Sam-Erik Walker

Residential Outdoor Air Pollution and Lung Function in Schoolchildren

Background: Long-term exposure to outdoor air pollution has typically been estimated on the aggregate level, and more individual measures of exposure are needed. We investigated the associations with lung function of residential outdoor air pollution in early life, total lifetime, and days before lung function test. Methods: In 2001–2002, spirometry was performed in 2307 9- and 10-year-old children who had lived in Oslo, Norway, since birth. Outdoor air pollution exposure for each child was assessed by the EPISODE dispersion model, calculating hourly concentrations of nitrogen dioxide (NO2), particulate matter (PM) with aerodynamic diameter less than 10 μm (PM10) and 2.5 μm (PM2.5). We applied linear regression analysis stratified by sex. Results: Early and lifetime exposures to outdoor air pollution were associated with reduced peak expiratory flow and reduced forced expiratory flow at 25% and 50% of forced vital capacity, especially in girls. One interquartile increase of lifetime exposure to NO2, PM10, and PM2.5 was associated with change in adjusted peak respiratory flow of, respectively, −79 mL/s (95% confidence interval = −128 to −31), −66 mL/s (−110 to −23), and −58 mL/s (−94 to −21). We also found short-term effects of NO2 that became stronger with increasing time lags, but no short-term effects of PM. When we included short- and long-term NO2 exposures simultaneously, only the long-term effect remained. We found no effect on forced volumes. Adjusting for a contextual socioeconomic factor diminished the associations. Conclusions: Short- and long-term residential exposures to traffic-related pollutants in Oslo were associated with reduced peak expiratory flow and forced expiratory flow at 25% and 50% in 9- to 10-year-old children, especially in girls, with weaker associations after adjusting for a contextual socioeconomic factor.

Ambient air pollution exposure, residential mobility and term birth weight in Oslo, Norway.

Environmental exposure during pregnancy may have lifelong health consequences for the offspring and some studies have association between maternal exposure to air pollution during pregnancy and offsprings birth weight. However, many of these studies do not take into account small-scale variations in exposure, residential mobility, and work addresses during pregnancy. We used information from the National Birth Registry of Norway to examine associations between ambient environmental exposure such as air pollution and temperature, and offsprings birth weight taking advantage of information on migration history and work address in a large population-based cohort. A dispersion model was used to estimate ambient air pollution levels at all residential addresses and work addresses for a total of 25,229 pregnancies between 1999 and 2002 in Oslo, Norway. Ambient exposure to traffic pollution for the entire pregnancy was associated with a reduction in term birth weight in crude analyzes when comparing children of the highest and lowest exposed mothers. No evidence for an association between exposure to traffic pollution at home and work addresses and term birth weight after adjustment for covariates known to influence birth weight during pregnancy. After stratification, small statistically non-significant reductions were present but only for multiparious mothers. This group also had less residential mobility and less employment during pregnancy. The overall findings suggest no clear association between term birth weight and traffic pollution exposure during pregnancy. However, mobility patterns could introduce possible confounding when examining small-scale variations in exposure by using addresses. This could be of importance in future studies.

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 model providing estimates of outdoor pollutant concentrations on an hourly basis. The estimates represent concentrations in receptor points and in a square kilometre grid. The estimates were used to assess development of air pollution load in the area, compliance with air quality guidelines, and to provide a basis for quantifying exposure-effect relationships in epidemiological 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 micrograms m-3). Compliance with air quality guidelines and other prescribed values has improved, even if high exposures still exist. The most important residential areas are now much less exposed, while areas around tunnel openings can be in periods exposed to high pollutant concentrations. The daily pattern of exposure shows smaller differences between peak and minimum concentrations than prior to the traffic changes. Exposures at home (in the investigation area) were reduced most, while exposures in other locations than at home showed only a small decrease. Highest hourly exposures are encountered in traffic.

Modelling long-term averages of local ambient air pollution in Oslo, Norway: evaluation of nitrogen dioxide, PM10 and PM2.5

Large seasonal variations in climate as in Norway give challenges for air pollution modelling, especially of Particulate Matter (PM) that seldom has been evaluated. The EPISODE model calculated ambient concentrations of nitrogen dioxide (NO2), PM with diameter <10 µm (PM10) and <2.5 µm (PM2.5), for geographical coordinates in Oslo, Norway, for the period 1992-2002. This paper describes EPISODE and the emission database used, and compares long-term model estimation of local ambient air pollution with available measurements from monitoring stations in Oslo during one winter season (1996/1997) and one year (2001/2002). We find good agreement between measured and modelled concentrations except for summertime PM10. Bias and scatter are lower at the urban background stations compared to the traffic stations. These results indicate that the EPISODE model can represent long-term concentrations of local ambient NO2, PM10 and PM2.5, suggesting future use of the model in epidemiological studies.

A Real-Time Operational Forecast Model for Meteorology and Air Quality During Peak Air Pollution Episodes in Oslo, Norway

A real-time operational forecast model for meteorology and air quality for Oslo, Norway is presented. The model systemconsists of an operational meteorological forecasts modeland an air quality model. A non-hydrostatic model operatedon two different domains with 1 and 3 km horizontalresolution is nested within the routine meteorologicalforecast model, which is run for North West Europe with 10 kmhorizontal resolution. The meteorological data are applied to an air quality model of Oslo with a 1 km grid and sub-grid treatment of line and point sources. Resultsfrom 22 days during the winter season 1999–2000 arepresented and discussed. Prediction of wind speed anddirections and relative humidity are clearly improved byincreasing the horizontal resolution of the meteorologicalmodel. Temperature inversion strengths are howeverconsiderably overestimated. The predictions of PM10corresponds best with measurements on winter days with wetor frozen surfaces in the city. On dry days, especiallyduring spring time with a large deposit of accumulated duston the roadside, the model under predicts the PM10concentrations considerably. It is in particularrecommended to improve the description of the PM10source strength in order to enhance the precision in theair quality forecasts.

Modelling atmospheric oxidation of 2-aminoethanol (MEA) emitted from post-combustion capture using WRF-Chem

Carbon capture and storage (CCS) is a technological solution that can reduce the amount of carbon dioxide (CO2) emissions from the use of fossil fuel in power plants and other industries. A leading method today is amine based post-combustion capture, in which 2-aminoethanol (MEA) is one of the most studied absorption solvents. In this process, amines are released to the atmosphere through evaporation and entrainment from the CO2 absorber column. Modelling is a key instrument for simulating the atmospheric dispersion and chemical transformation of MEA, and for projections of ground-level air concentrations and deposition rates. In this study, the Weather Research and Forecasting model inline coupled with chemistry, WRF-Chem, was applied to quantify the impact of using a comprehensive MEA photo-oxidation sequence compared to using a simplified MEA scheme. Main discrepancies were found for iminoethanol (roughly doubled in the detailed scheme) and 2-nitro aminoethanol, short MEA-nitramine (reduced by factor of two in the detailed scheme). The study indicates that MEA emissions from a full-scale capture plant can modify regional background levels of isocyanic acid. Predicted atmospheric concentrations of isocyanic acid were however below the limit value of 1 ppbv for ambient exposure. The dependence of the formation of hazardous compounds in the OH-initiated oxidation of MEA on ambient level of nitrogen oxides (NOx) was studied in a scenario without NOx emissions from a refinery area in the vicinity of the capture plant. Hourly MEA-nitramine peak concentrations higher than 40 pg m(-3) did only occur when NOx mixing ratios were above 2 ppbv. Therefore, the spatial variability and temporal variability of levels of OH and NOx need to be taken into account in the health risk assessment. The health risk due to direct emissions of nitrosamines and nitramines from full-scale CO2 capture should be investigated in future studies.

Air pollution exposure monitoring and estimation. Part IV. Urban exposure in children

In the winter of 1994, 2300 school-age children in Oslo participated in a panel study of the role of traffic pollution on the exacerbation of diseases of the respiratory system and other symptoms of reduced health and well being in children. The children filled out a diary daily with information for five time points over six weeks. In order to quantify exposure-effect relationships for the symptoms, individual exposure to NO2 and particulate matter (PM2.5) was estimated, using the DINEX method a combination of information from the diary as to the childrens whereabouts during the five time points each day, coupled with continuous dispersion modelling. An individual exposure estimate for each time point for each child was defined. Individual exposure estimated using dispersion modelling can be used to examine patterns of exposure such as isolating geographic areas with higher concentrations or describing concentrations of pollution by time of day. The diary allowed the time-use of the children to be described.

Evaluation of a model for hourly spatial concentration distributions

Abstract A time-dependent finite difference model in three levels combined with a puff model to account for subgrid effects close to single sources was used to calculate hour-to-hour concentration distributions. Measurements from several selected stations were used to account from time variation in background concentrations. For each hour, weight was given to observed values in areas that were not influenced by local sources. Results of concentration calculations based on hourly data on emission and dispersion are validated by measured time series of SO2 and NOx at five stations. A combination of hourly nephelometer readings and 12-h measurements of small particles at three stations are compared with calculated values. Hourly observed and calculated values from two periods (3 January–15 March 1988 and 18 April–24 June 1988) were used for the evaluation of the model for calculating hourly pollution concentrations in each square kilometre. The results showed that prediction of short-term average concentrations (e.g. hourly data) are usually poorly correlated with observations at the same time and location. Slight displacement errors may cause point-to-point correlation to be poor as a result of errors in input data. The pattern of NOx concentration variation with time was reproduced well at all stations. A subgrid model taking into account the influence of nearby roads would probably improved the model for NOx at some stations. For SO2 and small particles, industrial sources have the dominant influence and the correspondence between observed and calculated values were improved by taking into account spatial uncertainty and an hourly variation in background concentrations.

Air pollution exposure monitoring and estimation . Part VI. Ambient exposure of adults in an industrialised region

This paper presents methodology and results of a dynamic individual air pollution exposure model (DINEX) that calculates the hourly exposure for each adult in a panel study. Each of over 260 participants, through the use of a diary, provided information used in the model to calculate his/her personal, individualised exposure. The participants filled out the diary daily, hour by hour, over two, two month periods. The exposure assessment model coupled the diary information and results of an indoor/outdoor measurement program, with the results of dispersion modelling on an hourly basis for an industrial area in Norway. The estimated air pollution concentrations from the dispersion model, based on continuous meteorological measurements, were calibrated with air pollutant concentrations measured continuously.

Verification of Urban Scale Time-Dependent Dispersion Model with Subgrid Elements, in Oslo, Norway

Results from monitoring of air pollution concentrations in cities in Norway have shown that nitrogen dioxide (NO2) is one of the compounds which most often, and to the largest extent, exceeds current air quality guidelines (Hagen, 1992; Larssen, 1993). This is the case both in city streets and in the urban atmosphere in general. In Norway, the highest NO2 concentrations occur during the winter months, in connection with “episodes” with poor dispersion. In the general urban atmosphere, high 24-hour average values are of greatest concern relative to Air Quality Guideline (AQG), while in the street atmosphere, very high peak (hourly) concentrations may be the most important problem.