It’s no joke. Breathing nitrogen oxides (NOx) can make people sick. Nitrogen dioxide (NO2), a chemically stable and toxic NOx, is designated by the U.S. Environmental Protection Agency (EPA) as one of the “criteria” pollutants under the Clean Air Act, meaning it “may reasonably be anticipated to endanger public health or welfare.” The EPA is in the midst of reexamining the National Ambient Air Quality Standard (NAAQS) for NO2. Under a judicial consent decree, the EPA Administrator must issue a proposal on the primary NO2 standard by June 26, 2009. We urge the EPA Administrator to establish a new short-term NO2 standard that is protective of the public health.