Diesel Emissions

Diesel fuel is widely used to move goods and people across the country. However, a number of environmental and public health effects (both long and short-term) have been associated with exposures to diesel exhaust. Therefore, reducing the amount of diesel emissions that are released into the atmosphere and into surrounding communities is a regulatory concern for the Allegheny County Health Department. Within the county, the largest sources of diesel exhaust are:

• Public transit and school buses
• Heavy-duty trucks
• Locomotives
• Off-road construction equipment

Strategies for Reducing Diesel Emissions

There are many strategies for decreasing the amount of diesel emissions in surrounding communities.

1. Reduce Idling

Unnecessary idling of diesel vehicles impacts air quality, wastes fuel, and increases engine wear. Some examples of ways to reduced diesel idling include:

• Management practices
• Automatic start/stop devices
• Auxiliary power units, cab heaters, block heaters
• Shore power with on-board units
• Advanced truck stop electrification

Please see the following link from the U.S. Department of Energy on idle reduction technologies and strategies, and the PA DEP Act 124 - diesel idling regulations.

The Allegheny County Health Department assists with addressing diesel idling complaints within Allegheny County and provides referrals for the PA DEP for enforcement of Act 124. If vehicle is over 10,001 pounds (5 tons) is idling for more than five minutes, the general public can submit a complaint to the ACHD Air Quality Program. Please be sure to include a description of the vehicle, and the amount of time it was observed idling. Please note that gasoline vehicles, or diesel vehicles under 10,001 pounds are not regulated by Act 124.

2. Repair/Retrofit/Replace

Reducing diesel emissions can be done by conducting regular maintenance on diesel engines, installing exhaust aftertreatments technologies, replacing an older engine with a newer engine, or by replacing entire vehicles with newer vehicles. Many older diesel engines can be repaired or retrofitted with devices to aid in the reduction of diesel emissions. Replacing older diesel engines with newer ones also reduces diesel emissions as newer engines have been designed under stricter regulations and benefit from updated emission reducing technology.

3. Utilize Cleaner Fuels

The most effective way to reduce diesel emissions is to replace diesel with a cleaner fuel source.

Ultra-low Sulfur Diesel
Since 2006, almost all of the diesel fuel available in the United States is ultra-low sulfur. The burning of ultra-low sulfur diesel has been shown to substantially lower particulate matter from diesel exhaust. The Allegheny County Health Department enforces the use of ultra-low sulfur diesel for permitted equipment, such as emergency generators.

Alternative Fuels
There has been a larger movement of replacing diesel fuel with hybrid or alternative fuel options which can greatly, if not entirely, reduce the amount of tailpipe emissions, positively impacting the surrounding communities.

Alternate fuels to diesel could include the following:

• Biodiesel
• Hydrogen
• Electric
• Natural gas
• Ethanol
• Propane
• Renewable diesel

Related Links

• The CARB Report on Diesel Exhaust
• PA DEP - Diesel Emissions
• Mid-Atlantic Diesel Collaborative
• EPA - Diesel Emissions Reduction Act (DERA)

Grant & Rebate Opportunities

There are various opportunities for grants to reduce diesel emissions from a vehicle fleet.

• Grant Opportunity - EPA DERA School Bus Rebate
• Grant Opportunity - EPA DERA National

Projects and Studies - Diesel Emission Reduction

Since 2005, the ACHD has awarded over $36 million in funding to help offset the costs of installing various diesel pollution reduction equipment and taken other actions to reduce diesel emissions (see Diesel Emission Reduction Projects(PDF, 233KB)).

Recent Projects Replacing Diesel Powered Equipment

• ACHD Clean Air Fund Grants 2024: $986,789 – awarded to Mon Valley municipalities to purchase new battery electric powered refuse trucks and street sweeping fleet equipment.
• ACHD Clean Air Fund Grants 2023: $2,198,339 – awarded to Mon Valley communities to purchase new battery electric powered refuse and recycle trucks and street sweeping fleet equipment. 
• Targeted Airshed Grant 2022: $10,000,000 – awarded to Pittsburgh Regional Transit to purchase 6 new battery electric powered transit buses.
• Targeted Airshed Grant 2021: $2,800,000 - awarded to the City of Pittsburgh to purchase five new electric refuse trucks and install two vehicle charging stations. 

Diesel Particulate Study

From 2014 to 2016, the ACHD and the University of Pittsburgh completed a diesel particulate study for the downtown Pittsburgh area to determine the variability of concentrations of diesel particulates and to differentiate the sources of diesel exhaust. The Executive Summary, as well as the results of the study, detailed in three published papers by Dr. Clougherty, can be found below.

• Dr. Clougherty's Diesel Study Executive Summary(PDF, 1MB)
• “Spatial variation in diesel-related elemental and organic PM_2.5 components during workweek hours across a downtown core”(PDF, 2MB)
• “Spatial Patterns in Rush-Hour vs. Work-Week Diesel-Related Pollution across a Downtown Core”(PDF, 4MB)
• "Fine-Scale Source Apportionment Including Diesel-Related Elemental and Organic Constituents of PM_2.5 across Downtown Pittsburgh"(PDF, 1MB)