Association of Private Equity Firm Acquisition of Ophthalmology Practices with Medicare Spending and Use of Ophthalmology Services.

PURPOSE: Private equity (PE) firms increasingly are acquiring ophthalmology practices; little is known of their influence on care use and spending. We studied changes in use and Medicare spending after PE acquisition. DESIGN: Retrospective cohort study. PARTICIPANTS: Seven hundred sixty-two clinicians in 123 practices acquired by PE between 2017 and 2018 and 34 807 clinicians in 20 549 never-acquired practices. METHODS: We analyzed Medicare fee-for-service claims (2012-2019) combined with a novel national database of PE acquisitions of ophthalmology practices using a difference-in-differences method within an event study framework to compare changes after a practice was acquired with changes in practices that were not acquired. MAIN OUTCOME MEASURES: Numbers of beneficiaries seen; intravitreal injections and medications used for injections; and spending on ophthalmologist and optometrist services, ancillary services, and intravitreal injections. RESULTS: Comparing PE-acquired with nonacquired practices showed a 23.92% increase (n = 4.20 beneficiaries; 95% confidence interval [CI], 1.73-6.67) in beneficiaries seen per PE optometrist per quarter and no change for ophthalmologists, while spending per beneficiary increased 5.06% ($9.66; 95% CI, -2.82 to 22.14). Spending on clinician services decreased 1.62% (-$2.37; 95% CI, -5.78 to 1.04), with ophthalmologist services increasing 5.46% ($17.70; 95% CI, -2.73 to 38.15) and optometrists decreasing 4.60% (-$5.76; 95% CI, -9.17 to -2.34) per beneficiary per quarter. Ancillary services decreased 7.56% (-$2.19; 95% CI, 4.19 to -0.22). Intravitreal injection costs increased 25.0% ($20.02; 95% CI, -1.38 to 41.41) with the number increasing 5.10% (1.83; 95% CI, -0.1 to 3.80). There was a 74.09% increase (8.38 injections; 95% CI, 0.01-16.74) in ranibizumab and a 12.91% decrease (-3.40 injections; 95% CI, -6.86 to 0.07) in bevacizumab after acquisition. The event study showed consistent and often statistically significant increases in ranibizumab injections and decreases in bevacizumab injections after acquisition. CONCLUSIONS: Although not all results reached statistical significance, this study suggested that PE acquisition of practices showed little or no overall effect on use or total spending, but increased the number of unique patients seen per optometrist and the use of expensive intravitreal injections. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Facilitating deep learning through preprocessing of optical coherence tomography images.

BACKGROUND: While deep learning has delivered promising results in the field of ophthalmology, the hurdle to complete a deep learning study is high. In this study, we aim to facilitate small scale model trainings by exploring the role of preprocessing to reduce computational burden and accelerate learning. METHODS: A small subset of a previously published dataset containing optical coherence tomography images of choroidal neovascularization, drusen, diabetic macula edema, and normal macula was modified using Fourier transformation and bandpass filter, producing high frequency images, original images, and low frequency images. Each set of images was trained with the same model, and their performances were compared. RESULTS: Compared to that with the original image dataset, the model trained with the high frequency image dataset achieved an improved final performance and reached maximum performance much earlier (in fewer epochs). The model trained with low frequency images did not achieve a meaningful performance. CONCLUSION: Appropriate preprocessing of training images can accelerate the training process and can potentially facilitate modeling using artificial intelligence when limited by sample size or computational power.

Uveal lymphoid hyperplasia: treatment with combination antibiotics and steroids.

BACKGROUND/AIMS: Uveal lymphoid hyperplasia (formerly benign reactive hyperplasia of the choroid) spans histopatholological characteristics ranging from reactive hyperplasia to low-grade lymphoid neoplasm. There is strong evidence that other low-grade lymphoid neoplasms, particularly of gastric derivations, respond to oral antibiotics. Here, we explore that response of uveal lymphoid hyperplasia to treatment with only oral antibiotics and steroids. METHODS: Four eyes of three patients with clinically diagnosed uveal lymphoid hyperplasia were treated with a course of oral antibiotics and steroids. The main outcome was clinical response of choroidal infiltrate by optical coherence tomography (OCT) measurements of choroidal thickness and visual acuity. Secondary outcome measure included local and systemic recurrence. Clinical response was evaluated by clinical exam, fundus photography, ultrasound and OCT. RESULTS: All 4 eyes displayed a clinical response at a median 2 weeks after starting oral antibiotics and steroid course. The choroidal infiltration regressed as evidenced by: decrease of choroidal thickness by a median of 421 nm, myopic shift in refractive error by a median of 0.50 Diopters, and improved vision by a median of 1.5 Snellen lines. At a median of 51-month follow-up, all four eyes had a sustained complete response and no patient has developed systemic disease to date. CONCLUSIONS: In this small cohort of patients with uveal lymphoid hyperplasia, measurable and sustained clinical responses were observed with antibiotics/steroids, without systemic recurrence. This suggests combination antibiotic/steroid therapy is a reasonable treatment for select cases of uveal lymphoid hyperplasia, and may avoid the need for systemic chemotherapy/monoclonal antibody and/or external beam irradiation.

Postoperative Bioresorbable Chitosan-Based Dressing for Endoscopic Middle Meatal Dacryocystorhinostomy With Balloon Dilation.

PURPOSE: To evaluate the improvement in epiphora and need for surgical revision in patients with acquired nasolacrimal duct obstruction following balloon-assisted, middle meatal endoscopic dacryocystorhinostomy with chitosan-based dressing versus bioresorbable polyurethane packing versus no packing. PATIENTS AND METHODS: This was a retrospective study of consecutive adult patients seen from 2015 to 2018 with follow-up evaluation of epiphora at least 3 months after balloon-assisted, middle meatal endoscopic dacryocystorhinostomy. Patients with a history of prior punctoplasty, septoplasty, sinus surgery, or dacryocystorhinostomy of any kind were excluded. Those meeting criteria were stratified by postoperative hemostatic intervention: no packing, bioresorbable packing, and chitosan-based dressing (groups 1, 2, and 3, respectively). Procedural outcomes were graded as successes or failures based on subjective report and anatomical findings at most recent visit within an 18-month postoperative window. Instances of recommendation for revision surgery were also recorded. RESULTS: Forty-three cases (36 patients) met the abovementioned criteria. Groups 1, 2, and 3 comprised 12, 17, and 14 cases each, respectively. Average patient age was 55.3 years old, and average duration of follow-up was 6.7 months. Significant variation in outcomes was detected across the 3 groups (P = .0495), particularly between groups 1 and 3 (P = .033). Use of chitosan-based dressing trended toward reduced rates of recommendation for surgical revision (P = .203, P = .113). CONCLUSIONS: Use of chitosan-based dressing after endoscopic dacryocystorhinostomy was associated with improved subjective and anatomical outcomes. It may also contribute to less frequent need for revision surgery. Further study in a larger prospective trial is recommended.

Rheumatologists' perspective on hydroxychloroquine guidelines.

OBJECTIVE: Hydroxychloroquine (HCQ) retinal toxicity is an ongoing concern for rheumatologists. The revised 2016 American Academy of Ophthalmology (AAO) guidelines created controversy regarding the correct dosing and evaluation of HCQ toxicity. The current study was initiated to further understand rheumatologists' practices regarding HCQ. METHODS: A questionnaire-based survey was distributed electronically to rheumatologists. We collected information on HCQ dosing, clinical decision-making processes, familiarity with the AAO 2016 guidelines, and perceived disparities between the AAO 2016 guidelines and rheumatological clinical practice. RESULTS: 78 rheumatologists completed the survey (49% from USA, 90% academic practices, 82% self-identified as lupus experts). Only lupus expert (n=64) data were included in subsequent analysis. The mean cohort size was 747 (50-6571), a total cohort 45 612 patients. HCQ was prescribed to >75% of patients with SLE by 81.3% of SLE experts, with routine counselling about ophthalmic risks. The typical dose of HCQ used was 200-400 mg/day. 17% of rheumatologists use doses up to 600 mg/day, while 6.2% use up to 6.5 mg/kg/day. HCQ adherence is routinely assessed. 479 cases of HCQ retinal toxicity (1.05%) and 9 cases of HCQ-associated blindness (1.8 per 10 000 patients) were reported. 89.1% of respondents reported familiarity with the AAO guidelines. Those aware of the guidelines cited limited dosing options (54.7%), lack of supporting evidence (57.8%) and low patient adherence (43.8%) as obstacles to greater implementation of the guidelines. CONCLUSION: These data suggest that HCQ toxicity and blindness are rare in patients with SLE. Rheumatologists treating patients with SLE are aware of the guidelines and appreciate the importance of partnering with ophthalmologists in preventing retinal toxicity.

Wide Variability in Patient-Reported Outcomes Measures After Fusion for Lumbar Spinal Stenosis: A Systematic Review.

STUDY DESIGN: Systematic review. OBJECTIVES: The purpose of this study is to review outcomes reporting methodology in studies evaluating fusion for lumbar spinal stenosis. METHODS: A systematic review of PubMed and Embase databases was conducted from January 2007 to June 2017 for English language studies with minimum of 2 years postoperative follow-up reporting outcomes after fusion for lumbar spinal stenosis. Two reviewers assessed each study; those meeting inclusion criteria were examined for pertinent data. Outcome measures were categorized into relevant domains: pain/symptomatology, function/disability, and surgical satisfaction. Return to work reporting was also recorded. RESULTS: Of 123 studies meeting inclusion criteria, 76% included posterior-only fusion, 32% included posterior/transforaminal interbody fusion, and 5% included anterior/lateral interbody fusion (non-mutually exclusive). There was significant variation in patient-reported outcomes (PROs) used-studies reported 31 unique PROs assessing at least one domain: 22 evaluating pain, 23 evaluating function, and 3 evaluating surgical satisfaction. Most commonly utilized PROs were the Oswestry Disability Index (73% of studies), Visual Analog Scale (55%), and 36-Item Short Form Survey (32%). The remaining 28 measures were used in 14% of studies or fewer. PROs specific to symptoms of lumbar spinal stenosis, such as the Zurich Claudication Questionnaire, were only used rarely (7/123 studies). Only 14% of studies reported on time to return to work. CONCLUSIONS: The literature surrounding fusion in the setting of lumbar stenosis is characterized by substantial variability in outcomes reporting. Very few studies utilized measures specific to lumbar spinal stenosis. Efforts to standardize outcomes reporting would facilitate comparisons of surgical interventions.

Pediatric Onychophagia: A Survey-Based Study of Prevalence, Etiologies, and Co-Morbidities.

BACKGROUND: Onychophagia, defined as habitual nail biting, is a common disorder affecting 6-45% of the population and is more prevalent in children. OBJECTIVES: Our primary objective was to determine the prevalence of nail biting in the pediatric population. Secondary objectives were to assess the presence of psychiatric co-morbidities associated with nail biting, and the effect of treatment on nail biting. METHODS: An anonymous voluntary survey was administered to participants at an outpatient academic pediatric clinic at Weill Cornell Medicine. Age, sex, psychiatric diagnosis, treatment sought, family history, and frequency of nail biting were analyzed across 282 enrolled patients aged 3-21 years. One patient was subsequently excluded due to incomplete data. RESULTS: Of 281 patients, 101 (37%) reported past or present nail biting lasting more than a month. Median age of onset was 5 years old (range 1-13 years). A significantly higher percentage of biters (18%; 19/104) than non-biters (6%; 11/177) were diagnosed with a psychiatric disorder (p < 0.01). Amongst biters, concurrent fingernail and toenail involvement was much less common (12%; 12/104) than that of fingernails alone (88%; 92/104). However, the ratio of fingernail and toenail biters to fingernail biters alone was greater in those with psychiatric diagnosis (0.36) than without (0.09) (p = 0.07). CONCLUSIONS: Our study highlights behavioral patterns as well as familial, psychiatric, and other factors associated with pediatric nail biting. Familiarity with such factors, the clinical presentation of onychophagia, and available treatment options may aid in reducing its severity in affected patients and overall prevalence.

Cleaner fuels for ships provide public health benefits with climate tradeoffs.

We evaluate public health and climate impacts of low-sulphur fuels in global shipping. Using high-resolution emissions inventories, integrated atmospheric models, and health risk functions, we assess ship-related PM2.5 pollution impacts in 2020 with and without the use of low-sulphur fuels. Cleaner marine fuels will reduce ship-related premature mortality and morbidity by 34 and 54%, respectively, representing a ~ 2.6% global reduction in PM2.5 cardiovascular and lung cancer deaths and a ~3.6% global reduction in childhood asthma. Despite these reductions, low-sulphur marine fuels will still account for ~250k deaths and ~6.4 M childhood asthma cases annually, and more stringent standards beyond 2020 may provide additional health benefits. Lower sulphur fuels also reduce radiative cooling from ship aerosols by ~80%, equating to a ~3% increase in current estimates of total anthropogenic forcing. Therefore, stronger international shipping policies may need to achieve climate and health targets by jointly reducing greenhouse gases and air pollution.

Greater focus needed on methane leakage from natural gas infrastructure.

Natural gas is seen by many as the future of American energy: a fuel that can provide energy independence and reduce greenhouse gas emissions in the process. However, there has also been confusion about the climate implications of increased use of natural gas for electric power and transportation. We propose and illustrate the use of technology warming potentials as a robust and transparent way to compare the cumulative radiative forcing created by alternative technologies fueled by natural gas and oil or coal by using the best available estimates of greenhouse gas emissions from each fuel cycle (i.e., production, transportation and use). We find that a shift to compressed natural gas vehicles from gasoline or diesel vehicles leads to greater radiative forcing of the climate for 80 or 280 yr, respectively, before beginning to produce benefits. Compressed natural gas vehicles could produce climate benefits on all time frames if the well-to-wheels CH(4) leakage were capped at a level 45-70% below current estimates. By contrast, using natural gas instead of coal for electric power plants can reduce radiative forcing immediately, and reducing CH(4) losses from the production and transportation of natural gas would produce even greater benefits. There is a need for the natural gas industry and science community to help obtain better emissions data and for increased efforts to reduce methane leakage in order to minimize the climate footprint of natural gas.

Total fuel-cycle analysis of heavy-duty vehicles using biofuels and natural gas-based alternative fuels.

Heavy-duty vehicles (HDVs) present a growing energy and environmental concern worldwide. These vehicles rely almost entirely on diesel fuel for propulsion and create problems associated with local pollution, climate change, and energy security. Given these problems and the expected global expansion of HDVs in transportation sectors, industry and governments are pursuing biofuels and natural gas as potential alternative fuels for HDVs. Using recent lifecycle datasets, this paper evaluates the energy and emissions impacts of these fuels in the HDV sector by conducting a total fuel-cycle (TFC) analysis for Class 8 HDVs for six fuel pathways: (1) petroleum to ultra low sulfur diesel; (2) petroleum and soyoil to biodiesel (methyl soy ester); (3) petroleum, ethanol, and oxygenate to e-diesel; (4) petroleum and natural gas to Fischer-Tropsch diesel; (5) natural gas to compressed natural gas; and (6) natural gas to liquefied natural gas. TFC emissions are evaluated for three greenhouse gases (GHGs) (carbon dioxide, nitrous oxide, and methane) and five other pollutants (volatile organic compounds, carbon monoxide, nitrogen oxides, particulate matter, and sulfur oxides), along with estimates of total energy and petroleum consumption associated with each of the six fuel pathways. Results show definite advantages with biodiesel and compressed natural gas for most pollutants, negligible benefits for e-diesel, and increased GHG emissions for liquefied natural gas and Fischer-Tropsch diesel (from natural gas).

Marine vessels as substitutes for heavy-duty trucks in Great Lakes freight transportation.

This paper applies a geospatial network optimization model to explore environmental, economic, and time-of-delivery tradeoffs associated with the application of marine vessels as substitutes for heavy-duty trucks operating in the Great Lakes region. The geospatial model integrates U.S. and Canadian highway, rail, and waterway networks to create an intermodal network and characterizes this network using temporal, economic, and environmental attributes (including emissions of carbon dioxide, particulate matter, carbon monoxide, sulfur oxides, volatile organic compounds, and nitrogen oxides). A case study evaluates tradeoffs associated with containerized traffic flow in the Great Lakes region, demonstrating how choice of freight mode affects the environmental performance of movement of goods. These results suggest opportunities to improve the environmental performance of freight transport through infrastructure development, technology implementation, and economic incentives.

Assessment of near-future policy instruments for oceangoing shipping: impact on atmospheric aerosol burdens and the earth's radiation budget.

We apply the global climate model ECHAM5/MESSy1-MADE with detailed aerosol and cloud microphysics to study the impact of shipping on tropospheric aerosol burdens, clouds, and the radiation budget for four near-future ship emission policy scenarios for the year 2012. We compare a "No Control" scenario with global sulfur limits and regionally applied reductions. We show that, if no control measures are taken, near surface sulfate increases by about 10-20% over the main transoceanic shipping routes from 2002 to 2012. A reduction of the maximum fuel sulfur (S) content allowed within 200 nautical miles of coastal areas ("global emission control areas") to 0.5% or 0.1% (5000 or 1000 ppm S, respectively) results in a distinctive reduction in near surface sulfate from shipping in coastal regions compared with the year 2002. The model results also show that if emissions of nitrogen oxides (NO(x)) remain unabated, a reduction of the fuel sulfur content favors a strong increase in aerosol nitrate (NO3) which could counteract up to 20% of the decrease in sulfate mass achieved by sulfur emission reductions. The most important impact of shipping on the radiation budget is related to the modification of low maritime stratus clouds resulting in an increased reflectivity and enhanced shortwave cloud forcing. The direct aerosol effect from shipping is small. Our study shows that one can expect a less negative (less cooling) radiative forcing due to reductions in the current fuel sulfur content of ocean-going ships. The global annual average net cloud forcings due to shipping (year 2012) are in the range of -0.27 to -0.58 W/m2 with regional cooling occurring most over the remote oceans.

Assessing energy, environmental, and economic tradeoffs in intermodal freight transportation.

This paper presents an energy and environmental network analysis model to explore tradeoffs associated with freight transport. The geospatial model uses an intermodal network built by the authors to connect various modes (rail, road, water) via intermodal terminals. Routes along the network are characterized not only by temporal and distance attributes, but also by cost, energy, and emissions attributes (including emissions of carbon dioxide, particulate matter, sulfur oxides, volatile organic compounds, and oxides of nitrogen). Decision-makers can use the model to explore tradeoffs among alternative route selection across different modal combinations, and to identify optimal routes for objectives that feature energy and environmental parameters (e.g., minimize carbon dioxide emissions). The model is demonstrated with three case studies of freight transport along the U.S. eastern seaboard.

Emissions tradeoffs among alternative marine fuels: total fuel cycle analysis of residual oil, marine gas oil, and marine diesel oil.

Worldwide concerns about sulfur oxide (SOx) emissions from ships are motivating the replacement of marine residual oil (RO) with cleaner, lower-sulfur fuels, such as marine gas oil (MGO) and marine diesel oil (MDO). Vessel operators can use MGO and MDO directly or blended with RO to achieve environmental and economic objectives. Although expected to be much cleaner in terms of criteria pollutants, these fuels require additional energy in the upstream stages of the fuel cycle (i.e., fuel processing and refining), and thus raise questions about the net impacts on greenhouse gas emissions (primarily carbon dioxide [CO2]) because of production and use. This paper applies the Total Energy and Environmental Analysis for Marine Systems (TEAMS) model to conduct a total fuel cycle analysis of RO, MGO, MDO, and associated blends for a typical container ship. MGO and MDO blends achieve significant (70-85%) SOx emissions reductions compared with RO across a range of fuel quality and refining efficiency assumptions. We estimate CO2 increases of less than 1% using best estimates of fuel quality and refinery efficiency parameters and demonstrate how these results vary based on parameter assumptions. Our analysis suggests that product refining efficiency influences the CO2 tradeoff more than differences in the physical and energy parameters of the alternative fuels, suggesting that modest increases in CO2 could be offset by efficiency improvements at some refineries. Our results help resolve conflicting estimates of greenhouse gas tradeoffs associated with fuel switching and other emissions control policies.

Energy use and emissions from marine vessels: a total fuel life cycle approach.

Regional and global air pollution from marine transportation is a growing concern. In discerning the sources of such pollution, researchers have become interested in tracking where along the total fuel life cycle these emissions occur. In addition, new efforts to introduce alternative fuels in marine vessels have raised questions about the energy use and environmental impacts of such fuels. To address these issues, this paper presents the Total Energy and Emissions Analysis for Marine Systems (TEAMS) model. TEAMS can be used to analyze total fuel life cycle emissions and energy use from marine vessels. TEAMS captures "well-to-hull" emissions, that is, emissions along the entire fuel pathway, including extraction, processing, distribution, and use in vessels. TEAMS conducts analyses for six fuel pathways: (1) petroleum to residual oil, (2) petroleum to conventional diesel, (3) petroleum to low-sulfur diesel, (4) natural gas to compressed natural gas, (5) natural gas to Fischer-Tropsch diesel, and (6) soybeans to biodiesel. TEAMS calculates total fuel-cycle emissions of three greenhouse gases (carbon dioxide, nitrous oxide, and methane) and five criteria pollutants (volatile organic compounds, carbon monoxide, nitrogen oxides, particulate matter with aerodynamic diameters of 10 microm or less, and sulfur oxides). TEAMS also calculates total energy consumption, fossil fuel consumption, and petroleum consumption associated with each of its six fuel cycles. TEAMS can be used to study emissions from a variety of user-defined vessels. This paper presents TEAMS and provides example modeling results for three case studies using alternative fuels: a passenger ferry, a tanker vessel, and a container ship.

Cost-effectiveness of reducing sulfur emissions from ships.

We model cost-effectiveness of control strategies for reducing SO2 emissions from U.S. foreign commerce ships traveling in existing European or hypothetical U.S. West Coast SO(x) Emission Control Areas (SECAs) under international maritime regulations. Variation among marginal costs of control for individual ships choosing between fuel-switching and aftertreatment reveals cost-saving potential of economic incentive instruments. Compared to regulations prescribing low sulfur fuels, a performance-based policy can save up to $260 million for these ships with 80% more emission reductions than required because least-cost options on some individual ships outperform standards. Optimal simulation of a market-based SO2 control policy for approximately 4,700 U.S. foreign commerce ships traveling in the SECAs in 2002 shows that SECA emissions control targets can be achieved by scrubbing exhaust gas of one out of ten ships with annual savings up to $480 million over performance-based policy. A market-based policy could save the fleet approximately $63 million annually under our best-estimate scenario. Spatial evaluation of ship emissions reductions shows that market-based instruments can reduce more SO2 closer to land while being more cost-effective for the fleet. Results suggest that combining performance requirements with market-based instruments can most effectively control SO2 emissions from ships.

Mortality from ship emissions: a global assessment.

Epidemiological studies consistently link ambient concentrations of particulate matter (PM) to negative health impacts, including asthma, heart attacks, hospital admissions, and premature mortality. We model ambient PM concentrations from oceangoing ships using two geospatial emissions inventories and two global aerosol models. We estimate global and regional mortalities by applying ambient PM increases due to ships to cardiopulmonary and lung cancer concentration-risk functions and population models. Our results indicate that shipping-related PM emissions are responsible for approximately 60,000 cardiopulmonary and lung cancer deaths annually, with most deaths occurring near coastlines in Europe, East Asia, and South Asia. Under current regulation and with the expected growth in shipping activity, we estimate that annual mortalities could increase by 40% by 2012.

Optimal fleetwide emissions reductions for passenger ferries: an application of a mixed-integer nonlinear programming model for the New York-New Jersey Harbor.

Emissions from passenger ferries operating in urban harbors may contribute significantly to emissions inventories and commuter exposure to air pollution. In particular, ferries are problematic because of high emissions of oxides of nitrogen (NOx) and particulate matter (PM) from primarily unregulated diesel engines. This paper explores technical solutions to reduce pollution from passenger ferries operating in the New York-New Jersey Harbor. The paper discusses and demonstrates a mixed-integer, non-linear programming model used to identify optimal control strategies for meeting NOx and PM reduction targets for 45 privately owned commuter ferries in the harbor. Results from the model can be used by policy-makers to craft programs aimed at achieving least-cost reduction targets.

Controlling air pollution from passenger ferries: cost-effectiveness of seven technological options.

Continued interest in improving air quality in the United States along with renewed interest in the expansion of urban passenger ferry service has created concern about air pollution from ferry vessels. This paper presents a methodology for estimating the air pollution emissions from passenger ferries and the costs of emissions control strategies. The methodology is used to estimate the emissions and costs of retrofitting or re-powering ferries with seven technological options (combinations of propulsion and emission control systems) onto three vessels currently in service in San Francisco Bay. The technologies include improved engine design, cleaner fuels (including natural gas), and exhaust gas cleanup devices. The three vessels span a range of ages and technologies, from a 25-year-old monohull to a modern, high-speed catamaran built only four years ago. By looking at a range of technologies, vessel designs, and service conditions, a sense of the broader implications of controlling emissions from passenger ferries across a range of vessels and service profiles is provided. Tier 2-certified engines are the most cost-effective choice, but all options are cost-effective relative to other emission control strategies already in place in the transportation system.