In the 1940s “Smog” became a popular word in the Los Angeles basin; people were complaining about a white smoke or sometimes a yellow-brown haze that made their eyes tear and gave them throat discomfort. Unbeknownst to many, Los Angeles, with a population of 2.9 million people in 1940, was becoming the smog capital of America. By 1946, the year after World War II ended, with the addition of thousands of cars and an increasing population, Los Angeles was virtually the living laboratory for studying the cause and effects of massive doses of pollution on humans and vegetation.
Time moved on, it was now the 1950s. In 1955 Congress passed the National Air Pollution Control Act to generate research on air pollution and how automobile emissions fit into the overall story. The result was that it took several years to evaluate and even longer to address. A study conducted by the California Institute of Technology indicated that the various pollutants coming from automobile emissions came from four sources: engine exhaust, crankcase blowby, the carburetor, and the fuel tank. At the time, both the automotive and petroleum industry were not willing to spend time or money to address the problem. Eventually, with the threat of mandatory federal regulations, the auto industry began working on the problem.
The first solution was to install a crankcase blowby device called a PCV valve, (Positive Crankcase Ventilation). These valves returned unburned gasses to the combustion chambers and were installed on all new cars sold in California starting in 1966. By 1968 all new cars sold nationwide had the PCV valve. Another device introduced in 1966 was the air injection system. Fresh air was injected into the exhaust stream to allow further combustion of exhaust gasses. In 1967 California created the California Air Resources Board (CARB) followed by the U.S. Government enacting the Environmental Protection Agency (EPA). The first emission test (tailpipe emissions) took place in California in 1966. The rest of the country followed in 1968. Starting in 1971, all new vehicles had to have fully sealed fuel systems that did not vent directly into the atmosphere. In the system, vapors from the fuel tank and carburetor bowl vent were ducted to a charcoal canister containing activated carbon. By the 1974 model year the standards had tightened so much that mechanics were de-tuning engines to meet the emissions standards—this caused the engines to not run efficiently and therefore fuel mileage suffered.
In 1975 the catalytic converter arrived—this posed a problem when using leaded gasoline. The lead residue contaminated the platinum pellets inside the catalytic converter eventually rendering it useless. Platinum pellets were used to accelerate the oxidation of hydrocarbons. In 1975 unleaded gasoline became available for the new cars. A problem became evident with pre-1975 cars as their engines needed the lead as it acted as a lubricant on valve seats. The complete phase-out of leaded gasoline did not start until 1986. Notably, lead usage in gasoline dropped by 99% between 1975 and 1988. In 1976 the Volvo 240 came with an O2 sensor. This device monitored the air to fuel ratio and sent the data to the engine management computer. In 1980 California required the sensor on all new cars. Federal emission standards mandated the sensor on all new cars and light trucks in 1981. The Clean Air Amendments Act of 1990, passed by congress, set new tighter emission standards. In 2002 California set new tighter standards for exhaust emissions for cars and light trucks.
As the years passed, tighter and tighter emission regulations have become a reality. Yet, the automotive and petroleum industry have kept pace by introducing new engineering developments. We now have cleaner burning fuels. Our cars have become lighter and more aerodynamic. Engines are better designed, which now feature electronic ignition, more precise fuel metering, computerized engine management, and onboard diagnostics. These advances, along with hybrid and electric cars, have kept up with the stringent emission standards to clean up the air we breathe.