Economic and environmental benefits of greening a Mohs surgery clinic: A comprehensive intervention and analysis.

Major US electric utility climate pledges have the potential to collectively reduce power sector emissions by one-third

Energy-related activities are a major contributor of greenhouse gas (GHG) emissions. A growing body of knowledge clearly depicts the links between human activities and climate change. Over the last century the burning of fossil fuels such as coal and oil and other human activities has released carbon dioxide (CO2) emissions and other heat-trapping GHG emissions into the atmosphere and thus increased the concentration of atmospheric CO2 emissions. The main human activities that emit CO2 emissions are (1) the combustion of fossil fuels to generate electricity, accounting for about 37% of total U.S. CO2 emissions and 31% of total U.S. GHG emissions in 2013, (2) the combustion of fossil fuels such as gasoline and diesel to transport people and goods, accounting for about 31% of total U.S. CO2 emissions and 26% of total U.S. GHG emissions in 2013, and (3) industrial processes such as the production and consumption of minerals and chemicals, accounting for about 15% of total U.S. CO2 emissions and 12% of total ...

Well-to-wheel greenhouse gas emissions of electric versus combustion vehicles from 2018 to 2030 in the US

The greenhouse gas (GHG) emissions related to the recycling of wood waste have been assessed with the purpose to provide useful data that can be used in accounting of greenhouse gas emissions. Here we present data related to the activities in a material recovery facility (MRF) where wood waste is shredded and foreign objects are removed in order to produce wood chips for use in the production of particleboard. The data are presented in accordance with the UOD (upstream, operational, downstream) framework presented in Gentil et al. (Waste Management & Research, 27, 2009). The GHG accounting shows that the emissions related to upstream activities (5 to 41 kg CO(2)-equivalents tonne( -1) wood waste) and to activities at the MRF (approximately 5 kg CO(2)-equivalents tonne(-1) wood waste) are negligible compared to the downstream processing (-560 to -120 kg CO(2)equivalents tonne(-1) wood waste). The magnitude of the savings in GHG emissions downstream are mainly related to savings in energy consumption for drying of fresh wood for particleboard production. However, the GHG account highly depends on the choices made in the modelling of the downstream system. The inclusion of saved electricity from avoided chipping of virgin wood does not change the results radically (-665 to -125 kg CO(2)-equivalents tonne(- 1) wood waste). However, if in addition it is assumed that the GHG emissions from combustion of wood has no global warming potential (GWP) and that the energy produced from excess wood due to recycling substitutes energy from fossil fuels, here assumed to be coal, potentially large downstream GHG emissions savings can be achieved by recycling of waste wood (-1.9 to -1.3 tonnes CO(2)-equivalents tonne(- 1) wood waste). As the data ranges are broad, it is necessary to carefully evaluate the feasibility of the data in the specific system which the GHG accounting is to be applied to.

A guide to life-cycle greenhouse gas (GHG) emissions from electric supply technologies

PDF HTML阅读 XML下载 导出引用 引用提醒 产业园区温室气体排放清单 DOI: 10.5846/stxb201306091508 作者: 作者单位: 北京师范大学环境学院,北京师范大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(91325302,41271543);国家科技支撑计划课题(2012BAK30B03);国家基金委创新研究群体科学基金(51121003);高等学校博士学科点专项科研基金(20130003110027) Greenhouse Gas Inventory of industrial parks in China Author: Affiliation: School of Environment,Beijing Normal University,State Key Joint Laboratory of Environmental Simulation and Pollution Control,School of Environment,Beijing Normal University,State Key Joint Laboratory of Environmental Simulation and Pollution Control Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:温室气体排放所导致的全球气候变化是国际社会长期关注的热点问题,它严重限制了人类社会的发展并威胁着人类的生存。产业园区通常集中了一个区域主要的生产要素与生产能力,也代表着特定产业在该区域的发展水平,理应作为发展低碳经济的基础单元和减少温室气体排放的重要控制点,也可以成为解决区域资源、环境问题的突破口。明确了产业园区温室气体排放的系统边界和内部结构,梳理了产业园区全生命周期温室气体排放行为,综合考虑产业园区能源消耗、工业生产、物质材料消耗、仪器设备投入、废弃物处理处置、景观绿化等过程,建立产业园区温室气体排放核算方法,并对案例园区进行了清单分析。结果表明:案例园区整个生命周期的温室气体排放量为1872177 t CO2-eq,其中运行管理阶段占全生命周期排放的比例最高,为95.35%。建设阶段的温室气体排放总量中建筑材料消耗引起的排放占到96.95%,主要集中在建筑工程、内部装修工程和外部装饰工程3个环节。运行管理阶段电力消耗、热力消耗和污水处理过程的排放量占到总量的98.69%。根据核算及分析结果提出了案例园区在建设和运行管理阶段实现温室气体减排的建议。 Abstract:Global climate change caused by greenhouse gas (GHG) emissions, has severely limited the development of human society and threatened the survival of humanity. Gathering the primary production factors and capacity of the region, an industrial park represents the development level of specific industries in the region. Therefore, the industrial park should be regarded as the base unit for developing a low-carbon economy and reducing GHG emissions, and also a breakthrough in allocating regional resource and overcoming environmental problems. Low-carbon mode has become a trend of development in industrial parks. Researches about GHG emissions from industrial parks make suggestions on the critical points for controlling GHG emissions and provide guidance for the construction or reform projects of low-carbon industrial parks, as well as providing references for entry thresholds and emission standards of low-carbon industrial parks. This study selects the high-end industrial parks as research object, defines the boundary of GHG inventories, and clarifies the structure of the carbon sources. In this study, a GHG inventory is set up to analyze the life-cycle GHG emissions from industrial parks, which includes 6 types of GHG emission sources, namely energy consumption, industrial production, materials consumption, equipments investment, waste disposal and landscaping. The above method was used for one high-end low carbon industrial park in Beijing as a case study. The results were as follows: (1)the overall GHG emission of the whole life-cycle is 1872177 t CO2-eq. The construction stage takes up 4.546% which means 85105.82 t CO2-eq GHG emission with an intensity of 801.69 kg CO2-eq /m2; while the operation stage contributes the great majority of GHG emission, which achieves a proportion of 95.352%. The GHG emission of operation stage is 37717.18 t CO2-eq, and the intensity is 355.29 kg CO2-eq /m2. (2) During the construction stage of the case industrial park, the top 3 emission sources are S (59.71%), ID (20.33%) and OD (11.40%), followed by L (3.74%), V (1.78%) and R (1.09%). The other 6 steps only take up the proportion of less than 1%. (3) More attention should be given tothe processes of sewage treatment, heat energy consumption and electricity consumption, as they contribute 98.69% of the stage emission. Finally, based on the analysis of the results, suggestions for GHG reduction are proposed to guide the low-carbon development of the high-end industrial park, such as making use of the local materials to reduce the amount of fuel consumption and greenhouse gas emissions due to the long-range transport, using the low carbon and regeneration construction materials instead of the traditional ones to reduce the GHG emission from the upstream production process and downstream disposal, scientifically arranging the construction progress to promote a safe and low carbon form of construction work, applying advanced management methods and strengthening the propaganda of energy conservation and emissions reduction. 参考文献 相似文献 引证文献

Rivers play an important role in greenhouse gas emissions. Over the past decade, because of global urbanization trends, rapid land use changes have led to changes in river ecosystems that have had a stimulating effect on the greenhouse gas production and emissions. Presently, there is an urgent need for assessments of the greenhouse gas concentrations and emissions in watersheds. Therefore, this study was designed to evaluate river-based greenhouse gas emissions and their spatial-temporal features as well as possible impact factors in a rapidly urbanizing area. The specific objectives were to investigate how river greenhouse gas concentrations and emission fluxes are responding to urbanization in the Liangtan River, which is not only the largest sub-basin but also the most polluted one in Chongqing City. The thin layer diffusion model method was used to monitor year-round concentrations of pCO2, CH4, and N2O in September and December 2014, and March and June 2015. The pCO2 range was (23.38±34.89)-(1395.33±55.45) Pa, and the concentration ranges of CH4 and N2O were (65.09±28.09)-(6021.36±94.36) nmol·L-1 and (29.47±5.16)-(510.28±18.34) nmol·L-1, respectively. The emission fluxes of CO2, CH4, and N2O, which were calculated based on the method of wind speed model estimations, were -6.1-786.9, 0.31-27.62, and 0.06-1.08 mmol·(m2·d)-1, respectively. Moreover, the CO2 and CH4 emissions displayed significant spatial differences, and these were roughly consistent with the pollution load gradient. The greenhouse gas concentrations and fluxes of trunk streams increased and then decreased from upstream to downstream, and the highest value was detected at the middle reaches where the urbanization rate is higher than in other areas and the river is seriously polluted. As for branches, the greenhouse gas concentrations and fluxes increased significantly from the upstream agricultural areas to the downstream urban areas. The CO2 fluxes followed a seasonal pattern, with the highest CO2 emission values observed in autumn, then successively winter, summer, and spring. The CH4 fluxes were the highest in spring and the lowest in summer, while N2O flux seasonal patterns were not significant. Because of the high carbon and nitrogen loads in the basin, the CO2 products and emissions were not restricted by biogenic elements, but levels were found to be related to important biological metabolic factors such as the water temperature, pH, DO, and chlorophyll a. The carbon, nitrogen, and phosphorus content of the water combined with sewage input influenced the CH4 products and emissions. Meanwhile, N2O production and emissions were mainly found to be driven by urban sewage discharge with high N2O concentrations. Rapid urbanization accelerated greenhouse gas emissions from the urban rivers, so that in the urban reaches, CO2/CH4 fluxes were twice those of the non-urban reaches, and all over the basin N2O fluxes were at a high level. These findings illustrate how river basin urbanization can change aquatic environments and aggravate allochthonous pollution inputs such as carbon, nitrogen, and phosphorus, which in turn can dramatically stimulate river-based greenhouse gas production and emissions; meanwhile, spatial and temporal differences in greenhouse gas emissions in rivers can lead to the formation of emission hotspots.

Downstream and Upstream Greenhouse Gas Emissions: The Proper Scope of NEPA Review

Recently, legal controversies have arisen regarding the scope of greenhouse gas emissions that should be considered in environmental reviews of fossil fuel extraction and transportation proposals under the National Environmental Policy Act (NEPA). The key question is whether and how agencies should account for emissions from activities that occur “downstream” from the proposed action, such the combustion of fossil fuels, and emissions from activities that occur “upstream” of the proposed action, such the extraction of fossil fuels. This question is important, because consideration of such emissions can alter the balance of costs and benefits for a proposed project, and the agency’s ability to justify approving the project in light of that balance.This Article argues that such emissions do typically fall within the scope of indirect and cumulative impacts that must be evaluated under NEPA, and provides recommendations on how agencies should evaluate such emissions in environmental review documents. To support the argument and recommendations, the Article makes several unique contributions to the growing literature on NEPA and climate change. First, we describe how federal approvals of fossil fuel extraction and infrastructure contribute to global climate change, and we explain why federal agencies have ample discretion to account for these impacts when deciding whether to issue such approvals. Second, we conduct an in-depth examination of NEPA’s requirements as they pertain to the analysis of upstream and downstream emissions, focusing in particular on the requirements to evaluate indirect effects, cumulative effects, and effects from related actions. Third, we describe how federal agencies currently account for upstream and downstream greenhouse gas emissions in their NEPA reviews, and we find that there are major inconsistencies in the analytical approaches both within and across agencies, but many agencies are nonetheless beginning to recognize that upstream and downstream emissions fall within the scope of impacts that should be reviewed under NEPA. Fourth, we synthesize all of the existing case law on this subject, and we find that courts have generally treated such emissions as the type of indirect effects that must be evaluated in a NEPA reviews. Finally, we outline an approach for evaluating upstream and downstream emissions that would improve the quality of federal decision-making, shield agencies from litigation, and provide much-needed information about the indirect and cumulative effects of fossil fuel development on global climate change.

Taking Stock of Strategies on Climate Change and the Way Forward: A Strategic Climate Change Framework for Australia

BackgroundPolicies to mitigate climate change by reducing greenhouse gas (GHG) emissions can yield public health benefits by also reducing emissions of hazardous co-pollutants, such as air toxics and particulate matter. Socioeconomically disadvantaged communities are typically disproportionately exposed to air pollutants, and therefore climate policy could also potentially reduce these environmental inequities. We sought to explore potential social disparities in GHG and co-pollutant emissions under an existing carbon trading program—the dominant approach to GHG regulation in the US and globally.Methods and findingsWe examined the relationship between multiple measures of neighborhood disadvantage and the location of GHG and co-pollutant emissions from facilities regulated under California’s cap-and-trade program—the world’s fourth largest operational carbon trading program. We examined temporal patterns in annual average emissions of GHGs, particulate matter (PM2.5), nitrogen oxides, sulfur oxides, volatile organic compounds, and air toxics before (January 1, 2011–December 31, 2012) and after (January 1, 2013–December 31, 2015) the initiation of carbon trading. We found that facilities regulated under California’s cap-and-trade program are disproportionately located in economically disadvantaged neighborhoods with higher proportions of residents of color, and that the quantities of co-pollutant emissions from these facilities were correlated with GHG emissions through time. Moreover, the majority (52%) of regulated facilities reported higher annual average local (in-state) GHG emissions since the initiation of trading. Neighborhoods that experienced increases in annual average GHG and co-pollutant emissions from regulated facilities nearby after trading began had higher proportions of people of color and poor, less educated, and linguistically isolated residents, compared to neighborhoods that experienced decreases in GHGs. These study results reflect preliminary emissions and social equity patterns of the first 3 years of California’s cap-and-trade program for which data are available. Due to data limitations, this analysis did not assess the emissions and equity implications of GHG reductions from transportation-related emission sources. Future emission patterns may shift, due to changes in industrial production decisions and policy initiatives that further incentivize local GHG and co-pollutant reductions in disadvantaged communities.ConclusionsTo our knowledge, this is the first study to examine social disparities in GHG and co-pollutant emissions under an existing carbon trading program. Our results indicate that, thus far, California’s cap-and-trade program has not yielded improvements in environmental equity with respect to health-damaging co-pollutant emissions. This could change, however, as the cap on GHG emissions is gradually lowered in the future. The incorporation of additional policy and regulatory elements that incentivize more local emission reductions in disadvantaged communities could enhance the local air quality and environmental equity benefits of California’s climate change mitigation efforts.

The body of life cycle assessment (LCA) literature is vast and has grown over the last decade at a dauntingly rapid rate. Many LCAs have been published on the same or very similar technologies or products, in some cases leading to hundreds of publications. One result is the impression among decision makers that LCAs are inconclusive, owing to perceived and real variability in published estimates of life cycle impacts. Despite the extensive available literature and policy need formore conclusive assessments, only modest attempts have been made to synthesize previous research. A significant challenge to doing so are differences in characteristics of the considered technologies and inconsistencies in methodological choices (e.g., system boundaries, coproduct allocation, and impact assessment methods) among the studies that hamper easy comparisons and related decision support. An emerging trend is meta-analysis of a set of results from LCAs, which has the potential to clarify the impacts of a particular technology, process, product, or material and produce more robust and policy-relevant results. Meta-analysis in this context is defined here as an analysis of a set of published LCA results to estimate a single or multiple impacts for a single technology or a technology category, either in a statisticalmore » sense (e.g., following the practice in the biomedical sciences) or by quantitative adjustment of the underlying studies to make them more methodologically consistent. One example of the latter approach was published in Science by Farrell and colleagues (2006) clarifying the net energy and greenhouse gas (GHG) emissions of ethanol, in which adjustments included the addition of coproduct credit, the addition and subtraction of processes within the system boundary, and a reconciliation of differences in the definition of net energy metrics. Such adjustments therefore provide an even playing field on which all studies can be considered and at the same time specify the conditions of the playing field itself. Understanding the conditions under which a meta-analysis was conducted is important for proper interpretation of both the magnitude and variability in results. This special supplemental issue of the Journal of Industrial Ecology includes 12 high-quality metaanalyses and critical reviews of LCAs that advance understanding of the life cycle environmental impacts of different technologies, processes, products, and materials. Also published are three contributions on methodology and related discussions of the role of meta-analysis in LCA. The goal of this special supplemental issue is to contribute to the state of the science in LCA beyond the core practice of producing independent studies on specific products or technologies by highlighting the ability of meta-analysis of LCAs to advance understanding in areas of extensive existing literature. The inspiration for the issue came from a series of meta-analyses of life cycle GHG emissions from electricity generation technologies based on research from the LCA Harmonization Project of the National Renewable Energy Laboratory (NREL), a laboratory of the U.S. Department of Energy, which also provided financial support for this special supplemental issue. (See the editorial from this special supplemental issue [Lifset 2012], which introduces this supplemental issue and discusses the origins, funding, peer review, and other aspects.) The first article on reporting considerations for meta-analyses/critical reviews for LCA is from Heath and Mann (2012), who describe the methods used and experience gained in NREL's LCA Harmonization Project, which produced six of the studies in this special supplemental issue. Their harmonization approach adapts key features of systematic review to identify and screen published LCAs followed by a meta-analytical procedure to adjust published estimates to ones based on a consistent set of methods and assumptions to allow interstudy comparisons and conclusions to be made. In a second study on methods, Zumsteg and colleagues (2012) propose a checklist for a standardized technique to assist in conducting and reporting systematic reviews of LCAs, including meta-analysis, that is based on a framework used in evidence-based medicine. Widespread use of such a checklist would facilitate planning successful reviews, improve the ability to identify systematic reviews in literature searches, ease the ability to update content in future reviews, and allow more transparency of methods to ease peer review and more appropriately generalize findings. Finally, Zamagni and colleagues (2012) propose an approach, inspired by a meta-analysis, for categorizing main methodological topics, reconciling diverging methodological developments, and identifying future research directions in LCA. Their procedure involves the carrying out of a literature review on articles selected according to predefined criteria.« less

Executive Summary: The California Climate Action Registry, which was initially established in 2000 and began operation in Fall 2002, is a voluntary registry for recording annual greenhouse gas (GHG) emissions. The purpose of the Registry is to assist California businesses and organizations in their efforts to inventory and document emissions in order to establish a baseline and to document early actions to increase energy efficiency and decrease GHG emissions. The State of California has committed to use its ''best efforts'' to ensure that entities that establish GHG emissions baselines and register their emissions will receive ''appropriate consideration under any future international, federal, or state regulatory scheme relating to greenhouse gas emissions.'' Reporting of GHG emissions involves documentation of both ''direct'' emissions from sources that are under the entity's control and indirect emissions controlled by others. Electricity generated by an off-site power source is consider ed to be an indirect GHG emission and is required to be included in the entity's report. Registry participants include businesses, non-profit organizations, municipalities, state agencies, and other entities. Participants are required to register the GHG emissions of all operations in California, and are encouraged to report nationwide. For the first three years of participation, the Registry only requires the reporting of carbon dioxide (CO2) emissions, although participants are encouraged to report the remaining five Kyoto Protocol GHGs (CH4, N2O, HFCs, PFCs, and SF6). After three years, reporting of all six Kyoto GHG emissions is required. The enabling legislation for the Registry (SB 527) requires total GHG emissions to be registered and requires reporting of ''industry-specific metrics'' once such metrics have been adopted by the Registry. The Ernest Orlando Lawrence Berkeley National Laboratory (Berkeley Lab) was asked to provide technical assistance to the California Energy Commission (Energy Commission) related to the Registry in three areas: (1) assessing the availability and usefulness of industry-specific metrics, (2) evaluating various methods for establishing baselines for calculating GHG emissions reductions related to specific actions taken by Registry participants, and (3) establishing methods for calculating electricity CO2 emission factors. The third area of research was completed in 2002 and is documented in Estimating Carbon Dioxide Emissions Factors for the California Electric Power Sector (Marnay et al., 2002). This report documents our findings related to the first areas of research. For the first area of research, the overall objective was to evaluate the metrics, such as emissions per economic unit or emissions per unit of production that can be used to report GHG emissions trends for potential Registry participants. This research began with an effort to identify methodologies, benchmarking programs, inventories, protocols, and registries that u se industry-specific metrics to track trends in energy use or GHG emissions in order to determine what types of metrics have already been developed. The next step in developing industry-specific metrics was to assess the availability of data needed to determine metric development priorities. Berkeley Lab also determined the relative importance of different potential Registry participant categories in order to asses s the availability of sectoral or industry-specific metrics and then identified industry-specific metrics in use around the world. While a plethora of metrics was identified, no one metric that adequately tracks trends in GHG emissions while maintaining confidentiality of data was identified. As a result of this review, Berkeley Lab recommends the development of a GHG intensity index as a new metric for reporting and tracking GHG emissions trends.Such an index could provide an industry-specific metric for reporting and tracking GHG emissions trends to accurately reflect year to year changes while protecting proprietary data. This GHG intensity index changes while protecting proprietary data. This GHG intensity index would provide Registry participants with a means for demonstrating improvements in their energy and GHG emissions per unit of production without divulging specific values. For the second research area, Berkeley Lab evaluated various methods used to calculate baselines for documentation of energy consumption or GHG emissions reductions, noting those that use industry-specific metrics. Accounting for actions to reduce GHGs can be done on a project-by-project basis or on an entity basis. Establishing project-related baselines for mitigation efforts has been widely discussed in the context of two of the so-called ''flexible mechanisms'' of the Kyoto Protocol to the United Nations Framework Convention on Climate Change (Kyoto Protocol) Joint Implementation (JI) and the Clean Development Mechanism (CDM).

BackgroundSocietal pressures exist to reduce greenhouse gas (GHG) emissions from farm animals, especially in beef cattle. Both total GHG and GHG emissions per unit of product decrease as productivity increases. Limitations of previous studies on GHG emissions are that they generally describe feed intake inadequately, assess the consequences of selection on particular traits only, or examine consequences for only part of the production chain. Here, we examine GHG emissions for the whole production chain, with the estimated cost of carbon included as an extra cost on traits in the breeding objective of the production system.MethodsWe examined an example beef production system where economic merit was measured from weaning to slaughter. The estimated cost of the carbon dioxide equivalent (CO2-e) associated with feed intake change is included in the economic values calculated for the breeding objective traits and comes in addition to the cost of the feed associated with trait change. GHG emission effects on the production system are accumulated over the breeding objective traits, and the reduction in GHG emissions is evaluated, for different carbon prices, both for the individual animal and the production system.ResultsMultiple-trait selection in beef cattle can reduce total GHG and GHG emissions per unit of product while increasing economic performance if the cost of feed in the breeding objective is high. When carbon price was $10, $20, $30 and $40/ton CO2-e, selection decreased total GHG emissions by 1.1, 1.6, 2.1 and 2.6% per generation, respectively. When the cost of feed for the breeding objective was low, selection reduced total GHG emissions only if carbon price was high (~ $80/ton CO2-e). Ignoring the costs of GHG emissions when feed cost was low substantially increased emissions (e.g. 4.4% per generation or ~ 8.8% in 10 years).ConclusionsThe ability to reduce GHG emissions in beef cattle depends on the cost of feed in the breeding objective of the production system. Multiple-trait selection will reduce emissions, while improving economic performance, if the cost of feed in the breeding objective is high. If it is low, greater growth will be favoured, leading to an increase in GHG emissions that may be undesirable.

Legislation to cap and trade greenhouse gas (GHG) emissions was approved by a 219-212 vote of the United States House of Representatives on June 26, 2009. Cap and trade policy articulated in the American Clean Energy and Security (ACES) act of 2009 regulates GHGs including carbon dioxide, methane, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons and nitrogen trifluoride. Debate over the ACES act focused heavily on economic issues contrasted against concerns about climate change1. However, discussion largely ignored the potential for cap and trade legislation to contribute to reductions in levels of other harmful air pollutants, such as sulfur dioxide, particulate matter, and ozone precursors that share emission sources with GHGs. Under the bill, domestic GHG emissions are to be capped at 2005 annual levels, and reduced to 17% of those marks by 20502. The bill provides for an initial round of pollution permits to be made available, some free, others at auction. Subsequently, these permits can be bought and sold in the open market by organizations such as utility companies and manufacturing firms. A key provision in the ACES act requires the president to impose tariffs on countries that do not implement similar regulations on GHG emissions. While other potentially viable legislation, such as a tax on carbon emissions, has been proposed3, the current cap and trade legislation is the first bill to pass in either the House or Senate. The greenhouse gases regulated under the ACES act do not generally pose serious direct health risks. For example, nitrous oxide is used in dental procedures, and carbon dioxide is an ingredient in carbonated beverages. Other GHGs, like nitrogen trifluoride and sulfur hexafluoride, are not harmful at their current concentration levels, but can be hazardous to persons working with them if safety precautions are not taken. Instead, substantial human health benefits from cap and trade legislation could potentially come from reductions in ambient levels of harmful pollutants, such as particulate matter and ozone, that share emissions sources with GHGs. For example, 94% of CO2 emissions in the US result from combustion of fossil fuels, with electricity generation and transportation alone comprising nearly 70%. These are also the leading source of sulfur dioxide, fine particles having diameter small than 2.5 micrometers (PM2.5), and precursors to ozone such as mono-nitrogen oxides (NOx)4. While the time scale for potential impacts of cap and trade legislation on climate change and related health benefits is likely decades or centuries, ancillary air pollution mitigation could have immediate health benefits. In two nationwide epidemiological studies, daily levels of ambient ozone and PM2.5 have been linked to increased risk of cardiovascular and respiratory mortality5 and to increased risk of emergency hospital admissions, especially for heart failure6, respectively. Estimates of the potential health benefits attributable to reductions in harmful air pollutants resulting from mitigation of GHG emissions, at the city, region and national, have been substantial7. While US cap and trade legislation would likely reduce domestic air pollution levels, two caveats deserve consideration. First, methods for reducing GHG emissions typically reduce air pollution levels, but not always. This problem can be highlighted using airplanes as an example8. Two methods to reduce CO2 emissions from airplanes are to decrease aircraft weight or increase engine combustion temperatures. The former reduces both GHG and air pollution emissions, whereas the later reduces GHG emissions at the cost of increasing precursors to ozone. In the broader context of energy production, it is likely cap and trade legislation would drive a shift away from fossil fuel combustion to sources such as solar technology that produce much less air pollution. However, the exact technology development path is still uncertain. A second problem is the potential for domestic cap and trade legislation to transfer US emissions to newly industrialized nations. Countries facing lower production costs associated with looser regulations on GHG emissions would have an economic advantage over manufacturing industries in the US. However, increased air pollution from new manufacturing could be a key public health issue for developing regions, such as China's Pearl River delta, where air pollution levels are already much higher than standards in the US9. The economic and physical systems that would be affected by cap and trade legislation are extremely complex, and impacts on air pollution will have to be considered in a broad context. For example, while the absence of tariffs would likely push manufacturing, air pollution and related negative health effects to developing regions, those regions might experience health benefits associated with increased per capita income. The discussion is similarly complex in the physical domain. For example, some air pollutants, such as sulfate particulate matter, can contribute to short term climate cooling. Though still somewhat unclear, there is an emerging debate over the possibility that air pollution mitigation could actually exacerbate global warming in the short term10. While it faces potentially significant opposition and alteration in the Senate, the cap and trade bill recently passed in the House has progressed further through Congress than any other similar legislation. There is tremendous potential for legislation regulating GHG emissions, via cap and trade or other strategies, to simultaneously decrease emissions of harmful air pollutants and reduce morbidity and mortality attributable to cardiovascular and respiratory illness. Such improvements in public health have been linked to economic benefits from recovered workforce productivity8, and add important support for progress on cap and trade legislation versus delayed action.