We’ve already discussed the development of early auto emissions standards. Here’s a concise summary of the early standards (prior to the passage of the Muskie Act in 1970) and when they each became effective.

Exhaust Emissions Standards

Although California established its first standards for motor vehicle hydrocarbon (HC) and carbon monoxide (CO) exhaust emissions in December 1959, exhaust controls were not actually required for new California cars or trucks until the 1966 model year. (Through 1980, some, though not all, 1955–1965 California used cars and trucks were also required to be retrofitted with exhaust controls, and some 1966–1970 vehicles were required to be retrofitted with additional controls to reduce emissions of oxides of nitrogen (NOx), which was not yet regulated when the vehicles were new.)

When U.S. federal HC and CO emissions standards took effect for the 1968 model year, they preempted state emissions standards for new cars and trucks (though not for used ones). However, a 1967 change in federal law allowed California to apply for waivers enabling the state to impose its own stricter standards, subject to federal approval. California received the first such waiver in 1969, and the state’s auto emissions standards again began to differ from federal requirements beginning with the 1970 model year.

N/S = no standard; cid = engine displacement in cubic inches; ppm = parts per million; g = mass in grams

Crankcase Emissions Standards

The early enactment of crankcase emissions standards in the U.S. was unusual in that most automakers installed positive crankcase ventilation devices to limit crankcase emissions before such controls were actually required by law: on most new California cars and trucks by 1961 and most new cars and trucks sold in the U.S. by 1963.

Here’s a summary of early U.S. requirements for crankcase emissions controls:

• California: Eventually required crankcase emissions controls for all 1963 and later passenger cars and light trucks and 1969 and later gasoline-powered heavy trucks and buses. (Some, though not all, used California cars and trucks as old as 1955 were required to be retrofitted with crankcase devices.)
• New York: Required crankcase emissions controls for all motor vehicles manufactured or assembled after June 20, 1963.
• Colorado: Beginning in 1964, required crankcase emissions controls for all U.S.-made gasoline-powered cars and trucks as a condition of receiving official certificates of inspection and approval. Colorado also required manufacturers of gasoline-powered cars and trucks to certify with the state that their vehicles were equipped with crankcase controls, beginning after the 1965 model year.
• U.S. federal: Required crankcase controls for all 1968 and later cars and light trucks with engines displacing more than 50 cubic inches.

The federal regulations, which preempted state crankcase emissions rules for new cars beginning in 1968, required that no crankcase emissions be discharged into the atmosphere — stricter than the earlier state standards.

Fuel System Evaporative Emissions Standards

Evaporative losses from motor vehicle fuel systems (vapors vented from the fuel tank, carburetor, or fuel injection system) were recognized in the 1950s as a significant source of hydrocarbon emissions. However, there were no U.S. state or federal evaporative emissions standards in effect prior to the 1970 model year.

N/S = no standard; cid = engine displacement in cubic inches; ppm = parts per million; g = mass in grams