greater than 90% as compared with today’s engines. The proposed standards would take effect for new engines starting as early as 2008 and be fully phased in by 2014. The regulations plan to lower sulfur concentrations in diesel fuel from the current uncontrolled level of 3,400 ppm to 500 ppm beginning in 2007 and then to 15 ppm in 2010 (EPA 2003i; 68 Fed. Reg. 28328 [2003]).

Control of Mobile-Source Air Toxic Emissions

According to the 1996 National Toxics Inventory (NTI), major stationary sources account for approximately 25% of hazardous air pollutant (HAP) emissions, mobile sources contribute 50%, and area sources (for example, commercial dry cleaning facilities) and miscellaneous sources contribute the remaining 25% (EPA 2001a).

Section 202 (l) of the CAA required EPA to study emissions of air toxics from mobile sources and fuels and set standards for benzene and formaldehyde at least. EPA issued a first draft of the study in 1993. The agency’s final rule on control of emissions of air toxics from mobile sources, incorporating the final version of the study, was issued in March 2001 (66 Fed. Reg. 17230 [2001]). The rule was issued in accordance with a judicial consent order that mandated EPA action once it had missed the CAA deadline.

The rule identifies 21 air toxics associated with mobile sources (including nonroad mobile sources as well as LDVs and HDVs). The agency projects that existing tailpipe, evaporative, and fuel formulation regulations on vehicles and fuels will reduce emissions of benzene, acetaldehyde, and formaldehyde by approximately 70% in 2020 as compared with 1990 levels and that emissions of diesel PM from on-road vehicles will be reduced by 90% (EPA 2000d). The rule requires gasoline refineries to maintain their average 1998–2000 levels of toxic-emission control in response to existing toxic-emission performance standards for reformulated gasoline (RFG) and gasoline. Because of the substantial progress projected from the other emission-control standards and from those soon to be promulgated (as discussed previously in the chapter), no other new standards are set for either vehicles or fuels. A lawsuit contending that the rule is inadequate was filed against EPA on May 24, 2001, by the attorneys general of New York and Connecticut and a consortium of environmental groups.

Implementation of Emission Standards for New Mobile Sources

Motor-vehicle emission standards are implemented through a certification procedure in which manufacturers provide EPA or the California Air Resources Board (CARB) with prototype data showing that the vehicles

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