by Ted Calvin, Charted Energy LLC
On October 1, EPA lowered the air quality standard for ground-level ozone from 75 parts per billion to 70 parts per billion. This change could provide additional support for alternative fuel vehicles in two ways. First, the higher standard will increase the number of air quality non-attainment areas in comparison to the old standard. Second, the higher standard will increase the need for emissions reductions in areas that were already considered non-attainment.
States that are not able to meet EPA’s air quality standards run the risk of losing federal highway funding. States are required to identify non-attainment areas and then develop a plan (state implementation plan, or SIP) to reduce the levels of pollutants in those areas. States will accept stakeholder input over the next year or two and then revise their SIP if the new standards require a revision.
How will the new standard impact fleets?
Ozone is an important component of local air quality. It is a chemical made up of three oxygen atoms that is unstable and therefore highly reactive. Internal combustion engines do not emit ozone directly, but they are sources of nitrogen oxides (collectively, NOx) and volatile organic compounds (VOCs). In the presence of sunlight, these emissions from vehicles’ tailpipes combine to form ozone. For more details on ozone formation and its health impacts, click here.
State air quality agencies will continue to push fleets to adopt better, cleaner technology. NOx is a much larger issue for diesel-powered vehicles than for gasoline-powered vehicles because the diesel engines, particularly in class VIII trucks, emit much more NOx per mile driven than lighter-weight gasoline-powered cars and trucks1. The NOx limits for heavy-duty diesel engines have been decreasing for several decades (see table).
If the 0.02 g/ bhp·hr standard becomes the threshold for all heavy-duty on-road engines, and not just an optional certification level, compliance will become a costly issue for diesel operators. The good news for fleets that are open to alternative fuels is spark-ignited natural gas engines will have an easier time meeting stricter NOx emissions requirements. In fact, Cummins-Westport has already certified one engine to the highest NOx standard3.
Why did EPA change the standard?
The Clean Air Act requires EPA to review air quality standards periodically. If the standards are found to be too lax to adequately protect the public’s health and the environment, EPA must revise the standards. The ground-level ozone standard was established in 1997 and then revised in 2008. The 2015 change is the first revision since 2008.
Ground-level ozone causes several kinds of acute (short-term) health problems for individuals. These include:
- Respiratory problems such as coughing and throat irritation
- Decreased lung capacity
- Inflammation of airways
The long-term effects of breathing high levels of ozone are not fully understood. Studies of lab animals show harmful effects from long-term exposure, but no consistent effects have been found studying human populations over long periods.