23 July 1999
The US EPA announced the final Urban Air Toxics Strategy, an integrated approach to control emissions of Hazardous Air Pollutants (HAP) in urban areas. An overview of the Strategy was published in the Federal Register on 19 July 1999. The Strategy presented in the FR notice has been developed through a public discussion process, which followed the publication of a first draft on 14 September 1998.
The US Clean Air Act in its section 112(b) identifies 188 HAPs. The Strategy targets 33 of these pollutants, which are considered to pose the greatest health risks in urban areas. Even though none of the major diesel exhaust pollutants has been included in the list, diesel emissions have been explicitly identified in the Strategy as a special concern.
During the public comment period on the draft Strategy, EPA received comments regarding the role of diesel engine emissions among urban air pollutants, with several commenters suggesting that diesel exhaust be included among the priority urban HAPs. EPA agreed with commenters that diesel exhaust plays an important role in urban air pollution, and plans to address diesel exhaust in the actions to be taken under the Strategy.
The Strategy represents an integration of EPA authorities to identify and address risks from both stationary and mobile sources. The goals of the Strategy are:
- Attain a 75-percent reduction in incidence of cancer attributable to exposure to HAPs in all urban areas nationwide.
- Attain a substantial reduction in public health risks posed by HAP emissions. This includes health effects other than cancer posed by all HAPs.
- Address disproportionate impacts of air toxics hazards across urban areas. This will involve consideration of both stationary and mobile source emissions of all HAPs.
Reductions in HAPs emissions can be the result of actions by Federal, State, local and/or Tribal governments, achieved by regulations or voluntary actions.
The following list of Urban HAPs has been compiled for the Integrated Urban Air Toxics Strategy:
coke oven emissions
1,2-dichloropropane (propylene dichloride)
ethylene dichloride (1,2-dichloroethane)
methylene chloride (dichloromethane)
polychlorinated biphenyls (PCBs)
polycyclic organic matter (POM)
2,3,7,8-tetrachlorodibenzo-p-dioxin (and congeners and TCDF congeners)
In addition to the above list, EPA is currently investigating the health risks associated with the mixture of compounds that comprise diesel exhaust which originates primarily from mobile sources. Diesel exhaust includes compounds that fall into the group of POM chemicals, as well as some other HAPs. Furthermore, EPA expressed concern about the potential health risks from the particulate matter (PM) component of diesel exhaust.
Diesel PM is a complex pollutant mixture that is emitted primarily by mobile sources. Today, heavy-duty highway and nonroad diesel engines are the largest source of diesel PM in the USA, with the total on-road and non-road diesel PM emissions for 1997 being estimated by EPA at 516 thousand tons nationwide. While diesel engines are used in a relatively small number of cars and light-duty trucks today, vehicle and engine manufacturers are developing new engine models that may be used in an increasing share of the light-duty fleet, particularly light-duty trucks. The EPA is concerned that, if sales of car and light trucks with diesel engines increase substantially over time, the potential health risks from diesel PM could also increase substantially.
Implementation of the Strategy will start in the early 2000 with an initial assessment of all urban areas in the United States. This assessment will define an appropriate hazard- or risk-based approach consistent with the available information on HAP emissions and ambient concentrations. The assessment will include at least the above listed 33 urban HAPs and diesel particulate matter.