Ecology made similar changes to the dynamometer test this spring in Spokane and the failure rate increased by one to two percent. In other words, when vehicles with high emissions are identified and repaired, the reduction in air pollution is like having everyone stop driving for three months. Motor vehicles emit a third of the region' s hydrocarbons and more than half of the oxides of nitrogen, pollutants that cause ozone pollution. Motor vehicles also produce more than half of the Vancouver area's carbon monoxide pollution. Ozone forms at ground level when hydrocarbons and oxides of nitrogen mix on hot, sunny days.
Ozone is a severe irritant that causes choking, coughing and stinging eyes associated with smog.
It also can harm plants and animals. Carbon monoxide is a clear odorless gas that reduces the blood's ability to carry oxygen.