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True Grit: How Particulate Matter in Air Affects Our Health

November 16, 2004
2:00 pm US Eastern Time

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Call Transcript

1. Welcome and Introductions: Moderator: Steve Heilig, MPH, Director of Public Health and Education, San Francisco Medical Society and Collaborative on Health and the Environment

We are going to start off today with a science update and today it will be coming from Dr. Pete Myers, whom most of you may know through reputation as the co-author of Our Stolen Future, but many of you may not know about his newest resource www.environmentalhealthnews.org. I encourage everyone to check it out. It is a compendium of environmental news from around the world, and thus he probably has one of the broadest views of environmental health developments of anyone we know. So, we’ve asked him to pick something that he thinks is of note and give us a distilled update. So, what have you got for us today Pete?

2. Science Update: Pete Myers, PhD, CEO, Environmental Health Sciences

Thanks, Steve. I would like to draw your attention to a new study that just came out yesterday, which is something that CHE has been concerned about for some time and actually had a conference call on a few months ago. The paper is about autism, by a team of researchers from Johns Hopkins University. What it concludes is that the causes of autism likely lie in something that’s disregulating the immune system during fetal development, particularly during the second trimester of fetal development. They don’t claim to explain all cases of autism, in fact, the study is quite small, with 11 patients who had autism and who died from other causes, compared to a control set that matched them. They studied patterns of immune system proteins within the brains of the autistic patients versus the control patients. What they find, they believe, is compelling evidence that at least for the set that they studied, are factors, unidentified, are disrupting immune system activation and making the brain hyper-reactive in development. We will be posting a summary of this study at: http://www.healthandenvironment.org/. You can find some of the press coverage of this at: http://www.environmentalhealthnews.org/.

Steve Heilig: Thank you Pete. Today’s theme is related to particulate matter. In a general sense, the issue of air pollution seems to be one of the most visible and perhaps the oldest concern of environmental issues. If you look back, at least since the start of the industrial revolution, there have been real severe incidences and a lot of concern in places where the air has become full of some of the by-products of modern life. I would like to refer our listeners to Devra Davis’ last book from 2002, When Smoke Ran Like Water, which details some of this in a striking way.

But more recently, what we’ve seen is a lot more concern and knowledge about the actual impacts of particles in the air that we breathe. This is a particularly timely call, because in the last few weeks alone there have been major stories in many of the scientific and medical journals; in the New England Journal of Medicine, the JAMA, and in Environmental Health Perspectives.

Prior to that there has been a lot of action and activism, for just a couple of examples in recent years, some of the health groups such as American Lung Association (ALA) and the American Heart Association (AHA), which just this last June released a statement from a panel of 11 scientists and doctors that for the first time, has the AHA establishing particulate matter as a serious public health problem.

So there’s a lot of movement on this, at least in terms of knowledge, in terms of looking into what types of particulates are, and what the size of them are, what the chronic and acute impacts are. In one of the recent stories, it was stated that there is no treatment at this point for these kinds of exposures. So avoiding exposure, or prevention is still the best way to approach the problem.

So, we are going to hear from some environmental and health groups today. We have asked our presenters to distill this very complicated topic into some of these presentations.

3. First Speaker: Gina Solomon, MD, MPH, Senior Scientist, Natural Resources Defense Council and Assistant Clinical Professor of Medicine at the University of California at San Francisco

I am going to talk very briefly about four things. First, I am going to define particulate matter, so that we all know the vocabulary that’s used in this area of research. Second, I am going to talk about why size matters, because it’s not just the composition, but actually the size that people focus on and talk about. Then I am sure people will want to know where it comes from, so I will summarize that briefly. Then I will talk about why we should care, before turning it over to Michael Lipsett, who will give much more detail on the science.

So, particulate pollution or particulate matter, also known as PM for short, is basically a lot of tiny, sooty particles. Usually there is a carbon core at the center, and depending on what the particle comes from, it may have all kinds of nasties embedded on the outside of the particle. These can include heavy metals, polycyclic aromatic hydrocarbons, also known as PAHs, dioxins, and other semi-volatile organic compounds. These can all be absorbed onto the exterior of these carbon cores and delivered into the air and into our bodies in that way.

Size matters for PM pollution because the size determines what happens to the particle and where it ends up. For example if a particle is larger than about 70 microns in size, which is about the diameter of a human hair, it’s not really going to remain air-borne, so it’s not a respirable problem. As particles get smaller, they become increasingly respirable, and what we call the coarse particle fraction, is what’s known as PM10 or particles that are 10 microns in diameter or smaller, that’s about 1/7th the diameter of a human hair. These are particles that can get down into our air-ways, though a fairly significant fraction of them get filtered out in the upper airways; nose, sinuses, pharynx, etc. and down into the bronchi. The fine particles or so-called, PM2.5, particles, which are smaller than 2 microns in diameter, or 1/30th of a human hair, are considered respirable. They end up bypassing all of our airway defenses, going all the way down into our alveoli, which are the air sacs where air exchange occurs. Regulation so far, has focused on both the PM10 and the PM2.5 fractions and research studies also are looking at both of those.

I also just want to mention that there are additional categories, the so-called ultra-fine particles and nano-particles. These are particles that increasingly smaller in size and that are of great interest to researchers and of increasing concern to some folks in public health, because of the fact that these are particles that appear to go not only all the way down into the alveoli, but easily across the alveoli membrane and into the blood stream and the into various organs, including across the blood-brain barrier.

The source of the particles varies a lot according to the size. The course particle fraction, PM10 and even larger often come from dust: road dust, construction dust, dust from grinding rock, and so forth, also to some degree from sea salt and pollen. The fine particles usually come from two types of sources. One is the burning of fossil fuels; from motor vehicles and stationary sources like heavy industry. Also these fine particles come from air-borne reactions of other chemicals that interact together; for example, sulfur-oxides and nitrogen-oxides and various volatile organic compounds that when released into the air tend to aggregate in the environment and into fine particles, which are then respirable. So, that’s where these things are coming from and as you can tell, the ones that are of greatest health concern tend to come from mostly man-made sources, the fuel-combustion sources.

So, why should we care about these particles? I think there are three main reasons why we should care. The first is that PM has been associated with a stunning array of health affects, which you are about to hear a lot more about. But I would just like to give you a litany, so you get a sense. In numerous studies these are definitely associated with: increased respiratory symptoms, with asthma exacerbations, increased emergency room visits, increased hospitalizations for cardiovascular and respiratory problems, stroke, cardiac rhythm disturbances, myocardial infarction, and pre-mature death. In addition PM has been associated with chronic or longer-term affects, such as: stunted lung development in children, cancer and in a few studies, pre-term birth and low birth weight. So, we see a huge array of health affects.

The second reason that we should we care is that the strength of the scientific evidence on many of these end-points is really overwhelming. In many of these cases, we have enough evidence to draw a causal link, which many of you know is very hard to do in environmental areas. We have dozens of huge, prospective cohort studies from all around the world in human populations. So we know a lot about what these particles do.

The third reason that we should care is that there is quite literally no margin of safety. Current ambient exposure levels in urban areas in many parts of the country are at a level that is predictably known to kill people, which has given me a lot of reason to put this issue very high on my priority list.

If there is a pollutant that CHE Partners want to focus on and stand up and take action on, this is really a very strong contender. As Debbie Shprentz will tell you, action is going to be needed on this issue very soon, because EPA is re-assessing the National Ambient Air-Quality Standard for Particulate Matter and just this month put out draft air-quality criteria documents. So there’s going to be a lot happening on this issue in the coming year.

4. Second Speaker: Michael Lipsett, MD, Chief, Exposure Assessment Section, Environmental Health Investigations Branch, California Department of Health Services

On the first slide I will be looking at epidemiologic studies that have looked at the effects of short-term exposures and focus particularly on mortality. As Gina mentioned PM, even at ambient concentrations today has been associated with mortality and the ambient standards that we have in the U.S. and in other countries have been based primarily on mortalities as an outcome because clearly that’s the most serious adverse health-affect that we could be addressing.

Much of what is known about this is based on what are called time-series studies that take usually several years of data in a given city or group of cities. There have been hundreds of these studies that have been conducted worldwide over a huge range of climates, seasonal patterns, with different kinds of populations with differing health backgrounds, age structures, housing stock, different pollutants and different sources of particulate matter. What these time series studies do is to examine associations between the daily concentrations of particulate matter and daily death counts and can do this statistically by taking into account changes in weather, seasonal affects and the other pollutants. (next slide)

One of the things that has been really remarkable about all of these studies is the consistency of these associations between daily averages of PM10, which is what most of the studies have used, and PM2.5, and daily mortality. It is a linear type of relationship. People have tried looking at other shapes of dose-response relationship, but all the studies are basically consistent with the linear relationship. There is no good evidence of a threshold, at least on a population basis. Biologically that doesn’t make sense, because at a very low level, we do have lots of good defense mechanisms against particles for low levels of exposures, but at least at levels at which people are being exposed to throughout the U.S. and Europe and not to mention areas that much more polluted in Asia and Central America, that there’s no good evidence of a threshold. Most of these mortality studies have shown associations of an increase of about between ½ and 1½ percent in daily mortality per 10 micrograms per cubic meter of PM10. Ten micrograms per cubic meter of PM10, if we’re only at that level, is pretty good air quality. In areas like in L.A. on a typical day we might have levels anywhere between 40-70 micrograms per cubic meter of PM10. So with each 10 microgram per cubic meter increase, the models predict about a one percent increase in daily mortality.

An example of this is this Air Pollution and Health: A European Approach (APHEA2). They looked at 43 million people in 29 European cities and they found about a .6 percent increase in daily total mortality, and .7 percent were cardiovascular deaths, per 10 microgram per cubic meter. One of the things that this and a number of other studies illustrate is that the biggest component of these deaths is cardiovascular. Interestingly it’s not respiratory types of deaths. (next slide)

So, there was a lot of skepticism about these studies when they first began to be published in any number which was like in the mid-1980’s, about whether there might be any kind of cause or relationship between these particles levels and daily mortality. But what one of the ideas about this is that if particles can kill people, then they should be having effects also on less serious health outcomes. So it does make more of a consistent and coherent and logical type of picture, that if particles can kill people, then they can also cause all these other sorts of problems. (next slide)

Is low-level PM exposure and cardiovascular effects believable? Well intuitively we can understand where we might have respiratory effects, because we’re breathing it in and that’s the target organ and it makes mechanical, causal sense. Until the past six or seven years there was no good mechanistic explanation for why there would be cardiovascular effects of PM (next slide). There is now evidence that shows the different kinds of outcomes including: Cardiac Arrhythmia and Cardiac Ischemia, which means the heart isn’t getting enough oxygen which is the basis for Angina and heart attacks. Evidence is accumulating rigorously and that’s one of the reasons the AHA put out this position paper a few months ago and that is one of the resources that’s now available. They also have a mechanistic diagram in that paper if you’re interested in going into this in any detail, along with several pages of explanation of potential biological mechanisms. (next slide)

Another example of an epidemiologic study that looked at cardiac outcomes was done by some investigators in Boston who interviewed almost 800 people who had non-fatal heart attacks. They interviewed them in hospitals about when their symptoms began. Then they compared this with the PM10 and PM2.5 measurements in the area two-hours and 24-hours before the symptom onset. The diagram on the right illustrates the odds ratio, measurements of increased risk and exposure. You can see that as the PM2.5 levels go up, the increase of heart attack symptoms occurred. Interestingly, in this particular study, all of PM2.5 concentrations were lower than the current federal PM2.5 24-hour standard.

I also want to talk about longer-term exposures. Unlike the time series studies of which there are hundreds, there are only a handful of these longer-term studies looking at longer-term exposures to PM2.5 and/or PM10. In these studies individuals are followed over a longer period of time and they have individual-level data on say smoking, weight, alcohol use, a whole variety of factors that could affect their development of chronic disease and mortality. Interestingly these studies show a markedly greater association of mortality with PM than the time series studies. One example of this is the American Cancer Society study, in which people began to be followed in 1982 for up to 16 years and investigators controlled for a variety of these different individual-level factors and what they found, in these 151 cities where the people lived, that in a 10 microgram per cubic meter increase in long-term average PM2.5, there was a six percent increase in all-cause mortality, nine percent cardio-pulmonary, and 14 percent in lung cancer. And within the cardio-pulmonary deaths, there was an 18 percent increase in ischemic heart disease, which is like heart attacks, and a 12 percent increase in arrhythmias and heart failures and cardiac arrest.

So compare this to the about one percent increase per 10 micrograms per cubic meter that you see on an acute basis, you see that these chronic exposures are likely related to the development of these diseases as well as their exacerbation, which is what you see in the time series studies.

I want to mention the Netherlands study, because this is a small cohort, but what the investigators found in this particular one was not that the air pollution measurements were important predictors, because they were important, but the strongest pollutant predictor of mortality in this cohort was living near a busy road. This is almost a doubling, a 95 percent increased risk for cardio-pulmonary mortality.

I want to finish with a study on traffic and fatal myocardial infarction, which was just published in the New England Journal. About 700 people in Germany who were interviewed about their activities prior to the onset of heart attack symptoms and what these investigators found was exposure to traffic within one to two hours prior to these symptoms more than doubled the risk of the heart attack. You might think these symptoms might be caused by the stress of driving and not just pollutant exposures, however the same magnitude of the increase in risk was also seen for people taking public transportation including buses and trolleys. The largest effects they found were for women, for people over the age of 60, diabetics and the unemployed.

The point of this and the prior study are that people are only now, over the past couple of years, starting to look closely at the impacts of traffic exposures. As Gina mentioned about ultra-fine particles, these are generally created freshly in traffic and the levels of exposure on or near busy roads are orders of magnitude higher than what you’d see in terms of general regional pollution.

5. Third Speaker: Deborah Shprentz, Consultant, American Lung Association

Under the Clean Air Act, EPA is required to set National Ambient Air Quality Standards (NAAQS) for common air pollutants like PM. These standards have to be set at levels that will protect public health with adequate margins of safety, which is defined to include protecting the health of susceptible populations. These are strictly health-based standards, cost cannot be considered during the standard-setting process. Under the act, the standards are required to be reviewed every five years to ensure that they are taking into account the latest medical evidence. The Clean Air Act also requires an independent committee, the Clean Act Scientific Advisory Committee (CASAC) to review the criteria that are used to develop the standards.

Basically the trend that we have seen for the regulation of PM is towards the regulation of smaller and smaller particles. EPA last reviewed the NAAQS in 1997 and they established new standards for PM2.5 or fine particles. I think the important thing about those standards, is that they will, for the first time, begin to regulate combustion forces of particle pollution. Now those standards were extremely controversial. Industry challenged those standards all the way up to the Supreme Court and lost. But, because of the controversy, industry pushed for a very prompt reconsideration of the standards. Almost immediately after the standards were promulgated in 1997, EPA began a review of the standards, which is ongoing now.

There were two standards set for fine particles, an annual average standard and a 24-hour standard. I would like to note that just two years after the standards were established, EPA set a public warning level for 24-hour exposure that was far more stringent than the actual standard itself. Which I think implies the critical need to strengthen the 1997 standards. EPA estimated enormous public health benefits for achieving the 1997 standards, 15,000 lives saved each year, tens of thousands fewer respiratory symptoms, hospitalizations and so on. Now back in 2002, California reviewed their ambient standards for PM under their law design to protect the health of children and they ended up setting annual standards that were far more stringent than the federal standards. They also proposed a far more stringent 24-hour standard and tightened their standards for coarse particles.

I mentioned that the 1997 standards were really controversial. They’ve been opposed by broad range of industry groups and the junk science people really went nuts over these standards. I think I counted 19 different conservative think tanks that have been bankrolling studies and analyses and opposition to these standards. So this has been an extremely politicized issue. One outcome of all of this opposition and criticism of the 1997 standards was that Congress authorized a $50 million per year, research program over the last five years, to look into the health-affects of PM. There have been over 3,000 new scientific papers published and much to the dismay of critics I think that the new science has actually addressed most of the major criticisms of the earlier standards.

So, EPA is now in the midst of its review and there are a couple of key steps before the agency puts out a proposed regulation. The first is to publish a criteria document, which is a compilation of the recent science. That’s followed by the publication of a staff paper, which puts the policy spin on the new science. Both of those documents are subject to peer-review by the CASAC and the public. In fact, it’s an amazingly open process as far as opportunities for public involvement, but I’d like to point out that there’s extremely heavy industry involvement in this process and the CASAC, which is very industry dominated, is very influential. They managed to hold up publication of the final criteria document for about six years. It is just out last month in its final form. The conclusion is that adverse effects are occurring at levels below the current standards.

The next step in the process will be for EPA to put out a second draft of the staff paper, which will suggest ranges from which the EPA administrator can select levels for the standard. The ranges in the earlier staff draft paper did imply that strengthening of the standards was necessary particularly for the 24-hour standards, but they also suggested ranges that could accommodate strengthening of the annual average standards. They are also proposing an establishment of a new form of the coarse particle standards.

There are a lot of opportunities for groups to get involved in the coming months, both prior to the issuance of the staff paper and after: once the staff paper is out presentations at the Spring 2005 CASAC meeting, and then once the regulatory proposal comes out, which will probably be late in 2005. Some suggestions are resolutions from different medical societies, letters from health groups, letters from public officials, sign-on letters, grass-roots action alerts, testimony at the meetings, public hearings and so on.

Implementation of the standards is a very long, drawn-out process, which is only just beginning now. We expect that any day now, the EPA will announce the different areas of the country that will be designated as being out of attainment with these 1997 fine particle standards which will just start the process of developing state plans to reduce the sources of emissions. That’s why the grass-roots efforts are so important.

I would also like to mention that I manage a listserv that focuses on these issues. Please contact me at Contact if you are interested in joining this listserv. We also have a website at: www.cleanairstandards.org.

6. Fourth Speaker: Swati Prakash, MPH, Environmental Health Director, West Harlem Environmental Action

West Harlem Environmental Action (WEACT) is a community-based organization. We have been working to build community power to fight for environmental justice in communities of color like Northern Manhattan, since 1988. I’ll start by painting a quick picture of the communities that we’re working in. Northern Manhattan is comprised of the four communities of East Harlem, Central Harlem, West Harlem and Washington Heights, where there is a total population of 600,000 predominantly African American and Latino people living in just 7.4 square miles. These communities have a median household income of between $19,000 and $28,000 per year. They are also communities that are very heavily burdened with asthma, which is the primary motivator that has really brought us to address the local sources of air pollution in these areas.

In terms of the asthma burden, a study released last year by Harlem Hospital and the Harlem Children’s Home found that one in four children in Central Harlem were living with asthma, which is three times the national average. We also know that childhood asthma hospitalization rates are nearly six times the national average in East Harlem. So you put those health statistics against the background of the environmental context locally, which is representative of many urban communities of color. In Northern Manhattan we’re home to six out of seven of the New York City transit agencies and Manhattan diesel bus depots. We’re surrounded by two highways and crisscrossed by the I-95 Highway, which leads to the George Washington Bridge, one of the most heavily trafficked bridge crossings in the nation with more than 100 million vehicle crossings every year. We’re also home to two sewage treatment facilities and several smaller bus and truck parking lots.

So these diesel sources and transportation sources have become a focus of our organizing. For one, because they’re so obvious to people, the sights and smells are in our faces. And, secondly because we know that the emissions from motor vehicles do have a toxic impact in terms of exacerbating asthma. We also know that the vast majority of the PM emitted by diesel exhaust is in that fine fraction range of 2.5 microns or smaller and even in the ultra-fine range. We also know that the borough of Manhattan is out of compliance with the National Ambient Air Quality Standards for fine PM. Like other urban areas anywhere, from 10-30 percent of ambient fine PM is coming from local diesel sources.

So, the concern around diesel exhaust has led us to a research collaboration with Doctors Patrick Kinney and Steve Chillrud at the Columbia School of Public Health and a sister environmental justice organization in the South Bronx, called For a Better Bronx. We’ve been working with them for the past two and a half years to measure fine PM and black carbon, which we used as a proxy for diesel exhaust in high schools in the South Bronx and now in Harlem, this year and have been comparing it to an upwind school in suburban New York. The first complete year of data has shown that the fine PM at the urban schools measures anywhere between three and five times higher than at the suburban school. The range has been roughly between 15 and 45 micrograms per cubic meter, measured over a 10-day period this past spring. This has confirmed our belief that local sources of fine PM, especially transportation related sources, have to be the focus of organizing efforts.

To that end our trademark issue has actually been the diesel bus depot and the city busses owned by NYC Transit. As I mentioned six other depots are located uptown. Since 1988 we’ve organizing and collaborating with groups like NRDC to pressure NYC Transit to clean up its diesel fleet. The angle has always been to switch away from diesel completely to a clean alternative fuel like compressed natural gas (CNG). What NYC Transit has done was to commit to cleaning up their diesel busses. They’ve phased in alternatives to diesel fuel and they’ve installed PM traps, which do a great deal to reduce the PM emissions from their busses. But we still haven’t reached the ultimate ideal for us, which would be to switch to CNG. Because, even though we see that the emissions from the latest diesel technologies appear to be comparable in terms of PM to emissions from CNG fueled vehicles, we remained concerned about the long-term viability of these so-called clean diesel technologies, the ability of NYC Transit to properly maintain the filters to make sure that those emission reductions stay at the level that they are now at and also whether the upcoming carbon monoxide standards, which will come into place in 2007 for diesel engines can be met at the same time as the PM standards can be met.

Just a quick bit of good news, is that NYC Transit has agreed to meet directly with community residents living near the six uptown bus depots to try to collaboratively address a lot of these health and technology questions that community residents have. It’s a real victory in terms of just having the transit agency show a measure of respect for the residents who are most impacted by the sources of air pollution.

Another source we’ve focused on has been yellow school buses that are some of the dirtiest vehicles out there, which is just atrocious considering that they are carrying some of our most precious passengers. We’ve just collaborated on a State Attorney General Enforcement Action against school bus fleets that have been idling in school districts, which resulted in a promise to live up to a no-idling policy within the school zones. And we continue again to fight for phasing in CNG for school buses, because in an urban community where school buses are centrally parked and fueled you can actually create a fuelling infrastructure to fuel multiple fleets, city buses and school buses as well as privately owned vehicles.

We have addressed a lot of local sources, but we are aware that upwind sources, such as dirty power plants, contribute significantly to all fine PM in the Northeast. We do try to make the links between communities of color locally and those that are living near power plants, those that are living near the oil refineries that are refining oil into the diesel fuel that’s burned to fuel public bus fleets. Another local source we’re looking into increasingly is home heating oil, which is some of the lowest grade fuel that’s burned and does contribute a great deal to urban fine PM. Making the connection between home heating oil and healthy homes is part of our Healthy Homes Campaign.

I’ll close by saying, when you think about where fine PM is coming from, it’s coming from fuel, it’s coming from combustion sources, it’s coming from the way that homes are heated, how vehicles are fueled and how electricity is produced. The frame that we’re increasingly using is to understand how energy is related to air pollution and then really pushing for alternative sources of energy, and renewable energy like geothermal, hydrogen and wind sources. In a local context we’re trying to put that into action by pushing for construction of green and affordable housing in low-income communities as a model for green buildings in all communities.

Steve Heilig: Thank you Swati. I want to mention that here in San Francisco we fought to get rid of diesel buses for so long and unsuccessfully that we resorted this year to a voter initiative that finally passed.

7. Questions/Comments/Discussion

David Schonbrunn, President, TRANSDEF (Transportation Solutions Defense and Education Fund): Can you differentiate the health affects of fugitive dust from the travel of motor vehicles over roads versus diesel PM?

Michael Lipsett: In terms of looking at road dust versus the combustion particles like diesel, in general, many of the diesel particles, as has been mentioned are in the ultra-fine range and they carry these PAHs or poly-cyclic aromatic hydrocarbon compounds, which traditionally people have thought of about as being responsible for causing cancer and that sort of thing, but as it turns out they are also mediators of something called oxidative stress. They can generate a tremendous amount of oxidative stress and initiate a cascade of reactions in the lung and systemically that you don’t get to the same extend from particles that are in like road dust. Some people have the idea that road dust, relative to some things is pretty benign, but I think part of that is that people haven’t really looked at it as carefully as they have the combustion sources, but without meaning to denigrate the importance of combustion sources like diesel, because I think they are extremely important in terms of causing a variety of adverse effects.

There have been a number of toxicologic studies that have just been published in the in the past two years, where people have actually begun to look at suspended road dust and have found that some of the constituents of that can also cause problems particularly in the lungs. One of the things that’s important in that is something called endo-toxin, which is a component of bacteria that are found all over in the soil. Endo-toxin can cause airway inflammation and it can cause bronchial constriction and that sort of thing too.

If I had to say which is more likely to be toxic, I would say that the diesel-type fumes would be but that one should not ignore things like re-suspended road dust.

Linda Weiner, Director of Communications and Air Quality Advocacy, American Lung Association of San Francisco/San Mateo: I would first like to say that the American Lung Association of San Francisco was instrumental in getting the anti-diesel bus initiative on the ballot, but there is still work to be done because the transit district is still dragging their feet.

Because I translate these studies to the public and to the media and to our local commissions, when you talk about the strongest pollutant predictor of mortality, for instance in the Netherlands Study, as living near a busy road, and we often have data talking about the correlation of living near a busy road and an increase in either cardiopulmonary mortality or respiratory disease. What are the parameters for saying “living near a busy road,” is that one block or 10 blocks, or a mile?

Michael Lipsett: In the Dutch study, what they considered to be “living near a busy road,” in that particular investigation was within 100 meters of a freeway or within 50 meters of a busy urban street. There have been some studies that have been done in this country, several in the Los Angeles area out of UCLA where people have measured the ultra-fine particle and black carbon concentrations at the 710 Freeway, on which about 25% of the vehicles are trucks. What they found was very high pollutant levels right at the side of the freeway, with a rapid decline within about 100–150 meters downwind. Particle levels were back down to near-background levels by about 300 meters downwind, with about 90% of this decline occurring within the first 100-150 meters.

Mark Mitchell, MD, MPH, President, Connecticut Coalition for Environmental Justice: I have a question about the ultra-fine particles in natural gas versus diesel emissions. Is there some recent data on that or can you clarify that for me?

Gina Solomon: There has been some controversy about emissions from natural gas engines around a couple of things. One is the aldahyde emissions issue, which seems to be largely addressed through the addition of oxidation catalysts, which are now fairly standard on CNG engines. But there’s also this concern about whether there’s more ultra-fine particles coming out, but it’s not just a CNG problem. There’s some concerns that the addition of some of the traps to even diesel engines may be shifting the size fractionation of the particles downward on the curve and that there may be relatively more ultra-fine particles coming out of these engines equipped with more state of the art emission control technologies. That’s a really distressing thing if it’s true, but the problem is that it’s still a little bit tricky to measure these things. And I haven’t seen a really definitive study on this issue yet.

Robert Gould, MD, President, San Francisco Bay Area Physicians for Social Responsibility: There was a report from the Harvard Medical School, by Paul Epstein, et al, that came out earlier this year laying out a theoretical model for diesel carrying pollen down into the lungs and therefore laying out a model for global climate change, that these two are acting synergistically to cause more asthma as a result of global climate change. Does anyone have any information on a substantiation of this model?

Gina Solomon: Actually that’s a really interesting question and there’s quite a lot of research on this issue right now, both in Japan and also in Los Angeles. Researchers have looked at interactions between diesel exhaust exposure and allergen exposure. The studies have consistently found that exposure in either an animal or a human, because some of these studies are actually done on volunteers, to a combination of diesel exhaust and common allergens, and for this purpose they’ve used such things as Japanese Cedar Pollen, Ovalbumen, which is basically egg-white protein, and various other common allergens, the combination of diesel exhaust and exposure to an allergen appears consistently to create an enhanced, almost synergistic immune response both in the upper airways and in the lower airways. There are a number of theories about why that might be the case. One of the theories is exactly what you said Bob, that the diesel particles somehow carry the pollen deeper into the airways, but when they did the exposures separately, with first the diesel and then the pollen, the effect remains. So it appears that it may be a sort of priming of the immune response, which would also be very distressing.

Eleni Sotos, MA, National Coordinator, CHE: I just wanted to mention that we have had some interest from the partnership in developing a working group on asthma and/or related issues including particulate matter. If anyone is interested in the possibility of participating, please contact Frieda Nixdorf.

Michael Lerner, PhD, President, Commonweal: I would like to say that I think this has been a brilliant call and the presenters did a great job. Viewing the participant list for this call we have an astonishingly diverse and sophisticated group of people who took the time to join us. It seems like there are real opportunities for American Lung, American Heart and American Cancer Society to explore shared interests in this particulate matter issue and I look forward to further conversations about exploring those ideas with other CHE Partners.