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Background: Air pollution exposure during pregnancy has been associated with adverse birth outcomes. Uncertainties remain about the effect at very low exposure levels. The aim of this study was to explore the association of maternal exposure to air pollutants during pregnancy at very low exposure levels with birth weight and estimate the health impact.

Methods: The MATEX birth cohort (226,551 singleton births in 2012–2016) was linked with eight modelled air pollutants (PM2.5, PM10, PMcoarse, NO2, NOx, CO, SO2, O3) at home address during pregnancy. Multiple regression was used to estimate the change in birth weight (in g) associated with individual-level mean exposure during pregnancy. We tested different adjustment models and conducted sensitivity analyses. We also estimated the potential number of low birth weight cases attributable to PM2.5 to quantify the public health issues at the prevailing low exposure levels.

Results: PM2.5 was associated with the largest reduction of birth weight (-6.5 g per 1 µg/m3) followed by PMcrs (-4.9 g) and PM10 (-3.0 g). Among the gaseous pollutants the strongest reduction in birth weight was observed for NO2 (-0.8 g), followed by CO (-0.5 g), NOx (-0.4 g) and SO2 (-0.2 g). On the contrary, O3 was associated with a modest increase in birth weight (+ 0.9 g). Effects on births weight were observed also below WHO guideline values. When accounting for the prevailing exposure levels in Finland, CO was associated with the biggest reduction in birth weight. The effect of PM2.5 exposure on birthweight corresponds to a loss of 30 g at mean exposure. Assuming a causal relationship, about 700 cases of low birth weight could be attributable to PM2.5 in Finland during the study period.

Conclusions: No clear evidence on safe exposure level was found in this study. All pollutants were associated with reduced birthweight except ozone. Causality and confounding due to correlations warrant specific attention.

Background: Wildfire activity is an important source of tropospheric ozone (O₃) pollution. However, no study to date has systematically examined the associations of wildfire-related O₃ exposure with mortality globally.

Methods: We did a multicountry two-stage time series analysis. From the Multi-City Multi-Country (MCC) Collaborative Research Network, data on daily all-cause, cardiovascular, and respiratory deaths were obtained from 749 locations in 43 countries or areas, representing overlapping periods from Jan 1, 2000, to Dec 31, 2016. We estimated the daily concentration of wildfire-related O₃ in study locations using a chemical transport model, and then calibrated and downscaled O3 estimates to a resolution of 0·25° × 0·25° (approximately 28 km2 at the equator). Using a random-effects meta-analysis, we examined the associations of short-term wildfire-related O₃ exposure (lag period of 0–2 days) with daily mortality, first at the location level and then pooled at the country, regional, and global levels. Annual excess mortality fraction in each location attributable to wildfire-related O₃ was calculated with pooled effect estimates and used to obtain excess mortality fractions at country, regional, and global levels.

Findings: Between 2000 and 2016, the highest maximum daily wildfire-related O₃ concentrations (≥30 μg/m³) were observed in locations in South America, central America, and southeastern Asia, and the country of South Africa. Across all locations, an increase of 1 μg/m³ in the mean daily concentration of wildfire-related O₃ during lag 0–2 days was associated with increases of 0·55% (95% CI 0·29 to 0·80) in daily all-cause mortality, 0·44% (–0·10 to 0·99) in daily cardiovascular mortality, and 0·82% (0·18 to 1·47) in daily respiratory mortality. The associations of daily mortality rates with wildfire-related O₃ exposure showed substantial geographical heterogeneity at the country and regional levels. Across all locations, estimated annual excess mortality fractions of 0·58% (95% CI 0·31 to 0·85; 31 606 deaths [95% CI 17 038 to 46 027]) for all-cause mortality, 0·41% (–0·10 to 0·91; 5249 [–1244 to 11 620]) for cardiovascular mortality, and 0·86% (0·18 to 1·51; 4657 [999 to 8206]) for respiratory mortality were attributable to short-term exposure to wildfire-related O₃.

Interpretation: In this study, we observed an increase in all-cause and respiratory mortality associated with short-term wildfire-related O₃ exposure. Effective risk and smoke management strategies should be implemented to protect the public from the impacts of wildfires.

Background: Parental allergic diseases and smoking influence respiratory disease in the offspring but it is not known whether they influence fractional exhaled nitric oxide (FeNO) in the offspring. We investigated whether parental allergic diseases, parental smoking and FeNO levels in parents were associated with FeNO levels in their offspring.

Methods: We studied 609 offspring aged 16–47 years from the Respiratory Health in Northern Europe, Spain and Australia generation (RHINESSA) study with parental information from the Respiratory Health in Northern Europe (RHINE) III study and the European Community Respiratory Health Survey (ECRHS) III. Linear regression models were used to assess the association between offspring FeNO and parental FeNO, allergic rhinitis, asthma and smoking, while adjusting for potential confounding factors.

Results: Parental allergic rhinitis was significantly associated with higher FeNO in the offspring, both on the paternal and maternal side (percent change: 20.3 % [95%CI 5.0–37.7], p = 0.008, and 13.8 % [0.4–28.9], p = 0.043, respectively). Parental allergic rhinitis with asthma in any parent was also significantly associated with higher offspring FeNO (16.2 % [0.9–33.9], p = 0.037). However, parental asthma alone and smoking were not associated with offspring FeNO. Parental FeNO was not associated with offspring FeNO after full adjustments for offspring and parental factors.

Conclusions: Parental allergic rhinitis but not parental asthma was associated with higher levels of FeNO in offspring. These findings suggest that parental allergic rhinitis status should be considered when interpreting FeNO levels in offspring beyond childhood.

Background: Temperature variability (TV) is associated with increased mortality risk. However, it is still unknown whether intra-day or inter-day TV has different effects. Objectives: We aimed to assess the association of intra-day TV and inter-day TV with all-cause, cardiovascular, and respiratory mortality.

Methods: We collected data on total, cardiovascular, and respiratory mortality and meteorology from 758 locations in 47 countries or regions from 1972 to 2020. We defined inter-day TV as the standard deviation (SD) of daily mean temperatures across the lag interval, and intra-day TV as the average SD of minimum and maximum temperatures on each day. In the first stage, inter-day and intra-day TVs were modelled simultaneously in the quasi-Poisson time-series model for each location. In the second stage, a multi-level analysis was used to pool the location-specific estimates.

Results: Overall, the mortality risk due to each interquartile range [IQR] increase was higher for intra-day TV than for inter-day TV. The risk increased by 0.59% (95% confidence interval [CI]: 0.53, 0.65) for all-cause mortality, 0.64% (95% CI: 0.56, 0.73) for cardiovascular mortality, and 0.65% (95% CI: 0.49, 0.80) for respiratory mortality per IQR increase in intra-day TV0–7 (0.9 °C). An IQR increase in inter-day TV0–7 (1.6 °C) was associated with 0.22% (95% CI: 0.18, 0.26) increase in all-cause mortality, 0.44% (95% CI: 0.37, 0.50) increase in cardiovascular mortality, and 0.31% (95% CI: 0.21, 0.41) increase in respiratory mortality. The proportion of all-cause deaths attributable to intra-day TV0–7 and inter-day TV0–7 was 1.45% and 0.35%, respectively. The mortality risks varied by lag interval, climate area, season, and climate type.

Conclusions: Our results indicated that intra-day TV may explain the main part of the mortality risk related to TV and suggested that comprehensive evaluations should be proposed in more countries to help protect human health.

Background: Exposure to cold spells is associated with mortality. However, little is known about the global mortality burden of cold spells.

Methods: A three-stage meta-analytical method was used to estimate the global mortality burden associated with cold spells by means of a time series dataset of 1960 locations across 59 countries (or regions). First, we fitted the location-specific, cold spell-related mortality associations using a quasi-Poisson regression with a distributed lag non-linear model with a lag period of up to 21 days. Second, we built a multivariate meta-regression model between location-specific associations and seven predictors. Finally, we predicted the global grid-specific cold spell-related mortality associations during 2000-19 using the fitted meta-regression model and the yearly grid-specific meta-predictors. We calculated the annual excess deaths, excess death ratio (excess deaths per 1000 deaths), and excess death rate (excess deaths per 100 000 population) due to cold spells for each grid across the world.

Findings: Globally, 205 932 (95% empirical CI [eCI] 162 692-250 337) excess deaths, representing 3·81 (95% eCI 2·93-4·71) excess deaths per 1000 deaths (excess death ratio), and 3·03 (2·33-3·75) excess deaths per 100 000 population (excess death rate) were associated with cold spells per year between 2000 and 2019. The annual average global excess death ratio in 2016-19 increased by 0·12 percentage points and the excess death rate in 2016-19 increased by 0·18 percentage points, compared with those in 2000-03. The mortality burden varied geographically. The excess death ratio and rate were highest in Europe, whereas these indicators were lowest in Africa. Temperate climates had higher excess death ratio and rate associated with cold spells than other climate zones.

Interpretation: Cold spells are associated with substantial mortality burden around the world with geographically varying patterns. Although the number of cold spells has on average been decreasing since year 2000, the public health threat of cold spells remains substantial. The findings indicate an urgency of taking local and regional measures to protect the public from the mortality burdens of cold spells.

Air pollution's short-term effects on a wide range of health outcomes have been studied extensively, primarily focused on vulnerable groups (e.g., children and the elderly). However, the air pollution effects on the adult working population through sick leave have received little attention. This study aims to 1) estimate the associations between particulate matter ≤2.5 μm³ (PM_2.5) and sick leave episodes and 2) calculate the attributable number of sick leave days and the consequential productivity loss in the City of Stockholm, Sweden. Individual level daily sick leave data was obtained from Statistics Sweden for the years 2011–2019. Daily average concentrations of PM_2.5 were obtained from the main urban background monitoring station in Stockholm. A case-crossover study design was applied to estimate the association between short-term PM_2.5 and onset of sick leave episodes. Conditional logistic regression was used to estimate the relative increase in odds of onset per 10 μg/m³ of PM_2.5, adjusting for temperature, season, and pollen. A human capital method was applied to estimate the PM2.5 attributable productivity loss. In total, 1.5 million (M) individual sick leave occurrences were studied. The measured daily mean PM_2.5 concentration was 4.2 μg/m³ (IQR 3.7 μg/m³). The odds of a sick leave episode was estimated to increase by 8.5% (95% CI: 7.8–9.3) per 10 μg/m³ average exposure 2–4 days before. Sub-group analysis showed that private sector and individuals 15–24 years old had a lower increase in odds of sick leave episodes in relation to PM_2.5 exposure. In Stockholm, 4% of the sick leave episodes were attributable to PM_2.5 exposure, corresponding to €17 M per year in productivity loss. Our study suggests a positive association between PM_2.5 and sick leave episodes in a low exposure area.

Short-term exposure to ground-level ozone in cities is associated with increased mortality and is expected to worsen with climate and emission changes. However, no study has yet comprehensively assessed future ozone-related acute mortality across diverse geographic areas, various climate scenarios, and using CMIP6 multi-model ensembles, limiting our knowledge on future changes in global ozone-related acute mortality and our ability to design targeted health policies. Here, we combine CMIP6 simulations and epidemiological data from 406 cities in 20 countries or regions. We find that ozone-related deaths in 406 cities will increase by 45 to 6,200 deaths/year between 2010 and 2014 and between 2050 and 2054, with attributable fractions increasing in all climate scenarios (from 0.17% to 0.22% total deaths), except the single scenario consistent with the Paris Climate Agreement (declines from 0.17% to 0.15% total deaths). These findings stress the need for more stringent air quality regulations, as current standards in many countries are inadequate.

Background: A large part of the Swedish population is exposed to higher levels of air pollution than the health-centered air quality guidelines recommended by the World Health Organization (WHO).

Aim: The aim of the study was to illustrate the potential health benefits of cleaner air in Sweden by conducting a comprehensive health impact assessment, using a population sample of 100,000 individuals representing the country’s demographics.

Methods: Exposure-response functions for various health outcomes were derived from epidemiological literature, mainly from systematic reviews and low-exposure settings. Two hypothetical scenarios were studied: a 1 µg/m³ decrease in particulate matter with an aerodynamic diameter <2.5µm (PM_2.5) and nitrogen dioxide (NO²), and a reduction in PM_2.5 or NO² from average exposure corresponding to Sweden’s Clean Air objectives to WHO’s air quality guidelines.

Results: The findings demonstrated that even a modest decrease in air pollution concentrations can yield significant health benefits. For example, reducing PM_2.5 by 1 µg/m³ was projected to correspond to a 1% to 2% decrease in mortality, a 2% reduction in myocardial infarction cases, a 4% decrease in stroke incidence, a 2% decline in chronic obstructive pulmonary disease, and a 1% decreases in lung cancer and type 2 diabetes annually. Moreover, this reduction is estimated to lower childhood asthma cases, incidences of hypertension during pregnancy, and premature births by 3%, 3% and 2%, respectively, each year.

Conclusions: The results highlighted that even minor enhancements in air quality would lead to substantial improvements in public health.

Objective: To examine the associations between characteristics of daily rainfall (intensity, duration, and frequency) and all cause, cardiovascular, and respiratory mortality.

Design: Two stage time series analysis.

Setting: 645 locations across 34 countries or regions.

Population: Daily mortality data, comprising a total of 109 954 744 all cause, 31 164 161 cardiovascular, and 11 817 278 respiratory deaths from 1980 to 2020.

Main outcome measure: Association between daily mortality and rainfall events with return periods (the expected average time between occurrences of an extreme event of a certain magnitude) of one year, two years, and five years, with a 14 day lag period. A continuous relative intensity index was used to generate intensity-response curves to estimate mortality risks at a global scale.

Results: During the study period, a total of 50 913 rainfall events with a one year return period, 8362 events with a two year return period, and 3301 events with a five year return period were identified. A day of extreme rainfall with a five year return period was significantly associated with increased daily all cause, cardiovascular, and respiratory mortality, with cumulative relative risks across 0-14 lag days of 1.08 (95% confidence interval 1.05 to 1.11), 1.05 (1.02 to 1.08), and 1.29 (1.19 to 1.39), respectively. Rainfall events with a two year return period were associated with respiratory mortality only, whereas no significant associations were found for events with a one year return period. Non-linear analysis revealed protective effects (relative risk <1) with moderate-heavy rainfall events, shifting to adverse effects (relative risk >1) with extreme intensities. Additionally, mortality risks from extreme rainfall events appeared to be modified by climate type, baseline variability in rainfall, and vegetation coverage, whereas the moderating effects of population density and income level were not significant. Locations with lower variability of baseline rainfall or scarce vegetation coverage showed higher risks.

Conclusion: Daily rainfall intensity is associated with varying health effects, with extreme events linked to an increasing relative risk for all cause, cardiovascular, and respiratory mortality. The observed associations varied with local climate and urban infrastructure.

Summary:

• The risk of grandchild asthma related to grandmaternal smoking is transmitted via the maternal line.
• Paternal smoking at conscription was related to an increased risk of asthma in boys.