Direct NO2 Emissions & Their Influence on Measured Ambient NO2: The US Situation EU Workshop on Impact of Direct Emissions of NO2 From Road Vehicles on NO2 Concentrations Brussels 19 September 2006 Michael P. Walsh

PM2.5 and Ozone Are The Most Serious Air Pollution Problems Across the US Currently No NO2 Nonattainment Areas in US

Health effects of PM and NO2: PM10, PM2.5 evidence of effects independent of other pollutants NO2: Difficult to distinguish direct impacts from those of correlated pollutants Motor vehicles Other sources NOx NO2 O3, PAN, other oxidants PM (via HNO3) Increased risk of adverse health outcomes

NO2 ambient levels are highly correlated with PM2.5 Estimated annual means based on 2 week measurements and calibrated by routimne monitoring in ca 40 locations; TRAPCA study R2 Stockholm: 0.64 Munich: 0.71 Netherlands: 0.80 Lewne, Sc Total Environ 2004

Future Size of U.S. LDD Market? Ricardo predicts US light duty diesel market to grow from 43,000 units in 2004 to 1.5 million in 2015. Similarly, J.D. Power and Associates predicts 4X growth in the U.S. diesel car market by 2015.

EPA Funded Diesel Retrofit Projects

Addressing NO2 in Retrofit Applications USEPA – no provision yet but watching CARB – As of January 1, 2007, no more than a 20% increase over the baseline

Conclusions The US Differs From Europe Today in Two Important Respects US has no short term NO2 ambient standard or guideline US has almost no diesel cars and even less equipped with DPFs But This is Changing US Diesel Car Population, all equipped with DPFs is expected to grow rapidly DPF Retrofits of Urban buses & Other Vehicles also expected to grow California Increasingly Concerned With Short Term NO2 Air Quality But Not As Much As WHO California Addressing NO2 From Retrofitted Vehicles