- NOx emissions
- Sulfur dioxide
- Particulate matter
- Carbon monoxide
Ozone is not directly emitted but it formed when oxides of nitrogen (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. Particulate matter is emitted but it is also formed from NOx emissions, sulfur oxides, ammonia, organic compounds and other gases that react in the atmosphere.
Diesel engines as a major source of NOx emissions
Gasoline engines remain as the major on-road source of carbon dioxide emissions but diesel engines are dominant sources of NOx emissions and particulate matter emissions. Manufacturers of diesel engines have undertaken several steps to control hazardous emissions significantly. Initial efforts required adjustments to fuel injection timing but it increased fuel consumption. As expected the reduction in emissions never materialized until the most stringent standards to reduce diesel emissions took effect in 2007. Vehicle manufacturers were mandated to equip trucks with filters to control particulate matter emissions and catalytic converters for the reduction of emissions. Older trucks that remain in service were retrofitted with particle filters to replace mufflers since catalytic converters were generally impractical for retrofitting on older engines. Truck owners had to make the decision on whether to retrofit or replace their existing equipment
Catalytic converters to reduce the emissions
A catalytic converter is a device used to reduce emissions from the internal combustion engine. This device was introduced to American production cars in 1975 in response to EPA regulations in the reduction of toxic emissions. The Clean Air Act required a 75% reduction in emissions in all new models of vehicles after 1975 through catalytic converters. Without catalytic converters, vehicles emit hydrocarbons, carbon monoxide and nitrogen oxide which are the major components of ground level ozone that causes smog. Almost everything with an internal combustion engine like generators, trains, trucks and buses were fitted with catalytic converters in the exhaust system. At least 98% of the harmful fumes produced by diesel engines were converted into less harmful gases. Without this reduction process, air quality particularly in big cities will be harmful to humans because smog has adverse effects on the lungs especially on children.
When NOx emissions react with sulfur dioxides, it produces acid rain that is highly destructive to everything it lands on. Acid rain in known to corrode cars, buildings and national monuments and pollutes lakes and streams to make them unsuitable for aquatic life. The emissions bind with ozone to create smog that affects the transmission of light. Carbon monoxide which is another pollutant is a colorless and odorless gas that is lethal to human. This gas has no useful functions to everyday life but cause health complications on both children and adults.