PNAS: Can you contextualize the harm from this indoor air pollution?

Smith: Most people recognize that the worst thing you can do is stick burning stuff in your mouth. The second worst thing is to have burning stuff inside your house, in your kitchen, and around your house even. A fire in the kitchen, if you’re cooking a meal, produces about the same pollution per hour in a typical house as a thousand cigarettes burning. So, if you think about a thousand cigarettes burning inside your kitchen, it’s not surprising that there are significant health effects. The big difference is that children and babies don’t smoke, but they are in kitchens and are also being exposed to the household pollution, so there’s a large impact on children.

PNAS: You have been studying this problem for decades. Why has it persisted?

Smith: We’re beginning to pin down the health effects more and more, and they’re consistent with what we know about smoking, outdoor air pollution, and second-hand tobacco smoke. But just because we know it’s a risk factor doesn’t necessarily mean we know how to fix it. And that’s a poverty issue, and it’s a technology issue, because we don’t have good stoves and fuels that meet local needs but are also clean. It’s also a behavior issue, because it’s at the household level—people have to change behavior and make a decision three times a day to use an improved stove or whatever you’re trying to promote. So, that’s where the work is needed to learn how to translate what we know about the impacts to what can be really done.

PNAS: Can you explain your approach?

Smith: The motto of my group is you don’t get what you expect, you get what you inspect.
There have been an awful lot of programs around the world introducing so called improved stoves but that haven’t done any inspecting and consequently, didn’t achieve anything verifiable. But there are so many parameters that you have to do an awful lot of monitoring and evaluation or regular checking to see what’s happening and modify the program accordingly. So, we’ve been developing electronic gadgets, to try to take advantage of modern world technology in doing monitoring and evaluation of this very ancient risk factor to help us do something about it.

PNAS: What sorts of gadgets have you developed?

Smith: Some years ago, I thought of the idea of using a smoke alarm as a potential way of monitoring exposure to particles. I thought, “Smoke alarms, what are they doing?"
They’ re measuring smoke. Maybe we could hack into it— take out the alarm and tap the signal from the sensor in it.” And that’ s what we did. We also developed ultrasound-based time-activity monitors, which tell us how much time people spend in the kitchen, how much time they spend cooking or doing various activities. And then the last one that we have currently available is the stove-use monitor, which really revolutionized our ability to understand what’s going on. We don’ t have to ask people anymore, we just find out whether they’re using their stove. And then we can see, for example, is it the poor woman who doesn’t use it or the woman with the poor education or the woman who has seven children as opposed to three? What are the risk factors, if you will, for adoption? How could we focus our dissemination more effectively to reach these people? However, we couldn’t do that before, because we can’t optimize something unless we can measure it. And we had no measure, except these relatively expensive and imprecise measures of just asking people.


PNAS: What have these gadgets revealed?

Smith: In our largest study, we introduced a very well operating chimney stove in Guatemala. People liked it, they used it— 8 years later, they’re still using it. We have our stove-use monitors on it. And the particle monitors showed that kitchen levels went down by a factor of 10. So that’s a very good chimney stove. But the exposures to people, because we also measured what they were actually exposed to, only went down by a factor of two. Because the people don’t spend all day in the kitchen, and those stoves don’t get rid of the smoke, they just move it around. They move it a meter and a half, it goes next door, goes in the bedroom, and downwind. What you have to do now, I believe, is eliminate it; don’t produce the stuff in the first place. We don’ t deal with smoke in our cities by just moving it a meter and a half anymore. Clean combustion is the answer. So, one of the things we’re doing in Guatemala now, rather than start from an entirely new stove— because people like and use the one we have now— we’ll just make this stove cleaner, with a much better combustion chamber. So that’s what we’ re working on.

Nicholette Zeliadt, Science Writer, PNAS