Many commenters stated that they believe that the proposed rule is a crucial component of the effort to meet health based air quality standards, such as the NAAQS, and improve visibility as required by the CAA and EPA's regional haze regulations. Some commenters (Oregon Department of Environmental Quality, WRAP, National Park Service) noted that this rule would especially help improve regional haze and visibility in the west. NESCAUM commented that attainment of the NAAQS is of immediate concern to the states in the northeast region. And SACE noted that emission reductions from nonroad sources would be particularly beneficial to metropolitan areas throughout the south. They added that many southern areas are struggling to address nonattainment designations that have resulted in part, from the tremendous growth this area has experienced. NRDC noted that L.A. is estimated to fall short of attainment by 183 tons of NOx per day and the San Joaquin Valley faces a similar shortfall, they asserted that since nonroad engines will account for almost 50 percent of the vehicle-related NOx emissions by 2007, and therefore it is crucial that EPA adopt this proposal as soon as possible. CARB noted that the CAA preempts California from controlling emissions from new farm and construction equipment under 175 hp, and that EPA action in this area is crucial in order to facilitate attainment with the standards. They added that 75 percent of the roughly 450,000 land-based and recreational marine diesel engines in California are in this category and constitute 21 percent and 58 percent of the total mobile source NOx and diesel PM, respectively, in California. The Connecticut Department of Environmental Protection commented that in 1999, NOx emissions from nonroad diesel engines alone were responsible for one-third of the total combined mobile and stationary source inventory in Connecticut, and as a result, this rule is crucial for assisting Connecticut in their efforts to attain and maintain the NAAQS for ozone. Environmental Defense provided additional discussion on this issue including an assessment of nonattainment areas throughout the nation and concludes that the problem could worsen without action to reduce nonroad emissions.