Christian Monn

Small-scale spatial variability of particulate matter < 10 μm (PM10) and nitrogen dioxide

Epidemiological studies often rely only on data from a single monitoring station at a study site. However, significant small-scale spatial gradients for air pollutants are inevitable and one monitoring station cannot be representative for the entire population living in the study region. Small- scale spatial gradients (horizontally and vertically) of particulate matter < 10 μm (PM10) and NO2 were examined along a roadside in Zurich during the winter and summer seasons (1994–1995). Horizontal and vertical concentration gradients for PM10 were about 13% (spatial coefficient of variation), and for NO2 about 15%. For PM10, the effect of season on the horizontal and vertical gradient was small. For NO2, the small-scale spatial gradients were highly influenced by season: during the spring-summer season, spatial gradients were much greater than during the autumn-winter season. This implies that future monitoring programmes, should include more monitoring sites for PM10 and, especially for NO2, the spring-summer season should include far more spatial resolution.

Personal exposure to nitrogen dioxide in Switzerland

Abstract Home indoor and outdoor levels, and personal exposures to NO 2 were determined for more than 500 subjects in a subpopulation of SAPALDIA by using passive samplers. The overall personal NO 2 average was found to be 27 μg m −3 , the overall indoor average 21 μg m −3 and the overall outdoor average 31 μg m −3 . Personal NO 2 levels ranged between the outdoor and indoor levels, with the exception of study areas with low NO 2 concentrations. In the winter, the indoor/outdoor ratios were lower than in the summer. Outdoor NO 2 levels were higher in winter. In some study areas, indoor NO 2 levels were lower in the winter than in the summer due to reduced ventilation but this was not consistent. Personal NO 2 concentrations were very similar during all seasons. Gas-cooking and smoking were important factors for elevated indoor and personal NO 2 levels (contribution: 5 μg m −3 , 2 μg m −3 , respectively). Personal exposure to NO 2 correlated best with the indoor NO 2 concentrations.

Associations between lung function and estimated average exposure to NO2 in eight areas of Switzerland

In this paper, we present results from the SAPALDIA study (Swiss Study on Air Pollution and Lung Diseases in Adults) regarding associations between lung function [forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1)], as assessed during the cross-sectional study in 1991, and average levels of NO2 exposure within the eight study communities. We distinguished average home outdoor exposure and average personal exposure to NO2 and obtained exposure estimates by computing regional averages of passive sampler measurements performed by a random subsample of SAPALDIA participants in 1993. Previous analyses had revealed associations between average lung function and average air pollution levels between communities. The present results show that such associations may also be seen within communities: a 10-μg per m3 increase in average home outdoor and personal exposure to NO2 between zones of residence of the same community was associated with a change in average FVC by −0.59% [95% confidence limits (CL) = 0.01, −1.19] and −0.74% (95% CL = −0.07, −1.41), respectively. These values, however, are smaller than the ones found for the corresponding associations between study communities: −1.67% (95% CL = −1.01, −2.33) and −2.93% (95% CL = −2.11, −3.75), respectively. The different magnitudes of these two types of associations might be explained by differences in spatial variation between various components of air pollution. (Epidemiology 1998;9:405–411)A common strategy for modeling dose-response in epidemiology is to transform ordered exposures and covariates into sets of dichotomous indicator variables (that is, to factor the variables). Factoring tends to increase estimation variance, but it also tends to decrease bias and thus may increase or decrease total accuracy. We conducted a simulation study to examine the impact of factoring on the accuracy of rate estimation. Factored and unfactored Poisson regression models were fit to follow-up study datasets that were randomly generated from 37,500 population model forms that ranged from subadditive to supramultiplicative. In the situations we examined, factoring sometimes substantially improved accuracy relative to fitting the corresponding unfactored model, sometimes substantially decreased accuracy, and sometimes made little difference. The difference in accuracy between factored and unfactored models depended in a complicated fashion on the difference between the true and fitted model forms, the strength of exposure and covariate effects in the population, and the study size. It may be difficult in practice to predict when factoring is increasing or decreasing accuracy. We recommend, therefore, that the strategy of factoring variables be supplemented with other strategies for modeling dose-response.

Direct determination of allergens in ambient aerosols : Methodological aspects

In Switzerland the birch tree (Betula verrucosa) major allergen Bet v 1 and the grass (Phleum pratense) pollen major allergen Phl p 5 are of particular relevance for inducing pollinosis. In this study, the protein and major allergen contents of aerosols of different aerodynamic diameters were determined. The aerosols were sampled by Andersen-Impactors and submitted to protein assays and allergen assays (ELISA) specific for Bet v 1 and Phl p 5. The total protein, Bet v 1 and Phl p 5 concentrations were correlated with the corresponding pollen counts. The presence of Bet v 1 in smaller aerosol fractions was demonstrated before and after birch pollen was counted, especially in the lower particle size ranges.

An assessment of indoor air contaminants in buildings with recreational activity

Indoor air quality measurements were carried out during three concerts and one ice hockey game in three different halls. Gas phase components consisted of CO2, CO, and NO whereas for particulate indicators, measurements of particle mass distributions (0.05-9 microm), particle number distributions (0.75-10 microm), and particle bound polycyclic aromatic hydrocarbons (pPAH) were carried out. The calculated ventilation rates did not meet the ventilation requirements for rooms with occupants who smoke to be perceived as acceptable by 80% of the occupants. Average PM9 (mass of particulate matter with an aerodynamic diameter < 9 microm) concentrations throughout the events ranged from 318 to 2000 microg m(-3). Particle concentrations in the size range < 0.4 microm measured 203-696 microg m(-3), the majority of it being attributed to environmental tobacco smoke (ETS). For particle numbers > 0.75 microm concentrations ranged from 2 x 10(4) to 1.9 x 10(5) particles per l while for pPAH, concentrations from 336 to 990 ng m(-3) were observed. The average event concentrations for the gaseous component CO2 ranged from 1110 to 1700 ppm, for CO 2-3.1 ppm and for NOx 237 ppb. The event to baseline concentration ratios for gaseous components ranged from 1.1 to 4.3 while for particulate indicators generally much greater ratios between 0.7 and 140 were found. Possible health effects inflicted by an exposure based on the measured concentrations of the various parameters are discussed.

Concentrations of total suspended particulates, fine particles and their anionic compounds in ambient air and Indoor air

Abstract This study has investigated the relationship between total suspended particulates (TSP) and fine particles (FP) and their anionic compounds (sulphate, nitrate) in ambient and indoor air. 24‐hour averages of TSP, FP and anionic compound outdoor concentrations were measured over a one year period in Zurich. Additionally, eight indoor environments (residences and offices in rural and urban areas) were chosen to measure indoor and outdoor concentrations of FP, anions and NO2 over a three month period. FP and TSP outdoor concentrations showed a good correlation. About 60 to 80% of TSP could be attributed to the FP fraction. Ambient levels of sulphate exceeded the levels of nitrate. Indoor levels of FP showed a good correlation with outdoor levels. FP concentrations in a room with heavy smoking and a gas‐stove were considerably higher than ambient levels. Indoor levels of nitrate were usually very low with the exception of a room with heavy smoking and a gas stove. Indoor levels of sulphate often were ...

Air pollution, climate and pollen comparisons in urban, rural and alpine regions in Switzerland (SAPALDIA study)

Abstract The aim of this paper is to show spatial differences and correlations in long- term air pollution measurements in the eight SAPALDIA sites (Swiss Study on Air Pollution and Lung Diseases in Adults, SAPALDIA). In addition, a comparison with climatic parameters and pollen counts are presented in a descriptive way. SAPALDIA investigated health effects from air pollutants and climate in a cross-sectional study (1991) and in a follow-up longitudinal study (1992–1993). Over the period 1991–1993, urban–rural–Alpine concentration gradients were found for SO2, NO2, PM10 and HNO3. For O3, average levels were higher in the Alps but peak levels were higher at sites on the Swiss Plateau. Levels of sulphuric acid were negligibly small; acidity was mainly determined by the content of HNO3. A statistical analysis of long-term data for SO2, NO2, TSP, PM10, HNO3 and size-fractions of suspended particulate matter (SPM) indicated strong correlations.

Measurements of ozone and nitrogen‐dioxide at different altitudes at eggbergen (Swiss alps) with passive sampling devices and continuous monitors

Abstract Measurements of ozone at different altitudes between 440 m and 1445 m on a mountainside of the Swiss Alps were carried out in the summer 1988. Results showed that the ozone concentration at higher altitudes is greater than at the ground of the valley. Not only the average but the shorttime peaks were higher at 1442 m than at 440 m. Diurnal variation of the ozone was much higher at the ground of the valley than at the mountain site. Additionally nitrogen‐dioxide was measured at all sites with passive sampling tubes. A drastic decrease with height was observed.

Passive Sampling of Aromatic Volatile Organic Compounds (VOC) in Ambient Air in Switzerland

Concentrations of benzene, toluene and m-xylene (BTX) were measured at urban, suburban, rural and alpine sites in Switzerland by means of passive sampling. Sampling time was two weeks and the sampling period was six months in succession. Concentrations ranged between 0.8 and 6 µg m−3 for benzene, between 2.9 and 14 µg m−3 for toluene and between 0.9 and 7.4 µg m−3 for m-xylene. The ratios between benzene toluene and m-xylene concentrations were on average 1:3:1.1. Passive samplers have been found to be a useful tool for the synchronical determination of VOC in different regions. Comparison with continuous monitors showed some systematic bias, however. Correlation of VOC with other air pollutants were strong with CO and NO.