The United States argued that it was well established that air pollution, and in particular
ground-level ozone, presented health risks to humans, animal and plants. Toxic air pollution was
a cause of cancer, birth defects, damage to the brain or other parts of the nervous system,
reproductive disorders and genetic mutation. It could affect not only people with impaired
respiratory systems, but healthy adults and children as well. Ozone was also responsible for
agricultural crop yield loss in the United States. Vehicular air toxic emissions accounted for
approximately 40 to 50 percent of total air toxic emissions. The Gasoline Rule provisions sought
to control toxic air pollution from mobile sources by addressing the fuel that creates these
emissions. Thus, its aim was to protect public health and welfare by reducing emissions of toxic
pollutants, VOCs and NOx for reformulated gasoline, and to avoid degradation of air quality for
emissions of NOx and toxic air pollutants for conventional gasoline. Therefore, the Gasoline
Rule fell within the range of policies specified in Article XX(b).