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In this study, the long-term mortality effects associated with exposure to PM 10 (particles with an aerodynamic diameter smaller than or equal to 10 µm), PM 2.5 (particles with an aerodynamic diameter smaller than or equal to 2.5 µm), BC (black carbon), and NO x (nitrogen oxides) were analyzed in a cohort in southern Sweden during the period from 1991 to 2016. Participants (those residing in Malmö, Sweden, born between 1923 and 1950) were randomly recruited from 1991 to 1996. At enrollment, 30,438 participants underwent a health screening, which consisted of questionnaires about lifestyle and diet, a clinical examination, and blood sampling. Mortality data were retrieved from the Swedish National Cause of Death Register. The modeled concentrations of PM 10 , PM 2.5 , BC, and NO x at the cohort participants' home addresses were used to assess air pollution exposure. Cox proportional hazard models were used to estimate the associations between long-term exposure to PM 10 , PM 2.5 , BC, and NO x and the time until death among the participants during the period from 1991 to 2016. The hazard ratios (HRs) associated with an interquartile range (IQR) increase in each air pollutant were calculated based on the exposure lag windows of the same year (lag0), 1-5 years (lag1-5), and 6-10 years (lag6-10). Three models were used with varying adjustments for possible confounders including both single-pollutant estimates and two-pollutant estimates. With adjustments for all covariates, the HRs for PM 10 , PM 2.5 , BC, and NO x in the single-pollutant models at lag1-5 were 1.06 (95% CI: 1.02-1.11), 1.01 (95% CI: 0.95-1.08), 1.07 (95% CI: 1.04-1.11), and 1.11 (95% CI: 1.07-1.16) per IQR increase, respectively. The HRs, in most cases, decreased with the inclusion of a larger number of covariates in the models. The most robust associations were shown for NO x , with statistically significant positive HRs in all the models. An overall conclusion is that road traffic-related pollutants had a significant association with mortality in the cohort.

Daily air pollution levels are known to influence the number of patients with acute asthma. We investigated the short-term effects of air pollution exposure on the daily number of asthma medication purchases in the Greater Stockholm area, Sweden., Methods: We conducted a time-series study with data on asthma medication purchases and daily mean values of particulate matter ≤10 µm (PM 10 ), nitrogen oxides (NO x ), and ozone during 2018-2019. We used nonlinear distributed lag quasi-Poisson regression models to estimate the associations between air pollution levels and medication purchases, adjusting for meteorological variables, pollen levels, day of the week, and long-term trends. The models established linear relationships between air pollutants and the outcome, and potential delayed effects were smoothed with a spline across a lag period of 2 weeks. We applied separate models for each municipality (n = 21) in Greater Stockholm, and calculated pooled estimates to achieve combined results for the whole region., Results: We observed associations between daily levels of air pollution and purchases of asthma medications, most clearly for PM 10 . The pooled estimates of the relative risks for asthma medication purchases across all 21 municipalities associated with a 10 μg m -3 increase in PM 10 the same day (lag 0) was 1.7% [95% confidence interval (CI): 1.2%, 2.1%], a cumulative increase of 4.6% (95% CI: 3.7%, 5.6%) over one week (lag 0-6), and a 6.5% (95% CI: 5%, 8%) increase over 2 weeks (lag 0-13). The corresponding pooled effect per 10 μg m -3 increase in NO x and ozone were 2.8% (95% CI: 1.6%, 4.1%) and 0.7% (95% CI: 0%, 1.4%) over 2 weeks (lag 0-13), respectively., Conclusions: Our study revealed short-term associations between air pollution, especially PM 10 , and purchases of asthma medications., Competing Interests: The authors declare that they have no conflicts of interest with regard to the content of this report., (Copyright © 2023 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of The Environmental Epidemiology. All rights reserved.)

Background: Residential wood combustion (RWC) is one of the largest sources of fine particles (PM 2.5 ) in the Nordic cities. The current study aims to calculate the related health effects in four studied city areas in Sweden, Finland, Norway, and Denmark., Methods: Health impact assessment (HIA) was employed as the methodology to quantify the health burden. Firstly, the RWC induced annual average PM 2.5 concentrations from local sources were estimated with air pollution dispersion modelling. Secondly, the baseline mortality rates were retrieved from the national health registers. Thirdly, the concentration-response function from a previous epidemiological study was applied. For the health impact calculations, the WHO-developed tool AirQ + was used., Results: Amongst the studied city areas, the local RWC induced PM 2.5 concentration was lowest in the Helsinki Metropolitan Area (population-weighted annual average concentration 0.46 µg m - 3 ) and highest in Oslo (2.77 µg m - 3 ). Each year, particulate matter attributed to RWC caused around 19 premature deaths in Umeå (95% CI: 8-29), 85 in the Helsinki Metropolitan Area (95% CI: 35-129), 78 in Copenhagen (95% CI: 33-118), and 232 premature deaths in Oslo (95% CI: 97-346). The average loss of life years per premature death case was approximately ten years; however, in the whole population, this reflects on average a decrease in life expectancy by 0.25 (0.10-0.36) years. In terms of the relative contributions in cities, life expectancy will be decreased by 0.10 (95% CI: 0.05-0.16), 0.18 (95% CI: 0.07-0.28), 0.22 (95% CI: 0.09-0.33) and 0.63 (95% CI: 0.26-0.96) years in the Helsinki Metropolitan Area, Umeå, Copenhagen and Oslo respectively. The number of years of life lost was lowest in Umeå (172, 95% CI: 71-260) and highest in Oslo (2458, 95% CI: 1033-3669)., Conclusions: All four Nordic city areas have a substantial amount of domestic heating, and RWC is one of the most significant sources of PM 2.5 . This implicates a substantial predicted impact on public health in terms of premature mortality. Thus, several public health measures are needed to reduce the RWC emissions., (© 2022. The Author(s).)

The old Swedish city Visby, located on the island Gotland, has, for several years, reported higher PM 10 concentrations than any other city in Sweden. In Visby, local limestone is used, both in road paving and as sand used for anti-slip measures, resulting in a clear annual pattern of PM 10 with the highest concentrations during winter/spring when studded tires are allowed. This study analyzes the short-term associations between PM 10 and daily number of patients with acute respiratory problems (ICD-10 diagnoses: J00-J99) seeking care at the hospital or primary healthcare units in Visby during the period of 2013-2019. The daily mean of PM 10 was on average 45 µg m -3 during winter/spring and 18 µg m -3 during summer/autumn. Four outcome categories were analyzed using quasi-Poisson regression models, stratifying for period and adjusting for calendar variables and weather. An increase in respiratory visits was associated with increasing concentrations in PM 10 during the summer/autumn period, most prominent among children, where asthma visits increased by 5% (95% CI: 2-9%) per 10 µg m -3 increase in PM 10 . For the winter/spring period, no significant effects were observed, except for the diagnose group 'upper airways' in adults, where respiratory visits increased by 1% (95% CI: 0.1-1.9%) per 10 µg m -3 increase. According to the results, limestone in particles seem to be relatively harmless at the exposure concentrations observed in Visby, and this is in line with the results from a few experimental and occupational studies.

Submicroscopic nanoparticles (NPs) in air have received much attention due to their possible effects on health and wellbeing. Adverse health impacts of air pollution may not only be associated with level of exposure, but also mediated by the perception of the pollution and by beliefs of the exposure being hazardous. The aim of this study was to test a model that describes interrelations between NP pollution, perceived air quality, health risk perception, stress, and sick building syndrome. In the NanoOffice study, the level of NPs was measured and a survey on health risk perception was conducted among 260 employees in twelve office buildings in northern Sweden. Path analyses were performed to test the validity of the model. The data refute the model proposing that the NP exposure level significantly influences stress, chronic diseases, or SBS symptoms. Instead, the perceived exposure influences the perceived risk of NP, and the effect of perceived exposure on SBS and chronic disease is mediated by stress. There was little concern about nanoparticles, despite relatively high levels in some facilities. Perceived pollution and health risk perception may explain a large part of the environmentally induced symptoms and diseases, particularly in relatively low levels of pollution. The research results raise important questions on the physiologically or psychologically mediated health effects of air pollution.

In this study, the effects on daily mortality in Stockholm associated with short-term exposure to ultrafine particles (measured as number of particles with a diameter larger than 4 nm, PNC₄), black carbon (BC) and coarse particles (PM 2.5⁻10 ) have been compared with the effects from more common traffic-pollution indicators (PM 10 , PM 2.5 and NO₂) and O₃ during the period 2000⁻2016. Air pollution exposure was estimated from measurements at a 20 m high building in central Stockholm. The associations between daily mortality lagged up to two days (lag 02) and the different air pollutants were modelled by using Poisson regression. The pollutants with the strongest indications of an independent effect on daily mortality were O₃, PM 2.5⁻10 and PM 10 . In the single-pollutant model, an interquartile range (IQR) increase in O₃ was associated with an increase in daily mortality of 2.0% (95% CI: 1.1⁻3.0) for lag 01 and 1.9% (95% CI: 1.0⁻2.9) for lag 02. An IQR increase in PM 2.5⁻10 was associated with an increase in daily mortality of 0.8% (95% CI: 0.1⁻1.5) for lag 01 and 1.1% (95% CI: 0.4⁻1.8) for lag 02. PM 10 was associated with a significant increase only at lag 02, with 0.8% (95% CI: 0.08⁻1.4) increase in daily mortality associated with an IQR increase in the concentration. NO₂ exhibits negative associations with mortality. The significant excess risk associated with O₃ remained significant in two-pollutant models after adjustments for PM 2.5⁻10 , BC and NO₂. The significant excess risk associated with PM 2.5⁻10 remained significant in a two-pollutant model after adjustment for NO₂. The significantly negative associations for NO₂ remained significant in two-pollutant models after adjustments for PM 2.5⁻10 , O₃ and BC. A potential reason for these findings, where statistically significant excess risks were found for O₃, PM 2.5⁻10 and PM 10 , but not for NO₂, PM 2.5 , PNC₄ and BC, is behavioral factors that lead to misclassification in the exposure. The concentrations of O₃ and PM 2.5⁻10 are in general highest during sunny and dry days during the spring, when exposure to outdoor air tend to increase, while the opposite applies to NO₂, PNC₄ and BC, with the highest concentrations during the short winter days with cold weather, when people are less exposed to outdoor air.

In this study, an Air Quality Health Index (AQHI) for Stockholm is introduced as a tool to capture the combined effects associated with multi-pollutant exposure. Public information regarding the expected health risks associated with current or forecasted concentrations of pollutants and pollen can be very useful for sensitive persons when planning their outdoor activities. For interventions, it can also be important to know the contribution from pollen and the specific air pollutants, judged to cause the risk. The AQHI is based on an epidemiological analysis of asthma emergency department visits (AEDV) and urban background concentrations of NO x , O₃, PM 10 and birch pollen in Stockholm during 2001⁻2005. This analysis showed per 10 µg·m ⁻3 increase in the mean of same day and yesterday an increase in AEDV of 0.5% (95% CI: -1.2⁻2.2), 0.3% (95% CI: -1.4⁻2.0) and 2.5% (95% CI: 0.3⁻4.8) for NO x , O₃ and PM 10 , respectively. For birch pollen, the AEDV increased with 0.26% (95% CI: 0.18⁻0.34) for 10 pollen grains·m ⁻3 . In comparison with the coefficients in a meta-analysis, the mean values of the coefficients obtained in Stockholm are smaller. The mean value of the risk increase associated with PM 10 is somewhat smaller than the mean value of the meta-coefficient, while for O₃, it is less than one fifth of the meta-coefficient. We have not found any meta-coefficient using NO x as an indicator of AEDV, but compared to the mean value associated with NO₂, our value of NO x is less than half as large. The AQHI is expressed as the predicted percentage increase in AEDV without any threshold level. When comparing the relative contribution of each pollutant to the total AQHI, based on monthly averages concentrations during the period 2015⁻2017, there is a tangible pattern. The AQHI increase associated with NO x exhibits a relatively even distribution throughout the year, but with a clear decrease during the summer months due to less traffic. O₃ contributes to an increase in AQHI during the spring. For PM 10 , there is a significant increase during early spring associated with increased suspension of road dust. For birch pollen, there is a remarkable peak during the late spring and early summer during the flowering period. Based on monthly averages, the total AQHI during 2015⁻2017 varies between 4 and 9%, but with a peak value of almost 16% during the birch pollen season in the spring 2016. Based on daily mean values, the most important risk contribution during the study period is from PM 10 with 3.1%, followed by O₃ with 2.0%.

Combustion-related carbonaceous particles seem to be a better indicator of adverse health effects compared to PM2.5 and PM10. Historical studies are based on black smoke (BS), but more recent studies use absorbance (Abs), black carbon (BC) or elemental carbon (EC) as exposure indicators. To estimate health risks based on BS, we review the literature regarding the relationship between Abs, BS, BC and EC. We also discuss the uncertainties associated with the comparison of relative risks (RRs) based on these conversions. EC is reported to represent a proportion between 5.2% and 27% of BS with a mean value of 12%. Correlations of different metrics at one particular site are higher than when different sites are compared. Comparing all traffic, urban and rural sites, there is no systematic site dependence, indicating that other properties of the particles or errors affect the measurements and obscure the results. It is shown that the estimated daily mortality associated with short-term levels of EC is in the same range as PM10, but this is highly dependent on the EC to BS relationship that is used. RRs for all-cause mortality associated with short-term exposure to PM10 seem to be higher at sites with higher EC concentrations, but more data are needed to verify this.