Dive summary:

• The U.S. Environmental Protection Agency has received a blessing of sorts from a judge who ruled against environmental groups that had challenged pending air-quality rules for ozone as too lenient, a decision that suggests EPA is on the right track.
• The standards have raised construction industry concern that states, which administer federal air regulations, could impose limits or expensive modifications on off-read machinery.
• Some estimates have said that 96% of U.S. cities would be in non-attainment conditions subject to more regulation if EPA promulgates a limit of 75 parts per million (ppm) of ozone, and critics have noted that background ozone levels in the lightly populated and non-industrialized intermountain West are 70 ppm.

From the article:

There has been widespread action and debate – in the federal courts, on Capitol Hill and at EPA – regarding the amount of ozone that can be present in the ambient air nationally and the scientific data used to justify the costs and benefits of a legally-enforceable limit ...