Personal exposure to nitrogen dioxide in Switzerland

https://doi.org/10.1016/S0048-9697(98)00124-7Get rights and content

Abstract

Home indoor and outdoor levels, and personal exposures to NO2 were determined for more than 500 subjects in a subpopulation of SAPALDIA by using passive samplers. The overall personal NO2 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 NO2 levels ranged between the outdoor and indoor levels, with the exception of study areas with low NO2 concentrations. In the winter, the indoor/outdoor ratios were lower than in the summer. Outdoor NO2 levels were higher in winter. In some study areas, indoor NO2 levels were lower in the winter than in the summer due to reduced ventilation but this was not consistent. Personal NO2 concentrations were very similar during all seasons. Gas-cooking and smoking were important factors for elevated indoor and personal NO2 levels (contribution: 5 μg m−3, 2 μg m−3, respectively). Personal exposure to NO2 correlated best with the indoor NO2 concentrations.

Introduction

Exposure is a term associated with some uncertainty. Exposure to an atmospheric pollutant may be defined as contact with the pollutant of a known concentration for a defined time period; this leads to information on an exposure-dose (Committee on Advances in Assessing Human Exposure to Airborne Pollutants, 1991). A simpler definition defines exposure as any contact of a human with a pollutant. In air pollution epidemiology, the use of (pollutant) concentrations is more widespread than the use of a dose (which is mainly used in biomarker studies). Exposure levels can be determined directly or indirectly (Committee on Advances in Assessing Human Exposure to Airborne Pollutants, 1991). Direct approaches use personal measurements at the individuals or biomarkers from body fluids. Indirect approaches use `surrogates', such as outdoor or indoor concentration and also models. Microenvironmental models are based on known concentrations in these so-called `microenvironments' (a location with a homogeneous pollution distribution) and known time activity (or budget) pattern. In order to establish and validate such models it is crucial to have a large-scale database of microenvironmental levels, time-activity patterns, and personal measurements. For NO2, a simple technology (passive samplers) is available for the determination of personal exposures. Passive samplers have the advantage that they can be used to determine individual exposures but also for establishing large-scale databases with indoor and outdoor data, which can be used to establish and validate models.

Within the framework of SAPALDIA (Swiss Study on Air Pollution and Lung Diseases in Adults), personal exposure to nitrogen dioxide was measured in a subsample of more than 500 subjects from the eight study regions from December 1992 to December 1993. In addition, parallel measurements were conducted outdoors of the home and indoors in the bedroom. To date, little information on personal exposure to NO2 of adults in Switzerland has been available, but in 1985/1986 in a study with children, personal levels of NO2 were determined (Braun et al., 1992). In this study, a strong relationship between personal exposure levels of NO2 and indoor levels was found. Exposure in adults, however, shows higher variation and covers more microenvironments. A preliminary study was conducted in 1992, in which personal exposure of adults to NO2 and O3 was investigated (Monn et al., 1993).

Moreover, in recent years, many studies have been conducted comparing indoor with outdoor levels, and they showed that indoor levels of NO2 are between 50 and 90% of outdoor levels, in the absence of indoor sources (Monn et al., 1993; Spengler et al., 1994; Tomingas and Grover, 1990; Wanner et al., 1990). In the absence of indoor sources, NO2 levels are a function of the outdoor concentrations and the ventilation rate, and the ventilation rate shows a seasonal pattern. In Switzerland, air conditioning is rarely used so that ventilation depends on the outdoor air temperature. Indoor sources, such as gas stoves and gas heaters, may lead to indoor NO2 levels exceeding levels measured outdoors. Such homes have to be treated separately when using NO2 as an indicator of ambient pollution, as the mixture of gas combustion emissions is different from the mixture of outdoor pollutants.

The purpose of this analysis was to evaluate the relationship between personal NO2 levels with indoor and outdoor levels at home. As from all participants of the passive sampler study, information on indoor sources (gas-stoves, smoking status), ventilation habits, situation of home with respect to streets as well as on occupational exposure was available, the effects of these parameters on personal exposure to NO2 were additionally estimated. In a multiple regression model, the effects of these parameters on personal NO2 exposures were quantified.

Section snippets

Participants

SAPALDIA is an eight-centre study with four urban/suburban regions (Geneva, Basle, Lugano, Aarau), two rural regions (Wald, Payerne) and two alpine regions (Montana, Davos).

In each region, more than 500 subjects were invited to participate in the follow-up study. From this sample, a stratified random subsample was selected in each area. Stratification was to ensure that any time measurements provided a faithful picture of differences in NO2 levels across subregions. The measurement program

Comparison between indoor, outdoor and personal NO2 concentrations (all subjects)

Fig. 1 shows the average values of outdoor, indoor and personal measurements. Comparing the outdoor concentrations, a gradient between the study sites was found. Looking at the indoor levels, a gradient was found between the urban sites, but from Aarau to Montana the variation of indoor levels was much smaller. Indoor levels were about 70–80% of the outdoor levels. For the personal levels, a gradient was found between the five most polluted regions and to a lesser extent in the least polluted

Discussion

Average personal exposure to NO2 was measured for more than five hundred adult subjects in eight regions of Switzerland. This is one of the largest data base of measured personal NO2 levels in adults. These values were compared with the average indoor and outdoor concentration at home. The average NO2 personal concentration (27 μg m−3) was between the average outdoor (31 μg m−3) and indoor levels (21 μg m−3). In three regions with lowest outdoor NO2 pollution (Wald, Davos and Montana), average

Acknowledgements

SAPALDIA is part of the Swiss National Research Programme 26A supported by the Swiss National Foundation (grant No. 4026-28099) and by the Federal Office of Education and Science. SAPALDIA Basle is part of the European Respiratory Survey.

References (12)

  • BG Armstrong

    The effect of measurement errors on relative risk regressions

    Am J Epidemiol

    (1990)
  • M Brauer et al.

    Indoor and outdoor concentrations of inorganic acidic aerosols and gases

    J Air Waste Manage Assoc

    (1990)
  • C Braun et al.

    Air pollution and respiratory symptoms in preschool children

    Am Rev Respir Dis

    (1992)
  • B Brunekreef et al.

    Variability of exposure measurements in environmental epidemiology

    Am J Epidemiol

    (1987)
  • Committee on Advances in Assessing Human Exposure to Airborne Pollutants. Human exposure assessment for airborne...
  • Hangartner M. Aktuelle Aufgaben der Messtechnik in der Luftreinhaltung. Kolloquium Heidelberg 29–31, VDI-Berichte No....
There are more references available in the full text version of this article.

Cited by (0)

1

SAPALDIA (Swiss Study on Air Pollution and Lung Diseases in Adults) Team: Study Director: P. Leuenberger (P), Programme Director: U. Ackermann-Liebrich (E). Investigators: P. Alean (AM), K. Blaser (A), G. Bolognini (P), J.P. Bongard (P), O. Brändli (P), P. Braun (P), C. Bron (L), M. Brutsche (L), C. Defila (M), G. Domenighetti (P), S. Elsasser (L), L. Grizé (S), P. Guldimann (L), P. Hufschmied (L), W. Karrer (P), H. Keller-Wossidlo (O), R. Keller (P), N. Künzli (E), J.C. Luthy (L), B.W. Martin (E), T. Medici (P), C. Monn (AM), A.G. Peeters (PA), A. Perruchoud (P), A. Radaelli (L), C. Schindler (S), J. Schwartz (S), M. Schöni (P), G. Solari (P), J.M. Tschopp (P), B. Villiger (P), B. Wüthrich (A), J.P. Zellweger (P), E. Zemp (E). Specialities: A, Allergology; AM, Air Pollution Monitoring; E, Epidemiology; L, Local Assistant MD; PA, Palynology; P, Pneumology; M, Meteorology; O, Occupational Medicine; S, Statistics.

View full text