to NO2 personal exposure levels in four microenvironment categories. The highest levels were found in transports and outdoors (from 30 to 115 μg.m−3 in average), the intermediate ones in other indoor places (from 29 to 92 μg.m−3) and the lowest in homes (from 14 to 27 μg.m−3). Nevertheless, the indoor pollution remains the main contributor to total NO2 personal exposure (superior to 78%) because people spent the main part of their time in indoor environments (from 20 to 23 hours per day). The average total NO2 personal exposure ranged from 17 μg.m−3 for the summer weekend period to 38 μg.m−3 for the winter weekday period. A Multiple Correspondence Analysis was carried out to highlight the determinants of NO2 personal exposure in homes and in transports. This led to a classification of NO2 personal exposure levels according to different means of transport: from the lowest to the highest exposure levels, train, tramway or underground, bicycle, car or motorcycle. In homes, the rise of NO2 personal exposures is mainly due to environmental tobacco smoke, the use of gas stoves and gas heating and the absence of automatic airing system. A classification of NO2 personal exposure levels was set up according to the characteristics of homes. An analysis of correlations between the home NO2 personal exposures and outdoor concentrations measured by fixed ambient air monitoring stations showed weak relations suggesting that the data of these stations are poor predictors of NO2 personal exposures in homes. In conclusion, this study shows the advantages to use an high sensitive diffusive sampler for personal monitoring to investigate the environmental determinants and contributions of microenvironments to NO2 exposure.