Clean diesel technology fleet transition programs

There is strong evidence that adopting clean diesel technology through diesel transition programs decreases environmental exhaust emissions (Zhang 2011, Barone 2010, Sandhu 2015, US EPA-Transportation 2006). Retrofitting diesel buses has also been shown to improve in-cabin air quality by decreasing particulate matter, organic carbon, and elemental carbon in some circumstances (Borak 2007, Trenbath 2009, Barone 2010). Vehicle replacement, especially with electric or alternative fuel vehicles, is suggested instead of retrofitting for vehicles nearing the end of their useful life; replacement improves vehicle safety, reliability, and fuel efficiency, and reduces maintenance costs and emissions (CDC-Cleaner fleets, US EPA-CSBP).

Decreases in emissions associated with retrofitted diesel buses appear to have positive effects on riders’ health. A Washington-based study, for example, indicates reductions in bronchitis, asthma, and pneumonia among children in school districts with retrofitted buses (Beatty 2011), as well as improvements in lung function and reductions in absenteeism, especially among children with asthma (Adar 2015). Retrofitting may also decrease the costs associated with respiratory disease-related hospitalizations and treatment (Beatty 2011).

Costs for diesel retrofit devices vary based on the manufacturer, labor requirements, and type of technology (US EPA-Diesel technologies). A Washington-based cost benefit analysis indicates that school bus retrofitting has positive net benefits (Beatty 2011). The U.S. EPA estimates that every federal dollar invested in clean diesel retrofits or replacements generates between $11 and $30 in savings from improvements in public health (CDC-Cleaner fleets).

Efforts to reduce diesel exhaust emissions – such as through fleet transitions to clean diesel technology or other alternative clean energy – have the potential to decrease existing disparities in air pollution exposure rates by race, ethnicity, and income (Demetillo 2021, Liu 2021, Nguyen 2018). Available evidence suggests that racial disparities in air pollution exposure have declined, although racial disparities persist (Liu 2021). Experts suggest programs should identify neighborhoods where emissions reductions can reduce average exposure, exposure inequality, and exposure injustice as well as account for meteorology and the movement of air pollution to reduce disparities in exposure (Nguyen 2018).

Diesel vehicles, especially heavy-duty diesel vehicles, are a primary source of toxic air pollution and disparities in pollutant exposure (Demetillo 2021). In a study of 52 cities across the country, air quality monitors recorded higher concentrations of nitrogen dioxide (NO2) exposure among people of color and people with lower incomes than among white people and those with higher incomes (Demetillo 2021). Combining race and income data reveals even larger disparities in air pollution exposure levels between people of color with incomes near or below the poverty line compared to white people with incomes above the poverty line (Demetillo 2021).

Higher exposure to air pollution and toxic emissions has been associated with people of color and people with low incomes experiencing poorer health outcomes than white people and people with higher incomes (Demetillo 2021). Air pollution exposure and living in neighborhoods with heavy traffic is associated with many adverse health effects, including asthma, respiratory disease, cardiovascular disease, cancers, adverse birth outcomes, cognitive decline, dementia, and more (Liu 2021, Commodore 2021). Children living near heavy traffic are more likely to have asthma than children living in neighborhoods without traffic; children of color are also more likely to have or develop asthma than white children (Commodore 2021). Other studies suggest more Black individuals are diagnosed with and hospitalized for asthma, compared with white individuals (McKane 2018).

Throughout U.S. history, discriminatory housing, lending, and exclusionary zoning policies entrenched racial residential segregation and concentrated poverty (Zdenek 2017, Kaplan 2007). Many urban areas in the U.S. experienced unrestrained industrialization without environmental regulations or land use controls creating environmental problems, including water and air pollution, waste production, overconsumption of natural resources, and loss of green space (Lampert 2021). Early U.S. environmental movements focused on conservation and nature preservation and did not consider urban environmental inequities or public health (NEJAC 2006). The built environment in under-resourced communities is a significant contributor to health inequities for people of color with low incomes (Prochnow 2022, McAndrews 2022, Brookings-Semmelroth 2020). Formerly redlined neighborhoods remain more likely to include vacant lots and blighted properties, older homes in poor condition, coal-fired power plants, hazardous waste disposal sites, and other health risks (Braveman 2022). Communities with low incomes and communities of color still have fewer places to engage in outdoor activities, have less access to cooling shade, experience more extreme heat, and experience poorer air quality (KFF-Ndugga 2022, CAP-Rowland-Shea 2020, TPL-Chapman 2021).

The Air Pollution Control Act of 1955 was the first federal legislation to identify and provide funds for air pollution research. The Clean Air Act of 1963 began the process of air pollution control, and many iterations of the legislation followed. Notably, the Clean Air Act of 1970 authorized the U.S. Environmental Protection Agency (EPA) to establish, regulate, monitor, and enforce National Ambient Air Quality Standards to protect public health from widespread hazardous air pollutants, especially particulate matter, ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead. This legislation regulates and enforces reductions of many types of air pollution from multiple pollution sources, including motor vehicles. The 1990 Clean Air Act Amendments established updated goals and technology standards to reduce hazardous air pollution (US EPA-Evolving federal legislation, US EPA-CAA History, US EPA-CAA). The federal Clean Air Act has reduced disparities in hazardous pollutant exposure, although racial disparities continue to persist (NBER-Currie 2021). EPA standards for cleaner vehicles and fuel aim to reduce pollutants which harm human health and the environment, as emissions from personal and commercial vehicles, and their fuel, continue to be a large source of pollution exposure (US EPA-Air pollution challenges).

The Energy Policy Act of 2005 established the Diesel Emissions Reduction Act (DERA) Program and authorized the EPA to fund efforts to reduce hazardous diesel emissions, including fleet transition programs for school buses and heavy-duty vehicles (US EPA-DERA Impacts). Many grant and funding efforts are shifting away from diesel retrofits or replacements to cleaner alternatives such as electric vehicles with zero tailpipe emissions; for example, increased funding for the Clean School Bus program (US EPA-CSBP).

• What neighborhoods in your community experience heavy traffic, especially from diesel vehicles? Which areas in your community suffer from poor air quality and high levels of pollutant exposures? Who is assessing the impacts of traffic on human and animal health and the environment, for example, near schools, public green spaces, and areas with tourism?
• How does your community engage neighborhood residents, especially residents of color and those with low incomes, in the planning and development of neighborhood spaces that influence traffic patterns? Do those making planning decisions about urban planning and traffic routes represent the local community?
• How are you considering local climate, wind patterns, and efforts to mitigate climate change, as part of city fleet transition programs?
• How are funds raised and allocated for fleet transitions in your community? Who is exploring grant opportunities for purchasing electric, alternative fuel, or cleaner diesel technology vehicles?

Many states have programs to support diesel retrofit efforts, as in Maryland and Oregon (MD DOE-Diesel, OR DEQ-Diesel). New Jersey had a mandatory diesel retrofit program from 2007-2017; the program regulated school buses, solid waste vehicles, commercial buses, and publicly-owned vehicles (NJ DOEP-Diesel). Many states are developing emissions reduction programs that support alternative fuel, electric, or hybrid fleets instead of diesel, as in Texas (TCEQ-TERP).

The U.S. Department of Transportation Federal Highway Administration’s Congestion Mitigation and Air Quality Improvement (CMAQ) Program funds efforts to improve air quality, including diesel engine retrofits (US DOT-CMAQ). The U.S. Environmental Protection Agency manages funds appropriated for the Diesel Emission Reduction Act (DERA) to retrofit older diesel vehicles (US EPA-DERA). The proposed federal budget for FY 2022 also includes grant funding for the DERA program, as well as additional funds to retrofit, replace or repower diesel equipment, especially school buses (NACAA-Appropriations).

US EPA-Clean diesel - U.S. Environmental Protection Agency (U.S. EPA). Learn about clean diesel: Impacts of diesel emissions, Diesel Emissions Reduction Act (DERA), and other federal funding.

US EPA-CSBP - U.S. Environmental Protection Agency (U.S. EPA). Clean School Bus Program (CSBP).

US EPA-DERA - U.S. Environmental Protection Agency (U.S. EPA). Diesel Emissions Reduction Act (DERA) Funding: Reducing emissions that impact our health.

World Emissions Clock - World Data Lab. World Emissions Clock.

* Journal subscription may be required for access.

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CDC-Cleaner fleets - Centers for Disease Control and Prevention (CDC), Office of the Associate Director for Policy and Strategy. Cleaner and alternative bus fleets. Health impact in 5 years (HI-5): Transitioning bus fleets, cleaner air for a healthier community.

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MD DOE-Diesel - Maryland Department of the Environment (MD DOE). Diesel retrofit projects.

NACAA-Appropriations - National Association of Clean Air Agencies (NACAA). FY 2021 budget and appropriations information.

NBER-Currie 2021 - Currie J, Voorheis J, Walker R. What caused racial disparities in particulate exposure to fall? New evidence from the Clean Air Act and satellite-based measures of air quality. National Bureau of Economic Research (NBER). 2021: Working Paper 26659.

NEJAC 2006 - The National Environmental Justice Advisory Council (NEJAC). Unintended impacts of redevelopment and revitalization efforts in five environmental justice communities. 2006.

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NJ DOEP-Diesel - New Jersey Department of Environmental Protection (NJ DOEP). Mandatory Diesel Retrofit Program.

OR DEQ-Diesel - Oregon Department of Environmental Quality (OR DEQ). Air quality: Clean diesel success stories including Oregon's Clean Diesel Initiative.

Prochnow 2022* - Prochnow T, Valdez D, Curran LS, et al. Multifaceted scoping review of Black/African American transportation and land use expert recommendations on activity-friendly routes to everyday destinations. Health Promotion Practice. 2022.

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TCEQ-TERP - Texas Commission on Environmental Quality (TCEQ). Texas Emissions Reduction Plan (TERP) program grants.

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WI DNR-Clean diesel - Wisconsin Department of Natural Resources (WI DNR). Clean diesel grant programs.

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