OSHA: Proposed Standard For Indoor Air Quality: ETS Hearings, January 6, 1995
OSHA: Proposed Standard For Indoor Air Quality: ETS Hearings, January 6, 1995
UNITED STATES DEPARTMENT OF LABOR
OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION
PUBLIC HEARING
PROPOSED STANDARD FOR INDOOR AIR QUALITY
Friday, January 6, 1995
Department of Labor
Washington, D.C.
The above-entitled matter came on for hearing, pursuant to notice, at 9:30 a.m.
BEFORE: HONORABLE JOHN VITTONE
Administrative Law Judge
AGENDA
PAGE
Washington Technical Information Group
Arthur Greenberg 10062
Questions:
Ms. Sherman 10070
Mr. Rupp 10092
Dr. O'Neil 10103
Ms. Sherman 10106
University of Arizona
Mark Van Ert 10107
Questions:
Ms. Sherman 10123
Mr. O'Neil 10196
Mr. Rupp 10199
Mr. McNeely 10209
Ms. Sherman 10219
EXHIBITS
EXHIBIT NO. IDENTIFIED RECEIVED
200 10091 10091
201 10195 10195
P R O C E E D I N G S
9:55 a.m.
JUDGE VITTONE: Good morning. We are on the record. This is a continuation of the hearing into the OSHA indoor air quality proposed rule.
We begin today with Mr. Arthur Greenberg.
Mr. Greenberg, that's your full name, sir?
DR. GREENBERG: Yes. Arthur Greenberg.
JUDGE VITTONE: And who are you associated with, sir?
DR. GREENBERG: My faculty association is I am a faculty member at the University of North Carolina at Charlotte. And I am working today at the request of the Washington Technical Information Group.
JUDGE VITTONE: All right. You can begin your presentation when you're ready.
DR. GREENBERG: Good morning, Your Honor and members of the OSHA panel. My name is Dr. Arthur Greenberg and I appreciate the opportunity to appear here today to offer my professional opinion regarding certain components of the recently proposed OSHA rule on indoor air quality.
I am a chemist and the recently appointed chair of the Department of Chemistry at the University of North Carolina at Charlotte. With regard to my training and employment history, I obtained my Ph.D. in chemistry from Princeton University in 1971. Until accepting my present position at UNC Charlotte, I was for many years a professor in the Department of Environmental Sciences at Rutgers University.
I also served as Deputy Director of the Exposure Measurements and Assessments Division of the Environmental and Occupational Health Sciences Institute which is jointly administered by Rutgers and the University of Medicine and Dentistry of New Jersey and as laboratory leader of the Organic Chemical Analysis Support Laboratory, which is under the auspices of the National Institute of Environmental Health Sciences, NIEHS.
Throughout my career, my research has focused on structural organic chemistry, complex environmental mixtures and human exposure to pollutants. I have published in and served as an editor and peer reviewer for journals and books in these areas for several years.
In the proposed rulemaking that is the focus of these hearings, OSHA contends that exposure to environmental tobacco smoke in the workplace constitutes a significant risk of material health impairment to non-smoking workers. Section III.A of that proposed rulemaking concerns the chemical characterization of environmental tobacco smoke. Based upon my expertise in matters that relate to this issue, I was asked by the Washington Technical Information Group, Inc., or Wash Tech, to evaluate this component of the rule.
Let me emphasize that although I am appearing at this proceeding at Wash Tech's invitation, the views I am about to offer are my own.
As was noted earlier at this meeting, the National Academy of Sciences and National Research Council and the Office of Technology Assessment have devised a four-step paradigm to guide federal agencies in conducting regulatory risk assessments.
The third step in this risk assessment paradigm after hazard identification and dose-response analysis is exposure assessment. In evaluating exposures, it is very important to accurately identify and characterize the chemicals of concern.
As the 1994 National Academy of Sciences report notes, the first step in exposure assessment is estimation of the quantity of toxic material emitted by a given source. Emission characterization involves identifying the chemical components of emissions and determining the rate at which they are emitted.
After reviewing the preamble of the proposed rule, I believe the agency's assessment of exposure to environmental tobacco smoke in the workplace is flawed because OSHA fails to present an adequate characterization of the physical or chemical composition of this mixture in the indoor atmosphere.
Environmental tobacco smoke is an aged mixture of an unknown number of compounds and substances contained in its two major compounds, sidestream smoke, the smoke released by the burning tip of the cigarette between smoke, and exhaled mainstream smoke, the smoke exhaled by the smoker.
Chemicals from these two components are distributed in the gas phase and particulate phase of the smoke. The relative contributions of mainstream and sidestream smoke in environmental tobacco smoke at a given point in time are determined by the frequency and depth of inhalation, as well as the properties of individual smoking products.
As the two components intermix and react with other chemicals present in the atmosphere, the composition of the mixture changes, a process known as aging. The mixture is also affected by dispersion, dilution, evaporation, condensation, coagulation and absorption or impaction surfaces.
It is imperative that any investigation of the inhalation effects of environmental tobacco smoke be designed to consider the exact physical and chemical nature of this mixture.
OSHA provides a description of the chemistry of environmental tobacco smoke that relies heavily on data presented in the much criticized 1992 EPA risk assessment. The discussion in the Federal Register primarily concerns differences and similarities between mainstream and sidestream smoke. The problem is that OSHA does not provide an accurate chemical characterization of environmental tobacco smoke that can be used to evaluate the studies the agency relies upon to support its contentions regarding exposure and health risk.
Generally, the combined effect of physical and chemical processes on its components renders environmental tobacco smoke a much more variable and complex mixture than those occurring in mainstream or laboratory-generated sidestream smoke.
Such proxy substances are not comparable to environmental tobacco smoke as it is experienced in the atmosphere. Thus, studies that examine these substances cannot be said to provide relevant factual evidence concerning the effects of environmental tobacco smoke on health, yet OSHA supports its position largely on studies of this kind.
There are several reasons why sidestream smoke is a poor surrogate for environmental tobacco smoke.
First, sidestream smoke collection systems impose artificial conditions on the burning of cigarettes that may be different than those found under normal room air conditions. These systems also may preferentially collect certain substances that might affect the analytic results.
Second, reliance solely upon sidestream smoke neglects the contribution of exhaled mainstream smoke to environmental tobacco smoke in the atmosphere.
Third, most analyses of sidestream smoke do not account for the effects of aging on environmental tobacco smoke.
Thus, in most sidestream smoke studies, the chemical composition of the tested smoke is unlikely to reflect the composition of environmental tobacco smoke observed in the workplace.
OSHA's extrapolation of results from laboratory investigations of sidestream smoke is therefore inappropriate.
Furthermore, in its discussion of the chemistry of environmental tobacco smoke OSHA makes several claims that are not supported by either the data in the record or by the available scientific literature. These include the following:
OSHA states that there is a lack of variability in sidestream smoke emissions and this refuted by recent research, citing some papers by Evans and Sefton, Weetman and Luceri, that indicates the composition of sidestream smoke varies with the curing of the tobacco, the cigarette brand and the cigarette type.
Moreover, correction methods and methods of analysis often vary and add to the overall variability of measurements.
OSHA assumes the collection of sidestream smoke at environmental tobacco smoke is uniform and that analytical results reflect the actual composition of the aerosol. However, certain collection methods and analytical techniques can cause chemical reactions that change the composition of the anilide relative to the original environmental sample.
OSHA assumes that toxic materials in sidestream smoke remain in environmental tobacco smoke without significant chemical degradation. This is not consistent with the technical literature.
Aging of sidestream smoke has been reported to reduce the cytotoxicity of sidestream smoke and the effects of the formation or disappearance of radicals in the smoke on the toxicity of the mixture are largely unknown. Short lived free radicals are known to occur in the vapor phase of sidestream smoke. Other reactive substances include the carcinogenic n-nitrosamines which readily decompose photochemically.
OSHA assumes that particulate matter in sidestream smoke has a close relationship with particulate matter in environmental tobacco smoke. However, because the number and mass median diameter of sidestream smoke particles increase with aging, it is inappropriate to extrapolate on this issue from sidestream smoke to environmental tobacco smoke.
OSHA employs nicotine as a gas phase marker for sidestream smoke and environmental tobacco smoke. This approach is flawed, however, because, one, nicotine exhibits a rapid decay relative to essentially inert species such as total hydrocarbons and, two, nicotine can physically adsorb to surfaces such as fabrics and ultimately be re-suspended.
A very straightforward statement of this problem was made by the Committee on Advances in Assessing Human Exposure to Air Pollutants and is published the National Academy of Sciences report, 1991 National Research Council report, and I quote, "It is not known how nicotine concentrations are related to concentrations of other contaminants in ETS, particle or gas phase, or to those contaminants that might be associated with health, e.g., benzene, or nuisance effects."
In conclusion, I believe that OSHA has not presented an adequate characterization of the chemistry of environmental tobacco smoke which is a necessary step in assessing exposures to allegedly harmful substances. By not doing so, the agency limits the credibility of its determination of the risk that environmental tobacco smoke allegedly presents in the workplace.
Thank you very much. That's the conclusion of my presentation.
JUDGE VITTONE: Thank you, Dr. Greenberg.
Ms. Sherman?
MS. SHERMAN: Dr. Greenberg, have you done any independent research on the chemistry of tobacco smoke?
DR. GREENBERG: On tobacco smoke itself, no. I have been involved in some studies on human exposure to polycyclic aromatic hydrocarbons in which smoking could conceivably have been a factor.
MS. SHERMAN: Have you done any independent research on the chemistry of ETS?
DR. GREENBERG: No.
MS. SHERMAN: Before this present assignment, have you worked for the Washington Technical Information Group?
DR. GREENBERG: No. Let me modify just very slightly and say that three years ago approximately the Washington Technical Information Group had talked with me about possible involvement in a case and at that point it was decided that I would not be involved in the case and that was the only interaction. So this is the first time I've ever worked on a case with them.
MS. SHERMAN: Did you write your own testimony that you gave today?
DR. GREENBERG: Yes.
MS. SHERMAN: Do you know Dr. Van Ert?
DR. GREENBERG: I do not.
MS. SHERMAN: Did you consult with him before submitting your testimony?
DR. GREENBERG: No, I did not.
MS. SHERMAN: On your August 9th submission to us --
DR. GREENBERG: Yes.
MS. SHERMAN: I believe on the top of page two you state that "Environmental tobacco smoke is an aged mixture of an unknown number of compounds and substances contained in its two major components."
DR. GREENBERG: Yes.
MS. SHERMAN: Under normal circumstances, how long is ETS aged?
DR. GREENBERG: When we talk about normal circumstances, we're talking about as in a bar?
MS. SHERMAN: Well, I guess -- I'm having trouble with a definition. What is aged sidestream smoke?
DR. GREENBERG: I think that aged sidestream smoke is something that has existed on the order probably of hours.
MS. SHERMAN: I mean, when does it start being aged?
DR. GREENBERG: I think that aging begins virtually as soon as the material leaves the cigarettes. It will happen in the first certainly minutes, seconds, and probably will continue for hours.
MS. SHERMAN: And it ends when one can no longer measure anything analytically?
DR. GREENBERG: I'm not sure there is such a moment. I think that it's -- presumably as long as you can measure tobacco smoke in a room, it's still aging. In other words, after people have left the room it's still aging.
MS. SHERMAN: May I ask for your indulgence for a moment?
(Pause)
MS. SHERMAN: Sorry. I just got a note from my office. Okay.
So you would say that aged sidestream smoke is from the time it leaves the cigarette until the time you can no longer measure it.
DR. GREENBERG: I think I would agree with that. Yes.
MS. SHERMAN: And is there any literature on the subject that would support that type of a definition?
DR. GREENBERG: I think that my feeling is that no one has given a precise definition to aging because people have done different kinds of experiments. I don't think that anyone has ever tried to see when cigarette smoke reached a point of no further analysis or detection. I think typically people will define aging -- you know, on the time scale that they actually do the experiment which probably starts on the order of minutes and goes for a few hours. So I don't think that there is a definition that's that encompassing.
MS. SHERMAN: If you'll indulge me another moment --
(Pause)
MS. SHERMAN: There are carcinogens in both cigarette smoke and environmental tobacco smoke.
DR. GREENBERG: Yes. That has been shown, both proven and suspected carcinogens. Yes.
MS. SHERMAN: Are any of the carcinogens that are found in cigarette smoke, have they been shown to be deactivated or neutralized by the aging process?
DR. GREENBERG: That's something of a complex question. In one sense, yes and in another sense, no. And let me expand upon that.
MS. SHERMAN: Okay.
DR. GREENBERG: First of all, a substance such as benzo(a)pyrine, which is an example --
MS. SHERMAN: Which everybody agrees is a carcinogen.
DR. GREENBERG: From a point of view of humans, I think it's considered a suspected carcinogen but that's a matter of definition. But in any case, benzo(a)pyrine certainly suffers decomposition upon aging, all right?
Now, if we talk about -- I guess I would talk about compounds called nitrosamines, which are also under the class of suspected human carcinogens, and these also are known to decompose chemically, photochemically, but the other case of interest and where there is a great deal more that needs to be known is on the subject of highly reactive substances called free radicals.
Now, free radicals are certainly capable of attacking many, many different types of substances, probably capable of attacking biological polymers in the lung and so on. And these things exist on the order -- normally, they exist on the order of actually seconds or fractions of a second. There seems to be evidence that they exist on the order of minutes in fresh sidestream smoke but there is no question that they will decompose on the order of minutes and the question is are these carcinogenic and the answer is it's very hard to do carcinogenicity studies on these things.
MS. SHERMAN: Okay. Well, how long would it take under normal circumstances benzo(a)pyrine to decompose?
DR. GREENBERG: I don't think that anyone has done -- benzo(a)pyrine is just one example of polycyclic aromatics.
MS. SHERMAN: Oh, I understand. Sure.
DR. GREENBERG: And it's not necessarily the most reactive. But I don't think that anyone has done a study of benzo(a)pyrine that's relevant to indoor air exposure. It's hard enough to do it on outdoor because when one does outdoor studies the sorts of things people have done is modeled by putting benzo(a)pyrine on particulates and then shining appropriate ultraviolet light on it. And there you may have lifetimes on the order of basically hours, even less than hours. But the problem is how relevant that is to outdoor conditions and I don't think that anyone has really been able to --
MS. SHERMAN: You mean to indoor conditions?
DR. GREENBERG: No, I first said outdoor conditions deliberately. And then I think that nobody that I'm aware of has studied the decomposition of benzo(a)pyrine and the other PAHs under indoor conditions. So I think that relatively little has been done in this area under anything resembling realistic indoor conditions.
MS. SHERMAN: Would it be fair to say that the more reactive a compound, the faster the decomposition or is that not a relevant consideration?
DR. GREENBERG: You know, the whole interesting question about more reactive is the chemist's question is more reactive with what.
MS. SHERMAN: Well, you used the term more reactive so I'm just sort of following your train of thought. And I'm not a chemist.
DR. GREENBERG: Okay. What I would say is this, that if we're talking about reactivity with the sorts of things that are present in the air, including indoor air, things like oxides of nitrogen, things like ozone, things like, you know, light, ultraviolet light, generally the more reactive, the faster it reacts, the faster it disappears.
MS. SHERMAN: Now, how long would it take for the nitrosamines to decompose photochemically?
DR. GREENBERG: Again, the evidence on nitrosamines have been done under very artificial conditions and one can decompose nitrosamines really on the order of really less than an hour doing these sorts of artificial studies. The question is how rapidly do they decompose under indoor conditions and I don't think that's known particularly.
MS. SHERMAN: Well, is there any reason to believe that these artificial conditions might not be a reasonable surrogate for indoor air conditions?
DR. GREENBERG: Well, the artificial conditions are conditions which exaggerate the decomposition and, if anything, I think that indoor air conditions may conceivably moderate it a little bit. So what I'm saying is one gets a more exaggerated sort of picture from that.
If we look at nitrosamines, for example, and compare their intrinsic reactivity to light and that's measured by something called quantum yield, you'll find that the sorts of quantum yields for the polycyclic aromatics are on the order of numbers like .01, .001, all right? For the nitrosamines, you're laking about numbers like .1, .2, .3, which means that they're really two orders of magnitude more reactive than things like the polycyclic aromatics.
But I don't think that anyone has really done a systematic study. I know that Eatough's group at Brigham Young has done some study on the decomposition of these things but this is a hard thing to do under indoor conditions.
MS. SHERMAN: Okay. So we've discussed the relationship of decomposition with the aging process.
DR. GREENBERG: Yes.
MS. SHERMAN: What about the carcinogens found in cigarette smoke? Are they deactivated or neutralized by intermixing with other components?
DR. GREENBERG: Well, again, when we talk about other components, the other components in the air, the other components can be things like nitric oxide, NO, NO2. It can mean ozone and so on. And these compounds are known to react with these sorts of compounds.
MS. SHERMAN: And what about evaporation? Would it be deactivated or neutralized by evaporation?
DR. GREENBERG: No. The chemical is still there. It's not chemically gone if it's evaporated.
MS. SHERMAN: And coagulation?
DR. GREENBERG: Well, particles coagulate. Now, the question of what the fate of the chemical is has to do with its volatility so there are some compounds that will volatize from the particles even as the particles are coagulating. There are other compounds that are in the gas phase to begin with so what you have is you may have a change in phase. As time goes on, compounds that had started out in the particulate phase may wind up being in the vapor phase.
MS. SHERMAN: Could you give me an example of that?
DR. GREENBERG: Well, actually, of course, the discussion of nicotine has always involved this issue where nicotine starts out largely in the particulate phase and then winds up going into the vapor phase.
MS. SHERMAN: But nicotine I don't think is considered a carcinogen.
DR. GREENBERG: Right. We agree. We agree.
MS. SHERMAN: How about an example of a carcinogen?
DR. GREENBERG: Well, I'm sure that this is the case with some of the polycyclic aromatics, some of the lighter polycyclic aromatics, which would start out in the particulate phase. Now, most of the carcinogenic polycyclic aromatics are not so volatile but some of them have enough volatility, something like benzanthracene has enough volatility to start out in the particulate phase and then be suspended into the vapor phase, so that would be one example. And I am willing to believe that certain other types of compounds, some of the nitrosamines of moderate molecular weight, of medium molecular weight, probably start out in the particulate phase and then go into the vapor phase with time.
MS. SHERMAN: Okay. Now, I believe that in some cases toxic chemicals in sidestream smoke remain in environmental tobacco smoke without a significant chemical degradation. However, in other cases, there is a significant chemical degradation. With some substances, doesn't the degradation make the substance more toxic?
DR. GREENBERG: That can happen. It's --
MS. SHERMAN: Like perhaps nitric oxide?
DR. GREENBERG: Nitric oxide turning into NO2, nitrogen dioxide, certainly the nitric oxide is more benign than NO2 is in terms of attacking organic compounds and there certainly are situations in which -- let me give you just two examples. It's a hard one to call. Pyrine, which is a polycyclic aromatic hydrocarbon, will react in the vapor phase to ultimately produce nitropyrine. Now, pyrine is not carcinogenic, nitropyrine is. On the other hand, benzo(a)pyrine, which is carcinogenic, will react to form 6-nitrobenz(a)pyrine which is either non-carcinogenic or has very, very low activity, so it's very hard to predict.
MS. SHERMAN: So it can go either way.
DR. GREENBERG: I would agree.
MS. SHERMAN: I think you also stated that reliance solely upon sidestream smoke neglects the contribution of exhaled mainstream smoke to environmental tobacco smoke in the atmosphere.
DR. GREENBERG: Yes.
MS. SHERMAN: Well, theoretically speaking, would you expect the toxicity of sidestream smoke to increase or decrease with the addition of exhaled mainstream smoke?
DR. GREENBERG: I don't think I know enough to answer that.
MS. SHERMAN: Well, would it at least be fair to say that there would be more of whatever it is?
DR. GREENBERG: There would be an addition of material, yes.
MS. SHERMAN: Do you have a suggestion as to what biomarker we should use to measure environmental tobacco smoke?
DR. GREENBERG: I don't have an independent suggestion.
MS. SHERMAN: You're a chemist, I thought perhaps you would have thought about this.
DR. GREENBERG: The only independent -- first of all, this is, of course, a very subtle problem and some very, very good people have worked on it. You know, Eatough's group, again, at Brigham Young has pointed out some of the problems with at least vapor phase nicotine and they looked at vinyl pyridine as one perhaps better marker because it doesn't seem to be adsorbed as easily, it doesn't seem to react, it seems to have fewer losses. So, you know, based upon what their work indicated, it seemed reasonable but I've made no independent investigation of that.
MS. SHERMAN: In preparing your testimony, did you conduct a literature search on the chemical components of environmental tobacco smoke?
DR. GREENBERG: Yes, I conducted my own literature search. It was not a totally exhaustive literature search. An exhaustive literature search would probably have literally thousands of references.
MS. SHERMAN: It would be a lifetime process, would it not?
DR. GREENBERG: I don't know if it would be -- well, it's a continuing process, that's for sure.
MS. SHERMAN: I believe on page four of your comments you said that OSHA makes several claims that are not supported by either the data in the record or by the available scientific literature.
DR. GREENBERG: Yes.
MS. SHERMAN: Have you read the references that we've cited?
DR. GREENBERG: Yes.
MS. SHERMAN: And what claims do you feel that OSHA makes that are not supported by the literature?
DR. GREENBERG: Well, I am specific about some areas in the points that I have read. There is the issue of lack of variability in sidestream smoke emissions. Now, it's fair to say that the references that I cited in the presentation you referred to were actually newer references. They were 1992, 1993 references. So in that sense it's actually a little bit more difficult to fault OSHA on that.
I will add, however, that one of the studies published by Pryor, which I believe was published in 1990, made a comparison between a burning cigarette, for example, and cigarette in which tobacco is heated and came up with really very markedly different compositions, especially in terms of radicals, in terms of small hydrocarbons that were emitted. So what I'm saying is that there does seem to be variability. There does seem to be variability in the compounds that are present in sidestream smoke and it seems that the OSHA has -- largely indicates that there is great similarity, very great similarity in the sidestream smoke.
MS. SHERMAN: Well, okay. You point out that sidestream smoke is subject to many variables and I think that you specifically discussed this morning the differences in aging and in the curing process that would contribute to this variability.
DR. GREENBERG: Yes.
MS. SHERMAN: Well, now, does this mean that research done with standard laboratory reference cigarettes is really not appropriate?
DR. GREENBERG: What I am saying are two things, I think, at this moment. One is that the research that's done with standard laboratory cigarettes using a standard smoking technique, what is collected is basically sidestream smoke, all right? Not particularly aged, not aged really. The second thing --
MS. SHERMAN: However, it can be aged as part of the experiment, of course.
DR. GREENBERG: In principle but a very hard thing to do under controlled conditions. So that's the first point. And I'm trying to recall the line of questioning that got us into this because there was a second point I wanted to make on the relevance of this and it's just missing me right now.
MS. SHERMAN: I'm sorry, I didn't mean to confuse the issue. Well, then, how would OSHA proceed? How would you suggest that we deal with this variability?
DR. GREENBERG: Well, first of all, I think it's difficult and I think there have been a lot of clever experiments done by EPA and by other researchers to try to handle this issue. I mean, people have attempted to look at aging, let's say, in a big plastic bag, things on the order of 30 cubic meters, but it's hard to do that because the plastic is not necessarily typical of what one confronts under normal circumstances. Thirty cubic meters sounds very large but in fact it's very small relative to normal rooms and so on. So wall effects and surface effects are significant. So it is a difficult problem.
The other thing that is the big unknown in this, I think, is the issue of looking at the very short lived substances, the free radicals and the things associated with them. And I guess if I were to try and concentrate on a particular area, if I were OSHA, if I were EPA and if I were working contractually with them, I guess what I would probably be trying to do is to look at these very reactive substances, the things which last on the order of seconds to minutes, and get a feeling for what happens to them as smoke ages and just see what the relevance of sidestream smoke is in the content of these reactive things relative to more aged smoke. If I had to concentrate on something, that's probably what I'd concentrate on.
MS. SHERMAN: Because that's what you identify as the most variable aspect of sidestream smoke? Is that why you're advocating concentrating on it?
DR. GREENBERG: I would say that the whole issue of aging is extremely complicated but to my way of thinking, that's probably the simplest thing to start out with it. It's the thing where you can see the most major difference. Again, we talk about things like free radicals and you're talking about things which are extremely reactive, you know, capable of attacking protein, capable of attacking DNA and essentially existing on the order of minutes at most and in many cases shorter than that. So what I would say is I would probably concentrate on looking at that issue first. In many ways --
MS. SHERMAN: Do you think that these perhaps might be the most potentially harmful aspects of sidestream smoke?
DR. GREENBERG: That I can't comment on but I do think that they are a source of concern and I think that they are the most, to me at least, the most obvious difference between -- you know, new sidestream smoke and smoke that's been aged.
MS. SHERMAN: Is there any literature you're aware of that discusses this issue?
DR. GREENBERG: Yes. I would say that to my way of thinking the best literature on the issue is the work that Pryor has done, William Pryor, and this was work that has been done now for at least 14 years or so.
MS. SHERMAN: And it involved tobacco smoke? I thought you said the work was done in 1990.
DR. GREENBERG: It's work that has continued. I'm sorry for confusing the issue. Pryor's work on free radicals an