fuel and emission control system changes include:•More stringent standards and test procedures

• More stringent standards and test procedures
To date, there are no specific standards for air toxics emissions from motor
vehicles. However, the 1990 Clean Air Act does set specific emission
standards for hydrocarbons and for diesel particulate matter. Air toxics
are present in both of these pollutant categories. As vehicle manufacturers
develop technologies to comply with the hydrocarbon and/or particulate
standards (e.g., more efficient catalytic converters), air toxics are reduced
as well. Requirements under the Act for testing carbon monoxide
emissions at cold temperatures will also have an indirect but important
effect in reducing air toxics emissions in the critical first moments of
vehicle operation.