Henrik Olstrup

Background: High concentrations of coarse particulate matter PM₁₀ from road dust are a major air quality concern in Visby, Sweden. To mitigate these levels, local authorities replaced soft limestone with crushed granite as an anti-slip material starting in the winter of 2023/2024. This is a follow-up study evaluating the impact of this intervention on PM₁₀ concentrations and the associated short-term respiratory health effects. Methods: Daily counts of healthcare visits for respiratory diseases (ICD-10: J00–J99) and daily mean PM₁₀ concentrations were analyzed using a quasi-Poisson regression model. This study compared the limestone period (2015–2019) with the granite period (2023–2025), stratified by season (winter/spring and summer/autumn) and age group (children 0–17 years and adults >17 years). Results: The transition to crushed granite reduced peak PM₁₀ concentrations during the spring. For adults, the relative risks for respiratory visits during winter/spring decreased during the granite period when compared to the limestone period (Wald p < 0.05). However, when considering that there were a majority of non-statistically significant differences when comparing the granite and limestone periods, these results should be interpreted with caution. Among children, more pronounced associations were observed during summer, although no significant differences in risk were detected between the limestone and granite periods. Conclusions: Although the intervention effectively lowered particle mass concentrations, only minor changes were observed in the overall epidemiological pattern. This suggests that public health improvements may be limited by factors beyond total mass reduction, such as particle mineralogy or seasonal exposure dynamics.

Purpose: The purpose of this case-control study was to investigate the associations between maternal serum concentrations of vitamin D early in pregnancy and the occurrence of preterm birth. Methods: The study included 269 women (cases) whose children were born preterm (< 37 gestational weeks [gw]) and 332 women (controls) whose children were born term (≥ 37 gw). Among the cases, 59 were extreme preterm (< 28 gw), 74 severe preterm (28‒32 gw), and 136 late preterm (33‒36 gw). All women gave birth in Scania, the most Southern County of Sweden. Concentrations of 25-hydroxyvitamin D₃ (vitamin D) in maternal serum collected early in pregnancy were analyzed using liquid chromatography-tandem-mass-spectrometry (LC/MS/MS). The serum concentrations of vitamin D were trichotomized based on the distributions among the controls (≤ 44.9; 45.0‒68.8; and ≥ 68.9 nmol/L) as well as dichotomized at a predefined cut-off (< 50 and ≥ 50 nmol/L). Logistic regression was used to estimate the associations between vitamin D and preterm births, partly when all cases were included in the analyses, and partly when the three different case groups were included separately. The category with the highest vitamin D concentration was used as a reference in the regression analyzes. The analyses were performed without as well as with adjustments for potential confounders. Results: When the category with the lowest vitamin D concentrations were compared with the reference category in the analyses where the vitamin D concentrations were trichotomized, no statistically significant associations were observed. However, among the extreme preterm an adjusted odds ratio of 1.93 (95% confidence interval 0.83‒4.48) was observed. The patterns were similar when 50 nmol/L was used as the cut-off. Conclusion: Although all comparisons gave adjusted odds ratios in the direction that low maternal vitamin D concentrations early in pregnancy increase the risk of preterm birth, none of these were statistically significant. Accordingly, the present study gives no to very weak support for an association.

Purpose The purpose of this case-control study was to investigate the associations between maternal serum concentrations of vitamin D early in pregnancy and the occurrence of preterm birth. Methods The study included 269 women (cases) whose children were born preterm (< 37 gestational weeks [gw]) and 332 women (controls) whose children were born term (≥ 37 gw). Among the cases, 59 were extreme preterm (< 28 gw), 74 severe preterm (28‒32 gw), and 136 late preterm (33‒36 gw). All women gave birth in Scania, the most Southern County of Sweden. Concentrations of 25-hydroxyvitamin D₃ (vitamin D) in maternal serum collected early in pregnancy were analyzed using liquid chromatography-tandem-mass-spectrometry (LC/MS/MS). The serum concentrations of vitamin D were trichotomized based on the distributions among the controls (≤ 44.9; 45.0‒68.8; and ≥ 68.9 nmol/L) as well as dichotomized at a predefined cut-off (< 50 and ≥ 50 nmol/L). Logistic regression was used to estimate the associations between vitamin D and preterm births, partly when all cases were included in the analyses, and partly when the three different case groups were included separately. The category with the highest vitamin D concentration was used as a reference in the regression analyzes. The analyses were performed without as well as with adjustments for potential confounders. Results When the category with the lowest vitamin D concentrations were compared with the reference category in the analyses where the vitamin D concentrations were trichotomized, no statistically significant associations were observed. However, among the extreme preterm an adjusted odds ratio of 1.93 (95% confidence interval 0.83‒4.48) was observed. The patterns were similar when 50 nmol/L was used as the cut-off. Conclusion Although all comparisons gave adjusted odds ratios in the direction that low maternal vitamin D concentrations early in pregnancy increase the risk of preterm birth, none of these were statistically significant. Accordingly, the present study gives no to very weak support for an association.

In this study, the long-term mortality effects associated with exposure to PM₁₀ (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 PM₁₀, 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 PM₁₀, 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 PM₁₀, 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.

In this study, long-term mortality effects associated with exposure to PM10, PM2.5, BC (black carbon), and NOx were analyzed in a cohort in southern Sweden during the period from 1991‒2016. Participants (those residing in Malmö, Sweden, born between 1923‒1950) were randomly recruited from 1991‒1996. 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 PM10 (particles with an aerodynamic diameter smaller than or equal to 10 µm), PM2.5 (particles with an aerodynamic diameter smaller than or equal to 2.5 µm), BC (black carbon), and NOx (nitrogen oxides) 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 PM10, PM2.5, BC, and NOx and the time until death among the participants during the period from 1991‒2016. 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 PM10, PM2.5, BC, and NOx 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 were in most cases decreased by the inclusion of a larger number of covariates in the models. The most robust associations were shown for NOx, with statistically significant positive HRs in all models. An overall conclusion is that road traffic-related pollutants had a significant association with mortality in the cohort.

Background: 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 (PM₁₀), 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 PM₁₀. The pooled estimates of the relative risks for asthma medication purchases across all 21 municipalities associated with a 10 μg m⁻³ increase in PM₁₀ 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 PM₁₀, and purchases of asthma medications.

Although the association between air pollution and mortality is well established, less is known about the effects in different age groups. This study analyzes the short-term associations between mortality in different age groups (0–14 years of age, 15–64 years of age, and 65+ years of age) and a number of air pollutants in two relatively clean northern European capitals: Stockholm and Tallinn. The concentrations in PM₁₀ (particles with an aerodynamic diameter smaller than or equal to 10 µm), PM_2.5–10 (coarse particles), PM_2.5 (particles with an aerodynamic diameter smaller than or equal to 2.5 µm), BC (black carbon), PNC₄ (particle number count of particles larger than or equal to 4 nm), NO₂ (nitrogen dioxide), and O₃ (ozone) were measured during the period of 2000–2016 in Stockholm and 2001–2018 in Tallinn (except for BC and PNC₄ which were only measured in Stockholm). The excess risks in daily mortality associated with an interquartile range (IQR) increase in the measured air pollutants were calculated in both single- and multi-pollutant models for lag01 and lag02 (average concentration during the same and the previous day, and the same and the previous two days, respectively) using a quasi-Poisson regression model with a logistic link function. In general, the calculated excess risks per IQR increase were highest in the age group 0–14 years of age in both Stockholm and Tallinn. However, in Stockholm, a statistically significant effect was shown for PM_2.5–10, and in Tallinn for O₃. In the oldest age group (65+), statistically significant effects were shown for both PM_2.5–10, PM₁₀, and O₃ in Stockholm, and for O₃ in Tallinn.

The old Swedish city Visby, located on the island Gotland, has, for several years, reported higher PM₁₀ 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 PM₁₀ with the highest concentrations during winter/spring when studded tires are allowed. This study analyzes the short-term associations between PM₁₀ 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 PM₁₀ 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 PM₁₀ 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 PM₁₀. 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.