by Felix Barber
figures by Hannah Zucker

We live in exceptional times, with extreme weather events in recent memory including devastating wildfires in California, flooding and polar conditions in the Midwest USA, and extreme rainfall in the wake of hurricane Harvey. Such events are predicted to only become more common with global climate change. In the US, the Clean Air Act (CAA) is a major piece of legislation in empowering action against climate change by targeting air pollution, a bill with such bipartisan support that it received only a single vote against when it first became law in 1970.

However, recent times have seen substantial challenges to vehicle emissions standards based on the CAA, and to one of the powers granted by the CAA itself. In August 2018, the Trump Administration’s EPA proposed a revision of vehicle emissions standards that would freeze the previously established Obama-era standards at their 2020 levels. The effect of this proposed rule will be to cancel all planned increases in vehicle efficiency beyond this year, representing a stark movement away from evidence-based policy. The Trump EPA is now also creating a legal challenge to limit California’s higher emission standards, thereby weakening an ability granted by the CAA that allowed California to set such higher standards. These changes are clearly opposed to the purpose of the CAA, whose aims were to protect public health, public welfare, and to regulate the emissions of hazardous air pollutants. With respect to these goals, the CAA has been extremely successful, as outlined in Figure 1.  Additionally, given California’s recent history of influence and leadership in policy-based approaches to mitigate climate change, these changes promise to set back air pollution regulation in the USA for many years. Finally, the above changes threaten to undermine the same car manufacturing industry they purport to help.

Figure 1: Selected outcomes of the Clean Air Act and CAFE standards by the numbers.

History of the Clean Air Act

The modern CAA dates from 1970, when it was introduced to give minimum standards for air quality nationwide, empowering the EPA to enforce these standards on an ongoing basis. However, local governments had already begun to tackle the problem of air pollution in a number of cases . In particular, smog in the Los Angeles basin had become such a debilitating issue that during WWII it was suspected to be the result of a Japanese chemical attack. To align this law with ongoing attempts to regulate smog – and in acknowledgement of the densely populated cities in California – an exemption was built into the CAA allowing California to request special waivers from the EPA. These waivers allow California to set its own higher standards of air pollutant reduction, above and beyond those of the national level. Any other state is allowed to follow the California standards, with 13 states currently doing so.  

In its early stages, the scope of the CAA was limited to poisons like carbon monoxide and chemicals that contribute to acid rain, such as sulfur dioxide. However, in 2007, the Supreme Court ruling in Massachusetts v. EPA expanded the scope of the CAA to include the regulation of carbon dioxide and other greenhouse gases, effectively extending these laws that were initially designed to regulate conventional pollutants to also address the gases responsible for climate change. To date, the public health outcomes as a result of the CAA have been outstandingly positive: an analysis by the EPA estimated that the CAA led to savings of $22 trillion in health care costs in just the 20-year period between 1970 and 1990. That analysis also predicted 230,000 fewer premature deaths each year by 2020 as a result of CAA amendments.

Present-day emissions standards

We now turn to 2009, when the Obama-era Corporate Average Fuel Economy (CAFE) standards were introduced to regulate vehicle emissions in line with the new requirements of the EPA to regulate greenhouse gases. The CAFE standards were set to dramatically increase the efficiency of new passenger cars nationwide to an equivalent of 54 mpg by 2025, almost doubling the efficiency prior to the new standards. California also chose to align itself with the new CAFE standards in the goal of setting one single, national standard. The standards were predicted to create jobs; an analysis by the Blue Green Alliance predicted that these standards would add an estimated 570,000 new full-time equivalent jobs to the US economy by 2030. Finally, to make matters easier for auto manufacturers, these standards included a slow ramp period for the increases prior to 2016, with the standards set to increase dramatically from then until 2025. However, automakers negotiated for a key provision: that in 2017, these standards could be revisited by a new administration and revoked if they were deemed to be too onerous for the industry to manage.

Under the Trump administration, automakers moved swiftly to request a review of the CAFE standards, and in August of 2018 the EPA proposed its new Safer Affordable Fuel-Efficient (SAFE) vehicle-emissions standards, freezing the standards at their 2020 levels. The proposed SAFE standards are based on claims of increased safety and cost effectiveness that have been widely criticized for their inaccuracy, and California and 17 other states have initiated a lawsuit against the EPA for this move. However, the rule went several steps further, proposing to revoke both California’s waiver to set higher vehicle emissions standards than those mandated by the EPA, and California’s waiver for its Zero Emissions Vehicle program (a program designed to increase the use of zero emissions electric, hybrid, and fuel cell vehicle technologies). The legality of removing of a waiver that has already been granted remains subject to debate, since a waiver that has already been granted has never been removed in the roughly 50 years that the waiver scheme has operated.

Automakers balked – they had advocated for more relaxed standards, but freezing the CAFE standards at 2020 levels was more than they had bargained for. Additionally, should California be successful in maintaining its waivers, then automakers’ worst nightmare of two different national standards would effectively split the US auto market in two. The question of why the proposed rule went beyond what automakers had wanted was clarified by a recent New York Times investigation that revealed a campaign by the US oil giant Marathon to prevent higher fuel efficiency standards from reducing oil consumption.

The proposed EPA rule justifies removing California’s waivers because its greenhouse gas and zero emissions vehicle standards “address environmental problems that are not particular or unique to California.” However, California’s air pollution concerns and its need for special provisions to address them are as valid today as they were when the CAA was passed. Not only are some of the most populous cities in the US located in California, but also the specific geography of the Los Angeles basin retains the same capacity to trap pollutants that it had 50 years ago. The consequent health risks posed by pollutants from motor vehicles are severe in and of themselves, quite apart from the trapping of smoke from California’s wildfires, whose intensity is increasing with global climate change. Smog in Los Angeles has certainly improved relative to levels seen before the Clean Air Act, but such improvements were in part caused by safeguards like the CAA. To use these improvements as justification for weakening the same safeguards that produced them appears short-sighted.

The SAFE vehicle emissions standards and the proposed removal of California’s 2013 greenhouse gas and zero emissions vehicle standards have been justified based on opaque methodology, using data that is the subject of an ongoing legal dispute. In contrast, the efficacy of the CAA in safeguarding public health has been demonstrably proven, with an EPA analysis estimating trillions of dollars in healthcare savings, and significant reductions in premature loss of life from air pollution. Given this success, a modest approach to obtaining scientifically sound policy would require that any proposal to limit the scope of current emissions regulations should at least meet that same public health standard.


Felix Barber is a Ph.D. student in Molecular and Cellular Biology at Harvard University.

Hannah Zucker is a second-year Ph.D. candidate in the Program in Neuroscience at Harvard University.

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