Environmental Protection Agency Estimates Research Articles

Sensitivity of air quality to vehicle ammonia emissions in the United States

The US Environmental Protection Agency (EPA) estimates on-road vehicles emissions using the Motor Vehicle Emission Simulator (MOVES). We developed updated ammonia emission rates for MOVES based on road-side exhaust emission measurements of light-duty gasoline and heavy-duty diesel vehicles. The resulting nationwide on-road vehicle ammonia emissions are 1.8, 2.1, 1.8, and 1.6 times higher than the MOVES3 estimates for calendar years 2010, 2017, 2024, and 2035, respectively, primarily due to an increase in light-duty gasoline vehicle NH3 emission rates. We conducted an air quality simulation using the Community Multi-Scale Air Quality (CMAQv5.3.2) model to evaluate the sensitivity of modeled ammonia and fine particulate matter (PM2.5) concentrations in calendar year 2017 using the updated on-road vehicle ammonia emissions. The average monthly urban ammonia ambient concentrations increased by up to 2.3 ppbv in January and 3.0 ppbv in July. The updated on-road NH3 emission rates resulted in better agreement of modeled ammonia concentrations with 2017 annual average ambient ammonia measurements, reducing model bias by 5.8 % in the Northeast region. Modeled average winter PM2.5 concentrations increased in urban areas, including enhancements of up to 0.5 μg/m3 in the northeast United States. The updated ammonia emission rates have been incorporated in MOVES4 and will be used in future versions of the NEI and EPA's modeling platforms.

A top-down estimation of subnational CO2 budget using a global high-resolution inverse model with data from regional surface networks

Top-down approaches, such as atmospheric inversions, are a promising tool for evaluating emission estimates based on activity-data. In particular, there is a need to examine carbon budgets at subnational scales (e.g. state/province), since this is where the climate mitigation policies occur. In this study, the subnational scale anthropogenic CO2 emissions are estimated using a high-resolution global CO2 inverse model. The approach is distinctive with the use of continuous atmospheric measurements from regional/urban networks along with background monitoring data for the period 2015–2019 in global inversion. The measurements from several urban areas of the U.S., Europe and Japan, together with recent high-resolution emission inventories and data-driven flux datasets were utilized to estimate the fossil emissions across the urban areas of the world. By jointly optimizing fossil fuel and natural fluxes, the model is able to contribute additional information to the evaluation of province–scale emissions, provided that sufficient regional network observations are available. The fossil CO2 emission estimates over the U.S. states such as Indiana, Massachusetts, Connecticut, New York, Virginia and Maryland were found to have a reasonable agreement with the Environmental Protection Agency (EPA) inventory, and the model corrects the emissions substantially towards the EPA estimates for California and Indiana. The emission estimates over the United Kingdom, France and Germany are comparable with the regional inventory TNO–CAMS. We evaluated model estimates using independent aircraft observations, while comparison with the CarbonTracker model fluxes confirms ability to represent the biospheric fluxes. This study highlights the potential of the newly developed inverse modeling system to utilize the atmospheric data collected from the regional networks and other observation platforms for further enhancing the ability to perform top-down carbon budget assessment at subnational scales and support the monitoring and mitigation of greenhouse gas emissions.

Chemical Characterization of Natural Gas Leaking from Abandoned Oil and Gas Wells in Western Pennsylvania.

The U.S. Environmental Protection Agency estimates that there are over 3.2 million abandoned wells in the United States. Studies conducted on gas emissions from abandoned wells have been limited to methane, a powerful greenhouse gas, due to concerns regarding climate change. However, volatile organic compounds (VOCs), including benzene, a known human carcinogen, are known to be associated with upstream oil and gas development and hence could also be released when methane is emitted to the atmosphere. In this investigation, we analyze gas from 48 abandoned wells in western Pennsylvania for fixed gases, light hydrocarbons, and VOCs and estimate associated emission rates. We demonstrate that (1) gas from abandoned wells contains VOCs, including benzene; (2) VOCs are emitted from abandoned wells, the magnitude of which depends on the flow rate and concentration of VOCs in the gas stream; and (3) nearly one-quarter of abandoned wells are located within 100 m of buildings, including residences, in Pennsylvania. Together, these observations indicate that further investigation is necessary to determine whether emissions from abandoned wells pose an inhalation risk to people living, working, or congregating near abandoned wells.

Autonomy Is Key to Revitalizing Water Utilities

Allentown, Pa.; Bayonne, N.J.; Flint, Mich.; Newark, N.J.; and Jackson, Miss., are a few of the communities that have had serious water issues involving an underfunded utility in need of critical intervention. That intervention came, and it arrived in a variety of forms. In Allentown a public–public arrangement with the independent authority, Lehigh County Authority, turned things around. In Bayonne a public–private partnership sparked a recovery. Flint, Newark, and Jackson required massive infusions of public dollars and outside management to address the emergencies in the short term. In these and other communities, revenues have been diverted to other municipal needs, or rates have been held artificially low for years because of political resistance or interference. The common denominator for failing or distressed utilities is being embedded in municipal government and managed by elected political officials—mayors, city councils, and boards—who view water rate increases as taxes and thus a political “root canal.” Because charging more for service is not generally popular, political leaders have every incentive to defer or oppose rate increases until they leave office. Embedded utilities are not permitted to operate as independent enterprises, so they are not always able to make financial decisions that are based on public health and business or infrastructure needs. This has meant that many American communities have not adequately invested in infrastructure. AWWA's 2012 report, Buried No Longer, estimated the investment gap or needs at a trillion dollars. The US Environmental Protection Agency estimates that cost to be just under half a trillion dollars. This is a case of government failure—local government, primarily. Recently, I spoke to a utility manager in the capital of a midwestern state who told me they have not had a rate increase in 11 years. At 2%, 3%, or 4% annual inflation rates, the financial hole gets deep very fast. When I asked why, he responded, “The mayor does not support rate increases.” Politically depressed water rates and revenue stifle capital planning and development. Meanwhile, water infrastructure continues to slowly degrade. Seth Siegel, in his critique of the drinking water sector, Troubled Water: What's Wrong With What We Drink, argued to “keep mayors away from water.” Siegel explained that “to improve decision-making, the counterproductive connection between water utilities and municipal government needs to be decoupled.” Political mismanagement and neglect may be the unified field theory of public utility failure, and it deserves serious research. Indeed, a 2019 study in AWWA Water Science by Jennifer Biddle and Karen Baehler found that “autonomy matters” (https://doi.org/10.1002/aws2.1140). This quantitative study focused on 22 US managers from water utilities across the country. The researchers found that there was an overarching sentiment that utility performance improved with insulation from political interference, and utilities with organizational autonomy possess greater decision-making power and flexibility in spending. Removed from direct municipal control and political influence, independent water utilities may focus intently on water service delivery. According to one mid-Atlantic participant in the study, “The city was always very, very reluctant to spend money on infrastructure replacement, renewal upgrades, you name it. They didn't want to want to raise the rate.” There are alternative models of governance. Louisville Water is a separate corporation owned by the city, which preserves independence and pays dividends to the municipality. In addition to Lehigh County Authority mentioned earlier, Denver Water is a fine utility and part of an independent authority from the city. Washington, D.C., (DC Water) has improved immensely since becoming a separate authority. Massachusetts General Law (Part I, Title VII, 40N, Section 1) provides for the adoption by towns of an independent political subdivision to operate water and sewer systems modeled after Boston's Enabling Act of 1977. Another model to consider is the investor-owned utility regulated by a public utility commission. Seth Siegel points out, “De-linking water utilities from mayoral politics, though, need not lead to unaccountability.” Local officials can appoint board members or commissioners of these independent authorities, ideally for fixed terms, ensuring autonomy to provide effective management of the assets entrusted to them. Not all embedded utilities fail, but most failed utilities are embedded in municipal government. Autonomous utility governance is the key to a revitalization of the water sector. Author's note: The views expressed herein are entirely the author's and not those of AWWA. G. Tracy Mehan III is executive director of government affairs in AWWA's Washington, D.C., office; [email protected].

Methodology for Mobile Toxics Deterministic Human Health Risk Assessment and Case Study

Air toxic emissions from on-road mobile sources are significant contributors to the degradation of air quality in urban and dense population centers. Research led by the United States Environmental Protection Agency (EPA) identified more than 1162 hazardous air pollutants (HAPs) in the exhaust and evaporative emissions from on-road mobile sources. However, less than 70 hazardous air pollutants are monitored by regulatory agencies. HAPs emitted from Mobile Sources are known as Mobile Source Air Toxics (MSATs). The EPA estimates that approximately half of the cancer risk and 74% of noncancer health impacts from air toxics is attributed to mobile sources. The quantification of the risk associated with MSATs exposure remains limited to date, and only a few MSATs have ambient air quality standards to protect human health and welfare. This work presents a novel and validated methodology to quantify the myriad health risks associated with exposure to on-road mobile emissions. This methodology is introduced in the form of a pipelined analysis process, which may be employed in existing and new transportation projects. The proposed new methodology integrates results from three different types of models: on-road vehicle emissions inventory models such as MOVES and IVE, air dispersion models such as AERMOD and SCIPUFF, and risk estimate models for human and ecological receptors such as the 2005 Final U.S. EPA Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities. The result of this research work is a new methodology that provides regulators and risk analysts with a more detailed awareness of the health impacts of MSATs. A case study of Saint Paul, Minnesota, validated the air dispersion modeled results against monitored data, and the agreement was acceptable (i.e., the estimates were within a factor of two of the observations). Three high-population locations in the Saint Paul area were evaluated for human health risk, with the observation that at two of these locations, the Saint Paul—Ramsey Health Center and Anderson Office Building, the calculated cancer risk is in excess of the target risk level of 1.0E-05 for benzo(a)pyrene. The methodology presented in this paper allows regulators, risk analysts, and air quality engineers to better estimate multi-pathway cancer and noncancer risk associated with acute and chronic exposure to MSATs. Moreover, this work provides a science-based aid to policy decision makers when considering factors that most significantly affect population health and ecology.

Leaded aviation gasoline exposure risk and child blood lead levels.

Lead-formulated aviation gasoline (avgas) is the primary source of lead emissions in the United States today, consumed by over 170,000 piston-engine aircraft (PEA). The U.S. Environmental Protection Agency (EPA) estimates that four million people reside within 500m of a PEA-servicing airport. The disposition of avgas around such airports may be an independent source of child lead exposure. We analyze over 14,000 blood lead samples of children (≤5y of age) residing near one such airport-Reid-Hillview Airport (RHV) in Santa Clara County, California. Across an ensemble of tests, we find that the blood lead levels (BLLs) of sampled children increase in proximity to RHV, are higher among children east and predominantly downwind of the airport, and increase with the volume of PEA traffic and quantities of avgas sold at the airport. The BLLs of airport-proximate children are especially responsive to an increase in PEA traffic, increasing by about 0.72 μg/dL under periods of maximum PEA traffic. We also observe a significant reduction in child BLLs from a series of pandemic-related interventions in Santa Clara County that contracted PEA traffic at the airport. Finally, we find that children's BLLs increase with measured concentrations of atmospheric lead at the airport. In support of the scientific adjudication of the EPAs recently announced endangerment finding, this in-depth case study indicates that the deposition of avgas significantly elevates the BLLs of at-risk children.

Implied climate warming contributions of enteric methane emissions are dependent on the estimate source and accounting methodology

The objective of this project was to dem- onstrate differences in methane (CH4) emission estimates between 2 reporting entities and to illustrate how the con- tribution to climate warming of enteric CH4 emissions is dependent on accounting methodologies. United States enteric CH4 emissions were accessed from the Food and Agriculture Organization (FAO) and US Environmental Protection Agency (EPA), and cattle inventory numbers were ob- tained from the USDA-National Agricultural Statistics Service (NASS) website and EPA spreadsheet. Enteric CH4 emission estimates from both sources were then ex- pressed as CO2 equivalence (CO2-e) and warming equiva- lence (CO2-we) using both the 100-yr global warming potential (GWP100) and the newer global warming po- tential* (GWP*) methodologies. Almost all of the year-to- year variability in the FAO data set was explained by NASS cow and calves inventory (R2 = 0.99), whereas much less variability was explained by EPA cattle inven- tory for the EPA data set (R2 = 0.45). The EPA estimates were consistently greater than FAO estimates, and only a small amount of variation was accounted for (R2 = 0.41). Despite these differences, GWP* methodologies produced much smaller CO2-e values compared with GWP100 for both data sets. This work highlight- ed several important concepts to understand. First, it is important to understand the methodology for estimating enteric CH4 emissions used by different reporting bodies. Second, with both the FAO and EPA data sources, GWP* methodology provides a smaller estimate of warming con- tribution than the GWP100 method. Finally, this evalu- ation also highlights how this greenhouse gas accounting method is not a panacea for this source of greenhouse gas emissions.

Mixed Potential Electrochemical Sensors – Ceramic Substrate and Electrolyte Effects on Sensor Response to Methane and Simulated Natural Gas

The US Environmental Protection Agency estimates emissions from US natural gas drilling and processing amounted to 197 million metric tons of CO2 equivalent in 2019.1 Research by Marchese et al. suggests that CH4 emissions could be up to three times higher.2 Current natural gas emissions detection methods consist mainly of active optical monitoring, typically with long path IR sensors.3 These monitoring methods capable of ppb level accuracy are expensive, fragile, and require accurately calibrated mirrors. Mixed potential electrochemical sensors (MPES) are robust, low-cost, and selective sensors, making them appropriate option for methane emission monitoring.4 Previously we have reported on a four electrode MPES with 3 mol% YSZ electrolyte fabricated with direct write 3D printing5, here we investigate substrate and electrode material effects on the sensor response.The response of a four electrode La0.87Sr0.13CrO3, Indium Tin Oxide (In2O3 90 wt%, SnO2 10 wt%), Au, Pt mixed potential electrochemical sensor to methane and simulated natural gas at operating temperatures of 450 – 600 °C was studied. Sensors were fabricated on substrates of yttria stabilized zirconia, ceria stabilized zirconia, and magnesia stabilized zirconia manufactured by direct write extrusion 3D printing of aqueous pastes. These materials are selected to maximize the mixed potential difference by better isolation of the sensing electrodes. Data is presented with a solid electrolyte of 3 mol % yttria stabilized zirconia, and various other solid ceramic electrolytes will be studied. The effect of sensor response with respect to the ionic conductivity of substrate material is studied. The sensor limit of detection for CH4, natural gas, CH4/NH3, and CH4/H2 mixes will be reported. We will also train artificial neural networks to quantify the concentration of CH4 and other subcomponents given a subset of signals taken from the sensors operated at different temperatures.AcknowledgementsThis project was supported by US Department of Energy Office of Fossil Energy and Carbon Management through award DE-FE0031864.References(1) US EPA, O. Estimates of Methane Emissions by Segment in the United States https://www.epa.gov/natural-gas-star-program/estimates-methane-emissions-segment-united-states (accessed 2021 -12 -13).(2) Marchese, A. J.; Vaughn, T. L.; Zimmerle, D. J.; Martinez, D. M.; Williams, L. L.; Robinson, A. L.; Mitchell, A. L.; Subramanian, R.; Tkacik, D. S.; Roscioli, J. R.; Herndon, S. C. Methane Emissions from United States Natural Gas Gathering and Processing. Environ. Sci. Technol. 2015, 49 (17), 10718–10727. https://doi.org/10.1021/acs.est.5b02275.(3) Aldhafeeri, T.; Tran, M.-K.; Vrolyk, R.; Pope, M.; Fowler, M. A Review of Methane Gas Detection Sensors: Recent Developments and Future Perspectives. Inventions 2020, 5 (3), 28. https://doi.org/10.3390/inventions5030028.(4) Garzon, F. H.; Mukundan, R.; Brosha, E. L. Solid-State Mixed Potential Gas Sensors: Theory, Experiments and Challenges. Solid State Ion. 2000, 136, 633–638.(5) Halley, S.; Tsui, L.; Garzon, F. Combined Mixed Potential Electrochemical Sensors and Artificial Neural Networks for the Quantificationand Identification of Methane in Natural Gas Emissions Monitoring. J. Electrochem. Soc. 2021, 168 (9), 097506. https://doi.org/10.1149/1945-7111/ac2465. Figure 1. Four electrode MPES response at 600 °C to CH4 in simulated air, low ethane simulated natural gas in air, and high ethane simulated natural gas in air, from left to right, respectively. Top row – ceria stabilized zirconia substrate. Bottom row – magnesia stabilized zirconia substrate. Figure 1

ANALYSIS OF RADON GAS EXPOSURE IN THE HOME ON THE RISK OF LUNG CANCER (NARRATIVE REVIEW)

According to WHO 2009, exposure to radon gas is known to be the second highest cause of lung cancer. The United States Environmental Protection Agency (U.S.EPA) estimates that 21,000 lung cancer deaths annually result from exposure to radon in the United States. Radon (ð‘…ð‘›222) naturally originates in soil and rock and it is the decay of Uranium-238 (𑈠238). This study used a literature review study that aims to review several research journal articles regarding exposure to Radon gas in the home with the risk of lung cancer. The data base used to search for research journal articles are Science Direct, PubMed, DOAJ, JSTOR, and Taylor & Francis. The results of this study were: (1) nine out of twelve journal articles described a significant association between Rn in the home (concentration of Rn 37 Bq/ð‘š3 until ≥ 300 Bq/ð‘š3 ) and the risk of lung cancer; (2) the duration of stay of the occupants in the house lasted from 2-30 years; and (3) eight journal articles presented that the most common lung cancer cell subtype associated with Rn exposure in the home was adenocarcinoma and squamous cell carcinoma. People need to maintain indoor airflow and choosing safe building material (not containing Rn).

Evaluating urban methane emissions from space using TROPOMI methane and carbon monoxide observations

Anthropogenic methane emissions from urban centers are important and addressable, yet remain poorly characterized, and the representativeness of studies from individual cities is unknown. A satellite-based approach provides a pathway to tackle this challenge on a national or global scale. Here we present a space-based method that uses the simultaneous, daily observation of methane and carbon monoxide from the TROPOMI satellite to estimate urban methane emissions. We assess and validate the method and demonstrate that using these simultaneous observations enables robust assessment of methane emissions from urban centers without relying on atmospheric transport models. Initial assessments with this approach in eight United States cities suggest emission inventory underestimates previously discovered in older East Coast cities are more broadly representative, with aggregated emissions totaling 1.47 (0.56, 3.19, 95% confidence interval) Tg CH4/year, compared to the Environmental Protection Agency estimate of 0.52 Tg CH4/year. We show this data driven approach provides a pathway to study urban methane emissions across the globe and track how emissions respond if urban mitigation measures are implemented by investigating three additional megacities outside the United States.

Majority of US urban natural gas emissions unaccounted for in inventories

Across many cities, estimates of methane emissions from natural gas (NG) distribution and end use based on atmospheric measurements have generally been more than double bottom-up estimates. We present a top-down study of NG methane emissions from the Boston urban region spanning 8 y (2012 to 2020) to assess total emissions, their seasonality, and trends. We used methane and ethane observations from five sites in and around Boston, combined with a high-resolution transport model, to calculate methane emissions of 76 ± 18 Gg/yr, with 49 ± 9 Gg/yr attributed to NG losses. We found no significant trend in the NG loss rate over 8 y, despite efforts from the city and state to increase the rate of repairing NG pipeline leaks. We estimate that 2.5 ± 0.5% of the gas entering the urban region is lost, approximately three times higher than bottom-up estimates. We saw a strong correlation between top-down NG emissions and NG consumed on a seasonal basis. This suggests that consumption-driven losses, such as in transmission or end-use, may be a large component of emissions that is missing from inventories, and require future policy action. We also compared top-down NG emission estimates from six US cities, all of which indicate significant missing sources in bottom-up inventories. Across these cities, we estimate NG losses from distribution and end use amount to 20 to 36% of all losses from the US NG supply chain, with a total loss rate of 3.3 to 4.7% of NG from well pad to urban consumer, notably larger than the current Environmental Protection Agency estimate of 1.4% [R. A. Alvarez et al., Science 361, 186-188 (2018)].

Ability of mathematical models to predict human in vivo percutaneous penetration of steroids

Human skin is a common route for topical steroids to enter the body. To aid with risk management of therapeutic steroid usage, the US Environmental Protection Agency estimates percutaneous penetration using mathematical models. However, it is unclear how accurate are mathematical models in estimating percutaneous penetration/absorption of steroids. In this study, accuracy of predicted flux (penetration/absorption) by the main mathematical model used by the EPA, the Potts and Guy model based on in vitro data is compared to actual human in vivo data from our laboratory of percutaneous absorption of topical steroids. We focused on steroids due to the availability of steroid in vivo human data in our laboratory. For most steroids the flux was underestimated by a factor 10–60. However, within the group itself, there was an association between the Potts and Guy model and experimental human in vivo data (Pearson Correlation = 0.8925, p = 0.000041). Additionally, some physiochemical parameters used in the Potts and Guy equation, namely log Kp (Pearson Correlation = 0.7307, p = 0.0046) and molecular weight (Pearson correlation = −0.6807, p = 0.0105) correlated significantly with in vivo flux. Current mathematical models used in estimating percutaneous penetration/absorption did not accurately predict in vivo flux of steroids. Why? Proposed limitations to mathematical models currently used include: not accounting for volatility, lipid solubility, hydrogen bond effects, drug metabolism, as well as protein binding. Further research is needed in order to increase the predictive nature of such models for in vivo flux.

28435 Sex steroids percutaneous penetration in vivo in man: Relationship to mathematical predictive model

Background: Human skin is a common route for topical sex steroids to enter the body. To aid with assessing the proper dosage for therapeutic sex steroid usage for conditions such as menopause, the US Environmental Protection Agency (EPA) estimates percutaneous penetration using mathematical models, namely the Potts and Guy model (PGM).

Ambient particulate matter, ozone, and neurologic symptoms in U.S. Gulf states adults.

Research on neurologic effects of air pollution has focused on neurodevelopment or later-life neurodegeneration; other effects throughout adulthood have received less attention. We examined air pollution levels and neurologic symptoms among 21,467 adults in US Gulf Coast states. We assigned exposure using Environmental Protection Agency estimates of daily ambient particulate matter 2.5 (PM2.5) and ozone. Gulf Long-term Follow-up Study participants reported neurologic symptoms at enrollment (2011-2013). We estimated cross-sectional associations between each air pollutant and prevalence of "any" neurologic, central nervous system (CNS), or peripheral nervous system (PNS) symptoms. Ambient PM2.5 was consistently associated with prevalence of neurologic symptoms. The highest quartile of 30-day PM2.5 was associated with any neurologic symptom (prevalence ratio [PR] = 1.16; 95% confidence interval [CI] = 1.09, 1.23) and there were increasing monotonic relationships between 30-day PM2.5 and each symptom category (P-trend ≤ 0.01). Associations with PM2.5 were slightly stronger among nonsmokers and during colder seasons. The highest quartile of 7-day ozone was associated with increased prevalence of PNS symptoms (PR = 1.09; 95% CI = 1.00, 1.19; P-trend = 0.03), but not with other outcomes. Ozone concentrations above regulatory levels were suggestively associated with neurologic symptoms (PR = 1.06; 95% CI = 0.99, 1.14). Mutual adjustment in co-pollutant models suggests that PM2.5 is more relevant than ozone in relation to prevalence of neurologic symptoms.

15438 Ability of mathematical models to predict human percutaneous penetration

Background: Human skin is a common route for organic chemicals and drugs to enter the body. To aid with risk management of environmental chemical exposure, the US Environmental Protection Agency estimates percutaneous penetration using mathematical models.

Air pollutant source characterization using the revised regional haze tracking metric and a photochemical grid model and implications for regional haze planning

ABSTRACTThe 2017 revisions to the Regional Haze Rule clarify that visibility progress at Class I national parks and wilderness areas should be tracked on days with the highest anthropogenic contributions to haze (impairment). We compare the natural and anthropogenic contributions to haze in the western United States in 2011 estimated using the Environmental Protection Agency (EPA) recommended method and using model projections from the Comprehensive Air Quality Model with Extensions (CAMx) and the Particulate Source Apportionment Tool (PSAT). We do so because these two methods will be used by states to demonstrate visibility progress by 2028. If the two methods assume different natural and anthropogenic contributions, the projected benefits of reducing U.S. anthropogenic emissions will differ. The EPA method assumes that episodic elevated carbonaceous aerosols greater than an annual 95th percentile threshold are natural events. For western U.S. IMPROVE monitoring sites reviewed in this paper, CAMx-PSAT confirms these episodes are impacted by carbon from wildfire or prescribed fire events. The EPA method assumes that most of the ammonium sulfate is anthropogenic in origin. At most western sites CAMx-PSAT apportions more of the ammonium sulfate on the most impaired days to global boundary conditions and anthropogenic Canadian, Mexican, and offshore shipping emissions than to U.S. anthropogenic sources. For ammonium nitrate and coarse mass, CAMx-PSAT apportions greater contributions to U.S. anthropogenic sources than the EPA method assigns to total anthropogenic contributions. We conclude that for western IMPROVE sites, the EPA method is effective in selecting days that are likely to be impacted by anthropogenic emissions and that CAMx-PSAT is an effective approach to estimate U.S. source contributions. Improved inventories, particularly international and natural emissions, and further evaluation of global and regional model performance and PSAT attribution methods are recommended to increase confidence in modeled source characterization.Implications: The western states intend to use the CAMx model to project visibility progress by 2028. Modeled visibility response to changes in U.S. anthropogenic emissions may be less than estimated using the EPA assumptions based on total U.S. and international anthropogenic contributions to visibility impairment. Additional model improvements are needed to better account for contributions to haze from natural and international emissions in current and future modeling years. These improvements will allow more direct comparison of model and EPA estimates of natural and anthropogenic contributions to haze and future visibility progress.

Methane Emissions from Natural Gas Production Sites in the United States: Data Synthesis and National Estimate.

We used site-level methane (CH4) emissions data from over 1000 natural gas (NG) production sites in eight basins, including 92 new site-level CH4 measurements in the Uinta, northeastern Marcellus, and Denver-Julesburg basins, to investigate CH4 emissions characteristics and develop a new national CH4 emission estimate for the NG production sector. The distribution of site-level emissions is highly skewed, with the top 5% of sites accounting for 50% of cumulative emissions. High emitting sites are predominantly also high producing (>10 Mcfd). However, low NG production sites emit a larger fraction of their CH4 production. When combined with activity data, we predict that this creates substantial variability in the basin-level CH4 emissions which, as a fraction of basin-level CH4 production, range from 0.90% for the Appalachian and Greater Green River to >4.5% in the San Juan and San Joaquin. This suggests that much of the basin-level differences in production-normalized CH4emissions reported by aircraft studies can be explained by differences in site size and distribution of site-level production rates. We estimate that NG production sites emit total CH4 emissions of 830 Mg/h (95% CI: 530-1200), 63% of which come from the sites producing <100 Mcfd that account for only 10% of total NG production. Our total CH4 emissions estimate is 2.3 times higher than the U.S. Environmental Protection Agency's estimate and likely attributable to the disproportionate influence of high emitting sites.

Consider Energy‐Saving Options for Wastewater Treatment Plants

According to the US Department of Energy, as much as 10 percent of a local government's budget is typically allocated to energy use. On average, more than one‐third of that municipal energy usage—about 35 percent—is used to provide water and wastewater services. For a typical wastewater treatment facility, electrical usage accounts for 25–40 percent of the annual operating budget. Overall, the US Environmental Protection Agency estimates that water and wastewater utilities use about 3–4 percent of total US energy consumed.

QUANTIFICATION OF MUNICIPAL SOLID WASTE MANAGEMENT IN THE UNITED STATES – WITH COMPARATIVE ANALYSIS TO OTHER ESTIMATES

The Environmental Research and Education Foundation (EREF) recently completed a study to quantify the amount of MSW managed in the United States. The study represents the first to use a bottom-up, facility-based methodology in the U.S. to improve accuracy and more discretely track the amount of waste managed. Over 9,000 facilities managing municipal solid waste (MSW) were identified through the course of the study (landfills, WTE incinerators, recycling facilities, composting operations, and anaerobic digesters), and information on the amount and types of waste managed were collected. Results suggest 1.4 times more MSW is managed in 2013 than previously suggested by U.S. Environmental Protection Agency (U.S. EPA) estimates. Data show that the majority of MSW was landfilled and the least amount of tonnage was composted.​

Treated sludge harbors antibiotic-resistance genes

To kill microorganisms that can potentially cause disease, the world’s most advanced sewage treatment plants essentially pressure-cook wastewater. But new research indicates that this process may not get rid of genes that impart antibiotic resistance to microbes. Because treated sludge is regularly spread on lands used to grow crops for human consumption, this finding could have public health implications, said Sarah Fischer, an environmental chemist at the University of Maryland, College Park, during a Division of Environmental Chemistry session at the ACS national meeting in Washington, D.C. The U.S. Environmental Protection Agency estimates that more than 7 million metric tons of biosolids—the residue from wastewater treatment, also called sludge—is applied to U.S. lands each year as fertilizer. Increasingly, organic farmers are debating the possible use of biosolids, pointed out Mustafa Selim of East Carolina University’s Brody School of Medicine, who co-organized the symposium. The U.S. Department of...