It's been roughly eight years since stricter Environmental Protection Agency (EPA) diesel-engine emissions standards took effect.
After a hiatus, significant numbers of cleaner diesel engines are now being sold each year in new vehicles on U.S. roads.
And a new study confirms that they are achieving the low emissions they were expected to.
Conducted by the Boston-based Health Effects Institute, the Advanced Collaborative Emissions Study (via the Diesel Technology Forum) found that they emitted only a fraction of the particulates and other pollutants that older diesels did.
Researchers focused on whether diesel engines built to comply with tougher regulations in place since 2007 achieved the expected emissions reductions.
These regulations call for reducing emissions of nitrogen oxides (NOx) and particulate matter from heavy-duty diesel engines by 98 percent compared to 1988 vehicles.
2014 Peterbilt 579
Engines complying with those regulations currently power about one third of the commercial trucks on U.S. roads.
Examining the emissions from these heavy-duty truck engines, researchers looked for corresponding decreases in toxic emitted substances.
The study concluded that exposure to exhaust from new diesel engines did not cause any increase in the risk of lung cancer--or any other adverse health effects--in lab animals.
The Health Effects Institute conducted its study in collaboration with the Coordinating Research Council, and it was sponsored by manufacturers of emissions-control equipment as well as regulatory bodies that include the EPA and California Air Resources Board.
Diesel engines used in commercial vehicles will likely continue to be regulated by ever-stricter emissions standards, paralleling developments with passenger cars and trucks.
Manufacturers of tractors and other agricultural equipment are cutting emissions in compliance with new EPA "Tier 4" standards.
Walmart WAVE concept truck.
Introduced for the 2014 model year, these standards call for a 90-percent reduction in NOx and particulate matter compared to 1996 models.
President Barack Obama has also asked the EPA to draft tougher standards for heavy-duty trucks.
These standards will take effect in 2019 and run through 2025, picking up where the current standards--which date to 2011--leave off.