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.