Once known as the smog capital of the world, Los Angeles is on its way to shedding that reputation. Beijing, take notice!
If you grew up in or near a large US city in the 1980s and 90s, you might recall the frequent warnings—especially on hot days—of high ozone (O3) levels. Breathing ground-level ozone—a product of the reaction between certain industrial and vehicle emissions—can trigger a variety of health problems, especially in young children, the elderly, and people suffering from asthma and other respiratory illnesses. Ozone can also damage plants and crops.
In the last decade, however, the warnings have grown fewer. The simple explanation: ozone levels dropped. According to the Environmental Protection Agency’s (EPA) webpage discussing the National Trends in Ozone Levels over three decades, “…average ozone levels declined in the 1980’s, leveled off in the 1990’s, and showed a notable decline after 2002.”
So what happened? In large part, the 1963 Clean Air Act happened (more on that later). Also, technologies were developed to prevent or reduce emissions from industrial facilities and motor vehicles. Arguably nowhere else in the US were those reductions more badly needed than Los Angeles, once known as the smog capital of the world.
Smog is a toxic soup of chemicals, including ozone, nitrogen oxides (NOx), volatile organic compounds (VOCs), and peroxyacetyl nitrate (PAN). As shown in the plots below, concentrations of all these air pollutants have fallen since 1960.
Air quality improvements in LA and other US megacities can be directly traced to the 1963 Clean Air Act, which gave EPA the authority to monitor air quality, set standards, and enforce them. As a result, meters and sensors were developed to optimize industrial production processes and lower emissions and “end-of-pipe” systems were used to capture whatever emissions were produced. For automobiles, the catalytic converter was invented to convert noxious combustion byproducts into water and carbon dioxide.
Was it worth the cost? That is perhaps the ultimate question for such sweeping regulatory measures. EPA’s own studies discovered that from 1970 to 1990, the cost to meet the limits set under the Clean Air Act was an inflation-adjusted $523 billion—much of that cost was passed on to consumers and taxpayers.
However, the EPA’s estimates for the business-as-usual case show that “an additional 205 000 Americans would have died prematurely and millions more would have suffered illnesses ranging from mild respiratory symptoms to heart disease, chronic bronchitis, asthma attacks, and other severe respiratory problems.” Expressed in dollars, the mean estimate of the total benefits to humans and the environment of Clean Air Act programs was about $22 trillion.
In addition to the potential economic payoff, what else can other megacities (technically defined as having a population of 10+ million), learn from LA? That question is addressed in the review article, Urbanization and Air Pollution: Then and Now, by David Parrish at the University of Colorado, Boulder, and William Stockwell at Howard University.
Stockwell is a faculty member in the Howard-based NOAA Center for Atmospheric Sciences, one of three programs that “have played major roles in entraining more minority students into careers in the atmospheric science at Howard University.”
Sixty-five years later, is Beijing the new LA?
Parrish and Stockwell write that maximum concentrations of particulate matter (like soot) in Beijing “may be higher than those ever experienced in Los Angeles.” In contrast, reported ozone concentrations in Beijing are about half the values LA suffered with in the 1960s. But the rapidly increasing number of motor vehicles in Beijing and other developing megacities may lead to higher concentrations of ground-level ozone.
Developing megacities face a host of other challenges. For one, it may take a while, as it did in LA, for the national, regional, and local governments to be unified in their regulatory efforts. Another challenge is complacency: For example, LA residents who didn’t grow up with the worst of the smog and ozone, and those who forgot about them, may be willing to compromise on air quality for the sake of development. Also, air pollution knows no borders. Ozone blown in from other countries, or neighboring locales, may make it unfeasible for some areas to meet more stringent requirements.
While acknowledging that the improvements seen in LA and other US megacities may not apply elsewhere, the authors note that “the EPA reports can assure developing megacities that investments in air quality improvement are rewarded by improved health and general well-being of the urban populations.”