Vehicle Emissions and Air Quality: The Early Years (1940s–1950s)

Abstract

During the 1940s, an unusual form of air pollution was experienced in the Los Angeles (LA) area of Southern California. Referred to as LA smog, this pollution differed from previously known air pollution with respect to its temporal patterns (daytime formation and nighttime dissipation), eye irritation, high oxidant levels, and plant damage. Early laboratory and field experimentation discovered the photochemical origins of LA smog. Though mechanistic understanding was incomplete, it was determined that hydrocarbon (HC) compounds in the atmosphere participate in smog formation, enabling build-up of higher ozone concentrations than would otherwise occur. It being a significant source, there was great interest in characterizing and controlling HC emissions from motor vehicles. Considerable work was done in the 1940s and 1950s to understand how emissions varied with vehicle operating conditions and deterioration of engine components. During this time, procedures were developed (and improved) to sample and quantify vehicle emissions. Besides exhaust, HC emissions from crankcase blowby, carburetor evaporation, and fuel tank losses were measured and characterized. Initial versions of both catalytic and non-catalytic exhaust after-treatment systems were developed. The knowledge gained from this pre-1960 work laid the foundation for many advancements that reduced vehicle emissions and improved air quality during subsequent decades.

Emissions from Light-Duty Vehicles—From Statistics to Emission Regulations and Vehicle Testing in the European Union

“…In the USA in the 1940s and 1950s, there was a dynamic development of cities, which resulted in the appearance of a large number of motor vehicles on the roads. In Los Angeles County, California, the population increased from 2.8 million to over 4.1 million during this period, while the number of vehicles in motion increased from 2.5 to 4 million, half of which were on Los Angeles City roads [188]. Simultaneously, during this period, the observation of photochemical smog as a phenomenon commenced.…”

Characterizing Ultrafine Particle Mobile Monitoring Data for Epidemiology

“…Mobile monitoring of air pollution likely dates back to the 1950s and 1960s . Over the past decade, mobile monitoring has increasingly been used to characterize fine-scale spatial variation in exposure to traffic-related air pollution (TRAP) in urban environments. − One such pollutant, ultrafine particles (UFPs; particles ≤100 nm in diameter), varies over space and time with a rapid decrease in concentration over a scale of 100–300 m , and comes from many sources in urban areas, including vehicular traffic, aircraft emissions, industrial sources, and biomass burning, among others .…”