Variation in estimated ozone-related health impacts of climate change due to modeling choices and assumptions

Study on O3-NOx-VOCs combined air pollution and ozone health effects in the Hexi Corridor

In order to study the ecological and atmospheric recovery of the Hexi Corridor region, this paper analyzes the migration changes of land use characteristics and utilizes multivariate data and BenMAP-CE software to study the pollution characteristics of ozone and its precursors and the impact on human health in the Hexi Corridor region. The results showed that the increase of cultivated land area in the Hexi Corridor mainly originated from grassland. The MDA8-O3 concentrations met the primary and secondary standards of the Ambient Air Quality Standards on 43% and 99% of the days, respectively. NO2 showed a negative weekend effect with O3, and HCHO was opposite to it. Temperature, barometric pressure, and vegetation were highly correlated with O3-NO2-HCHO. Ozone pollution in the study area caused about 60% of all-cause premature deaths due to cardiovascular diseases. The study suggests that controlling exogenous transport in Wuwei City during the high ozone period (except August) is mainly dominated by the west and northwest, and that synergistic management of VOCs and NOx emissions can reduce O3 pollution and, consequently, reduce the risk to human health.

Improving consistency in estimating future health burdens from environmental risk factors: Case study for ambient air pollution

Future changes in exposure to risk factors should impact mortality rates and population. However, studies commonly use mortality rates and population projections developed exogenously to the health impact assessment model used to quantify future health burdens attributable to environmental risks that are therefore invariant to projected exposure levels. This impacts the robustness of many future health burden estimates for environmental risk factors. This work describes an alternative methodology that more consistently represents the interaction between risk factor exposure, population and mortality rates, using ambient particulate air pollution (PM2.5) as a case study. A demographic model is described that estimates future population based on projected births, mortality and migration. Mortality rates are disaggregated between the fraction due to PM2.5 exposure and other factors for a historic year, and projected independently. Accounting for feedbacks between future risk factor exposure and population and mortality rates can greatly affect estimated future attributable health burdens. The demographic model estimates much larger PM2.5-attributable health burdens with constant 2019 PM2.5 (∼10.8 million deaths in 2050) compared to a model using exogenous population and mortality rate projections (∼7.3 million), largely due to differences in mortality rate projection methods. Demographic model-projected PM2.5-attributable mortality can accumulate substantially over time. For example, ∼71 million more people are estimated to be alive in 2050 when WHO guidelines (5 µg m-3) are achieved compared to constant 2019 PM2.5 concentrations. Accounting for feedbacks is more important in applications with relatively high future PM2.5 concentrations, and relatively large changes in non-PM2.5 mortality rates.

Observed sensitivities of PM2.5 and O3 extremes to meteorological conditions in China and implications for the future

Frequent extreme air pollution episodes in China accompanied with high concentrations of particulate matters (PM2.5) and ozone (O3) are partly supported by meteorological conditions. However, the relationships between meteorological variables and pollution extremes can be poorly estimated solely based on mean pollutant level. In this study, we use quantile regression to investigate meteorological sensitivities of PM2.5 and O3 extremes, benefiting from nationwide observations of air pollutants over 2013-2019 in China. Results show that surface winds and humidity are identified as key drivers for high PM2.5 events during both summer and winter, with greater sensitivities at higher percentiles. Higher humidity favors the hydroscopic growth of particles during winter, but it tends to decrease PM2.5 through wet scavenging during summer. Surface temperature play dominant role in summer O3 extremes, especially in VOC-limited regime, followed by surface winds and radiation. Sensitivities of O3 to meteorological conditions are relatively unchanging across percentiles. Under the fossil-fueled development pathway (SSP5-8.5) scenario, meteorological conditions are projected to favor winter PM2.5 extremes in North China Plain (NCP), Yangtze River Delta (YRD) and Sichuan Basin (SCB), mainly due to enhanced surface specific humidity. Summer O3 extremes are likely to occur more frequently in the NCP and YRD, associated with warmer temperature and stronger solar radiation. Besides, meteorological conditions over a relatively longer period play a more important role in the formation of pollution extremes. These results improve our understanding of the relationships between extreme PM2.5 and O3 pollution and meteorology, and can be used as a valuable reference of model predicted air pollution extremes.

Spatiotemporal variation of ozone pollution and health effects in China

With the rapid urbanization and industrialization in China, ozone pollution has become increasingly serious and poses a greater threat to human health. In this study, the spatiotemporal distribution of ozone pollution in China's cities and urban agglomerations from 2015 to 2019 was analyzed. The health effects and health economic costs of ozone pollution in China were estimated by applying the environmental Benefits Mapping and Analysis Program-Community Edition (BenMAP-CE) model. The results are as follows: (1) ozone pollution was more serious in Chinese urban agglomerations from 2015 to 2019; (2) the hot spots of ozone concentration mainly distributed in the North China Plain, expanding from north to south; the cold spots decreased year by year and were located in the northeast, northwest, and southwest of China, shifting from northwest to southwest; (3) the seasonal average of ozone concentration in China was the highest in summer, followed by spring and autumn, and the lowest in winter; (4) the number of all-cause premature deaths of ozone pollution in China increased slowly from 2015 to 2019, and the average of urban agglomerations was significantly higher than cities, with similar spatial distribution characteristics as ozone concentration; (5) the health economic costs of ozone pollution from 2015 to 2019 slowly expanded to surrounding cities with Beijing, Shanghai, Xi'an, and Chongqing as the centers of high values, while the low value areas decreased year by year and were mainly concentrated in southwest and northeast China. The health economic costs of ozone pollution at urban agglomerations scale were higher in the eastern coastal regions and lower in the northwest inland regions. Thus, this study presents policy recommendations to provide decision-making reference for realizing the inter-regional prevention and control of ozone pollution.

Regional temperature-ozone relationships across the U.S. under multiple climate and emissions scenarios

The potential effects of 21st century climate change on ozone (O₃) concentrations in the United States are investigated using global climate simulations to drive higher-resolution regional meteorological and chemical transport models. Community Earth System Model (CESM) and Coupled Model version 3 (CM3) simulations of the Representative Concentration Pathway 8.5 scenario are dynamically downscaled using the Weather Research and Forecasting model, and the resulting meteorological fields are used to drive the Community Multiscale Air Quality model. Air quality is modeled for five 11-year periods using both a 2011 air pollutant emission inventory and a future projection accounting for full implementation of promulgated regulatory controls. Across the U.S., CESM projects daily maximum temperatures during summer to increase 1-4°C by 2050 and 2-7°C by 2095, while CM3 projects warming of 2-7°C by 2050 and 4-11°C by 2095. The meteorological changes have geographically varying impacts on O₃ concentrations. Using the 2011 emissions dataset, O₃ increases 1-5 ppb in the central Great Plains and Midwest by 2050 and more than 10 ppb by 2095, but it remains unchanged or even decreases in the Gulf Coast, Maine, and parts of the Southwest. Using the projected emissions, modeled increases are attenuated while decreases are amplified, indicating that planned air pollution control measures ameliorate the ozone climate penalty. The relationships between changes in maximum temperature and changes in O₃ concentrations are examined spatially and quantified to explore the potential for developing an efficient approach for estimating air quality impacts of other future climate scenarios.Implications: The effects of climate change on ozone air quality in the United States are investigated using two global climate model simulations of a high warming scenario for five decadal periods in the 21st century. Warming summer temperatures simulated under both models lead to higher ozone concentrations in some regions, with the magnitude of the change increasing with temperature over the century. The magnitude and spatial extent of the increases are attenuated under a future emissions projection that accounts for regulatory controls. Regional linear regression relationships are developed as a first step toward development of a reduced form model for efficient estimation of the health impacts attributable to changes in air quality resulting from a climate change scenario.

Factors That Influence Climate Change-Related Mortality in the United States: An Integrative Review

Global atmospheric warming leads to climate change that results in a cascade of events affecting human mortality directly and indirectly. The factors that influence climate change-related mortality within the peer-reviewed literature were examined using Whittemore and Knafl’s framework for an integrative review. Ninety-eight articles were included in the review from three databases—PubMed, Web of Science, and Scopus—with literature filtered by date, country, and keywords. Articles included in the review address human mortality related to climate change. The review yielded two broad themes in the literature that addressed the factors that influence climate change-related mortality. The broad themes are environmental changes, and social and demographic factors. The meteorological impacts of climate change yield a complex cascade of environmental and weather events that affect ambient temperatures, air quality, drought, wildfires, precipitation, and vector-, food-, and water-borne pathogens. The identified social and demographic factors were related to the social determinants of health. The environmental changes from climate change amplify the existing health determinants that influence mortality within the United States. Mortality data, national weather and natural disaster data, electronic medical records, and health care provider use of International Classification of Disease (ICD) 10 codes must be linked to identify climate change events to capture the full extent of climate change upon population health.

Analysis of Ozone Pollution Characteristics and Influencing Factors in Northeast Economic Cooperation Region, China

The increase in tropospheric ozone (O3) concentration has become one of the factors restricting urban development. This paper selected the important economic cooperation areas in Northeast China as the research object and collected the hourly monitoring data of pollutants and meteorological data in 11 cities from 1 January 2015 to 31 December 2019. The temporal and spatial variation trend of O3 concentration and the effects of meteorological factors and other pollutants, including CO (carbon monoxide), SO2 (sulfur dioxide), NO2 (nitrogen dioxide), and PM2.5 and PM10 (PM particles with aerodynamic diameters less than 2.5 μm and 10 μm) on ozone concentration were analyzed. At the same time, the variation period of O3 concentration was further analyzed by Morlet wavelet analysis. The results showed that the O3 pollution in the study area had a significant spatial correlation. The spatial distribution showed that the O3 concentration was relatively high in the south and low in the northeast. Seasonally, the O3 concentration was the highest in spring, followed by summer, and the lowest in winter. The diurnal variation of O3 concentration presented a “single peak” pattern. O3 concentration had a significant positive correlation with temperature, sunshine duration, and wind speed and a significant anticorrelation with CO, NO2, SO2, and PM2.5 concentration. Under the time scale of a = 9, 23, O3 had significant periodic fluctuation, which was similar to those of wind speed and temperature.

The objects, agents, and tools of Chinese co-governance on air pollution: a review

The social and economic development in China has not only made a series of great achievements but also suffered from increasingly serious air pollution. It is of great significance to explore the co-governance mechanism of air pollution in order to promote high-quality development and the construction of "beautiful China." Based on an analysis using the concept of co-governance, this paper reviews the research from four aspects: the multi-object relationships, multi-agent framework, and the co-governance technical tools and policy tools. The results show that the current research has many deficiencies: a lack of research on the size, direction, and driving factors of the correlation of objects; the construction of the multi-agent framework focused only on concepts and lacking the design of core mechanisms; evaluating only the effect of tools but ignoring the optimal combination of governance tools, and paying attention only to the traditional pollutants and disregarding the latest air pollution. Accordingly, this paper finds that the research should be expanded from four aspects, which include taking into account the co-governance of new air pollution, clarifying the relationship between the various types of air pollutants and the driving factors, building a multi-disciplinary research framework for co-governance, and optimizing the combination of governance policies and technical tools in order to realize high-quality development of China.

Study on the variation characteristics of tropospheric ozone in Northeast China

The goal of this study was to understand the current status of ozone pollution in Northeast China and to distinguish the main influencing factors of ozone, in order to provide a scientific basis for the future prevention and control of ozone in this region. In this study, the Ozone Monitoring Instrument data product was used as the source data, and the pixel space analysis method and grey correlation analysis method were utilized to examine the tropospheric ozone column concentration in Northeast China from 2010 to 2018. The results revealed that the ozone column concentration in Northeast China was relatively high compared to other parts of the country. The high-value areas were primarily distributed in Tahe County, Heihe City, Hegang City, and Qiqihar City. The temporal variation of the ozone column concentration in Northeast China exhibited an obvious periodicity of 9 years, and its interannual change displayed a downward trend. The maximum value occurred in 2010, and the minimum value was found in 2016. The seasonal changes manifested a relative trend of spring > winter > summer > autumn, which was contrary to the research results for other parts of China, which showed a summer maximum. Among the influencing factors, atmospheric pressure, relative humidity, sunshine hours, GDP, and primary and secondary industries exhibited the closest relationships with ozone. The high concentration of ozone in Northeast China was determined to result from the superimposed effects of long-distance atmospheric transport and anthropogenic emissions.

Associations Between Simulated Future Changes in Climate, Air Quality, and Human Health

IMPORTANCE

Future changes in climate are likely to adversely affect human health by affecting concentrations of particulate matter sized less than 2.5 μm (PM2.5) and ozone (O3) in many areas. However, the degree to which these outcomes may be mitigated by reducing air pollutant emissions is not well understood.

OBJECTIVE

To model the associations between future changes in climate, air quality, and human health for 2 climate models and under 2 air pollutant emission scenarios.

DESIGN, SETTING, AND PARTICIPANTS

This modeling study simulated meteorological conditions over the coterminous continental US during a 1995 to 2005 baseline and over the 21st century (2025-2100) by dynamically downscaling representations of a high warming scenario from the Community Earth System Model (CESM) and the Coupled Model version 3 (CM3) global climate models. Using a chemical transport model, PM2.5 and O3 concentrations were simulated under a 2011 air pollutant emission data set and a 2040 projection. The changes in PM2.5 and O3-attributable deaths associated with climate change among the US census-projected population were estimated for 2030, 2050, 2075, and 2095 for each of 2 emission inventories and climate models. Data were analyzed from June 2018 to June 2020.

MAIN OUTCOMES AND MEASURES

The main outcomes were simulated change in summer season means of the maximum daily 8-hour mean O3, annual mean PM2.5, population-weighted exposure, and the number of avoided or incurred deaths associated with these pollutants. Results are reported for 2030, 2050, 2075, and 2095, compared with 2000, for 2 climate models and 2 air pollutant emissions data sets.

RESULTS

The projected increased maximum daily temperatures through 2095 were up to 7.6 °C for the CESM model and 11.8 °C for the CM3 model. Under each climate model scenario by 2095, compared with 2000, an estimated additional 21 000 (95% CI, 14 000-28 000) PM2.5-attributable deaths and 4100 (95% CI, 2200-6000) O3-attributable deaths were projected to occur. These projections decreased to an estimated 15 000 (95% CI, 10 000-20 000) PM2.5-attributable deaths and 640 (95% CI, 340-940) O3-attributable deaths when simulated using a future emission inventory that accounted for reduced anthropogenic emissions.

CONCLUSIONS AND RELEVANCE

These findings suggest that reducing future air pollutant emissions could also reduce the climate-driven increase in deaths associated with air pollution by hundreds to thousands.

Ozone-related asthma emergency department visits in the US in a warming climate

Ozone exposure is associated with higher risk of asthma-related emergency department visits. The meteorological conditions that govern ozone concentration are projected to be more favorable to ozone formation over much of the United States due to continued climate change, even as emissions of anthropogenic ozone precursors are expected to decrease by 2050. Our goal is to quantify the health benefits of a climate change mitigation scenario versus a "business-as-usual" scenario, defined by the United Nations Intergovernmental Panel on Climate Change Representative Concentration Pathways (RCPs) 4.5 and 8.5, respectively, using the health impact analytical program Benefits Mapping and Analysis Program - Community Edition (BenMAP - CE) to project the number of asthma ED visits in 2045-2055. We project an annual average of 3100 averted ozone-related asthma ED visits during the 2045-2055 period under RCP4.5 versus RCP8.5, with all other factors held constant, which translates to USD $1.7 million in averted costs annually. We identify counties with tens to hundreds of avoided ozone-related asthma ED visits under RCP4.5 versus RCP8.5. Overall, we project a heterogeneous distribution of ozone-related asthma ED visits at different spatial resolutions, specifically national, regional, and county levels, and a substantial net health and economic benefit of climate change mitigation.

Health impacts and cost-benefit analyses of surface O3 and PM2.5 over the U.S. under future climate and emission scenarios

Health impacts of surface ozone (O₃) and fine particulate matter (PM_2.5) are of major concern worldwide. In this work, the Environmental Benefits Mapping and Analysis Program tool is applied to estimate the health and economic impacts of projected changes in O₃ and PM_2.5 in the U.S. in future (2046-2055) decade relative to current (2001-2010) decade under the Representative Concentration Pathway (RCP) 4.5 and 8.5 climate scenarios. Future annual-mean O₃ reductions under RCP 4.5 prevent ~1,800 all-cause mortality, 761 respiratory hospital admissions (HA), and ~1.2 million school loss days annually, and result in economic benefits of ~16 billion, 29 million, and 132 million U.S. dollars (USD), respectively. By contrast, the projected future annual-mean O₃ increases under RCP8.5 cause ~2,400 mortality, 941 respiratory HA, and ~1.6 million school loss days annually and result in economic disbenefits of ~21 billion, 36 million, and 175 million USD, respectively. Health benefits of reduced O₃ double under RCP4.5 and health dis-benefits of increased O₃ increase by 1.5 times under RCP8.5 in future with 2050 population and baseline incidence rate. Because of the reduction in projected future PM_2.5 over CONUS under both scenarios, the annual avoided all-cause deaths, cardiovascular HA, respiratory HA, and work loss days are ~63,000 and ~83,000, ~5,300 and ~7,000, ~12,000 and ~15,000, and ~7.8 million and ~10 million, respectively, leading to economic benefits of ~560 and ~740 billion, ~240 and ~320 million, ~450 and ~590 million, and ~1,400 and ~1,900 million USD for RCP4.5 and 8.5, respectively. Health benefits of reduced PM_2.5 for future almost double under both scenarios with the largest benefits in urban areas. RCP8.5 projects larger health and economic benefits due to a greater reduction in PM_2.5 but with a warmer atmosphere and higher O₃ pollution than RCP4.5. RCP4.5 leads to multiple-benefit goals including reduced O₃ and PM_2.5, reduced mortality and morbidity, and saved costs. Greater reduction in future PM_2.5 under RCP4.5 should be considered to achieve larger multi-benefits.

A Framework for Climate Change-Related Research to Inform Environmental Protection

A critical charge for science to inform environmental protection is to characterize the risks associated with climate change, to support development of appropriate responses. The nature of climate change, however, presents significant challenges that must be overcome to do so, including the need for integration and synthesis across the many disciplines that contain knowledge relevant for achieving environmental protection goals. This paper describes an interdisciplinary research framework organized around three "Science Challenges" that directly respond to the needs of environmental protection organizations. Broadly, these Science Challenges refer to the research needed to: inform actions to enhance resilience across a broad range of environmental and social stresses to environmental management endpoints; actions to limit GHG emissions and slow the underlying rate of climate change; and the transition to sustainability across the full spectrum of climate change impacts and solutions; all as situated within an overarching risk management perspective. These Challenges span all media and systems critical to effective environmental protection, highlighting the cross-cutting nature of climate change and the need to address its impacts across systems and places. While this framework uses EPA's programs as an illustrative example, the research directions articulated herein are broadly applicable across the spectrum of environmental protection organizations. Going forward, we recommend that climate-related research to inform environmental protection efforts should accelerate its evolution toward research that is inherently cross-media and cross-scale; explicitly considers the social dimensions of change; and focuses on designing solutions to the specific risks climate change poses to the environment and society.

Exploration of the heterogeneous effect of climate change on ozone concentration in an urban environment

Ozone is a significant causative agent of mortality in cities. Urban environments are expressly vulnerable to global warming because of the extensive emission of air pollutants with urban heat island effect enhancing much rapidly the ozone concentration than in the less urbanized regions. This effect previously was not studied in local scale. It was hypothesized that climate change will cause heterogenic increase of ozone concentration in the different parts of the cities. To study this effect, the near-surface ozone concentration of 10 points of a Hungarian city was measured and modeled. At first step, the local correlations between solar radiation, air temperature, relative humidity and the near surface ozone concentrations at 3 m height were determined, specifying the local ozone-producing conditions. Then, based on the scenario of the Intergovernmental Panel on Climate Change 5th assessment report, the future seasonal near-surface ozone concentrations were modeled. Based on the model, it was determined that climate change will result in a heterogenic increase of near-surface ozone concentration.

Aging Exacerbates Neuroinflammatory Outcomes Induced by Acute Ozone Exposure

The role of environmental stressors, particularly exposure to air pollution, in the development of neurodegenerative disease remains underappreciated. We examined the neurological effects of acute ozone (O3) exposure in aged mice, where increased blood-brain barrier (BBB) permeability may confer vulnerability to neuroinflammatory outcomes. C57BL/6 male mice, aged 8-10 weeks or 12-18 months were exposed to either filtered air or 1.0 ppm O3 for 4 h; animals received a single IP injection of sodium fluorescein (FSCN) 20 h postexposure. One-hour post-FSCN injection, animals were transcardially perfused for immunohistochemical analysis of BBB permeability. β-amyloid protein expression was assessed via ELISA. Flow cytometric characterization of infiltrating immune cells, including neutrophils, macrophages, and microglia populations was performed 20 h post-O3 exposure. Flow cytometry analysis of brains revealed increased microglia "activation" and presentation of CD11b, F4/80, and MHCII in aged animals relative to younger ones; these age-induced differences were potentiated by acute O3 exposure. Cortical and limbic regions in aged brains had increased reactive microgliosis and β-amyloid protein expression after O3 insult. The aged cerebellum was particularly vulnerable to acute O3 exposure with increased populations of infiltrating neutrophils, peripheral macrophages/monocytes, and Ly6C+ inflammatory monocytes after insult, which were not significantly increased in the young cerebellum. O3 exposure increased the penetration of FSCN beyond the BBB, the infiltration of peripheral immune cells, and reactive gliosis of microglia. Thus, the aged BBB is vulnerable to insult and becomes highly penetrable in response to O3 exposure, leading to greater neuroinflammatory outcomes.

Effect of Health-Related Uncertainty and Natural Variability on Health Impacts and Cobenefits of Climate Policy

Climate policy can mitigate health risks attributed to intensifying air pollution under climate change. However, few studies quantify risks of illness and death, examine their contribution to climate policy benefits, or assess their robustness in light of natural climate variability. We employ an integrated modeling framework of the economy, climate, air quality, and human health to quantify the effect of natural variability on U.S. air pollution impacts under future climate and two global policies (2 and 2.5 °C stabilization scenarios) using 150 year ensemble simulations for each scenario in 2050 and 2100. Climate change yields annual premature deaths related to fine particulate matter and ozone (95CI: 25 000-120 000), heart attacks (900-9400), and lost work days (3.6M-4.9M) in 2100. It raises air pollution health risks by 20%, while policies avert these outcomes by 40-50% in 2050 and 70-88% in 2100. Natural variability introduces "climate noise", yielding some annual estimates with negative cobenefits, and others that reach 100% of annual policy costs. This "noise" is three times the magnitude of uncertainty (95CI) in health and economic responses in 2050. Averaging five annual simulations reduces this factor to two, which is still substantially larger than health-related uncertainty. This study quantifies the potential for inaccuracy in climate impacts projected using too few annual simulations.

Sensitivity of projected PM2.5- and O3-related health impacts to model inputs: A case study in mainland China

In China, fine particulate matter (PM_2.5) and ground-level ozone (O₃) are anticipated to continuously affect large populations in the coming decades. Simulations of the levels of these pollutants largely depend on emissions inputs, which are highly uncertain both in magnitude and spatial distribution. Our goal was to explore sensitivities of projected changes in PM_2.5- and O₃-related short-term health impacts in mainland China to emissions and other model inputs. We simulated winter PM_2.5 and summer O₃ concentrations using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) for both 2008 and 2050. We used three emission inventories in 2008 and four emissions scenarios in 2050. The resulting air pollutant concentrations were combined with eight population projections and three concentration-response functions (CRFs) to estimate future PM_2.5- and O₃-related health impacts including total, cardiovascular, and respiratory mortalities in mainland China. Multivariate analysis of variance was used to apportion the uncertainty due to different model parameters. Combinations of different parameters produced a wide range of national PM_2.5- and O₃-related mortalities. CRFs and present emissions each contribute 38%-56% and 20%-28% of the total sum of squares for PM_2.5-related mortalities. Future emissions are the largest source of uncertainty in O₃-related mortality estimates, contributing 24%-48% of total sum of squares. Our results suggest that conducting more epidemiological studies and constraining the present day emissions are essential for projecting future air pollutant-related health impacts in mainland China.

Importance of Cross-Sector Interactions When Projecting Forest Carbon across Alternative Socioeconomic Futures

In recent decades, the carbon sink provided by the U.S. forest sector has offset a sizable portion of domestic greenhouse gas (GHG) emissions. In the future, the magnitude of this sink has important implications not only for projected U.S. net GHG emissions under a reference case but also for the cost of achieving a given mitigation target. The larger the contribution of the forest sector towards reducing net GHG emissions, the less mitigation is needed from other sectors. Conversely, if the forest sector begins to contribute a smaller sink, or even becomes a net source, mitigation requirements from other sectors may need to become more stringent and costlier to achieve economy wide emissions targets. There is acknowledged uncertainty in estimates of the carbon sink provided by the U.S. forest sector, attributable to large ranges in the projections of, among other things, future economic conditions, population growth, policy implementation, and technological advancement. We examined these drivers in the context of an economic model of the agricultural and forestry sectors, to demonstrate the importance of cross-sector interactions on projections of emissions and carbon sequestration. Using this model, we compared detailed scenarios that differ in their assumptions of demand for agriculture and forestry products, trade, rates of (sub)urbanization, and limits on timber harvest on protected lands. We found that a scenario assuming higher demand and more trade for forest products resulted in increased forest growth and larger net GHG sequestration, while a scenario featuring higher agricultural demand, ceteris paribus led to forest land conversion and increased anthropogenic emissions. Importantly, when high demand scenarios are implemented conjunctively, agricultural sector emissions under a high income-growth world with increased livestock-product demand are fully displaced by substantial GHG sequestration from the forest sector with increased forest product demand. This finding highlights the potential limitations of single-sector modeling approaches that ignore important interaction effects between sectors.

The Exposome and Asthma

This article on exposome and asthma focuses on the interaction of patients and their environments in various parts of their growth, development, and stages of life. Indoor and outdoor environments play a role in pathogenesis via levels and duration of exposure, with genetic susceptibility as a crucial factor that alters the initiation and trajectory of common conditions such as asthma. Knowledge of environmental exposures globally and changes that are occurring is necessary to function effectively as medical professionals and health advocates.

Current and Future Disease Burden From Ambient Ozone Exposure in India

Long-term ambient ozone (O₃) exposure is a risk factor for human health. We estimate the source-specific disease burden associated with long-term O₃ exposure in India at high spatial resolution using updated risk functions from the American Cancer Society Cancer Prevention Study II. We estimate 374,000 (95UI: 140,000-554,000) annual premature mortalities using the updated risk function in India in 2015, 200% larger than estimates using the earlier American Cancer Society Cancer Prevention Study II risk function. We find that land transport emissions dominate the source contribution to this disease burden (35%), followed by emissions from power generation (23%). With no change in emissions by 2050, we estimate 1,126,000 (95UI: 421,000-1,667,000) annual premature mortalities, an increase of 200% relative to 2015 due to population aging and growth increasing the number of people susceptible to air pollution. We find that the International Energy Agency New Policy Scenario provides small changes (+1%) to this increasing disease burden from the demographic transition. Under the International Energy Agency Clean Air Scenario we estimate 791,000 (95UI: 202,000-1,336,000) annual premature mortalities in 2050, avoiding 335,000 annual premature mortalities (45% of the increase) compared to the scenario of no emission change. Our study highlights that critical public health benefits are possible with stringent emission reductions, despite population growth and aging increasing the attributable disease burden from O₃ exposure even under such strong emission reductions. The disease burden attributable to ambient fine particulate matter exposure dominates that from ambient O₃ exposure in the present day, while in the future, they may be similar in magnitude.

Heat-Related Health Impacts under Scenarios of Climate and Population Change

Recent assessments have found that a warming climate, with associated increases in extreme heat events, could profoundly affect human health. This paper describes a new modeling and analysis framework, built around the Benefits Mapping and Analysis Program-Community Edition (BenMAP), for estimating heat-related mortality as a function of changes in key factors that determine the health impacts of extreme heat. This new framework has the flexibility to integrate these factors within health risk assessments, and to sample across the uncertainties in them, to provide a more comprehensive picture of total health risk from climate-driven increases in extreme heat. We illustrate the framework's potential with an updated set of projected heat-related mortality estimates for the United States. These projections combine downscaled Coupled Modeling Intercomparison Project 5 (CMIP5) climate model simulations for Representative Concentration Pathway (RCP)4.5 and RCP8.5, using the new Locating and Selecting Scenarios Online (LASSO) tool to select the most relevant downscaled climate realizations for the study, with new population projections from EPA's Integrated Climate and Land Use Scenarios (ICLUS) project. Results suggest that future changes in climate could cause approximately from 3000 to more than 16,000 heat-related deaths nationally on an annual basis. This work demonstrates that uncertainties associated with both future population and future climate strongly influence projected heat-related mortality. This framework can be used to systematically evaluate the sensitivity of projected future heat-related mortality to the key driving factors and major sources of methodological uncertainty inherent in such calculations, improving the scientific foundations of risk-based assessments of climate change and human health.

Future ozone-related acute excess mortality under climate and population change scenarios in China: A modeling study

BACKGROUND

Climate change is likely to further worsen ozone pollution in already heavily polluted areas, leading to increased ozone-related health burdens. However, little evidence exists in China, the world's largest greenhouse gas emitter and most populated country. As China is embracing an aging population with changing population size and falling age-standardized mortality rates, the potential impact of population change on ozone-related health burdens is unclear. Moreover, little is known about the seasonal variation of ozone-related health burdens under climate change. We aimed to assess near-term (mid-21st century) future annual and seasonal excess mortality from short-term exposure to ambient ozone in 104 Chinese cities under 2 climate and emission change scenarios and 6 population change scenarios.

METHODS AND FINDINGS

We collected historical ambient ozone observations, population change projections, and baseline mortality rates in 104 cities across China during April 27, 2013, to October 31, 2015 (2013-2015), which included approximately 13% of the total population of mainland China. Using historical ozone monitoring data, we performed bias correction and spatially downscaled future ozone projections at a coarse spatial resolution (2.0° × 2.5°) for the period April 27, 2053, to October 31, 2055 (2053-2055), from a global chemistry-climate model to a fine spatial resolution (0.25° × 0.25°) under 2 Intergovernmental Panel on Climate Change Representative Concentration Pathways (RCPs): RCP4.5, a moderate global warming and emission scenario where global warming is between 1.5°C and 2.0°C, and RCP8.5, a high global warming and emission scenario where global warming exceeds 2.0°C. We then estimated the future annual and seasonal ozone-related acute excess mortality attributable to both climate and population changes using cause-specific, age-group-specific, and season-specific concentration-response functions (CRFs). We used Monte Carlo simulations to obtain empirical confidence intervals (eCIs), quantifying the uncertainty in CRFs and the variability across ensemble members (i.e., 3 predictions of future climate and air quality from slightly different starting conditions) of the global model. Estimates of future changes in annual ozone-related mortality are sensitive to the choice of global warming and emission scenario, decreasing under RCP4.5 (-24.0%) due to declining ozone precursor emissions but increasing under RCP8.5 (10.7%) due to warming climate in 2053-2055 relative to 2013-2015. Higher ambient ozone occurs under the high global warming and emission scenario (RCP8.5), leading to an excess 1,476 (95% eCI: 898 to 2,977) non-accidental deaths per year in 2053-2055 relative to 2013-2015. Future ozone-related acute excess mortality from cardiovascular diseases was 5-8 times greater than that from respiratory diseases. Ozone concentrations increase by 15.1 parts per billion (10-9) in colder months (November to April), contributing to a net yearly increase of 22.3% (95% eCI: 7.7% to 35.4%) in ozone-related mortality under RCP8.5. An aging population, with the proportion of the population aged 65 years and above increased from 8% in 2010 to 24%-33% in 2050, will substantially amplify future ozone-related mortality, leading to a net increase of 23,838 to 78,560 deaths (110% to 363%). Our analysis was mainly limited by using a single global chemistry-climate model and the statistical downscaling approach to project ozone changes under climate change.

CONCLUSIONS

Our analysis shows increased future ozone-related acute excess mortality under the high global warming and emission scenario RCP8.5 for an aging population in China. Comparison with the lower global warming and emission scenario RCP4.5 suggests that climate change mitigation measures are needed to prevent a rising health burden from exposure to ambient ozone pollution in China.

The Interplay of Climate Change and Air Pollution on Health

PURPOSE OF REVIEW

Air pollution significantly affects health, causing up to 7 million premature deaths annually with an even larger number of hospitalizations and days of sick leave. Climate change could alter the dispersion of primary pollutants, particularly particulate matter, and intensify the formation of secondary pollutants, such as near-surface ozone. The purpose of the review is to evaluate the recent evidence on the impacts of climate change on air pollution and air pollution-related health impacts and identify knowledge gaps for future research.

RECENT FINDINGS

Several studies modelled future ozone and particulate matter concentrations and calculated the resulting health impacts under different climate scenarios. Due to climate change, ozone- and fine particle-related mortalities are expected to increase in most studies; however, results differ by region, assumed climate change scenario and other factors such as population and background emissions. This review explores the relationships between climate change, air pollution and air pollution-related health impacts. The results highly depend on the climate change scenario used and on projections of future air pollution emissions, with relatively high uncertainty. Studies primarily focused on mortality; projections on the effects on morbidity are needed.

The impact of climate change and emissions control on future ozone levels: Implications for human health

Overwhelming evidence has shown that, from the Industrial Revolution to the present, human activities influence ground-level ozone (O3) concentrations. Past studies demonstrate links between O3 exposure and health. However, knowledge gaps remain in our understanding concerning the impacts of climate change mitigation policies on O3 concentrations and health. Using a hybrid downscaling approach, we evaluated the separate impact of climate change and emission control policies on O3 levels and associated excess mortality in the US in the 2050s under two Representative Concentration Pathways (RCPs). We show that, by the 2050s, under RCP4.5, increased O3 levels due to combined climate change and emission control policies, could contribute to an increase of approximately 50 premature deaths annually nationwide in the US. The biggest impact, however, is seen under RCP8.5, where rises in O3 concentrations are expected to result in over 2,200 additional premature deaths annually. The largest increases in O3 are seen in RCP8.5 in the Northeast, the Southeast, the Central, and the West regions of the US. Additionally, when O3 increases are examined by climate change and emissions contributions separately, the benefits of emissions mitigation efforts may significantly outweigh the effects of climate change mitigation policies on O3-related mortality.

Co-benefits of global, domestic, and sectoral greenhouse gas mitigation for US air quality and human health in 2050

Reductions in greenhouse gas (GHG) emissions can bring ancillary benefits of improved air quality and reduced premature mortality, in addition to slowing climate change. Here we study the co-benefits of global and domestic GHG mitigation on US air quality and human health in 2050 at fine resolution using dynamical downscaling of meteorology and air quality from global simulations to the continental US, and quantify for the first time the co-benefits from foreign GHG mitigation. Relative to the reference scenario from which RCP4.5 was created, global GHG reductions in RCP4.5 avoid 16000 PM_2.5-related all-cause deaths yr^-1 (90% confidence interval, 11700-20300), and 8000 (3600-12400) O₃-related respiratory deaths yr^-1 in the US in 2050. Foreign GHG mitigation avoids 15% and 62% of PM_2.5- and O₃-related total avoided deaths, highlighting the importance of foreign mitigation for US health. GHG mitigation in the US residential sector brings the largest co-benefits for PM_2.5-related deaths (21% of total domestic co-benefits), and industry for O₃ (17%). Monetized benefits for avoided deaths from ozone and PM_2.5 are $137 ($87-187) per ton CO₂ at high valuation and $45 ($29-62) at low valuation, of which 31% are from foreign GHG reductions. These benefits likely exceed the marginal cost of GHG reductions in 2050. The US gains significantly greater air quality and health co-benefits when its GHG emission reductions are concurrent with reductions in other nations. Similarly, previous studies estimating co-benefits locally or regionally may greatly underestimate the full co-benefits of coordinated global actions.

Characterizing the impact of projected changes in climate and air quality on human exposures to ozone

The impact of climate change on human and environmental health is of critical concern. Population exposures to air pollutants both indoors and outdoors are influenced by a wide range of air quality, meteorological, behavioral, and housing-related factors, many of which are also impacted by climate change. An integrated methodology for modeling changes in human exposures to tropospheric ozone (O₃) owing to potential future changes in climate and demographics was implemented by linking existing modeling tools for climate, weather, air quality, population distribution, and human exposure. Human exposure results from the Air Pollutants Exposure Model (APEX) for 12 US cities show differences in daily maximum 8-h (DM8H) exposure patterns and levels by sex, age, and city for all scenarios. When climate is held constant and population demographics are varied, minimal difference in O₃ exposures is predicted even with the most extreme demographic change scenario. In contrast, when population is held constant, we see evidence of substantial changes in O₃ exposure for the most extreme change in climate. Similarly, we see increases in the percentage of the population in each city with at least one O₃ exposure exceedance above 60 p.p.b and 70 p.p.b thresholds for future changes in climate. For these climate and population scenarios, the impact of projected changes in climate and air quality on human exposure to O₃ are much larger than the impacts of changing demographics. These results indicate the potential for future changes in O₃ exposure as a result of changes in climate that could impact human health.

Climate change impacts on projections of excess mortality at 2030 using spatially varying ozone-temperature risk surfaces

We project the change in ozone-related mortality burden attributable to changes in climate between a historical (1995-2005) and near-future (2025-2035) time period while incorporating a non-linear and synergistic effect of ozone and temperature on mortality. We simulate air quality from climate projections varying only biogenic emissions and holding anthropogenic emissions constant, thus attributing changes in ozone only to changes in climate and independent of changes in air pollutant emissions. We estimate non-linear, spatially varying, ozone-temperature risk surfaces for 94 US urban areas using observed data. Using the risk surfaces and climate projections we estimate daily mortality attributable to ozone exceeding 40 p.p.b. (moderate level) and 75 p.p.b. (US ozone NAAQS) for each time period. The average increases in city-specific median April-October ozone and temperature between time periods are 1.02 p.p.b. and 1.94 °F; however, the results varied by region. Increases in ozone because of climate change result in an increase in ozone mortality burden. Mortality attributed to ozone exceeding 40 p.p.b. increases by 7.7% (1.6-14.2%). Mortality attributed to ozone exceeding 75 p.p.b. increases by 14.2% (1.6 28.9%). The absolute increase in excess ozone mortality is larger for changes in moderate ozone levels, reflecting the larger number of days with moderate ozone levels.

Projecting ozone-related mortality in East China

BACKGROUND

The concentrations of ozone (O3) in China are increasing, especially in East China, but its future trends and potential health impacts remain to be explored.

OBJECTIVES

The objective was to assess future trends in O3 concentrations and related premature death in East China between 2005 and 2030.

METHODS

First, a global chemical transport model (MIROC-ESM-CHEM) and regional chemical transport modelling system (including the Weather Research and Forecasting model and the Community Multiscale Air Quality model) were combined to estimate daily O3 concentrations in 2005 and 2030 in East China under the "current legislation" (CLE) and "maximum technically feasible reduction" (MFR) scenarios which were applied globally. O3 concentrations were then linked with population projections, mortality projections, and O3-mortality associations to estimate changes in O3-related mortality in East China.

RESULTS

The annual mean O3 concentration was projected to increase in East China between 2005 and 2030 under the CLE scenario, while decrease under the MFR scenario. Under the CLE scenario, O3-attributable health burden could increase by at least 40,000 premature deaths in East China, without considering the population growth. Under the MFR scenario, the health burden could decrease by up to 260,000 premature deaths as a result of the reduction in O3 concentration with a static population. However, when the population growth was considered, O3-attributable health burden could increase by up to 46,000 premature deaths in East China under the MFR scenario.

CONCLUSIONS

The results suggest that the health burden attributable to O3 may increase in East China in 2030.

The effect of future ambient air pollution on human premature mortality to 2100 using output from the ACCMIP model ensemble

Ambient air pollution from ground-level ozone and fine particulate matter (PM_2.5) is associated with premature mortality. Future concentrations of these air pollutants will be driven by natural and anthropogenic emissions and by climate change. Using anthropogenic and biomass burning emissions projected in the four Representative Concentration Pathway scenarios (RCPs), the ACCMIP ensemble of chemistry-climate models simulated future concentrations of ozone and PM_2.5 at selected decades between 2000 and 2100. We use output from the ACCMIP ensemble, together with projections of future population and baseline mortality rates, to quantify the human premature mortality impacts of future ambient air pollution. Future air pollution-related premature mortality in 2030, 2050 and 2100 is estimated for each scenario and for each model using a health impact function based on changes in concentrations of ozone and PM_2.5 relative to 2000 and projected future population and baseline mortality rates. Additionally, the global mortality burden of ozone and PM_2.5 in 2000 and each future period is estimated relative to 1850 concentrations, using present-day and future population and baseline mortality rates. The change in future ozone concentrations relative to 2000 is associated with excess global premature mortality in some scenarios/periods, particularly in RCP8.5 in 2100 (316 thousand deaths/year), likely driven by the large increase in methane emissions and by the net effect of climate change projected in this scenario, but it leads to considerable avoided premature mortality for the three other RCPs. However, the global mortality burden of ozone markedly increases from 382,000 (121,000 to 728,000) deaths/year in 2000 to between 1.09 and 2.36 million deaths/year in 2100, across RCPs, mostly due to the effect of increases in population and baseline mortality rates. PM_2.5 concentrations decrease relative to 2000 in all scenarios, due to projected reductions in emissions, and are associated with avoided premature mortality, particularly in 2100: between -2.39 and -1.31 million deaths/year for the four RCPs. The global mortality burden of PM_2.5 is estimated to decrease from 1.70 (1.30 to 2.10) million deaths/year in 2000 to between 0.95 and 1.55 million deaths/year in 2100 for the four RCPs, due to the combined effect of decreases in PM_2.5 concentrations and changes in population and baseline mortality rates. Trends in future air pollution-related mortality vary regionally across scenarios, reflecting assumptions for economic growth and air pollution control specific to each RCP and region. Mortality estimates differ among chemistry-climate models due to differences in simulated pollutant concentrations, which is the greatest contributor to overall mortality uncertainty for most cases assessed here, supporting the use of model ensembles to characterize uncertainty. Increases in exposed population and baseline mortality rates of respiratory diseases magnify the impact on premature mortality of changes in future air pollutant concentrations and explain why the future global mortality burden of air pollution can exceed the current burden, even where air pollutant concentrations decrease.

Projecting Fine Particulate Matter-Related Mortality in East China

China is suffering from severe air pollution from fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM2.5)], especially East China. But its future trends and potential health impacts remain unclear. The study objectives were to project future trends of PM2.5 and its short-term effect on mortality in East China by 2030. First, daily changes in PM2.5 concentrations between 2005 and 2030 were projected under the "current legislation" scenario (CLE) and the "maximum technically feasible reduction" scenario (MFR). Then, they were linked to six population projections, two mortality rate projections, and PM2.5-mortality associations to estimate the changes in PM2.5-related mortality in East China between 2005 and 2030. Under the CLE scenario, the annual mean PM2.5 concentration was projected to decrease by 0.62 μg/m(3) in East China, which could cause up to 124,000 additional deaths, when considering the population growth. Under the MFR scenario, the annual mean PM2.5 concentration was projected to decrease by 20.41 μg/m(3) in East China. At least 230,000 deaths could be avoided by such a large reduction in PM2.5 concentration under MFR scenario, even after accounting for the population growth. Therefore, our results suggest that reducing PM2.5 concentration substantially in East China would benefit the public health. Otherwise, it may still remain as a great health risk in the future, especially when the population keeps growing.

A Bayesian model for quantifying the change in mortality associated with future ozone exposures under climate change

Climate change is expected to have many impacts on the environment, including changes in ozone concentrations at the surface level. A key public health concern is the potential increase in ozone-related summertime mortality if surface ozone concentrations rise in response to climate change. Although ozone formation depends partly on summertime weather, which exhibits considerable inter-annual variability, previous health impact studies have not incorporated the variability of ozone into their prediction models. A major source of uncertainty in the health impacts is the variability of the modeled ozone concentrations. We propose a Bayesian model and Monte Carlo estimation method for quantifying health effects of future ozone. An advantage of this approach is that we include the uncertainty in both the health effect association and the modeled ozone concentrations. Using our proposed approach, we quantify the expected change in ozone-related summertime mortality in the contiguous United States between 2000 and 2050 under a changing climate. The mortality estimates show regional patterns in the expected degree of impact. We also illustrate the results when using a common technique in previous work that averages ozone to reduce the size of the data, and contrast these findings with our own. Our analysis yields more realistic inferences, providing clearer interpretation for decision making regarding the impacts of climate change.

U.S. Air Quality and Health Benefits from Avoided Climate Change under Greenhouse Gas Mitigation

We evaluate the impact of climate change on U.S. air quality and health in 2050 and 2100 using a global modeling framework and integrated economic, climate, and air pollution projections. Three internally consistent socioeconomic scenarios are used to value health benefits of greenhouse gas mitigation policies specifically derived from slowing climate change. Our projections suggest that climate change, exclusive of changes in air pollutant emissions, can significantly impact ozone (O3) and fine particulate matter (PM2.5) pollution across the U.S. and increase associated health effects. Climate policy can substantially reduce these impacts, and climate-related air pollution health benefits alone can offset a significant fraction of mitigation costs. We find that in contrast to cobenefits from reductions to coemitted pollutants, the climate-induced air quality benefits of policy increase with time and are largest between 2050 and 2100. Our projections also suggest that increasing climate policy stringency beyond a certain degree may lead to diminishing returns relative to its cost. However, our results indicate that the air quality impacts of climate change are substantial and should be considered by cost-benefit climate policy analyses.

Estimation of future PM2.5- and ozone-related mortality over the continental United States in a changing climate: An application of high-resolution dynamical downscaling technique

This paper evaluates the PM2.5- and ozone-related mortality at present (2000s) and in the future (2050s) over the continental United States by using the Environmental Benefits Mapping and Analysis Program (BenMAP-CE). Atmospheric chemical fields are simulated by WRF/CMAQ (horizontal resolution: 12×12 km), applying the dynamical downscaling technique from global climate-chemistry model under the Representative Concentration Pathways scenario (RCP 8.5). Future air quality results predict that the annual mean PM2.5 concentration in continental U.S. decreases nationwide, especially in the Eastern U.S. and west coast. However, the ozone concentration is projected to decrease in the Eastern U.S. but increase in the Western U.S. Future mortality is evaluated under two scenarios (1) holding future population and baseline incidence rate at the present level and (2) using the projected baseline incidence rate and population in 2050. For PM2.5, the entire continental U.S. presents a decreasing trend of PM2.5-related mortality by the 2050s in Scenario (1), primarily resulting from the emissions reduction. While in Scenario (2), almost half of the continental states show a rising tendency of PM2.5-related mortality, due to the dominant influence of population growth. In particular, the highest PM2.5-related deaths and the biggest discrepancy between present and future PM2.5-related deaths both occur in California in 2050s. For the ozone-related premature mortality, the simulation shows nation-wide rising tendency in 2050s under both scenarios, mainly due to the increase of ozone concentration and population in the future. Furthermore, the uncertainty analysis shows that the confidence interval of all causes mortality is much larger than that for specific causes, probably due to the accumulated uncertainty of generating datasets and sample size. The confidence interval of ozone-related all cause premature mortality is narrower than the PM2.5-related all cause mortality, due to its smaller standard deviation of the concentration-mortality response factor.

IMPLICATIONS

The health impact of PM2.5 is more linearly proportional to the emission reductions than ozone. The reduction of anthropogenic PM2.5 precursor emissions is likely to lead to the decrease of PM2.5 concentrations and PM2.5 related mortality. However, the future ozone concentrations could increase due to increase of the greenhouse gas emissions of methane. Thus, to reduce the impact of ozone related mortality, anthropogenic emissions including criteria pollutant and greenhouse gas (i.e. methane) need to be controlled.

The geographic distribution and economic value of climate change-related ozone health impacts in the United States in 2030

In this United States-focused analysis we use outputs from two general circulation models (GCMs) driven by different greenhouse gas forcing scenarios as inputs to regional climate and chemical transport models to investigate potential changes in near-term U.S. air quality due to climate change. We conduct multiyear simulations to account for interannual variability and characterize the near-term influence of a changing climate on tropospheric ozone-related health impacts near the year 2030, which is a policy-relevant time frame that is subject to fewer uncertainties than other approaches employed in the literature. We adopt a 2030 emissions inventory that accounts for fully implementing anthropogenic emissions controls required by federal, state, and/or local policies, which is projected to strongly influence future ozone levels. We quantify a comprehensive suite of ozone-related mortality and morbidity impacts including emergency department visits, hospital admissions, acute respiratory symptoms, and lost school days, and estimate the economic value of these impacts. Both GCMs project average daily maximum temperature to increase by 1-4°C and 1-5 ppb increases in daily 8-hr maximum ozone at 2030, though each climate scenario produces ozone levels that vary greatly over space and time. We estimate tens to thousands of additional ozone-related premature deaths and illnesses per year for these two scenarios and calculate an economic burden of these health outcomes of hundreds of millions to tens of billions of U.S. dollars (2010$).

IMPLICATIONS

Near-term changes to the climate have the potential to greatly affect ground-level ozone. Using a 2030 emission inventory with regional climate fields downscaled from two general circulation models, we project mean temperature increases of 1 to 4°C and climate-driven mean daily 8-hr maximum ozone increases of 1-5 ppb, though each climate scenario produces ozone levels that vary significantly over space and time. These increased ozone levels are estimated to result in tens to thousands of ozone-related premature deaths and illnesses per year and an economic burden of hundreds of millions to tens of billions of U.S. dollars (2010$).

A multi-scale health impact assessment of air pollution over the 21st century

BACKGROUND

Ozone and PM₂.₅ are current risk factors for premature death all over the globe. In coming decades, substantial improvements in public health may be achieved by reducing air pollution. To better understand the potential of emissions policies, studies are needed that assess possible future health impacts under alternative assumptions about future emissions and climate across multiple spatial scales.

METHOD

We used consistent climate-air-quality-health modeling framework across three geographical scales (World, Europe and Ile-de-France) to assess future (2030-2050) health impacts of ozone and PM₂.₅ under two emissions scenarios (Current Legislation Emissions, CLE, and Maximum Feasible Reductions, MFR).

RESULTS

Consistently across the scales, we found more reductions in deaths under MFR scenario compared to CLE. 1.5 [95% CI: 0.4, 2.4] million CV deaths could be delayed each year in 2030 compared to 2010 under MFR scenario, 84% of which would occur in Asia, especially in China. In Europe, the benefits under MFR scenario (219000 CV deaths) are noticeably larger than those under CLE (109,000 CV deaths). In Ile-de-France, under MFR more than 2830 annual CV deaths associated with PM₂.₅ changes could be delayed in 2050 compared to 2010. In Paris, ozone-related respiratory mortality should increase under both scenarios.

CONCLUSION

Multi-scale HIAs can illustrate the difference in direct consequences of costly mitigation policies and provide results that may help decision-makers choose between different policy alternatives at different scales.

Future premature mortality due to O3, secondary inorganic aerosols and primary PM in Europe--sensitivity to changes in climate, anthropogenic emissions, population and building stock

Air pollution is an important environmental factor associated with health impacts in Europe and considerable resources are used to reduce exposure to air pollution through emission reductions. These reductions will have non-linear effects on exposure due, e.g., to interactions between climate and atmospheric chemistry. By using an integrated assessment model, we quantify the effect of changes in climate, emissions and population demography on exposure and health impacts in Europe. The sensitivity to the changes is assessed by investigating the differences between the decades 2000-2009, 2050-2059 and 2080-2089. We focus on the number of premature deaths related to atmospheric ozone, Secondary Inorganic Aerosols and primary PM. For the Nordic region we furthermore include a projection on how population exposure might develop due to changes in building stock with increased energy efficiency. Reductions in emissions cause a large significant decrease in mortality, while climate effects on chemistry and emissions only affects premature mortality by a few percent. Changes in population demography lead to a larger relative increase in chronic mortality than the relative increase in population. Finally, the projected changes in building stock and infiltration rates in the Nordic indicate that this factor may be very important for assessments of population exposure in the future.

Projecting future air pollution-related mortality under a changing climate: progress, uncertainties and research needs

BACKGROUND

Climate change may affect mortality associated with air pollutants, especially for fine particulate matter (PM2.5) and ozone (O3). Projection studies of such kind involve complicated modelling approaches with uncertainties.

OBJECTIVES

We conducted a systematic review of researches and methods for projecting future PM2.5-/O3-related mortality to identify the uncertainties and optimal approaches for handling uncertainty.

METHODS

A literature search was conducted in October 2013, using the electronic databases: PubMed, Scopus, ScienceDirect, ProQuest, and Web of Science. The search was limited to peer-reviewed journal articles published in English from January 1980 to September 2013.

DISCUSSION

Fifteen studies fulfilled the inclusion criteria. Most studies reported that an increase of climate change-induced PM2.5 and O3 may result in an increase in mortality. However, little research has been conducted in developing countries with high emissions and dense populations. Additionally, health effects induced by PM2.5 may dominate compared to those caused by O3, but projection studies of PM2.5-related mortality are fewer than those of O3-related mortality. There is a considerable variation in approaches of scenario-based projection researches, which makes it difficult to compare results. Multiple scenarios, models and downscaling methods have been used to reduce uncertainties. However, few studies have discussed what the main source of uncertainties is and which uncertainty could be most effectively reduced.

CONCLUSIONS

Projecting air pollution-related mortality requires a systematic consideration of assumptions and uncertainties, which will significantly aid policymakers in efforts to manage potential impacts of PM2.5 and O3 on mortality in the context of climate change.

Changes in air quality and tropospheric composition due to depletion of stratospheric ozone and interactions with changing climate: implications for human and environmental health

UV radiation is an essential driver for the formation of photochemical smog, which includes ground-level ozone and particulate matter (PM).

Spatially resolved estimation of ozone-related mortality in the United States under two Representative Concentration Pathways (RCPs) and their uncertainty

The spatial pattern of the uncertainty in air pollution-related health impacts due to climate change has rarely been studied due to the lack of high-resolution model simulations, especially under the Representative Concentration Pathways (RCPs), the latest greenhouse gas emission pathways. We estimated future tropospheric ozone (O3) and related excess mortality and evaluated the associated uncertainties in the continental United States under RCPs. Based on dynamically downscaled climate model simulations, we calculated changes in O3 level at 12 km resolution between the future (2057-2059) and base years (2001-2004) under a low-to-medium emission scenario (RCP4.5) and a fossil fuel intensive emission scenario (RCP8.5). We then estimated the excess mortality attributable to changes in O3. Finally, we analyzed the sensitivity of the excess mortality estimates to the input variables and the uncertainty in the excess mortality estimation using Monte Carlo simulations. O3-related premature deaths in the continental U.S. were estimated to be 1,312 deaths/year under RCP8.5 (95% confidence interval (CI): 427 to 2,198) and -2,118 deaths/year under RCP4.5 (95% CI: -3,021 to -1,216), when allowing for climate change and emissions reduction. The uncertainty of O3-related excess mortality estimates was mainly caused by RCP emissions pathways. Excess mortality estimates attributable to the combined effect of climate and emission changes on O3 as well as the associated uncertainties vary substantially in space and so do the most influential input variables. Spatially resolved data is crucial to develop effective community level mitigation and adaptation policy.

Occurrence and persistence of future atmospheric stagnation events

Poor air quality causes an estimated 2.6 to 4.4 million premature deaths per year^1-3. Hazardous conditions form when meteorological components allow the accumulation of pollutants in the near-surface atmosphere^4-8. Global warming-driven changes to atmospheric circulation and the hydrological cycle^9-13 are expected to alter the meteorological components that control pollutant build-up and dispersal^5-8,14, but the magnitude, direction, geographic footprint, and public health impact of this alteration remain unclear^7,8. We utilize an air stagnation index and an ensemble of bias-corrected climate model simulations to quantify the response of stagnation occurrence and persistence to global warming. Our analysis projects increases in stagnation occurrence that cover 55% of the current global population, with areas of increase affecting 10 times more people than areas of decrease. By the late-21^st century, robust increases of up to 40 days per year are projected throughout the majority of the tropics and subtropics, as well as within isolated mid-latitude regions. Potential impacts over India, Mexico, and the western U.S. are particularly acute due to the intersection of large populations and increases in the persistence of stagnation events, including those of extreme duration. These results indicate that anthropogenic climate change is likely to alter the level of pollutant management required to meet future air quality targets.

A Statistical Modeling Framework for Projecting Future Ambient Ozone and its Health Impact due to Climate Change

The adverse health effects of ambient ozone are well established. Given the high sensitivity of ambient ozone concentrations to meteorological conditions, the impacts of future climate change on ozone concentrations and its associated health effects are of concern. We describe a statistical modeling framework for projecting future ozone levels and its health impacts under a changing climate. This is motivated by the continual effort to evaluate projection uncertainties to inform public health risk assessment. The proposed approach was applied to the 20-county Atlanta metropolitan area using regional climate model (RCM) simulations from the North American Regional Climate Change Assessment Program. Future ozone levels and ozone-related excesses in asthma emergency department (ED) visits were examined for the period 2041-2070. The computationally efficient approach allowed us to consider 8 sets of climate model outputs based on different combinations of 4 RCMs and 4 general circulation models. Compared to the historical period of 1999-2004, we found consistent projections across climate models of an average 11.5% higher ozone levels (range: 4.8%, 16.2%), and an average 8.3% (range: -7% to 24%) higher number of ozone exceedance days. Assuming no change in the at-risk population, this corresponds to excess ozone-related ED visits ranging from 267 to 466 visits per year. Health impact projection uncertainty was driven predominantly by uncertainty in the health effect association and climate model variability. Calibrating climate simulations with historical observations reduced differences in projections across climate models.

The impact of climate change on heat-related mortality in six major cities, South Korea, under representative concentration pathways (RCPs)

BACKGROUND

We aimed to quantify the excess mortality associated with increased temperature due to climate change in six major Korean cities under Representative Concentration Pathways (RCPs) which are new emission scenarios designed for the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC).

METHODS

We first examined the association between daily mean temperature and mortality in each during the summertime (June to September) from 2001 to 2008. This was done using a generalized linear Poisson model with adjustment for a long-term time trend, relative humidity, air pollutants, and day of the week. We then computed heat-related mortality attributable to future climate change using estimated mortality risks, projected future populations, and temperature increments for both future years 2041-2070 and 2071-2100 under RCP 4.5 and 8.5. We considered effects from added days with high temperatures over thresholds and shifted effects from high to higher temperature.

RESULTS

Estimated excess all-cause mortalities for six cities in Korea ranged from 500 (95% CI: 313-703) for 2041-2070 to 2,320 (95% CI: 1430-3281) deaths per year for 2071-2100 under two RCPs. Excess cardiovascular mortality was estimated to range from 192 (95% CI: 41-351) to 896 (95% CI: 185-1694) deaths per year, covering about 38.5% of all-cause excess mortality. Increased rates of heat-related mortality were higher in cities located at relatively lower latitude than cities with higher latitude. Estimated excess mortality under RCP 8.5, a fossil fuel-intensive emission scenario, was more than twice as high compared with RCP 4.5, low to medium emission scenario.

CONCLUSIONS

Excess mortality due to climate change is expected to be profound in the future showing spatial variation. Efforts to mitigate climate change can cause substantial health benefits via reducing heat-related mortality.

The impact of climate change on ozone-related mortality in Sydney

Coupled global, regional and chemical transport models are now being used with relative-risk functions to determine the impact of climate change on human health. Studies have been carried out for global and regional scales, and in our paper we examine the impact of climate change on ozone-related mortality at the local scale across an urban metropolis (Sydney, Australia). Using three coupled models, with a grid spacing of 3 km for the chemical transport model (CTM), and a mortality relative risk function of 1.0006 per 1 ppb increase in daily maximum 1-hour ozone concentration, we evaluated the change in ozone concentrations and mortality between decades 1996–2005 and 2051–2060. The global model was run with the A2 emissions scenario. As there is currently uncertainty regarding a threshold concentration below which ozone does not impact on mortality, we calculated mortality estimates for the three daily maximum 1-hr ozone concentration thresholds of 0, 25 and 40 ppb. The mortality increase for 2051–2060 ranges from 2.3% for a 0 ppb threshold to 27.3% for a 40 ppb threshold, although the numerical increases differ little. Our modeling approach is able to identify the variation in ozone-related mortality changes at a suburban scale, estimating that climate change could lead to an additional 55 to 65 deaths across Sydney in the decade 2051–2060. Interestingly, the largest increases do not correspond spatially to the largest ozone increases or the densest population centres. The distribution pattern of changes does not seem to vary with threshold value, while the magnitude only varies slightly.

Air quality and climate--synergies and trade-offs

Air quality and climate are often treated as separate science and policy areas. Air quality encompasses the here-and-now of pollutant emissions, atmospheric transformations and their direct effect on human and ecosystem health. Climate change deals with the drivers leading to a warmer world and the consequences of that. These two science and policy issues are inexorably linked via common pollutants, such as ozone (methane) and black carbon. This short review looks at the new scientific evidence around so-called "short-lived climate forcers" and the growing realisation that a way to meet short-term climate change targets may be through the control of "air quality" pollutants. None of the options discussed here can replace reduction of long-lived greenhouse gases, such as CO2, which is required for any long-term climate change mitigation strategy. An overview is given of the underlying science, remaining uncertainties, and some of the synergies and trade-offs for addressing air quality and climate in the science and policy context.