Air pollution exposure monitoring and estimation Part V. Traffic exposure in adults

In Oslo, traffic has been one of the dominating sources of air pollution in the last decade. In one part of the city where most traffic collects, two tunnels were built. A series of before and after studies was carried out in connection with the tunnels in use. Dispersion models were used as a basis for estimating exposure to nitrogen dioxide and particulate matter in two fractions. Exposure estimates were based on the results of the dispersion m odel providing estimates of outdoor pollutant concentrations on an hourly b asis. The estimates represent concentrations in receptor points and in a sq uare kilometre grid. The estimates were used to assess development of air p ollution load in the area, compliance with air quality guidelines, and to p rovide a basis for quantifying exposure-effect relationships in epidemiolog ical studies. After both tunnels were taken in use, the pollution levels in the study area were lower than when the traffic was on the surface (a drop from 50 to 40 mu g m(-3)). Compliance with air qualify guidelines and othe r prescribed values has improved, even if high exposures still exist. The m ost important residential areas are now much less exposed, while areas arou nd tunnel openings can be in periods exposed to high pollutant concentratio ns. The daily pattern of exposure shows smaller differences between peak an d minimum concentrations than prior to the traffic changes. Exposures at ho me (in the investigation area) were reduced most, while exposures in other locations than at home showed only a small decrease. Highest hourly exposur es are encountered in traffic.