Sooty diesel exhaust plumes still billow from buses, trucks, construction equipment, locomotives and tugboats on Allegheny County's roads, rails and rivers and will continue to do so for quite some time.
But those black burps from dirty diesels are happening less and less often because of federal rules requiring all new diesels to run much cleaner and the Allegheny County Health Department's vehicle retrofit program that has helped accelerate that trend, said Jim Thompson, the air quality program director.
In a presentation to the Allegheny County Board of Health earlier this month, Mr. Thompson said the ongoing program has installed new filters, and in some cases new engines, in about 200 vehicles since 2005 at a cost of about $4 million. That includes retrofits of almost 100 school buses, two Port Authority hybrid buses, eight short-haul trucks serving U.S. Steel's Edgar Thomson and Irvin plants in Braddock and West Mifflin, 44 garbage and municipal trucks, and one CSX switchyard locomotive in Aliquippa.
Those retrofits have reduced diesel emissions from those vehicles by at least 90 percent, or a total of almost 400 tons a year. The reductions include 10 tons of highly carcinogenic diesel particulate matter containing soot, black carbon, heavy metals and polycyclic aromatic hydrocarbons.
Mr. Thompson said 1 ton of diesel particulate emissions poses the same cancer risk as 60 tons of benzene, which is known to cause human cancer. By way of comparison, he noted that stationary sources, power plants and factories, in the county emit a total of 50 tons of benzene annually.
"It's an extremely valuable emissions reduction, especially in areas where there are human exposures close to roadways," Mr. Thompson said. "Those would include refuse trucks, school buses and the U.S. Steel trucks that travel on Braddock Avenue."
Those targeted emissions reductions from retrofitted diesels help amplify air quality gains made due to tighter federal diesel emissions standards. Beginning in 2007, federal regulations required diesel engines to reduce sooty particle emissions by 90 percent and in 2010 to reduce emission of nitrogen oxides, a component of unhealthy smog, by 95 percent.
"The federal regulations are a big help with the newer vehicles, but the problem is with the 'legacy' fleet of older diesels," Mr. Thompson said. "Those vehicles can last and continue to operate for 30 to 50 years, even 60 years."
He said many bus companies replace buses faster, every 12 years or so, but many older diesel-powered vehicles remain in operation, especially at smaller trucking firms, which tend to buy those vehicles from bigger truck firms that have more resources to buy newer, cleaner trucks.
Other persistent sources of diesel emissions include towboats on rivers, construction equipment, train locomotives and off-peak electric generators run by industries, Mr. Thompson said.
Action against idling
In addition to its retrofit program, the county's 2004 anti-diesel idling regulation and a concurrent "No Idling" sign and education program has reduced school bus idling outside schools. In 2005, four years before the state acted, county regulations were extended to on-road vehicles, limiting diesel idling to no more than five minutes per hour. And in 2010 the county enacted an anti-idling regulation for off-road vehicles.
Nationwide, long-haul diesel trucks and buses use more than 1.2 billion gallons of fuel a year idling -- about 1 percent of all U.S. oil imports, according to the U.S. Environmental Protection Agency.
"From a public health standpoint, reducing diesel emissions has been a beneficial thing to do, and the county has been quite the leader in taking the initiative on diesel emission reduction projects," said Rachel Filippini, executive director of the Group Against Smog and Pollution, a Pittsburgh-based environmental group.
Mr. Thompson said the county's diesel idling enforcement has been hampered by the 2009 state idling law, Act 124, which contains idling limitations equal to the county's and therefore prohibits the county health department from enforcing the county regulation.
"The state law pre-empted our enforcement and allows enforcement only by law enforcement officers and certain members of the state Department of Environmental Protection," said Mr. Thompson, adding that the health department received 30 idling complaints from residents last year. "But this is not something we're turning our backs on. We turn the complaints over `to the state and try to provide support. Normally that's all that's required to get the idling stopped."
A detailed two-year study of diesel emissions was approved by the county health board in September 2011. The $865,000 study, by researchers from the University of Pittsburgh's Graduate School of Public Health and Carnegie Mellon University, began a month ago and will use 40 battery-operated multi-pollutant monitors at strategic locations along Downtown streets to identify the sources of diesel emissions.
Mr. Thompson said the study results will be used by the county to target areas and sources for the future control measures.
Ms. Filippini said a coalition of local environmental groups active in pushing for passage of the city clean diesel construction law in 2011 attended a city council committee meeting Wednesday to strongly urge the city to implement and enforce the law.
"There has been a huge delay, and we want to know what's going on," Ms. Filippini said. "The law says regulations were supposed to be written in six months, and yet the air quality has not benefited and the dirty emissions are continuing to affect people living nearby various construction projects as well as the construction workers."
Don Hopey: firstname.lastname@example.org or 412-263-1983.