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BACKGROUND: Exhaust emissions from vehicles is a well known problem with both epidemiological and experimental studies showing increasing adverse health effects with elevating levels. Many of the studies concerning vehicle exhausts and health are focused on health outcomes where the proportion attributed to exhaust is low, while there is less information on early and more frequent subjective indicators of adverse effects.

METHODS: The primary aim of this study was to study perceived annoyance in relation to vehicle exhaust concentrations using modelled levels of nitrogen dioxide outside the home as an indicator with high spatial resolution. Almost 2800 persons in a random sample from three Swedish cities (Umea, Uppsala and Gothenburg) responded to our questionnaire. Questions were asked to determine the degree of annoyance related to vehicle exhausts and also the prevalence of irritating and asthmatic symptoms. Exposure was described for each participants home address by meteorological dispersion models with a 50 meter resolution.

RESULTS: We found a significant increase of peoples' self-assessed annoyance with rising levels of NO2. The odds of being very annoyed by vehicle exhausts increased by 14% per 1 microg/m3 increase of the NO2 level (odds ratio (OR) = 1.14, 95% confidence interval (CI) = 1.11-1.18), and the odds of reporting the air as daily or almost daily irritating increased by 9% (OR = 1.09, 95% CI = 1.05-1.13). Also the odds of reporting asthmatic symptoms increased significantly with elevated NO2 levels (OR = 1.04, 95% CI = 1.01-1.07).

CONCLUSION: This study found the degree of annoyance related to vehicle exhaust and irritating and asthmatic symptoms to be significantly dependent on the levels of traffic related pollutants outside the home. The detailed exposure assessment lowers the degree of misclassification as compared to between-city analyses, which makes the results more accurate and applicable on the local scale.

The objective of this case–control study was to evaluate whether traffic-related air pollution exposure at home increases the risk of asthma in adults and to compare two commonly used exposure variables and differences between urban and rural living. Incident cases of asthma and matched controls of subjects aged 20–60 yrs were recruited in Luleå, Sweden. In total 203 cases and 203 controls were enrolled in the study. Exposure was estimated by traffic flow and measured levels of outdoor nitrogen dioxide (NO2) in the surrounding environment of each home, respectively. The relationship between measured levels of NO2 and traffic flow was studied using linear regression. The results indicated a nonsignificant tendency between living in a home close to a high traffic flow and an increased risk of asthma. The association between asthma and measured NO2 was weak and not significant, but the skin-prick test result acted as an effect modifier with a borderline significant association among positives. The correlation between traffic flow and outdoor NO2 was low. The results suggest that living close to high traffic flows might increase the asthma incidence in adults, while the tendency for nitrogen dioxide was only seen among atopics. Traffic flow and nitrogen dioxide had a lower than expected correlation.

Few studies have investigated the relationship between vehicle exhaust and new onset of asthma among adults. The aim of this prospective cohort study was to investigate the relationship between the cumulative incidence of asthma and onset asthma among adults and vehicle exhaust concentrations at home.Participants from three Swedish cities included in the RHINE (Respiratory Health in Northern Europe) Cohort constituted the study population. Exposure at each participant's home was calculated using dispersion models. We also used less than 50 meter distance to nearest major road as a more simple indicator of exposure. The adjusted model included 3609 participants of which 107 were classified as onset cases and 55 as true incident cases of asthma.There was a positive association between asthma onset (Odds Ratio, OR per 10 microg.m(-3) = 1.46, 95% Confidence Interval (CI) 1.07-1.99) and incident asthma (OR per 10 microg.m(-3) = 1.54, 95% CI 1.00-2.36) and the levels of NO2 which remained statistically significant after adjusting for potential confounders. The relationship between asthma and NO2 was not significantly modified by sex, hay fever or wheeze.This study suggests that elevated levels of vehicle exhaust outside the home increase the risk of onset and incident asthma among adults.