Air Toxics Standards Research Articles

Positive Spillovers from Infrastructure Investment: How Pipeline Expansions Encourage Fuel Switching

Abstract This paper studies the role of the U.S. pipeline infrastructure in the country's transition from coal to natural gas energy. I leverage the Environmental Protection Agency's Mercury and Air Toxics Standards as a plausibly exogenous intervention, which encouraged many coal plants to convert to natural gas. Combining this quasi-experimental variation with a plant's preexisting proximity to the pipeline network, I isolate implied pipeline connection costs within a dynamic discrete choice model of plant conversions. Key model results indicate that infrastructure-related costs prevent $9 billion in emissions reductions from taking place, suggesting a $2.4 million per mile external benefit of pipeline expansions.

Sociodemographic Disparities in Mercury Exposure from United States Coal-Fired Power Plants.

Hazardous air pollutants emitted by United States (U.S) coal-fired power plants have been controlled by the Mercury and Air Toxics Standards (MATS) since 2012. Sociodemographic disparities in traditional air pollutant exposures from U.S. power plants are known to occur but have not been evaluated for mercury (Hg), a neurotoxicant that bioaccumulates in food webs. Atmospheric Hg deposition from domestic power plants decreased by 91% across the contiguous U.S. from 6.4 Mg in 2010 to 0.55 Mg in 2020. Prior to MATS, populations living within 5 km of power plants (n = 507) included greater proportions of frequent fish consumers, individuals with low annual income and less than a high school education, and limited English-proficiency households compared to the US general population. These results reinforce a lack of distributional justice in plant siting found in prior work. Significantly greater proportions of low-income individuals lived within 5 km of active facilities in 2020 (n = 277) compared to plants that retired after 2010, suggesting that socioeconomic status may have played a role in retirement. Despite large deposition declines, an end-member scenario for remaining exposures from the largest active power plants for individuals consuming self-caught fish suggests they could still exceed the U.S. Environmental Protection Agency reference dose for methylmercury.

National-Scale Assessment of Total Gaseous Mercury Isotopes Across the United States.

With the 2011 promulgation of the Mercury and Air Toxics Standards by the U.S. Environmental Protection Agency, and the successful negotiation by the United Nations Environment Program of the Minamata Convention, emissions of mercury (Hg) have declined in the United States. While the declines in atmospheric Hg concentrations in North America are encouraging, linking the declines to changing domestic and global source portfolios remains challenging. To address these research gaps, the U.S. Geological Survey initiated the first national-scale effort to establish a baseline of total gaseous mercury stable isotope values at 31 sites distributed across the United States. Results indicated that unique Hg sources, such as Hg evasion from an elemental Hg contaminated site or free tropospheric intrusions in high altitude sites, were distinguishable from background atmospheric values. Minor gradients were observed across the nation, with regions of heavy industrial activity demonstrating lower , but no consistent changes in other isotopes such as and were observed. Furthermore, was impacted by foliar uptake and senescence but trends varied between forested regions in the northeastern and midwestern United States. These data demonstrate regional emission sources and other environmental variables can impact total gaseous Hg (TGM) isotope values, highlighting the need to characterize atmospheric Hg isotopes over larger geographical areas to evaluate changes related to national and international Hg regulations.

Mortality Risk from : A Comparison of Modeling Approaches to Identify Disparities across Racial/Ethnic Groups in Policy Outcomes.

Background:Regulatory analyses of air pollution policies require the use of concentration–response functions and underlying health data to estimate the mortality and morbidity effects, as well as the resulting benefits, associated with policy-related changes in fine particulate matter ()]. Common practice by U.S. federal agencies involves using underlying health data and concentration–response functions that are not differentiated by racial/ethnic group.Objectives:We aim to explore the policy implications of using race/ethnicity-specific concentration–response functions and mortality data in comparison to standard approaches when estimating the impact of air pollution on non-White racial/ethnic subgroups.Methods:Using new estimates from the epidemiological literature on race/ethnicity-specific concentration–response functions paired with race/ethnicity-specific mortality rates, we estimated the mortality impacts of air pollution from all sources from a uniform increase in concentrations and from the regulations imposed by the Mercury Air Toxics Standards.Results:Use of race/ethnicity-specific information increased premature mortality estimates in older populations by 9% and among older Black Americans by 150% for all-source pollution exposure. Under a uniform degradation of air quality and race/ethnicity-specific information, older Black Americans were found to have approximately 3 times higher mortality relative to White Americans, which is obscured under a non–race/ethnicity-specific modeling approach. Standard approaches of using non–racial/ethnic specific information underestimate the benefits of the Mercury Air Toxics Standards to older Black Americans by almost 60% and overestimate the benefits to older White Americans by 14% relative to using a race/ethnicity-specific modeling approach.Discussion:Policy analyses incorporating race/ethnicity-specific concentration–response functions and mortality data relative to nondifferentiated inputs underestimate the overall magnitude of mortality burden and the disparity in impacts on older Black American populations. Based on our results, we recommend that the best available race/ethnicity-specific inputs are used in regulatory assessments to understand and reduce environmental injustices. https://doi.org/10.1289/EHP9001

The Role of Retrospective Analysis in an Era of Deregulation: Lessons from the U.S. Mercury and Air Toxic Standards

As of late 2020, the Trump administration had initiated almost one hundred rollbacks of U.S. environmental regulations. A careful assessment of the benefits and costs of rolling back an existing regulation can and should inform such decisions. When assessing the potential rollback of an existing regulation, analysts can often learn from the regulation’s implementation through retrospective analysis as well as from advances in scientific knowledge. We discuss recent actions concerning the Mercury and Air Toxics Standards (MATS) to illustrate the potential lessons from doing so. In the case of MATS, advances in science have shed light on broader exposure pathways and previously unquantified health effects, suggesting that the benefits of reducing mercury emissions may exceed previous estimates. At the same time, changes in the energy sector have altered the mix of fuels used to produce electricity, which impacts both the benefits and costs of the regulation.

Principles for setting air quality guidelines to protect human health in Australia.

The current air quality framework to mitigate against the health effects of exposure to air pollution within Australia relies on national environmental protection standards — set out under the National Environmental Protection (Ambient Air Quality) Measure (the ambient air quality NEPM) — and the jurisdictional requirements for monitoring and reporting exceedances.1, 2 The ambient air quality NEPM sets reportable limits for key criteria air pollutants.1 Criteria air pollutants are those that are legislated internationally as measures of air quality and include particulate matter (PM), nitrogen dioxide (NO2), carbon monoxide, ozone, sulfur dioxide (SO2) and lead1 (Box). Air toxics are non-criteria air pollutants that are considered to pose a hazard to human health.7 Air toxics are legislated under a separate NEPM which has the goal of generating baseline data for later development of standards for five compounds: benzene, benzo(a)pyrene, formaldehyde, toluene and xylenes.7 The air toxics standards, based on the gathered baseline data, were due to be set in 20127 but are yet to be reviewed.

The Role of Retrospective Analysis in an Era of Deregulation: Lessons from the US Mercury and Air Toxics Standards

As of late 2020, the Trump administration had initiated almost 100 rollbacks of US environmental regulations. A careful assessment of the benefits and costs of rolling back an existing regulation can and should inform such decisions. When assessing the potential rollback of an existing regulation, analysts can often learn from the regulation’s implementation through retrospective analysis as well as from advances in scientific knowledge. We discuss recent actions concerning the Mercury and Air Toxics Standards (MATS) to illustrate the potential lessons from doing so. In the case of MATS, advances in science have shed light on broader exposure pathways and previously unquantified health effects, suggesting that the benefits of reducing mercury emissions may exceed previous estimates. At the same time, changes in the energy sector have altered the mix of fuels used to produce electricity, which impacts both the benefits and the costs of the regulation.

Mercury source changes and food web shifts alter contamination signatures of predatory fish from Lake Michigan

To understand the impact reduced mercury (Hg) loading and invasive species have had on methylmercury bioaccumulation in predator fish of Lake Michigan, we reconstructed bioaccumulation trends from a fish archive (1978 to 2012). By measuring fish Hg stable isotope ratios, we related temporal changes in Hg concentrations to varying Hg sources. Additionally, dietary tracers were necessary to identify food web influences. Through combined Hg, C, and N stable isotopic analyses, we were able to differentiate between a shift in Hg sources to fish and periods when energetic transitions (from dreissenid mussels) led to the assimilation of contrasting Hg pools (2000 to present). In the late 1980s, lake trout δ202Hg increased (0.4‰) from regulatory reductions in regional Hg emissions. After 2000, C and N isotopes ratios revealed altered food web pathways, resulting in a benthic energetic shift and changes to Hg bioaccumulation. Continued increases in δ202Hg indicate fish are responding to several United States mercury emission mitigation strategies that were initiated circa 1990 and continued through the 2011 promulgation of the Mercury and Air Toxics Standards rule. Unlike archives of sediments, this fish archive tracks Hg sources susceptible to bioaccumulation in Great Lakes fisheries. Analysis reveals that trends in fish Hg concentrations can be substantially affected by shifts in trophic structure and dietary preferences initiated by invasive species in the Great Lakes. This does not diminish the benefits of declining emissions over this period, as fish Hg concentrations would have been higher without these actions.

Effects of temperature and SO3 on re-emission of mercury from activated carbon under flue gas conditions

Mercury (Hg) is a toxic and bio-accumulating heavy metal that is predominantly released via the combustion of coal. Due to its toxicity, the Environmental Protection Agency (EPA) has introduced Mercury and Air Toxics Standards (MATS) Rule regarding allowable Hg emissions. In order to reduce emissions, power plants have widely adopted activated carbon (AC) injection. AC injection has proven to be an effective method to reduce Hg emissions, but the re-emission of previously adsorbed Hg during unit operation, likely due to changing temperature or flue gas composition, could be problematic. This study specifically examined the effects of temperature and sulfur trioxide (SO3) concentration, by ramping temperature and SO3 concentration independently and simultaneously, on AC samples that are already exposed to flue gas and saturated in presence of Hg, sulfur dioxide (SO2) and nitric oxide (NO). Of these two suspected factors to cause re-emission, temperature had the greater impact and resulted in re-emission of both elemental and oxidized Hg with a greater fraction of oxidized Hg, which can be attributed to elemental Hg being more strongly bonded to the AC surface. Surprisingly, exposing the samples to increasing concentrations of SO3 had nearly no effect under the conditions examined in this study, possibly as a result of the samples being already saturated with sulfur prior to the SO3 ramp tests to simulate transient conditions in the plant.

Mercury pollution, information, and property values

In the State of New York, atmospheric deposition of mercury ranks among the 10 most prevalent causes of adverse impacts on water quality. This paper examines the impacts of mercury pollution by exploring the relationship between property values and fish consumption advisory (FCA) designation on New York lakes. We find that New York State property values within one mile of an FCA-designated lake decrease by 6–7 percent on average. This negative impact decreases as the distance between properties and lakes increases. Regressions using samples derived with Mahalanobis metric matching find an even larger FCA effect, ranging from 7 to 10 percent. Our results can serve as a partial indication of the benefits of the Mercury and Air Toxics Standards (MATS), which includes the first mercury emission standard in the United States.

Characteristics and Compositions of Airborne Fine Particulate Matter in Southwest Ohio, USA

Southwest Ohio has been known for PM2.5 issues due to emissions from multiple local sources, such as industry and multimodal traffic, as well as regional impacts from sulfates, nitrates, and ammonia. To better understand the speciation characteristics of PM2.5 in this area, data from five monitoring sites, Taft, Hook Field, St. Bernard, Lower Price Hill, and Chase, were studied for the time period of 2003 to 2013. The total concentration of PM2.5 has decreased significantly since the last decade, from 13.41 µg m–3 in 2003 to 10.55 µg m–3 in 2013. The overall PM2.5 concentration also exhibited seasonal variations, with four out of five of the highest concentrations occurring in summer and the fifth one occurring in winter. Due to various air pollution control measures (such as the Cross-State Air Pollution Rule, and Mercury and Air Toxics Standards), both the total concentrations and the speciation of PM2.5 have changed over time. The most dominant components of PM2.5 include sulfates, organic matter (OM), and nitrates, which contributed 33.4%, 31.7%, and 17.7%, respectively (Taft data from 2009 to 2013). Elemental carbon (EC) and crustal materials, on the other hand, accounted for much smaller portions—2.84% and 3.61%, respectively. The highest concentrations of sulfate occurred in summer, while those for nitrates occurred in winter. EC and OM followed the same seasonal trends, peaking in fall and summer and dropping to their lowest levels in winter. Crustal materials exhibited the lowest concentrations in winter. A comparison of Cincinnati (the Taft site) with other major cities nearby reveals that the highest concentration of PM2.5 and the largest fraction of sulfates is found in Cincinnati. Efforts to control these emissions are still necessary.

Cabot has setback in mercury abatement

Cabot Corp. has indefinitely idled three of the seven production lines at its activated carbon plant in Marshall, Texas. Cabot and other activated carbon producers have been anticipating increased demand for the material to capture power-plant mercury after implementation of the Mercury & Air Toxics Standards regulation in the U.S. However, Cabot says demand for activated carbon has been lower than originally expected. The decision will affect 40 employees.

Laboratory investigation of three distinct emissions monitors for hydrochloric acid

ABSTRACTThe measurement of hydrochloric acid (HCl) on a continuous basis in coal-fired plants is expected to become more important if HCl standards become implemented as part of the Federal Mercury and Air Toxics Standards (MATS) standards that are under consideration. For this study, the operational performance of three methods/instruments, including tunable diode laser absorption spectroscopy (TDLAS), cavity ring down spectroscopy (CRDS), and Fourier transform infrared (FTIR) spectroscopy, were evaluated over a range of real-world operating environments. Evaluations were done over an HCl concentration range of 0–25 ppmv and temperatures of 25, 100, and 185 °C. The average differences with respect to temperature were 3.0% for the TDL for values over 2.0 ppmv and 6.9% of all concentrations, 3.3% for the CRDS, and 4.5% for the FTIR. Interference tests for H2O, SO2, and CO, CO2, and NO for a range of concentrations typical of flue gases from coal-fired power plants did not show any strong interferences. The possible exception was an interference from H2O with the FTIR. The instrument average precision over the entire range was 4.4% for the TDL with better precision seen for concentrations levels of 2.0 ppmv and above, 2.5% for the CRDS, and 3.5% for the FTIR. The minimum detection limits were all on the order of 0.25 ppmv, or less, utilizing the TDL values with a 5-m path. Zero drift was found to be 1.48% for the TDL, 0.88% for the CRDS, and 1.28% for the FTIR.Implications: This study provides an evaluation of the operational performance of three methods/instruments, including TDL absorption spectroscopy (TDLAS), cavity ring down spectroscopy (CRDS), and FTIR spectroscopy, for the measurement of hydrochloric acid (HCl) over a range of real-world operating environments. The results showed good instrument accuracy as a function of temperature and no strong interferences for flue gases typical to coal-fired power plants. The results show that these instruments would be viable for the measurement of HCl in coal-fired plants if HCl standards become implemented as part of the Federal Mercury and Air Toxics Standards (MATS) standards that are under consideration.

Powder Resistivity Inferred Differential Collection of Heterogeneous Coal Fly Ash and Powered Activated Carbon Admixtures Within a Cylindrical Electrostatic Precipitator

One of the primary goals of U.S. EPA’s Mercury Air Toxics Standards (MATS) is to remove approximately 90 % of mercury emissions from coal-fired power plants (CFPPs). Sorbent injection upstream of electrostatic precipitators (ESPs) has been the leading method for capturing mercury at CFPPs. However, electrostatic precipitators (ESPs) that are marginally sized and/or operated may face new performance challenges due to sorbent injection. Injected mercury sorbent particles having different properties (i.e., particle size, surface chemistry, or electrical properties), mixing with native fly ash, can potentially affect the collection behaviors of ESPs. The present study uses powder resistivity to study the differential collection behaviors within a cylindrical ESP by manually feeding admixtures containing Norit DarcoⓇ FGD powdered activated carbon (PAC) and fly ash samples from either Powder River Basin (PRB) or Illinois bituminous coals. Powder resistivity measurements, performed on fly ash admixtures at various PAC ratios (i.e. 0−10 wt. %) prior to ESP processing, serve as the initial resistivity data to infer the impact of PAC injection on ESP collection by comparing to powder resistivity of samples collected from the collection electrode. This study presents not only the evidence of differential collection behaviors within an ESP but also the implications for mercury emissions and the particulate matter (PM) control through ESPs.

Meeting Minamata: Cost-effective compliance options for atmospheric mercury control in Chinese coal-fired power plants

A new international treaty, Minamata Convention, identifies mercury (Hg) as a global threat to human health and seeks to control its releases and emissions. Coal-fired power plants are a major source of mercury pollution worldwide and are expected to be the first key sector to be addressed in China under Minamata Convention. A best available technique (BAT) adoption model was developed in the form of a decision tree and cost-effectiveness for each technological option. Co-benefit control technologies and their enhancement with coal blending/switching and halogen injection (HI) can provide early measures to help China meet the Minamata Convention obligations. We project future energy and policy scenarios to simulate potential national mercury reduction goals for China and estimate costs of the control measures for each scenario. The “Minamata Medium” scenario, equivalent to the goal of the US Mercury and Air Toxics Standards (MATS) rule, requires the application of activated carbon injection (ACI) and HI on 30% and 20% of power plants, respectively. The corresponding total costs would be $2.5 billion, approximately one-fourth the costs in the US. An emission limit of 3µg/m3 in 2030 was identified as a feasible policy option for China to comply with Minamata Convention.

Inconsistencies in Risk Analyses for Ambient Air Pollutant Regulations.

This article describes inconsistencies between health risk analyses that the U.S. Environmental Protection Agency (EPA) uses to support its decisions on primary National Ambient Air Quality Standards (NAAQS), and in the associated Regulatory Impact Analyses (RIAs) that accompany each NAAQS rulemaking. Quantitative risk estimates are prepared during the NAAQS-setting deliberations using inputs derived from statistical associations between measured pollutant concentrations and health effects. The resulting risk estimates are not directly used to set a NAAQS, but incorporated into a broader evidence-based rationale for the standard that is intended to demonstrate conformity with the statutory requirement that primary NAAQS protect the public health with a margin of safety. In a separate process, EPA staff rely on the same risk calculations to prepare estimates of the benefits of the rule that are reported in its RIA for the standard. Although NAAQS rules and their RIAs are released simultaneously, the rationales used to set the NAAQS have become inconsistent with their RIAs' estimates of benefits, with very large fractions of RIAs' risk-reduction estimates being attributed to populations living in areas that will already be attaining the respective NAAQS. This article explains the source of this inconsistency and provides a quantitative example based on the 2012 revision of the fine particulate matter (PM2.5 ) primary NAAQS. This article also demonstrates how this inconsistency is amplified when criteria pollutant co-benefits are calculated in RIAs for non-NAAQS rules, using quantitative examples from the 2011 Mercury and Air Toxics Standards and the currently proposed Clean Power Plan.

1. United States

In 2015, his penultimate full year in office, President Barack Obama moved aggressively to make the United States a leader in global efforts to combat climate change. The United States provided strong support for the negotiations that produced the Paris Agreement in December 2015. The US Environmental Protection Agency (EPA) adopted significant regulations to limit greenhouse gas (GHG) emissions from power plants and to clarify the reach of federal authority to protect wetlands. Fierce opposition from Republicans in Congress failed to curtail EPA actions due to Obama’s veto of resolutions disapproving the regulations. Even a Supreme Court decision requiring the EPA to consider costs before limiting emissions of mercury and air toxics standards was founded on such narrow grounds that the EPA was able to leave the regulations in place. The Republican Party, which fiercely opposes environmental regulation, now holds a majority in both houses of Congress. However, its majority is not large enough to over-ride a presidential veto, which requires a two-thirds majority in each house of Congress. Congress does hold the ‘power of the purse,’ but, fearing political backlash from another government shutdown, Republicans were unable to de-fund the EPA’s environmental initiatives. The future of President Obama’s environmental initiatives will thus depend on decisions by courts hearing legal challenges to them and, ultimately, the results of the 2016 elections.

Songbirds as sentinels of mercury in terrestrial habitats of eastern North America.

Mercury (Hg) is a globally distributed environmental contaminant with a variety of deleterious effects in fish, wildlife, and humans. Breeding songbirds may be useful sentinels for Hg across diverse habitats because they can be effectively sampled, have well-defined and small territories, and can integrate pollutant exposure over time and space. We analyzed blood total Hg concentrations from 8,446 individuals of 102 species of songbirds, sampled on their breeding territories across 161 sites in eastern North America [geometric mean Hg concentration=0.25μg/g wet weight (ww), range <0.01-14.60μg/g ww]. Our records span an important time period-the decade leading up to implementation of the USEPA Mercury and Air Toxics Standards, which will reduce Hg emissions from coal-fired power plants by over 90%. Mixed-effects modeling indicated that habitat, foraging guild, and age were important predictors of blood Hg concentrations across species and sites. Blood Hg concentrations in adult invertebrate-eating songbirds were consistently higher in wetland habitats (freshwater or estuarine) than upland forests. Generally, adults exhibited higher blood Hg concentrations than juveniles within each habitat type. We used model results to examine species-specific differences in blood Hg concentrations during this time period, identifying potential Hg sentinels in each region and habitat type. Our results present the most comprehensive assessment of blood Hg concentrations in eastern songbirds to date, and thereby provide a valuable framework for designing and evaluating risk assessment schemes using sentinel songbird species in the time after implementation of the new atmospheric Hg standards.

Environmental Strategies: Strategies for Compliance With Mercury and Air Toxics Standards

AbstractThe Environmental Protection Agency's Mercury and Air Toxics Standards (MATS) rule comes into effect for existing coal‐ and oil‐fired electric utility steam generating units (EGUs) on April 16, 2015. This article summarizes the rule's requirements and sets forth considerations for affected sources evaluating their compliance options under the rule.

New Source Review and coal plant efficiency gains: How new and forthcoming air regulations affect outcomes

Forthcoming carbon dioxide (CO2) regulations for existing power plants in the United States have heightened interest in thermal efficiency gains for coal-fired power plants. Plant modifications to improve thermal efficiency can trigger New Source Review (NSR), a Clean Air Act requirement to adopt of state-of-the-art pollution controls. This article explores whether existing coal plants would likely face additional pollution control requirements if they undertake modifications that trigger NSR. Despite emissions controls that are or will be installed under the Mercury and Air Toxics Standards (MATS) and Clean Air Interstate Rule (CAIR) or its replacement, 80% of coal units (76% of capacity) that are expected to remain in operation are not projected to meet the minimum NSR requirements for at least one pollutant: nitrogen oxides or sulfur dioxide. This is an important consideration for the U.S. Environmental Protection Agency and state policymakers as they determine the extent to which CO2 regulation will rely on unit-by-unit thermal efficiency gains versus potential flexible compliance strategies such as averaging, trading, energy efficiency, and renewable energy. NSR would likely delay and add cost to thermal efficiency projects at a majority of coal units, including projects undertaken to comply with forthcoming CO2 regulation.