Association of Short-term Air Pollution Exposure With SARS-CoV-2 Infection Among Young Adults in Sweden.

Importance: Mounting ecological evidence shows an association between short-term air pollution exposure and COVID-19, yet no study has examined this association on an individual level. Objective: To estimate the association between short-term exposure to ambient air pollution and SARS-CoV-2 infection among Swedish young adults. Design, Setting, and Participants: This time-stratified case-crossover study linked the prospective BAMSE (Children, Allergy Milieu, Stockholm, Epidemiology [in Swedish]) birth cohort to the Swedish national infectious disease registry to identify cases with positive results for SARS-CoV-2 polymerase chain reaction (PCR) testing from May 5, 2020, to March 31, 2021. Case day was defined as the date of the PCR test, whereas the dates with the same day of the week within the same calendar month and year were selected as control days. Data analysis was conducted from September 1 to December 31, 2021. Exposures: Daily air pollutant levels (particulate matter with diameter ≤2.5 µm [PM2.5], particulate matter with diameter ≤10 µm [PM10], black carbon [BC], and nitrogen oxides [NOx]) at residential addresses were estimated using dispersion models with high spatiotemporal resolution. Main Outcomes and Measures: Confirmed SARS-CoV-2 infection among participants within the BAMSE cohort. Distributed-lag models combined with conditional logistic regression models were used to estimate the association. Results: A total of 425 cases were identified, of whom 229 (53.9%) were women, and the median age was 25.6 (IQR, 24.9-26.3) years. The median exposure level for PM2.5 was 4.4 [IQR, 2.6-6.8] µg/m3 on case days; for PM10, 7.7 [IQR, 4.6-11.3] µg/m3 on case days; for BC, 0.3 [IQR, 0.2-0.5] µg/m3 on case days; and for NOx, 8.2 [5.6-14.1] µg/m3 on case days. Median exposure levels on control days were 3.8 [IQR, 2.4-5.9] µg/m3 for PM2.5, 6.6 [IQR, 4.5-10.4] µg/m3 for PM10, 0.2 [IQR, 0.2-0.4] µg/m3 for BC, and 7.7 [IQR, 5.3-12.8] µg/m3 for NOx. Each IQR increase in short-term exposure to PM2.5 on lag 2 was associated with a relative increase in positive results of SARS-CoV-2 PCR testing of 6.8% (95% CI, 2.1%-11.8%); exposure to PM10 on lag 2, 6.9% (95% CI, 2.0%-12.1%); and exposure to BC on lag 1, 5.8% (95% CI, 0.3%-11.6%). These findings were not associated with NOx, nor were they modified by sex, smoking, or having asthma, overweight, or self-reported COVID-19 respiratory symptoms. Conclusions and Relevance: The findings of this case-crossover study of Swedish young adults suggest that short-term exposure to particulate matter and BC was associated with increased risk of positive PRC test results for SARS-CoV-2, supporting the broad public health benefits of reducing ambient air pollution levels.

Regulating and Cultural Ecosystem Services of Urban Green Infrastructure in the Nordic Countries: A Systematic Review.

In the Nordic countries (Denmark, Finland, Iceland, Norway and Sweden), the Urban Green Infrastructure (UGI) has been traditionally targeted at reducing flood risk. However, other Ecosystem Services (ES) became increasingly relevant in response to the challenges of urbanization and climate change. In total, 90 scientific articles addressing ES considered crucial contributions to the quality of life in cities are reviewed. These are classified as (1) regulating ES that minimize hazards such as heat, floods, air pollution and noise, and (2) cultural ES that promote well-being and health. We conclude that the planning and design of UGI should balance both the provision of ES and their side effects and disservices, aspects that seem to have been only marginally investigated. Climate-sensitive planning practices are critical to guarantee that seasonal climate variability is accounted for at high-latitude regions. Nevertheless, diverging and seemingly inconsistent findings, together with gaps in the understanding of long-term effects, create obstacles for practitioners. Additionally, the limited involvement of end users points to a need of better engagement and communication, which in overall call for more collaborative research. Close relationships and interactions among different ES provided by urban greenery were found, yet few studies attempted an integrated evaluation. We argue that promoting interdisciplinary studies is fundamental to attain a holistic understanding of how plant traits affect the resulting ES; of the synergies between biophysical, physiological and psychological processes; and of the potential disservices of UGI, specifically in Nordic cities.

Climate and emission changes contributing to changes in near-surface ozone in Europe over the coming decades: results from model studies.

We used an off-line, regional, model of atmospheric transport and chemistry to investigate current and future levels of near-surface ozone and accumulated ozone exposure over a threshold of 40 ppb(v) (AOT40) in Europe. To describe the current situation and enable an evaluation of the model's performance we simulated a number of years around 2000. To assess changes in ozone concentrations due to possible emission changes in Europe, the model was run with the meteorology of the early 2000s and precursor emissions from a set of Clean Air for Europe (CAFE) emissions scenarios. By extrapolation of the observed increase in near-surface O3 at coastal locations in northwest Europe we constructed model boundaries that were used to simulate the impact of increasing hemispheric background in 2020. To assess changes in ozone concentrations due to climate change, the model was run with recent (2000) emissions but using meteorology from a regional climate model simulating a control (1961-1990) and a future (2021-2050) climate. The results indicate that climate change will have a small impact on ozone concentrations and AOT40 in the Nordic countries. Changes in hemispheric background concentrations and changes in precursor emissions in Europe will have a larger effect on ozone in Northern Europe. The situation is quite different in southern Europe, where climate change is expected to result in a very large increase in near-surface ozone concentrations.

Climate change impact on atmospheric nitrogen deposition in northwestern Europe: a model study.

A high-resolution chemical transport model, driven by meteorology representing current and future climate, was used to investigate the effects of possible future changes in climate on nitrogen deposition in northwestern Europe. The model system was able to resolve the climatology of precipitation and chemical properties observed in northern Europe during the 1980s, albeit with some underestimation of the temporal and spatial variability of meteorological parameters and chemical components. The results point toward a substantial increase (30% or more) in nitrogen deposition over western Norway as a consequence of increasing precipitation but more moderate changes for other areas. Deposition of oxidized nitrogen will increase more than the deposition of reduced nitrogen. Over Sweden, oxidized nitrogen will increase only marginally and reduced nitrogen will decrease, although annual precipitation is expected to increase here as well. This is probably because more reduced nitrogen will be removed further west in Scandinavia because of the strong increase in precipitation along the Norwegian coast. The total deposition of oxidized nitrogen over Norway is expected to increase from 96 Gg N y(-1) during the current climate to 107 Gg N y(-1) by 2100 due only to changes in climate. The corresponding values for Sweden are more modest, from 137 Gg N y(-1) to 139 Gg N y(-1).

Past, present and future concentrations of ground-level ozone and potential impacts on ecosystems and human health in northern Europe.

This review summarizes new information on the current status of ground-level ozone in Europe north of the Alps. There has been a re-distribution in the hourly ozone concentrations in northern Europe during 1990-2015. The highest concentrations during summer daytime hours have decreased while the summer night-time and winter day- and night-time concentrations have increased. The yearly maximum 8-h mean concentrations ([O3]8h,max), a metric used to assess ozone impacts on human health, have decreased significantly during 1990-2015 at four out of eight studied sites in Fennoscandia and northern UK. Also the annual number of days when the yearly [O3]8h,max exceeded the EU Environmental Quality Standard (EQS) target value of 60ppb has decreased. In contrast, the number of days per year when the yearly [O3]8h,max exceeded 35ppb has increased significantly at two sites, while it decreased at one far northern site. [O3]8h,max is predicted not to exceed 60ppb in northern UK and Fennoscandia after 2020. However, the WHO EQS target value of 50ppb will still be exceeded. The AOT40 May-July and AOT40 April-September metrics, used for the protection of vegetation, have decreased significantly at three and four sites, respectively. The EQS for the protection of forests, AOT40 April-September 5000ppbh, is projected to no longer be exceeded for most of northern Europe sometime before the time period 2040-2059. However, if the EQS is based on Phytotoxic Ozone Dose (POD), POD1, it may still be exceeded by 2050. The increasing trend for low and medium range ozone concentrations in combination with a decrease in high concentrations indicate that a new control strategy, with a larger geographical scale than Europe and including methane, is needed for ozone abatement in northern Europe.