Daily O3 Concentrations Research Articles

Short-term ozone exposure and cancer mortality in Brazil: A nationwide case-crossover study.

Exposure to ambient ozone (O3) is linked to increased mortality risks from various diseases, but epidemiological investigations delving into its potential implications for cancer mortality are limited. We aimed to examine the association between short-term O3 exposure and site-specific cancer mortality and investigate vulnerable subgroups in Brazil. In total 3,459,826 cancer death records from 5570 Brazilian municipalities between 2000 and 2019, were included. Municipal average daily O3 concentration was calculated from a global estimation at 0.25°×0.25° spatial resolution. Thetime-stratified case-crossover design was applied to assess the O3-cancer mortality association. Subgroup analyses by age, sex, season, time-period, region, urban hierarchy, climate classification, quantiles of GDP per capita and illiteracy rates were performed. A linear and non-threshold exposure-response relationship was observed for short-term exposure to O3 with cancer mortality, with a 1.00% (95% CI: 0.79%-1.20%) increase in all-cancer mortality risks for each 10-μg/m3 increment of three-day average O3. Kidney cancer was most strongly with O3 exposure, followed by cancers of the prostate, stomach, breast, lymphoma, brain and lung. The associated cancer risks were relatively higher in the warm season and in southern Brazil, with a decreasing trend over time. When restricting O3 concentration to the national minimum value during 2000-2019, a total of 147,074 (116,690-177,451) cancer deaths could be avoided in Brazil, which included 17,836 (7014-28,653) lung cancer deaths. Notably, these associations persisted despite observed adaptation within the Brazilian population, highlighting the need for a focus on incorporating specific measures to mitigate O3 exposure into cancer care recommendations.

Characteristics of Ozone Concentration in Shanghai and Its Associated Atmospheric Circulation Background During Summer Half-years from 2006 to 2021

It is of great importance to scientifically evaluate the impact of weather and climate conditions on the occurrence of O3 pollution in order to improve the accuracy of O3 pollution forecasts， as well as to reasonably control and reduce the adverse effects of O3 pollution. The characteristics of O3 concentration and climate background were analyzed based on daily O3 concentration data， meteorological factors， and NCEP/NCER reanalysis data from 2006 to 2021 in Shanghai. In addition， the differences in atmospheric circulation situations during years with anomalous O3 concentrations were compared and diagnosed from the perspective of climatology. Additionally， the monthly O3 concentration prediction model （seasonal autoregressive integrated moving average with exogenous regressors， SARIMAX） was further established by adding the key meteorological factors. The results indicated that both the whole-year average and summer half-year average O3 concentrations in Shanghai were increasing with fluctuation， and the summer half-year average was much higher than the annual average， up to 36.2%. Furthermore， there was a significant negative correlation between O3 concentration and wind speed （correlation coefficient of -0.826） and a significant positive correlation with the frequency of static wind and the number of days in which the low cloud cover was less than 20% （correlation coefficients of 0.836 and 0.724， respectively）. The monthly mean O3 concentration had a clear periodicity， showing a pattern with a high concentration in the middle period （April to September） and a low concentration at the beginning and end of the periods. High O3 concentration years （2013-2021） were accompanied by more polluted days， lower average wind speed， more small wind （≤1.5 m·s-1） days， more days of low cloud cover of less than 20%， more days of high temperature， higher direct solar radiation， and more sunshine hours. When the location of the stronger West Pacific subtropical high was westward and southward in the summer half-year， Shanghai was influenced by an anomalous westerly wind， which was not conducive to the transportation of clean air from the sea to Shanghai and thus led to the high concentration of O3 pollution. When the long wave radiation emitted from the ground was low in the summer half-year， it was favorable for the increase in ground temperature and caused a high concentration of O3 pollution. Adding direct solar radiation， maximum temperature， and wind speed as exogenous variables to the monthly O3 forecast model could significantly improve the effectiveness of the monthly forecast， with the root mean square error decreasing by 47.7% （from 22 to 11.5） and the correlation coefficient increasing by 11.2% （from 0.819 to 0.911）， which could be applied to the practical prediction of monthly O3 concentration.

Joint effect of heat and air pollution on mortality in 620 cities of 36 countries

BackgroundThe epidemiological evidence on the interaction between heat and ambient air pollution on mortality is still inconsistent. ObjectivesTo investigate the interaction between heat and ambient air pollution on daily mortality in a large dataset of 620 cities from 36 countries. MethodsWe used daily data on all-cause mortality, air temperature, particulate matter ≤ 10 μm (PM10), PM ≤ 2.5 μm (PM2.5), nitrogen dioxide (NO2), and ozone (O3) from 620 cities in 36 countries in the period 1995–2020. We restricted the analysis to the six consecutive warmest months in each city. City-specific data were analysed with over-dispersed Poisson regression models, followed by a multilevel random-effects meta-analysis. The joint association between air temperature and air pollutants was modelled with product terms between non-linear functions for air temperature and linear functions for air pollutants. ResultsWe analyzed 22,630,598 deaths. An increase in mean temperature from the 75th to the 99th percentile of city-specific distributions was associated with an average 8.9 % (95 % confidence interval: 7.1 %, 10.7 %) mortality increment, ranging between 5.3 % (3.8 %, 6.9 %) and 12.8 % (8.7 %, 17.0 %), when daily PM10 was equal to 10 or 90 μg/m3, respectively. Corresponding estimates when daily O3 concentrations were 40 or 160 μg/m3 were 2.9 % (1.1 %, 4.7 %) and 12.5 % (6.9 %, 18.5 %), respectively. Similarly, a 10 μg/m3 increment in PM10 was associated with a 0.54 % (0.10 %, 0.98 %) and 1.21 % (0.69 %, 1.72 %) increase in mortality when daily air temperature was set to the 1st and 99th city-specific percentiles, respectively. Corresponding mortality estimate for O3 across these temperature percentiles were 0.00 % (-0.44 %, 0.44 %) and 0.53 % (0.38 %, 0.68 %). Similar effect modification results, although slightly weaker, were found for PM2.5 and NO2. ConclusionsSuggestive evidence of effect modification between air temperature and air pollutants on mortality during the warm period was found in a global dataset of 620 cities.

Relationships between ozone and particles during air pollution episodes in arid continental climate

For human health, tropospheric ozone (O3), particles (PM2.5 and PM10, particles with aerodynamic diameter <2.5 and 10 μm), and nitrogen dioxide (NO2) are the most harmful air pollutants. We have investigated the simultaneity of PM2.5, PM10, NO2, and O3 occurrence by using data from 21 ground-based monitoring stations in a megacity of the Middle East, Tehran (Iran), between 2011 and 2022. In Tehran, the daily PM2.5 (21–45 μg m−3), PM10 (52–108 μg m−3) and NO2 (75–146 μg m−3) mean concentrations have largely exceeded the 24-h limit value established by the 2021 World Health Organization for the protection of human health, i.e., 15, 45 and 25 μg m−3, respectively, in particular for NO2. The ground-level daily O3 concentrations ranged from 26 to 47 μg m−3. Changes in aerosols burden (e.g., PM2.5 and PM10) affect surface O3 through changes in aerosol chemistry and photolysis rates. Following the dust events and for the days with PM2.5 and PM10 exceeding 50 and 100 μg m−3, respectively, we observed a reduction of surface O3 levels (- 30.0% and - 13.5%), concurrently to surface NO2 (+27.9% and +16.6%) levels increases compared to the non-dusty clear-sky days over Tehran city. Surface O3 formation is suppressed under high particulate matter (PM) levels in the atmosphere, in particular PM2.5, likely due to weakened photochemical reactions (lower solar radiation and air temperature), dilution effect, and heterogeneous chemical processes occurring onto the PM2.5 surface (reactive uptake of nitrogen oxides, NOx, and hydrogen oxide radicals, HOx). To achieve O3-PM co-improvement in cities, we recommend reductions in NOx emissions concurrently with significant reductions in PM and Volatile Organic Compounds emissions, for instance by suitable greening and re-naturing programs.

Optimized neural network for daily-scale ozone prediction based on transfer learning

Tropospheric ozone (O3) pollution is worsening in China, and an accurate forecast is a prerequisite to lower the O3 peak level. In recent years, machine learning techniques have attracted increasing attention in O3 prediction owing to their high efficiency and simple operation. However, the accuracy of predicting the daily O3 level is low. This study proposed a novel model by coupling long short-term memory neural network with transfer learning (TL-LSTM), with meteorology and pollutant concentration information as the model input. L2 regularization was applied to reduce the risk of overfitting and to improve the accuracy and generalization ability of the model prediction. Our results indicated that by transferring the knowledge in the model configuration from the hourly LSTM module, TL-LSTM greatly improves the predictability of the daily maximum 8 h average (MDA8) of O3 in Hong Kong. The coefficient of determination (R2) increased from 0.684 to 0.783 and the mean square error (MSE) reduced from 1.36 × 10−2 to 1.05 × 10−2. Furthermore, R2 and MSE were the highest in summer, indicating an under-prediction of peak O3 levels. This was a result of the limited number of high O3 days, which did not provide sufficient knowledge for the model to make an accurate prediction. Sobol analysis indicated that wind speed was the most sensitive factor in O3 prediction, largely due to the development of land-sea breeze circulation which effectively traps pollutants and expedites O3 formation. The results clearly demonstrate the effectiveness of the TL-LSTM in predicting the daily O3 concentration in Hong Kong. Thus, TL-LSTM can be promulgated into other photochemically active regions to assist in O3 pollution forecasting and management.

Patterns related to the pollutant concentration data in the Metropolitan Area of Belo Horizonte, Brasil

Air pollution from human and industrial activities has been a major concern in recent years. Among the various pollutants found in the atmosphere, particulate matter (PM) and ozone (O3) show significant occurrences, with high concentrations in several urban centers frequently associated with environmental and public health problems. Therefore, this study uses the Analysis of Variance (ANOVA) technique and Tukey's test to investigate the patterns related to the variability of maximum daily concentrations of O3 and mean daily concentrations of particulate matter with a diameter inferior to 10 μm (PM10), registered between 2007 and 2012 through six sites in the Metropolitan Area of Belo Horizonte (MABH), Brazil. To this end, the data were analyzed using ANOVA arranged in a factorial scheme (6 x 4 x 2) with four repetitions per treatment, followed by Tukey’s test. In the ANOVA and Tukey's test, the first factor (A) represents the six air quality monitoring stations, the second (B) represents the seasons, and the third (C) the measurements carried out during working days and weekends. Seasonal variability patterns show higher concentrations of O3 in the Spring and PM10 in the Winter. The mean values for working days and weekends showed different patterns for the two pollutants. For PM10, the concentrations were higher during the working days when compared to the weekends. For O3, the weekend effect was found only in one of the stations. The profiles of vehicular and industrial emissions have been identified as a potential factor that led to these results.

Assessment of ozone risk to Central European forests: Time series indicates perennial exceedance of ozone critical levels

In this study, the stomatal ozone (O3) fluxes were investigated at five low-elevation forest sites in Western Germany (Rhineland Palatinate) over the time period 1998–2019. The Phytotoxic Ozone Dose with an hourly threshold of uptake (Y), to represent the detoxification capacity of trees (POD1 in mmol m−2 per leaf area, with Y = 1 nmol O3 m−2 s−1), and the number of exceedances of the O3 critical level of 5.2 mmol O3 m−2 per leaf area for European beech and 9.2 mmol O3 m−2 per leaf area for Norway spruce were calculated by using the DO3SE model. A Principal Component Analysis revealed strong correlations between daily O3 concentrations, daytime O3 (for hours with global radiation exceeding 50 W m−2), POD1, global radiation, vapor pressure deficit and air temperature. Moreover, a significant correlation was obtained between POD1 and soil water content (SWC) at all sites (r = 0.51–0.74). The Random Forests Analysis confirmed that the SWC is the most important predictor of stomatal O3 fluxes. The soil water supply is very important for POD1 estimation, because drought decreases stomatal conductance, leading to a reduction of transpiration, as well as to lower O3 uptake through stomata. Between 1998 and 2019, the drier and warmer climate induced a soil drought (on average, SWC - 0.15 % per year) leading to lower stomatal O3 uptake by forests (- 0.36 mmol O3 m−2 per year). Hence, during growing seasons with sufficient water supply and often lower O3 levels compared to hot and dry periods, forests are at higher O3 risk than during hot and dry periods when the drought stress is more significant than O3 stress despite relatively higher O3 levels. Irrespective of these differences in O3 uptake between relatively cool and humid as compared to relatively hot and dry years in the study region, the Critical Level for O3 was exceeded in late spring/early summer (May/June) during all 22 years. Risk assessment for the protection of European forests, which is urgently needed due to the forests current critical state after several successive years of drought and exceedance of the O3 critical level in large areas of Europe, should therefore become flux-based to account for the inter-twined effects of drought and O3 on the physiology and health of forest trees in the region. For stomatal O3 fluxes estimation, a better soil water and leaf parameterization is needed e.g., by taking into account both O3- and drought-induced effects.

Estimating short-term mortality benefits associated with a reduction in tropospheric ozone

ObjectiveGround-level ozone (O3) is an air contaminant and can be harmful to the human health and environment. The objective of this study is to analyze the statistical trend of O3 and the association between the daily O3 exposure and mortality in Tehran, and to estimate the short-term health benefits of reducing the concentration of O3 in the ambient air of Tehran. MethodsThe statistical parameters such as the mean, coefficient of variation, skewness, and kurtosis of O3 concentration for warm and cold seasons were calculated. The association and temporal relationship between the daily O3 concentration and different causes of mortality were analyzed using the generalized additive model (GAM). We utilized the BenMAP software to estimate the (short-term) avoidable mortality associated with reducing O3 concentration to the US EPA's standard level (70 ppb) for a full year and the warm seasons only. ResultsThe statistical analysis of O3 revealed an increase in the 1-h maximum and 8-h maximum concentrations in recent years. The association between O3 exposure and mortality was significant for the warm seasons when the concentration was highest. For every 10 ppb increase in the O3 concentration, there was 1.2% increase in mortality. Furthermore, the association was more significant for cardiovascular than respiratory attributed mortality. The analysis also showed a 3-day lag from the time of O3 exposure and mortality for the total population. The aforementioned scenario (for a full year) run in BenMAP resulted in 508 (90% CI: 69–937) annual all-cause avoidable deaths in Tehran. ConclusionThe maximum O3 concentration in Tehran has been increasing in the recent years, raising the alarm for potential adverse health impacts. In this study we found a significant association between short-term exposure to O3 and mortality during the warm seasons and a substantial predicted health benefit in reduction of this pollutant. Given the increasing ambient O3 concentration, it is necessary to further explore the aetiology/ies behind this increase and to consider how reductions in O3 precursors can reduce the public health burden in Tehran.

Ozone pollution mitigation in guangxi (south China) driven by meteorology and anthropogenic emissions during the COVID-19 lockdown.

With the implementation of COVID-19 restrictions and consequent improvement in air quality due to the nationwide lockdown, ozone (O3) pollution was generally amplified in China. However, the O3 levels throughout the Guangxi region of South China showed a clear downward trend during the lockdown. To better understand this unusual phenomenon, we investigated the characteristics of conventional pollutants, the influence of meteorological and anthropogenic factors quantified by a multiple linear regression (MLR) model, and the impact of local sources and long-range transport based on a continuous emission monitoring system (CEMS) and the HYSPLIT model. Results show that in Guangxi, the conventional pollutants generally declined during the COVID-19 lockdown period (January 24 to February 9, 2020) compared with their concentrations during 2016–2019, while O3 gradually increased during the resumption (10 February to April 2020) and full operation periods (May and June 2020). Focusing on Beihai, a typical Guangxi region city, the correlations between the daily O3 concentrations and six meteorological parameters (wind speed, visibility, temperature, humidity, precipitation, and atmospheric pressure) and their corresponding regression coefficients indicate that meteorological conditions were generally conducive to O3 pollution mitigation during the lockdown. A 7.84 μg/m3 drop in O3 concentration was driven by meteorology, with other decreases (4.11 μg/m3) explained by reduced anthropogenic emissions of O3 precursors. Taken together, the lower NO2/SO2 ratios (1.25–2.33) and consistencies between real-time monitored primary emissions and ambient concentrations suggest that, with the closure of small-scale industries, residual industrial emissions have become dominant contributors to local primary pollutants. Backward trajectory cluster analyses show that the slump of O3 concentrations in Southern Guangxi could be partly attributed to clean air mass transfer (24–58%) from the South China Sea. Overall, the synergistic effects of the COVID-19 lockdown and meteorological factors intensified O3 reduction in the Guangxi region of South China.

Ozone weekend effect in cities: Deep insights for urban air pollution control

Studying weekend-weekday variation in ground-level ozone (O3) allows one to better understand O3 formation conditions, with a potential for developing effective strategies for O3 control. Reducing inappropriately the O3 precursors emissions can either produce no reduction or increase surface O3 concentrations. This paper analyzes the weekend-weekday differences of O3 at 300 rural and 808 urban background stations worldwide from 2005 to 2014, in order to investigate the O3 weekend effect over time and assess the effectiveness of the precursors emissions control policies for reducing O3 levels. Data were analyzed with the non-parametric Mann-Kendall test and Theil-Sen estimator. Rural sites typically did not experience a weekend-weekday effect. In all urban stations, the mean O3 concentration on the weekend was 12% higher than on weekdays. Between 2005 and 2014, the annual mean of daily O3 concentrations increased at 74% of urban sites worldwide (+ 0.41 ppb year−1) and decreased in the United Kingdom (- 0.18 ppb year−1). Over this time period, emissions of O3 precursors declined significantly. However, a greater decline in nitrogen oxides (NOx) emissions caused an increase in Volatile Organic Compounds (VOCs) to NOx ratios leading to O3 formation. In France, South Korea and the United Kingdom, most urban stations showed a significant upward trend (+ 1.15% per year) for O3 weekend effect. Conversely, in Canada, Germany, Japan, Italy and the United States, the O3 weekend effect showed a significant downward trend (- 0.26% per year). Further or inappropriate control of anthropogenic emissions in Canada, Southern Europe, Japan, South Korea and the United States might result in increased daily O3 levels in urban areas.

Trends in ambient O3 concentrations at twelve sites in the Czech Republic over the past three decades: Close inspection of development

Ambient or ground-level ozone (O3), a key player in atmospheric chemistry, has been studied extensively throughout the world in recent decades due to its harmful effects on human health and the environment. The aim of this study is to examine in detail the time patterns of O3 in the Czech Republic, a Central European country with a long–term history of ambient air pollution. We have examined the interplay between annual trends and within-a-year seasonality in daily O3 concentrations at twelve stations representing different environments, geographical regions and altitudes in the Czech Republic in 1993–2018. We base our analysis on a generalised additive model (GAM) framework as a modern regression approach suitable for addressing non-linear trend shapes in a formalised and unified way. In particular, we use penalised splines. The inconsistent behaviour of the stations prior to 1998, two local maxima around 2003 and 2006 and a steady increase in O3 at all sites from 2014 to the present are the main features of our study. A seasonality O3 pattern with a clear maximum in May–June is similar for all stations. In parallel with the O3 concentration changes over the years, the deformation of seasonality profiles over a long period of time occurs, resulting in a shift of the peak O3 concentrations towards later days in the year. Our statistical modelling offers a detailed view of both long-term trend and seasonality components separately. Additionally, in a model with trend*seasonality interaction, we are able to study the gradual deformation of the seasonality profile over the years.Capsule: Our analysis of daily mean O3 concentrations at twelve Czech sites in 1993–2018 revealed a steady increase in O3 from 2014 and deformation of the seasonality O3 profiles over the year.

The effect of short-term exposure to O3, NO2, and their combined oxidative potential on mortality in Rome

There is large epidemiological evidence on the short-term health effects of O3 and NO2. These gaseous pollutants induce oxidative stress through their oxidative potential. Therefore, the evaluation of their combined oxidative capacity (Ox) has been proposed rather than studying the effect of either gas individually. To study the short-term effects of daily concentrations of O3, NO2, and Ox on mortality in Rome, in 2002–2015, daily deaths from the city mortality registry were analyzed along with O3 and NO2 levels observed in Rome and with estimated Ox and Owt (Ox, weighted by the redox potential of O3 and NO2). A Poisson regression model was used considering trends, and meteorological and population changes. The effects on mortality were estimated at lag 0–1 and 0–5 for 10 μg/m3. O3 and NO2 were associated with mortality, with the highest effects at lag 0–5, 0.81% (0.45–1.17) and 2.72% (2.07–3.37), respectively. Ox had an intermediate effect between the two gases. After adjusting for PM10, Owt had a stronger effect (1.72%; 1.14–2.30) than either gas, 0.86% (0.50–1.22) for O3 and 1.61% (1.15–2.06) for NO2. Both Ox and Owt were associated with cerebrovascular, respiratory and, to a lesser extent, cardiac mortality more than either gas. These results suggest that the use of Ox (or Owt) can provide a better assessment of the combined role of O3 and NO2 on mortality and can avoid the uncertainty of the threshold level for ozone. The brain and lungs seem to be the main targets of O3 and NO2.

Heterogeneous production of Cl2 from particulate chloride: Effects of composition and relative humidity

Reactions initiated by chlorine atoms can enhance the formation of ozone (O3) and secondary organic aerosol (SOA) in the troposphere. Environmental chamber experiments were conducted to quantify heterogeneous Cl2 production from NH4Cl and NaCl particles exposed to O3 and hydroxyl radicals (•OH). Observations are inconsistent with models of Cl2 production resulting solely from surface‐mediated reactions of •OH and suggest that O3 plays a significant role. The production of Cl2 increased with relative humidity and decreased in the presence of SOA or nitric oxides (NOx). Heterogeneous reactive uptake coefficients for the production of Cl2 from O3 on pure NH4Cl ( ) averaged 1.4 ± 1.0 × 10−3. Cl2 production was six times more efficient on NH4Cl aerosol than on NaCl aerosol. Model calculations under atmospheric conditions suggest this heterogeneous Cl2 production could increase peak daily O3 concentrations by over 10%. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3151–3158, 2018

Comparison of spatiotemporal prediction models of daily exposure of individuals to ambient nitrogen dioxide and ozone in Montreal, Canada

BackgroundIn previous studies investigating the short-term health effects of ambient air pollution the exposure metric that is often used is the daily average across monitors, thus assuming that all individuals have the same daily exposure. Studies that incorporate space-time exposures of individuals are essential to further our understanding of the short-term health effects of ambient air pollution. ObjectivesAs part of a longitudinal cohort study of the acute effects of air pollution that incorporated subject-specific information and medical histories of subjects throughout the follow-up, the purpose of this study was to develop and compare different prediction models using data from fixed-site monitors and other monitoring campaigns to estimate daily, spatially-resolved concentrations of ozone (O3) and nitrogen dioxide (NO2) of participants’ residences in Montreal, 1991–2002. MethodsWe used the following methods to predict spatially-resolved daily concentrations of O3 and NO2 for each geographic region in Montreal (defined by three-character postal code areas): (1) assigning concentrations from the nearest monitor; (2) spatial interpolation using inverse-distance weighting; (3) back-extrapolation from a land-use regression model from a dense monitoring survey, and; (4) a combination of a land-use and Bayesian maximum entropy model. We used a variety of indices of agreement to compare estimates of exposure assigned from the different methods, notably scatterplots of pairwise predictions, distribution of differences and computation of the absolute agreement intraclass correlation (ICC). For each pairwise prediction, we also produced maps of the ICCs by these regions indicating the spatial variability in the degree of agreement. ResultsWe found some substantial differences in agreement across pairs of methods in daily mean predicted concentrations of O3 and NO2. On a given day and postal code area the difference in the concentration assigned could be as high as 131ppb for O3 and 108ppb for NO2. For both pollutants, better agreement was found between predictions from the nearest monitor and the inverse-distance weighting interpolation methods, with ICCs of 0.89 (95% confidence interval (CI): 0.89, 0.89) for O3 and 0.81 (95%CI: 0.80, 0.81) for NO2, respectively. For this pair of methods the maximum difference on a given day and postal code area was 36ppb for O3 and 74ppb for NO2. The back-extrapolation method showed a higher degree of disagreement with the nearest monitor approach, inverse-distance weighting interpolation, and the Bayesian maximum entropy model, which were strongly constrained by the sparse monitoring network. The maps showed that the patterns of agreement differed across the postal code areas and the variability depended on the pair of methods compared and the pollutants. For O3, but not NO2, postal areas showing greater disagreement were mostly located near the city centre and along highways, especially in maps involving the back-extrapolation method. ConclusionsIn view of the substantial differences in daily concentrations of O3 and NO2 predicted by the different methods, we suggest that analyses of the health effects from air pollution should make use of multiple exposure assessment methods. Although we cannot make any recommendations as to which is the most valid method, models that make use of higher spatially resolved data, such as from dense exposure surveys or from high spatial resolution satellite data, likely provide the most valid estimates.

Short-term Exposure to Ozone and Mortality in Subjects With and Without Previous Cardiovascular Disease.

Exposure to ground level ozone (O3) is a public health problem associated with a range of risks across population subgroups. Our aim was to investigate the role of previous cardiovascular diseases (CVDs) in mortality related to short-term O3 exposure. Deaths between 1990 and 2010 in Stockholm County were matched with previous hospitalizations in Swedish registries. An urban background monitoring station provided hourly values of air quality data, from which we calculated 8-hour running averages and daily 8-hour maximum. We analyzed associations between daily O3 concentrations and mortality among persons with and without previous CVD hospitalization with a generalized additive model adjusted for time trend, influenza, and weather. We also performed two-pollutant models. There were 302,283 nontrauma-related deaths, out of which 196,916 had previous CVD hospitalization. The mean concentration of daily maximum 8-hour O3 was 62.9 μg/m. An average 10 μg/m increase in the same and preceding day was associated with an increased mortality of 1.72% (95% confidence interval: 0.44%, 3.02%) in those with prior admission for acute myocardial infarction (AMI), which was more than three times higher than for those with no previous AMI (0.50, 95% confidence interval: 0.10%, 0.89%, P value for interaction 0.098). The association between O3 and mortality remained essentially unchanged in two-pollutant models with NO2, NOx, and PM10. Our study indicates that short-term exposure to O3 is associated with increased mortality in those with a previous hospitalization for AMI.

Annual and weekly patterns of ozone and particulate matter in Jeddah, Saudi Arabia

Air pollution has been an increasing concern within the Kingdom of Saudi Arabia and other Middle Eastern countries. In this work the authors present an analysis of daily ozone (O3), nitrogen oxide (NOx), and particulate matter (<10 μm aerodynamic diameter; PM10) concentrations for two years (2010 and 2011) at sites in and around the coastal city of Jeddah, as well as a remote background site for comparison. Monthly and weekly variations, along with their implications and consequences, were also examined. O3 within Jeddah was remarkably low, and exhibited the so-called weekend effect—elevated O3 levels on the weekends, despite reduced emissions of O3 precursors on those days. Weekend O3 increases averaged between 12% and 14% in the city, suggesting that NOx/volatile organic compound (VOC) ratios within cities such as Jeddah may be exceptionally high. Sites upwind or far removed from Jeddah did not display this weekend effect. Based on these results, emission control strategies in and around Jeddah must carefully address NOx/VOC ratios so as to reduce O3 at downwind locations without increasing it within urban locations themselves. PM10 concentrations within Jeddah were elevated compared with North American cites of similar climatology, though comparable to other large cities within the Middle East.Implications:Daily concentrations of O3, PM10, and NOx in and around the city of Jeddah, Saudi Arabia, are analyzed and compared with those of other reference cities. Extremely low O3 levels, along with a significant urban weekend effect (higher weekend O3, despite reduced NOx concentrations), is apparent, along with high levels of PM10 within the city. Urban O3 in Jeddah was found to be lower than that of other comparable cities, but the strong weekend effect suggests that care must be taken to reduce downwind O3 levels without increasing them within the city itself. Further research into the emissions and chemistry contributing to the reduced O3 levels within the city is warranted.

Intraseasonal variability of surface ozone in Santiago, Chile: Modulation by phase of the Madden–Julian Oscillation (MJO)

In Santiago, Chile, summertime surface ozone (O3) concentrations regularly exceed local and international health thresholds due to high antecedent pollutants, frequent clear skies, and warm surface air temperatures. However, few (if any) studies exist that have examined the intraseasonal variability of surface O3 or its modulation by phase of the Madden–Julian Oscillation (MJO). Therefore, the main objectives of this study were to investigate the intraseasonal variability of surface O3 and the meteorological parameters known to affect O3 concentrations during summer months in Santiago, and connect any observed variability to phase of the MJO. Ozone concentrations at seven stations in the Chilean National Air Quality Information System (SINCA), along with upper-air, surface, and reanalysis data, were used to create composites for each phase of the MJO. Results confirm that for the Santiago metropolitan region, both maximum daily O3 concentrations, as well as the diurnal cycle of O3, depend on MJO Phase. Ozone concentrations were highest during Phases 5 and 6 and lowest during Phases 1 and 2. Cloud cover anomalies best agreed with this pattern of O3 variability, with low (high) cloud cover anomalies occurring during days with high (low) ozone. Surface temperature and strength and height of the lower-troposphere temperature inversion had similar, but less pronounced, connections to O3, with slightly warmer surface temperatures and stronger inversions closer to the ground occurring on days with higher O3. Wind velocity was found to vary little between days with low and high ozone.

On Surface O3 Associated with Long-Range Transport in the Yellow Sea Region

Measurements of surface ozone (O3) and nitrogen oxides (NOx) were conducted at Tae-ahn (TAP) and Chongwon (CHN) on the Korean Peninsula, during the Aerosol Characterization Experiment—Asian Pacific region (ACE-Asia) campaign, March–May 2001. The measurements provide ground-based data at a western remote site of south Korea and characterize the long-range transport of O3 over the Yellow Sea region during spring. The mean values of O3 and NO2 concentration at TAP were 42 ppb and 12 ppb, respectively. The average O3 diurnal variation of 17 ppb at TAP indicates that the loss of O3 was not pronounced during the night. The highest NO2 concentrations, with an average diurnal variation of 8 ppb, occurred in the afternoon at 13–15 LST. The day-to-day variation of daily O3 concentrations at TAP is strongly influenced by the movement of synoptic scale weather patterns. In general, the O3 concentration in a southwesterly airflow tended to increase when a moving anticyclone crossed the site, ahead of a cold front. By contrast, north-northwesterly airflows associated with the passage of a cold front bring fresh continental outflow and decrease O3 concentrations.

Comparison of spectrophotometric and radioisotopic methods for the assay of Rubisco in ozone‐treated plants

Radioisotopic and spectrophotometric assays for ribulose‐1,5‐bisphosphate carboxy‐lase/oxygenase (Rubisco) initial and final activities and Rubisco content were compared in plants chronically exposed to ozone (O3) in a greenhouse and the field. In a greenhouse experiment, Glycine max was treated in exposure chambers with either charcoal‐filtered air (CF air) or 100 nl O3 1−1 for 6 h daily during vegetative growth. Samples were collected after 7 days of exposure. In a field experiment, G. max was treated in open‐top chambers with either CF air or nonfiltered air with O3 added at 1.5 times ambient O3 for 12 h daily. Average daily O3 concentrations were 21 and 92 nl T1 in the CF and O3 treatments, respectively. Samples were collected during vegetative and reproductive growth. Both assays generally yielded comparable Rubisco initial and final activities for greenhouse‐grown plants regardless of the O3 treatment. However for field‐grown plants, Rubisco initial and final activities averaged 15 and 23% lower when assayed by the spectrophotometric rather than the radioisotopic method. For Rubisco content estimated by the spectrophotometric method, lower r2 values for the regression of Rubisco activity vs concentratio of carboxyarabinitol‐1,5‐bisphos‐phate were observed in O3 than in CF‐treated plants. Both assays yielded comparable Rubisco contents in the greenhouse and in the field although the variation was larger with the spectrophotometric method in field‐grown plants. Growth conditions, field vs greenhouse, were more critical to the spectrophotometric assay performance than the O3 treatments for measurement of Rubisco activity and content.