Cars: Reducing Pollution Since The 1960S

The efforts to reduce vehicle pollution started in the 1950s, when a California researcher first linked air pollution and cars, determining that pollutants from traffic were to blame for the smoggy skies over Los Angeles. In the following years, the US Environmental Protection Agency (EPA) was established and set standards to bring down the levels of these pollutants, with the auto industry responding by developing new emission control technologies.

In the 1960s, the first tailpipe emissions standards were introduced in California, and the Federal Air Quality Act of 1967 gave California the ability to set its own more stringent air quality rules. The Clean Air Act of 1970 then gave the EPA the legal authority to regulate pollution from cars and other forms of transportation, with Congress passing the first major Clean Air Act, requiring a 90% reduction in emissions from new automobiles by 1975.

Since then, the EPA has continued to set and implement emissions standards for various types of vehicles and equipment, leading to significant improvements in air quality and public health.

The Clean Air Act

The 1970 Clean Air Act was a response to the growing problem of air pollution in the United States, particularly in cities. This pollution was largely due to the increasing number of cars and trucks on the road, as well as the closing of some public transit systems, which led to more reliance on personal vehicles for transportation. The Act set the goal of achieving NAAQS in every state by 1975.

Despite these successes, there is still more work to be done to improve air quality in the United States. Many places still have poor local air quality, and the transportation sector remains one of the largest sources of carbon pollution in the country. The EPA is now focusing on the critical challenge of addressing climate change by reducing carbon emissions from passenger cars, trucks, and aircraft.

California's role in shaping modern car emissions standards

California has played a significant role in shaping modern car emissions standards in the United States. The state's efforts to combat air pollution and reduce vehicle emissions have had a lasting impact on policies and regulations at both the state and federal levels.

In the early 1950s, a California researcher first established the link between air pollution and cars, attributing the smoggy skies over Los Angeles to pollutants from vehicle traffic. This discovery marked the beginning of California's journey towards implementing stricter vehicle emissions standards.

Los Angeles, known as the "smog capital of America," was the first city to raise significant public concern over auto emissions. The state of California became a pioneer in establishing new-car emission standards, with Dr. A.J. Haagen-Smit and other scientists at the California Institute of Technology playing a pivotal role in understanding the chemistry of air pollution. Their research revealed that nitrogen oxides and hydrocarbons, when exposed to sunlight, produced secondary pollutants (photochemical smog) that caused eye and throat irritations and reduced visibility in the Los Angeles area.

California's recognition of the urgency to address air pollution led to it becoming a testing ground for emissions-control devices and pioneering legislation. Despite initial reluctance from the automobile and petroleum industries, California mandated the installation of crankcase blowby devices on all cars sold in the state starting with the 1963 models. This was a significant step forward, as crankcase blowby accounted for 25% of the engine's hydrocarbon emissions.

California continued to push for more stringent measures, requiring exhaust-control devices on all new cars from 1966. While this led to a decrease in hydrocarbon emissions and carbon monoxide levels in Los Angeles, it also resulted in a rise in nitrogen oxide levels due to the limitations of the available anti-emissions technology at the time. This challenge prompted the development of catalytic exhaust devices, which successfully converted nitrogen oxides into harmless by-products. Catalytic converters were mandated on all cars sold in California from 1975 onwards.

The state's leadership in tackling vehicle emissions was further solidified by its unique authority under the federal Clean Air Act. Enacted in 1967, this legislation explicitly allowed California to set its own motor vehicle emissions standards due to the state's distinct pollution challenges. With more motor vehicles than any other state and pre-existing stricter air pollution standards, California was granted the ability to maintain its stringent requirements.

The impact of California's emissions standards extends beyond its borders. While other states are generally pre-empted from enacting their own limits, they can choose to adopt California's emission rules if approved by the federal government. This has led to a situation where automakers produce more fuel-efficient passenger vehicles that comply with California's stricter standards, benefiting the entire nation.

The catalytic converter

The Birth of the Catalytic Converter

The innovation of the catalytic converter marked a turning point in reducing vehicle emissions. In the 1950s, researchers like John J. Mooney and Carl D. Keith recognised the need for emission control solutions and began exploring catalytic oxidation, using catalysts to transform exhaust pollutants into less toxic compounds. Their work laid the foundation for the development of catalytic converters.

Early Environmental Concerns

As automobiles rapidly increased in the early and mid-20th century, their uncontrolled emissions caused significant urban air pollution. By the 1950s, smog and reduced visibility had become severe issues in cities like Los Angeles. Scientific studies linked this directly to the millions of vehicles on the road, emitting pollutants like nitrogen oxides, hydrocarbons, and carbon monoxide into the atmosphere.

Regulatory Influences

While engineers worked on advancing catalytic converter technology, government regulatory actions played a crucial role in compelling automakers to adopt emission control measures. Beginning with California establishing the nation's first vehicle emission standards in 1966, regulators provided the push to make emission control a non-negotiable priority for the industry.

The 1970 Clean Air Act Amendment took this nationwide by authorising the Environmental Protection Agency (EPA) to set vehicle emission limits and requiring a significant reduction in auto pollution within five years. This spurred rapid advancements in catalytic converter technology, leading to the development of more efficient and effective systems.

The Three-Way Catalytic Converter

The invention of the three-way catalytic converter in the 1970s was a significant leap forward in emissions control. Prior to this, catalytic converters could only handle the oxidation of carbon monoxide and hydrocarbons. The three-way catalytic converter, utilising platinum and rhodium catalysts, was able to reduce nitrogen oxide emissions while simultaneously oxidising carbon monoxide and hydrocarbons within a single converter. This innovation became the workhorse of emissions control, enabling vehicles to meet increasingly strict Clean Air Act standards.

Impact on Air Quality

Since their introduction in 1975, catalytic converters have become pervasive worldwide, with hundreds of millions of vehicles now equipped with this technology. Studies have correlated the mandated use of catalytic converters with drastic improvements in urban air quality. For example, the installation of converters in Mexico City taxis reduced carbon monoxide emissions by nearly 75%, and converters decreased London's hydrocarbon levels by 35% in just five years.

Challenges and Future Innovations

While modern catalytic converters have made significant improvements in reducing emissions, challenges remain. These include the reliance on scarce and costly precious metals, as well as the need to keep up with the growing demand for emission control solutions as the global vehicle volume increases. Researchers are exploring sustainable alternatives, such as palladium-gold alloy catalysts and lower-temperature operation using alternative catalysts, to address these challenges.

The reduction of lead in gasoline

The use of tetraethyl lead as a gasoline additive was introduced in 1923, adding yet another toxic substance to automobile emissions that threatened human health. Despite concerns among public health officials about the poisonous nature of the substance, General Motors and others promoted leaded gasoline.

In the 1940s, citizens of the car-dominated Los Angeles basin complained about a white or sometimes yellow-brown haze that made their eyes tear. They called this "smog". Dr. A.J. Haagen-Smit and other scientists at the California Institute of Technology discovered that nitrogen oxides and hydrocarbons exposed to sunlight produced secondary pollutants (photochemical smog or PCS) that caused eye and throat irritations and reduced visibility in the Los Angeles area. Further studies indicated that the complex and various pollutants existing in automobile emissions came from four sources: engine exhaust, crankcase blowby (through the engine ventilation system), the carburetor, and the fuel tank.

In 1959, eye irritation was reported in Los Angeles County on 187 days; in 1962, 212 days. A typical car produced in 1963 (without pollution control devices) discharged 520 pounds of hydrocarbons, 1,700 pounds of carbon monoxide, and 90 pounds of nitrogen oxide for every 10,000 miles travelled. In 1966, 86 million of approximately 146 million tons of pollutants discharged into the air in the United States was attributable to motor vehicle traffic.

In 1966, motor vehicles contributed more than 60% of the pollutants in the atmosphere throughout the US. Temperature inversions in at least 27 states and the District of Columbia produced serious smog problems. The more widespread use of trucks and airplanes exacerbated the nation's air pollution problems. It became apparent during the 1960s that smog was not a local problem, but a national one requiring the attention of the federal government.

The Motor Vehicle Air Pollution Act of 1965 produced national standards comparable to California law for the 1968 model year. In 1967, the Air Quality Act was the first piece of federal legislation designed to control lead emissions. Federal funds became available to defray part of the cost of inspection programs. Hydrocarbon emissions came under federal jurisdiction in 1968.

The 1970 Clean Air Act gave the federal government limited enforcement power over interstate pollution. An amendment to the 1970 Clean Air Act called for further reductions in emissions and authorized the Environmental Protection Agency (EPA) to set emissions standards for new automobiles and other motor vehicles concerning pollutants that would adversely affect human health.

In 1973, the EPA issued regulations to reduce the lead content of leaded gasoline over a series of annual phases, which therefore came to be known as the "lead phasedown" program. The EPA mandated that lead additive be reduced by 91% by the end of 1986. The new standard was 0.10 grams per gallon.

In 1986, the US Environmental Protection Agency mandated the removal of lead from gasoline, beginning in 1975, because of two discoveries. Firstly, the recognition that lead released to the environment by the combustion of leaded gasoline was causing widespread lead poisoning in children. Secondly, the realisation that lead in gasoline was destroying the catalytic converters required on all new cars in compliance with the Clean Air Act Amendments of 1970.

In the United States, the removal of lead from gasoline was followed by a more than 90% reduction in mean blood lead concentration between 1976 and 1995. The percentage of children in the United States aged 1–5 years with blood lead levels greater than or equal to 10 μg/dl fell from nearly 80% in the late 1970s to less than 5% in the early 1990s.

In 1990, the Clean Air Amendments substantially revised the 1970 and 1977 acts. Two of the eleven titles focused particularly on transportation. They involved a new plan to classify cities according to the severity of their emission problems and their degree of attainment of earlier goals, with different levels of action required for each category.

The new law also set more stringent emissions standards for automobiles and some trucks for model years 1996 to 2003. Efforts to tighten exhaust standards essentially ratified innovations underway in California and being enacted by other states.

In 1995, leaded gasoline was fully prohibited. As a result, levels of lead in the air decreased by 94% between 1980 and 1999.

In 2000, leaded gasoline was withdrawn entirely from the European Union market, although it had been banned earlier in most member states. Other countries also phased out TEL. India banned leaded petrol in March 2000.

In 2011, the United Nations announced that it had been successful in phasing out leaded gasoline worldwide. However, the sale of leaded gasoline for cars was only completely phased out worldwide in July 2021. The last country to remove lead from automotive gasoline was Algeria, which did so in 2021.

The future of vehicle emissions and air quality

Historical perspective

The link between air pollution and cars was first established in the early 1950s by a California researcher who attributed the smoggy skies over Los Angeles to pollutants from vehicle emissions. At that time, new cars emitted high levels of hydrocarbons, nitrogen oxides, and carbon monoxide. This discovery spurred the US Environmental Protection Agency (EPA) to develop standards to reduce these pollutants, and the auto industry responded by creating new emission control technologies.

Improvements in air quality

Over the past six decades, vehicle emissions of particulate matter, nitrogen oxides, carbon monoxide, hydrocarbons, sulfur dioxide, and lead have been significantly reduced. The implementation of advanced emission after-treatment technologies for gasoline and diesel vehicles, along with increasingly stringent regulations, has led to absolute emission reductions from the on-road fleet, despite increased vehicle miles traveled. As a result, air quality in cities across the US and Europe has improved drastically.

Outlook for the future

The positive trend of decreasing vehicle emissions is expected to continue due to several factors. The turnover of the on-road fleet, with older, more polluting vehicles being replaced by newer, cleaner ones, will contribute to lower emissions. Additionally, the introduction of stricter emission regulations, such as Tier 3 in the US, LEV III in California, and Euro 6 in Europe, will further drive down pollution levels. Moreover, the large-scale adoption of electric vehicles, which produce zero tailpipe emissions, will accelerate the reduction in vehicle emissions, particularly in urban areas.

Remaining challenges

While great strides have been made, there are still areas that need improvement. Ground-level ozone, or smog, remains an issue in many US cities due to the complex nature of its formation, which involves reactions between local, regional, and hemispheric emissions of volatile organic compounds and nitrogen oxides. Reducing emissions of these ozone precursors will be crucial to improving air quality in affected areas.

Furthermore, with the significant decrease in vehicle tailpipe emissions, the relative contribution of non-tailpipe emissions, such as brake and tire wear, is becoming more prominent. As vehicle technology evolves, it is important to consider these alternative sources of pollution and develop strategies to mitigate their impact.

In summary, the future of vehicle emissions and air quality looks promising, with a continued downward trend in pollution levels expected over the next decade. However, ongoing efforts are still required to address remaining challenges, particularly those related to ground-level ozone and non-tailpipe emissions, to ensure further improvements in air quality.

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