With so much to worry about—the climate warming, coral reefs dying, marine fisheries collapsing, the Amazon rain forest dwindling faster than ever, and protections for U.S. public lands fraying—it may be hard to remember that an environmental problem generally considered solved is anything but. (Solved, that is.)
Take air pollution: It remains more than an annoyance—it’s a profound threat to public health, as studies by Cal researchers confirm.
In 2016, air pollution accounted for 14 percent of all diabetes cases worldwide, including 150,000 cases in the United States.
The most recent, co-authored by Joan Casey of Berkeley’s School of Public Health and published in May in the American Journal of Epidemiology, found that closing coal- and oil-fired power plants cut the incidence of preterm births in surrounding communities. A second study co-authored by Casey for Environmental Health determined that shuttering coal and oil plants bolstered fertility in adjacent populations.
“Air pollution has kind of fallen off the scope,” says Casey, a postdoctoral fellow in the Environmental Health Sciences Division. “Many people think the issues involving air pollution and health have been resolved and no additional research needs to be done. But clearly, that’s not the case.”
Indeed, says Casey, she and her co-authors “were surprised at the profound effects [of coal and oil power plants on preterm births and fertility], and we conducted many different analyses to see if we could make those associations go away, to ensure we weren’t missing some other factor. But in the end, we confirmed that most of the changes we were seeing [reduced preterm births and improved fertility] were linked to reductions in air pollution due to shuttering coal- and oil-fired plants.”
In Beijing when air pollution spiked, it reached levels equal to huffing 25 cigarettes daily.
The studies by Casey et al. reviewed preterm births (babies born prior to a gestation period of 37 weeks) and fertility (the number of live births for every 1,000 women) before and after eight California power plants were closed between 2001 and 2011. They found that the preterm birth rate dropped overall from 7 percent in the year prior to plant shutdown to 5.1 percent in the year after the closings. The reduction among non-Hispanic Asian and African-American women was even more dramatic, dropping from 14.4 to 11.3 percent.
This 20 to 25 percent downturn represents a great deal of avoided human misery and expense, given that the World Health Organization estimates preterm births rack up about $2 billion in global annual healthcare costs.
“The racial disparities could be due to a couple of issues,” says Casey. “African-American mothers typically have higher rates of preterm births, so it could be their rate just had more room to drop. But African-American mothers on average also lived closer to the power plants, so that could be a factor.”
In any case, says Casey, “This research is exciting because it points to intervention possibilities that could have significant public health benefits.”
The Journal of Epidemiology article buttresses other air pollution research, including a new study published in The Lancet Planetary Health that looks at the correlation between diabetes and air pollution. The research determined that in 2016, air pollution, including emissions from cars and trucks, accounted for 14 percent of all diabetes cases worldwide, including 150,000 cases in the United States.
But perhaps the most compelling recent research on air pollution impacts was a 2015 study by Cal physics professor emeritus Richard Muller and his daughter, Elizabeth Muller, that compared the ambient crud in the air with cigarette smoking. Their conclusions, published through Berkeley Earth, a nonprofit they founded to accrue and analyze land and marine temperature and pollution data, established impact equivalences between the small particulate matter in air pollution (labeled PM2.5for the particles’ minute size of 2.5 microns or less) and cigarette smoke. Using Beijing as one example, the authors concluded that a person living there for one year would inhale the equivalent of four cigarettes per day. At one point during their research, the authors were in Beijing when air pollution spiked, reaching levels equal to huffing 25 cigarettes daily. For the U.S., the Mullers cited 2013 estimates that compared average air pollution to smoking 0.41 cigarettes daily.
So alarming was the evidence, in fact, that it inspired two young technocrats, Marcelo Cohelo and Amaury Martiny, to develop Sh**t! I Smoke, an iOS and Android app that shows users the equivalence of the cigarettes they would “smoke” in a given city in real time.
“We took the [equivalence] equation presented in the Berkeley Earth article, linked it to an open source global database on air quality, and were able to come up with a functional app in a few weeks,” said Cohelo. “So far we have about 20,000 users. It’s really interesting to see how the [cigarette equivalence] numbers change depending on different factors. For example, when it rains, the number of ‘smoked’ cigarettes tends to go up. We don’t know why.”
Cohelo says the app was designed with both humor and ease of use in mind, and draws a lot of feedback from users, some of whom—wishfully, perhaps—maintain the cigarette equivalences are exaggerated.
“We welcome the criticism, but we went over the paper carefully, we talked to Elizabeth Mueller, and we’re convinced the work is sound and that they [Berkeley Earth] have a strong team,” Cohelo says. “In fact, they thought our app was great fun, and we’re talking with them about developing a Web version that has a more serious branding.”
As for Casey, she’s hopeful that the days are numbered for coal, the filthiest power plant feedstock. “I think coal will continue to phase out, if only because it’s losing its economic viability,” she says. “Hydraulic fracking has allowed access to vast stores of natural gas, so there’s no need to use coal to generate electricity. Natural gas produces far less particulate pollution and [harmful gases such as nitrogen oxide and sulfur dioxide] and only about half the CO2 as coal, so it can result in huge health and environmental benefits when used for electricity generation. So I’m fairly optimistic we can continue deep cuts to coal burning as we move toward natural gas and, ultimately, renewable sources.”
Nevertheless, says Casey, there were 380 active coal-fired power plants in the U.S. in 2016, and coal still produced about a third of the country’s electric power in 2017.
“There aren’t any coal-fired plants in California, but we do import electricity from other states that burn coal, so we’re contributors to the problem, at least indirectly. And as long as coal is burned, we need to be aware of the impacts.”
Casey and her co-authors haven’t extrapolated the health effects of coal- and oil-fired power plants beyond preterm births and fertility, “but it’s likely there are other health benefits to shutting down these plants. So we’re now looking at asthma exacerbation rates in areas on the East Coast where some plants were shut down and others are still operating. There’s a lot of work left to be done in this field.”