Beijing is shrouded in choking smog. Internationally, diesel cars have been rigged to cheat on emissions tests. How concerned should you be? Kirk R. Smith, PhD, MPH, Director of the Global Health and Environment Program at UC Berkeley, studies the dangers of airborne pollutants, and discusses what we can do to limit the risk.
We’ve been hearing a lot about cars rigged to cheat on smog tests. Why are automobile emissions hazardous?
Gasoline and diesel engines emit a variety of combustion-related pollutants that are known to cause respiratory disease, heart disease, and other health problems. In the US and other rich countries, we’ve been successful at controlling air pollution from most stationary sources such as power plants. Vehicle emissions still represent a significant portion of air pollution here and in rich countries around the world. It’s important to limit pollution from cars because we have a lot of vehicles and we drive them a lot. And vehicles, by definition, are close to people, so the pollution they emit doesn’t have far to travel to reach us.
There’s also increasing concern about pollution from wood-burning stoves and fireplaces. Are we talking about the same risks?
A considerable fraction of air pollution in places like the San Francisco Bay Area comes from wood smoke from households, especially during the winter. The same is true in many other parts of the country. But it has proved difficult both technically and politically to control wood smoke from households. Many Americans seem to feel they have a right to burn whatever they want in their own homes, but this comes up against the right of their neighbors to be protected from pollution. Regulations to restrict household wood burning have been very controversial. But the dangers of wood smoke are well known. The specific pollutants may vary a little, but there’s no reason to treat wood smoke differently from automobile emissions. Both pose serious health risks.
Why are these emissions dangerous?
Most research has focused on the smallest particles, called PM 2.5, which stands for particulate matter that is 2.5 microns or smaller. The body is able to trap and get rid of larger particles. The very small particles, in contrast, go deep into the lungs and are linked to a wide range of toxic effects. In many ways, particulates from car emissions and wood smoke are like the particulates from cigarettes. With smoking, you get a really high dose. You stick the source right in your mouth— a really dumb idea, when you think about it—so the health dangers are even greater. Like cigarettes, however, air pollution is linked to greater risk of stroke, lung cancer, chronic obstructive lung disease, heart disease, stroke, and pneumonia in children. It also worsens asthma.
Who’s most at risk?
Air pollution is most hazardous to elderly people with chronic heart or respiratory disease, to pregnant women, and to infants. With elderly people, very severe air pollution, like we’ve been seeing in China recently, can exacerbate existing diseases and even cause a fatal asthma attack or fatal heart attack. But we’re all vulnerable. The evidence shows that chronic exposure puts healthy people on a trajectory of getting these diseases earlier than before. Once you have them, air pollution becomes even more dangerous.
What can we do as individuals to limit the risk?
Don’t smoke, of course. And if you’re buying a car, choose one with the best gas mileage, or buy an electric car, which doesn’t produce any tailpipe emissions. As for wood smoke, if you burn wood for heat in your house, get the cleanest EPA-rated wood stove. If you burn wood in a fireplace because you enjoy the way it looks, install an EPA-approved insert that will make the fireplace burn much cleaner or, better yet, one that burns natural gas. Of course, don’t burn any garbage or trash, or leaves. That just adds to pollution right in the areas where you and other people live.
See also: 20 Indoor Air Pollution Tips.
You research indoor air pollution in the developing world. Why is it a threat in poorer countries?
In places like India, China, and Africa, people in poor households often burn wood or cow dung or crop residues for cooking. We’re talking about a lot of people—about 40 percent of the world—who burn solid fuel, which releases a large amount of particulates into the small space of a house. A stove in a village house produces about 400 cigarettes worth of smoke an hour—the equivalent of being in a bar with 400 smokers. Indoor air pollution from these solid fuel stoves is a major cause of respiratory and heart disease globally—causing about 4 million premature deaths annually.
What’s being done to reduce exposures?
One solution would be to lift people out of poverty. People burn solid fuels like wood or cow dung because they are too poor to buy cleaner fuel. The problem is, we’re not lifting people out of poverty. There are still 3 billion people on the planet using these solid fuels and the number is not decreasing. Another approach is to make biomass cooking stoves cleaner. My office is filled with examples. But it turns out to be extremely difficult from an engineering standpoint. We’ve made progress. But we don’t have a biomass stove available today that comes close to burning as clean as gas. The third approach is to make clean fuel more available and accessible to the world’s poorest people. And that’s where we’ve had considerable success with a project in India.
How does the program work?
In the major cities in India, you can order the most widely available clean fuel, LPG, or liquefied petroleum gas, on your smartphone and have it delivered to your door. The government offers a subsidy to people who use LPG. But poor people generally don't use it, because it’s expensive for them and not easy to get. In poorer rural areas, you have to drive or ride your bike to get your LPG cylinder. Service is often poor. But thanks to some very progressive, far-seeing leaders, India has embarked on programs to expand the availability of LPG. One program is called “Give It Up.” The idea is to ask the middle class to give up their subsidy for LPG. The subsidy, which is worth about $30 to $40, is then transferred to a poor family. Your name and the name of the family you’ve helped are posted on the Internet. The response has been overwhelming. Over 30,000 households a day are giving it up. That’s about 10 million households in 2015. Those subsidies represent about $1 billion dollars shift to the poor, all focused on clean fuels. That’s really remarkable.
Could that success inspire other similar initiatives?
I hope so. I’ve been brainstorming with colleagues about how we could use the same sort of “encouraged philanthropy” to address other problems. It helps to have enlightened political leaders who are looking for ways to improve people’s lives.
As far as air pollution goes, the lesson is the same around the world. A hundred years ago, when there were far fewer people on the planet, it was less damaging to burn wood and trash. Emissions from the tailpipe didn’t matter because there weren’t many cars. Now we have 7.3 billion people on the planet, and megacities with tens of millions of people, and more and more cars. The world isn’t the same today. And today we know much more than we did before about the health effects of air pollution. We can’t go on spewing particles into the air. We have to do everything we can to limit emissions and maintain clean air for everyone.
This opinion does not necessarily reflect the views of the UC Berkeley School of Public Health or of the Editorial Board at BerkeleyWellness.com.