Tiny, But Deadly: Air Pollution Researcher Raises Alarm over Diesel Soot

Interview with John Froines, director of the Southern California Particle Center

As director of the Southern California Particle Center, housed at UCLA, chemical toxicologist John Froines is an expert on very tiny things. He and a team of 50 researchers and staff at six universities in the United States and Japan are studying the health effects of diesel particulate matter, microscopic solid and liquid leftovers from the combustion of diesel in the engines of trucks, ships, cranes and construction equipment. Froines spoke to QUEST on the phone from his office on the UCLA campus, in West Los Angeles.

Gabriela Quirós is a Segment Producer for KQED-TV, and is the producer for this story.

How does diesel exhaust compare to exhaust from gas cars? Why is it more hazardous to our health?

There are two issues. The first one is how toxic is something that is emitted? And the second is, how much exposure is there? Gasoline-powered cars, their emissions have been reduced considerably over the years. Diesel engines produce nine to 10 times more emissions than gasoline-powered cars. On the other hand, it's not entirely clear, in terms of toxicity, that is, in terms of how potent the particles from gasoline or diesel are, which are the most toxic. Gasoline is an issue that needs continued investigation. We did some work in the Caldecott Tunnel, out in Orinda, and we found some evidence that the gasoline particles that we were looking at were more toxic than the diesel particles, even though there are more diesel particles. And so this is an issue that isn't completely resolved in terms of the relative toxicity. But for the most part, since you have so much more diesel, that obviously is going to have a dramatic effect on health effects.

Why is diesel exhaust so dangerous to our health?

Diesel particulate matter has a carbon core. Thousands of chemicals are absorbed onto this core and many of these chemicals are quite toxic.

What are some of these dangerous chemicals?

We think that the primary toxicity of diesel particulate matter derives from the organic compounds – made up of carbon, nitrogen, oxygen and sulfur – and from metals such as iron, copper and lead that are absorbed onto the core of the particles. And it's also true that the particles themselves can transfer electrons. And that has the potential to cause oxidative processes that produce toxic chemicals.

The local air quality management districts measure particulate matter that is 10 microns (PM 10) and 2.5 microns (PM 2.5) in diameter. This is many times smaller than the width of a hair. Your specialty is ultrafine particles – particles that are even smaller than the ones that are currently regulated. How much smaller are these ultrafine particles?

They're 25 times smaller than the smallest particles that are currently regulated. Ultrafine particles are absorbed not only into the cell, but also into subunits of the cell like the mitochondria, which is responsible for energy production. It's not a good thing to have particles disrupt the energy production within the cell. Between 85 and 95 percent of the particles produced by the combustion of fossil fuels are ultrafine particles. On the 710 freeway near the Los Angeles Port we have measured concentrations of ultrafine particles as high as 1.5 million per cubic centimeter. A cubic centimeter is the size of a sugar cube. So it's a lot of particles. And that's not particularly good from a health standpoint.

Is it because the particles are bringing in with them all the heavy metals?

They're bringing in everything. If you have – a wild guess – 1,000 toxic chemicals in your cell, you're going to have cellular defense processes happening. Your defense mechanism may produce inflammatory responses that have consequences for the cardiovascular system or asthma.

Does that inflammation make you more vulnerable to having an asthma attack?

There's a lot of evidence showing that particles exacerbate or enhance asthma. And there's an ongoing debate as to whether air pollution actually produces asthma. There's evidence for that now. It's still a debate, so I wouldn't want to be unequivocal about it. But certainly the exacerbation of atherosclerosis in the heart and the exacerbation of asthma in the lung appear to occur from these compounds.

What consequences can atherosclerosis – the hardening of blood vessels – have on your health?

One of our investigators here at UCLA, Andre Nel, has seen aortic lesions in mice that are susceptible to atherosclerosis. Nel and his co-workers are working out the mechanism of how that occurs. We don't know all the answers. But it's clear from our work that ultrafine particles are the particles most likely to cause effects in the heart.

Another health effect of diesel particulate matter is low birth weight and pre-term birth. Do researchers understand how this happens?

Researcher Beate Ritz at UCLA, has evidence for it occurring and she has associated it with traffic. The important thing to realize is that in 1997 there were these large epidemiologic studies that showed increased mortality and showed increased hospital admissions associated with particles. Our understanding of the health consequences was extremely limited. Now we know that particles are associated with allergic airway disease, including asthma, and with cardiovascular disease. We know that they're taken up into the brain and there may be health consequences in the brain's central nervous system from long-term exposure to the particles. We know about the low birth weight and pre-term birth consequences. And we know that diesel causes lung cancer. And so what you can say is that we now understand that the range of health consequences is much broader than we knew 10 years ago. That's really quite important. We know, for example, that cigarettes and passive smoking cause all sorts of health outcomes. And everybody takes that as a given. Over time we're going to find that air pollution causes a lot more in the way of health effects than we realize at this point.

Your group has done some work that shows it makes a difference how far you live from the freeway, in terms of the health impact. How far away from the freeway do you have to live in order to reduce the health impacts of diesel exhaust?

This is an issue that is very frustrating for me, even in the way you phrase it. The problem with the question is that there are some people who think that the primary health response from particles is associated with proximity to roadways. In Los Angeles we have enormous pollution. And so do you guys up there. And so you're talking about a difference in degree. You're not talking about how 300 meters (1,000 feet) away from a freeway suddenly the air becomes pristine. What we do know is that the number of ultrafine particles goes way up on the freeway. The mass stays about the same because the ultrafines don't weigh much. So you have a lot of particles that are very small very close to the freeway. It drops off at around 300 meters. And there is evidence with respect to asthma, and low birth weight and pre-term births and allergic airway reactions and so on that there seems to be a higher risk as you get closer to the freeway. But I wouldn't say that that then means that everybody who is more than 300 or 500 meters (1,000 to 1,600 feet) from a freeway isn't going to be impacted by air pollution.

Distance seems to have important public policy consequences, though. For example, there's a California law that prohibits building new schools within 500 feet of freeways and busy roadways. Do you think that's a useful regulation?

Yes. I think you're absolutely right that we should have rules like that. All I'm saying is I don't want people to say, "We've done that and so we don't have to do anything more."

Obviously everybody can't get up and move farther away from the freeway. But what things can people do?

We get dozens, if not hundreds, of letters about that. You're really asking a difficult question. Reducing commute time on the freeway, if you can. Obviously, people who are driving two hours each way a day are breathing a lot of particles. One of the things that concern us a lot are these kids who spend all these hours on buses, being bused around L.A. to go to school.

How do you collect something as small as ultrafine diesel particulate? The Bay Area Air Quality Management's lab showed me the filters they use to collect PM 2.5 and PM 10. You probably use something slightly different to collect ultrafine particles.

One device we use is called an impinger. You actually collect the particles in water. Let's assume that we want to study ultrafines. These are tiny particles that don't weigh anything. If you want to study them toxicologically, how are you going to get them off the filter? You can extract them with water or solvent. But to get all these tiny particles off the filter is not trivial. And so the idea of the impinger is that the stuff just comes directly into the water.

How much money does your Center have for this work?

The first five years, we had $16 million from the U.S. Environmental Protection Agency and the California Air Resources Board (ARB). And now we have about $10 million for the next five years. We're really broke.

It doesn't sound like the problem is being prioritized.

ARB is a regulatory agency, so it has a limited research budget. I certainly wouldn't be critical of them. But I think the state should be making a greater contribution to deal with this. Air pollution should be a priority in the state.

There was an ARB report that came out that says that in California the Port of Oakland is second only to the Port of Long Beach in terms of the pollution that it's generating.

My father worked at the shipyards in Oakland during World War II. So I go way back.

Did your father suffer any health consequences from his work at the shipyards?

Well, my father was murdered. So it's a sad story.

I'm so sorry to hear that. That's horrible.

We lived in Berkeley and in the old days people would drive home from the shipyards in Oakland and they'd stop on bars on San Pablo Avenue. And he must have gone into a bar to have a drink and cash a check and when he came out he was attacked by somebody to steal money and he fought back and was thrown over a bridge into a little creek and broke his neck. That person was, of course, never caught. That kind of thing was rampant in those days. So after my father died my mother went to work in the Richmond shipyard. So shipyards are clearly part of my family.

Did that motivate you in some way to want to study those health effects?

Oh no. That would make a good story, but it wouldn't be true (he laughs). I didn't discover environmental and occupational health until 1974. You probably don't know my background, do you?

I do know the more colorful part of it, that you were one of the Chicago Seven who were put on trial in 1969 for conspiring to incite a riot at the 1968 Democratic National Convention.

I kept having to figure out whether I was a social activist or I was a scientist. And getting into environmental issues was a way to deal with that schizophrenia. So it was about '74 when I decided that that was the path to take.

And has it worked out for you?

Sure. It's great, just terrific.