L'aréoport International Pearson de Toronto

Résumé

En 1989, Transport Canada a proposé la construction de trois nouvelles pistes à l'aéroport international Lester B. Pearson de Toronto, pour alléger la congestion de l'achalandage aérien dans le sud de l'Ontario. L'étude des polluants sonore, atmosphérique et de l'eau, étaient parmi les principales préoccupations environnementales découlant de la construction et de l'exploitation des pistes additionnelles.

Santé Canada a déposé devant le Comité les "Lignes directrices nationales de contrôle de l'environnement sonore" du Ministère, ainsi que des conseils scientifiques sur les répercussions sur la santé humaine que peuvent avoir les bruits liés à l'aviation aux abords de l'aéroport international Pearson. Compte tenu des expositions prévues par Transport Canada sur le bruit causé par les avions, les conclusions de Santé Canada sont les suivantes:

• Les trois pistes actuelles (ou les six pistes, dans l'éventualité de l'aval du projet) ne devraient pas causer de perte auditive importante.
  
  
• Il n'existe aucune preuve convaincante que trois ou même six pistes pourraient causer une augmentation des maladies coronariennes, de désordres mentaux ou de déformation foetale.
  
  
• Chez un nombre appréciable de résidents du secteur, le bruit suffit à empêcher la conversation normale et influe sur leur sommeil. Cette situation, déjà vécue à l'heure présente, pourrait se poursuivre encore cinq ans, à cause du fort embarras dans lequel le bruit des avions jette environ 40 000 résidents du secteur de l'AILBP; il n'y a toutefois aucune différence importante à cet égard entre une situation à trois pistes et une autre à six pistes. Sur une période de 20 ans, le nombre de résidents grandement affectés par le bruit diminuera, quelque peu plus rapidement et facilement avec six pistes qu'avec trois.

** Veuillez noter que lorsqu'une présentation a été effectuée au Comité, la transcription réflète la langue dans laquelle a été présentée. **

Transcripts Regarding Health Canada's Presentation at Panel ConcerningThe Lester B. Pearson International Airport

Presentation by Dr. Stephen Bly, Health Canada

Presentation by Dr. Stephen Bly
Questions to the Presenter

CHAIRPERSON: I have one further presentation scheduled this evening and I understand it will be quite short. It deals with the health aspects of noise. It is being delivered on behalf of Health and Welfare Canada. I want to extend a particular welcome to the gentleman who will present that report, Dr. Stephen Bly, because he is a former colleague of mine. I worked at Health and Welfare too.

Dr. Bly? I'm sorry we've kept you so late.

DR. STEPHEN BLY: As you know, I am here from the Bureau of Radiation and Medical Devices and the Health Protection Branch of Health and Welfare.

I am going to provide, I hope, a brief summary of the effects of aircraft noise on residents health in the neighbourhood of LBPIA.

The summary is that noise-induced permanent threshold shifts, NIPTS, would probably be negligible, as an increase in cardiovascular disease, birth defects or mental illness would have to be considered undetectable and so we could not reliably ascribe an impact now or in the future due to the aircraft noise in the neighborhood of LBPIA.

High annoyance, which is widely used as an intuitive way of measuring the well-being of residents, is significant, with approximately 40,000 people being affected now, and approximately 20,000 people being affected much later. All this is based on dose response relationships which are relatively well accepted, where they are known, and on what I believe is the consensus concerning non-auditory effects. That is combined with the population and exposure data provided by Transport Canada and the EIS.

The final conclusion, based on Transport Canada's exposure population data is that the three and six runway scenarios don't seem to make any difference, or very little.

I will just go through how I came to my conclusions about noise-induced permannent threshold shifts. The exposure relationship comes from an international standard, which actually pertains to determining hearing impairment from occupational noise, but the consensus at an NIH consensus conference several years ago was that, as Dr. Von Gierke put it, noise is noise more or less, and so one should be able to use this standard to assess possible hearing loss from the environmental noise from aircraft.

As we can see, at eight hour exposure, 75 dBA, produces no hearing loss, even at the most sensitive frequency. Going up to 80 we get about 2 dB of hearing loss at 4 kHz, nothing at the other frequencies. And then things start to really rise rapidly and become significant above 80, when you get to 85 you've got 10. This data is for 40 years of exposure and 95 per cent of the population would have less noise-induced permanent threshold shift than these values given in the table.

If we look at the exposure information given in the EIS, at the monitoring sites, this is in the NEF 35 to 40 contour, Ldn is 71, adding 5 dB to the Leq 24, which is all given in, I think, report 13, we get an effective Leq (8) of 74 dB. In site G which is 40 plus NEF' we wind up with Leq (8) of 74.

Well, based on this it would appear as through it is entirely negligible, even if we allowed for the fact that some of the 40 plus contour region was not as low as site G. Then we could start to say, all rights, there could be as many as 1,200 people who could still have some hearing loss, from the table on the previous page.

It is not likely from this data, and from the fact that the contours are generally in 5 dB intervals, that there is anything greater than 80 Leq(8). Certainly the hearing loss less than 2 dB at 4 kHz, this is not even including mitigating factors such as the fact that the exposure is much, much -- I'm appealing to your intuition now that exposrue of people will be much, much less than 24 hours per day, 40 hours per week for 40 years.

Even cutting people's expsoures down to 12 hours per day essentially diminished the noise-induced permenent threshold shift to zero. This assessment, using that standard, is consistent with the rather limited human studies which were also mentioned in the Environmental Impact Statement.

Non-auditory health effects, there are so many studies and it is so complex that I felt the best way to summarize it was to give some quotes of the conclusions from a number of relatively recent critical reviews.

Berglund et al -- these reviews are specifically on the effects of aircraft noise. Berglund et al said: "Overall evidence ..suggestive of moderate effects of aircraft noise on blood pressure. The clinical significance is not clear."

Thompson et al said: "...there has been no clear demonstration of adverse extra auditory effects of residential aircraft exposure...effects..., if they exist at all, are subtle, long term and indirect."

On a review of transportation noise in general, Taylor and Wilkins -- and this is Dr. Taylor the Panel's expert -- came to the conclusion that: "There was no strong evidence that noise has a direct causal effect on cardiovascular disease, reproductive abnormality or psychiatric disorder. ...the evidence is not strong enough to reject that noise is in some way involved..."

And then van Dijk in a recent review on occupation noise, the non-auditory health effects of occupational noise said: "Definite conclusions are still not possible."

In addition, if we just look at a few examples of specific studies, some of the studies that were criticized are studies showing increase in mental illness, increas in birth defects, and increase in cardiovascular disease or death due to stroke around the L.A. Airport increases in the high noise exposed areas compared to the low noise exposed areas.

The Schipol Airport Study by Nipshol, found an increase of about a factor of 1.5 in population experiencing hypertension when he compared populations living in a zone which had an Ldn greater than abou t 65 dBA compared to those living in zones that were less than 65 dBA.

The problems that have been noted with these types of studies is that either there is a sample bias or a lack of control for confounding factors. Some of the more rigorous studies, a few of the more rigorous studies, such as the Atlanta Airport Sutdy, which was mentioned in the EIS, and mentioned in the review by Taylor and Wilkins, indicated no sognificanct increase in birth defects.

In several studies around Heathrow they showed no statistically significant effect which could be related to mental illness. A re-analysis of Meecham and Shaw's work, which purportedly showed an increase in death due to stroke in the noisy areas around L.A. Airport, re-analysis which took into account age, race and sex, confounding factors, showed that there was no increase in mortality, the effect went away.

Based on this I would come to the conclusion that right now we cannot reliably ascribe any non-auditory health effect due to aircraft noise.

High annoyance. Well, the effects of noise that seem to be well accepted are intereference with speech communication and sleep disturbance or awakenings. Unfortunately, the way to describe this impact seems to be very complex; I haven't seen any standard way of describing it that would related to an Environmental Impact Statement.

What has traditionally been done, what has historically happened is that high annoyance, which is measured in community surveys, is used as an indicator of the well-being of the population, and has been found to be something which correlates with noise.

Recently, this has synthesis, as Dr. Von Gierke pointed out, has led to the Schultz curve. The new Schultz curve changed very little from the old Schultz curve; the 1989 or 1991 update showed very little change in the Schultz curve. But there is a lot of variability, if you look from study to study, in how the percentage of the community highly annoyed varies with the Ldn.

Fidell & Green came up with a theory that the reason why this variation occurs is essentially because different communities, on average, have different response criteria for saying they are highly annoyed. The reason for that comes -- there are many reasons for it; it has to do with non-acoustical factors; it has to do with the fact that different people experience the dose in different ways because of different amounts of attenuation. This has been gone through earlier tonight.

So what they found was the Schultz curve seems to lie fairly well for the areas of interest along one of their distributions that they could model, assuming there is a particular response criterion, average response criterion. So if we wanted to calculate the population highly annoyed, that's waht it means, that we can calculate it using the Schultz curve, assuming that this population has an average response criterion for saying they are highly annoyed.

Take this from the shifted Schultz curve, where, as Green and Fidell and co-workers found, there was a different mean response criterion for aircraft noise than there is for traffic noise. This data comes from the plots in the EIS, Ldn is a function of per cent highly annoyed. It is also in a table in a slightly different form. Then we have the population estimates as a function of Ldn.

There is something here I want to stress, and that is that in the relatively low Ldns, at least at the lower end of the scale here, there is very large population. The people who are experiencing more activity interference, therefore presumably leading to a greater percentage of highly annoyed people, has a relatively low population. As you can see the change here in the per cent highly annoyed of only a factor of 3, going from the lowest to the highest contours, is more than made up for, if we are going to look at total population, by this factor of 100 increase in population going from the highest to the lowest contours.

If we combine all the populations we wind up with three runways in the circles. The population of highly annoyed would be estimated, assuming there is an average response criterion for the population to say they are highly annoyed, would be approximately 40,000. It goes up slightly over the next five years and then drops dramatically, according to the proponents exposure predictions, and rises slightly again. In the six runway scenario, remarkably it keeps dropping to about 17,000.

So, in summary, essentially no effect in terms of hearing loss, nothing that we can reliably assess for non-auditory health effects, tens of thousands of people being highly annoyed, but because the exposure is supposed to diminish after the next five years, that number of people will drop by approximately a factor of 2.

That concludes my presentation.

THE CHAIRMAN: Thank you, Dr. Bly.

Dr. Welbourn?

Questions to the presenter

DR. PAMELA WELBOURN: Yes, Dr. Bly, thank you for a nice brief and a clear presentation.

Would it be correct to say that you essentially agree with the conclusions that Dr. Von Gierke made concerning non-auditory health effects earlier this evening, in terms of present or future effects of noise from the LBPIA?

DR. STEPHEN BLY: For the topics I have covered I think I would agree, yes.

DR. PAMELA WELBOURN: Which is the non-auditory complaints that have been evaluated, such as mental health, blood pressure, birth weight and things like that.

DR. STEPHEN BLY: I guess, just to get the language right, I would have to say that based on the conclusions of all the reviews and the mixed results from the studies would mean that we cannot reliably ascribe an impact on non-auditory health effects at this time.

That is the conclusion, if that is basically what you think Dr. Von Gierke said, then yes, I agree.

DR. PAMELA WELBOURN: Dr. Von Gierke expressed it one way; our consultant expressed it a different way.

DR. STEPHEN BLY: Right. So we are all using slightly different language, but I haven't heard anybody say that they could ascribe an impact on non-auditory health effects due to the noise around the airport, now nor in the future.

DR. PAMELA WELBOURN: To move on now, annoyance or even extreme annoyance is not considered to be a health effect; is that correct?

DR. STEPHEN BLY: Well, as Dr. Von Gierke pointed out, there is this expanded definition of health which pertains to the well being of the population and it seems as though historically, in an intuitive way, annoyance has become an accepted indicator of the well-being of the community.

So it's not a physical, clinical ---

DR. PAMELA WELBOURN: No, I understand.

So then what do you think is the significance or the meaning of having 20,000 to 40,000 people being highly annoyed?

DR. STEPHEN BLY: What do I think is the meaning of that?

DR. PAMELA WELBOURN: Or the significance.

DR. STEPHEN BLY: The significance.

It should meant that there are an awful lot of people whose well-being is probably being affected by noise, assuming that they have -- yes.

But we have to remember that annoyance is just something that is measured in responses to community surveys. People do interviews and they ask questions, and people say, as Dr. Von Gierke described, if they mention noise as something that bothers them then they wind up having to rate the noise on an annoyance scale. Historically, it has become accepted as a way to describe the impact, and has an intuitive meaning on well-being.

There is an article that Langdon wrote on this, I think it is called "Handbook of Transportation Noise". It goes through a long discussion, which was pretty difficult to understand and in the end he used these words, that in the end we are left with it simply being an intuitive -- something that we intuitively sense is the effect on the well-being of the community, on those people.

DR. PAMELA WELBOURN: So there is something wrong but it is a very subjective means of measuring.

DR. STEPHEN BLY: That's right.

DR. PAMELA WELBOURN: Do you think we are ever going to get any better?

DR. STEPHEN BLY: I don't know.

DR. PAMELA WELBOURN: Well, your expertise is on the technical side of measuring and interpreting noise and its effects, isn't it?

DR. STEPHEN BLY: So you are saying, am I going to be able to predict whether we are going to be able to get any better? Well, there are a lot of people -- now, let me think about it.

There are a lot of people doing sleep research and a lot of people doing research into the effects of noise and sleep; and some people trying to tie it together in terms of long-term effects. But there has been nothing that I have seen that really ties it all together.

In physical effects there have been some studies on, again, subjective judgments of sleep quality and on performance. Again, difficult to relate to what we normally think of as objective indicators of well-being.

I suppose the one thing that -- well, no, I can't say any more.

DR. PAMELA WELBOURN: I think what I am looking for is: Are there prospects of any improvement in the methodology, because Dr. Von Gierke said we need more research?

DR. STEPHEN BLY: You mean not looking at annoyance per se, but seeing how annoyance ties into the physiological effects, such as the cardiovascular disease.

DR. PAMELA WELBOURN: Yes.

DR. STEPHEN BLY: Well, there are people who are doing research on it and ---

DR. PAMELA WELBOURN: Yes, we heard that from psychologists, but we still couldn't get anything that we could actually get our minds around and see a prospect that it would improve.

DR. STEPHEN BLY: Well, I wouldn't like to predict the future of scientific discovery; it's not what I'm supposed to do. Sorry.

DR. PAMELA WELBOURN: Okay.

DR. MARTIN TAYLOR: What we are overlooking is the enormous amount of research that has been done on individual level responses. All of what we have been talking about tonight has been in terms of average response, per cent highly annoyed in relation to an averaged or integrated noise level.

There is a tremendous amount of work being done at the individual level to try and look at the factors that contribute individual level annoyance responses, trying to tie annoyance to activity interference, trying to tie annoyance to sleep disturbance, not only singly but in multi-variant combinations.

If you want to answer those kinds of questions, Pamela, I think you have really got to look there to begin with, to try and decompose the determinants of annoyance. You are not going to do it through these dose response studies because they deliberately remove all of those intervening factors.

DR. PAMELA WELBOURN: Yes, I understand. Thank you.

DR. STEPHEN BLY: I don't know whether the speech communication interference and the sleep effects, effects on quality of sleep or number of awakenings per night would have satisfied -- is that what would have satisfied what you were asking for? It seemed as though you were trying to relate it to -- I don't know, what were you --

DR. PAMELA WELBOURN: No, I was asking your opinion on the future prospects of tightening it up or making it less subjective.

DR. STEPHEN BLY: Well, if it could be related better to the speech communication or the sleep that would help. It sitll wouldn't be in terms of the usual clinical -- interference with speech communication doesn't have any clinical symptoms associated with that.

How do we intuitively relate that to some aspect of the well-being of the population? I've had a hard time doing that and I don't know if that is what you were grasping for.

DR. PAMELA WELBOURN: Well, that's helpful. Thank you.

THE CHAIRMAN: I have a question I would like to try, but I will need to do a little background first.

I think Dr. Von Gierke and Dr. Taylor and you have all agreed that at the noise exposure levels associated with Pearson Airport that there is no evidence of danger of auditory damage.

I think you have also all agreed that there is no evidence that the somewhat lower levels that are associated with Pearson Airport, that is to say lower than the level of which auditory damage might be anticipated, there is no clear evidence one way or the other on the question of whether there might be long-term health effects associated. It depends a bit on which point of view you are defending how you phrase this. I think you and Dr. Von Gierke have both said that there is no evidence of any such health effects. Dr. Taylor said there is no evidence to prove that there isn't such a health effect over the longer term. I believe that's essentially the same assessment of the facts, just a different presentation.

However, Dr. Taylor concluded his particular intervention earlier with the question: In the absence of proof that such levels do not have long-term health effects is it prudent to expose a substantial population to such levels of noise exposure?

Now, you are an officer of the Health Protection Branch of Health and Welfare Canada, does this prospect cause you any concern?

DR. STEPHEN BLY: I don't think I have a good answer to it because we do have guidelines that ---

THE CHAIRMAN: I will suggest an answer that I think you can probably agree with, that is to say, if all other things can be arranged in such a way that noise levels are significantly lower than the ones we have been talking about, that would be great, but it isn't a perfect world. Is this---

DR. STEPHEN BLY: Well, I mean, yes, that's right. I recommended ---

THE CHAIRMAN: There are risks in all situations, it's a matter of the magnitude of the risks and the ones that may or may not be substantial.

DR. STEPHEN BLY: Yes, that's right.

But you know we do have guidelines about the land use planning for the different NEF levels. There are international environmental noise guidelines which we did propose to the Panel a long time ago.

THE CHAIRMAN: That is true. Do you find those guidelines to be satisfactory, shall we say, from the point of view of the Health Protection Branch?

DR. STEPHEN BLY: Well, they haven't been superseded since they were published. So it is departmental policy.

THE CHAIRMAN: I have no further questions.

Are there any questions from the floor?

MR. LEO TURNER: My name is Leo Turner; I am a resident of Rockwood.

Correct me if I'm wrong, but I thought I saw that with six runways there are fewer highly annoyed people? Is that correct from your last slide?

DR. STEPHEN BLY: Perhaps because I missed the first hour today, or perhaps because I was too busy thinking about this, I don't think I could tell you why the six runway actually yields lower population exposure.

I mean even if we go back to the ---

MR. LEO TURNER: It would just seem to me that more people would be effected with ---

DR. STEPHEN BLY: If we boack to the --- let me see what I have here -- 2011 three and six, this is just the population exposure from the EIS.

MR. LEO TURNER: With more runways.

DR. STEPHEN BLY: Yes, we had better ask Transport Canada why that is. I mean supposedly that was dealt with today, but maybe neither of us quite sorted it out. Did I copy the data wrong from the table?

DR. LLOYD MCCOOMB: To confirm exactly what it is, but certainly my understanding is that -- I want to get this right -- that with the -- I regret that Peter's not here -- but with the six runways we look at the pros and cons; I believe he did say that the number of highly annoyed was higher than -- did grow over the three runway case. There wa a substantial number of people who moved out of the highly annoyed area as a result of the project, but the balance was still that there were more people moving into the highly annoyed category because of the six runway.

Just a second, Mr. Miller has an interpretation.

MR. ROBERT MILLER: I just wanted to say, instead of -- let's not even go to the highly annoyed concept, let's just go back to that population exposure table, because everything follows from that. I mean that is the key.

DR. STEPHEN BLY: Again, I am doing this partially from memory and partially from understanding where the contours are shifting, but in general what is happening, I believe, is that the noise is shifting with the six runway case into areas which are not as highly populated as they are now, or are expected to be. And so in fact there is a slight reduction overall in per cent highly annoyed.

MR. LEO TURNER: Or could it also be that as you move down the Ldn numbers it might just be that there are fewer numbers of highly annoyed people but greater numbers of slightly less annoyed people?

DR. STEPHEN BLY: No, no. I mean I have applied those percentages -- just forget about the top of my transparency and just look at the bottom. The numbers from the highly annoyed curve are applied to both columns. So it's the same numbers; it's the population that determines everything.

MR. LEO TURNER: But if you're flying over a broader area, whether the density is the same or not you are still going to be affecting that many more people, would you not?

DR. STEPHEN BLY: Yes.

MR. LEO TURNER: So it just seems odd that the numbers wo uld go down.

DR. STEPHEN BLY: Sorry, I -- perhaps -- I mean I don't know whether you are taking issue with the calculation or -- if you just multiply that 20 per cent by the 100,000 or multiply it by the 70,000, you see what the determining factor is, is the amount of people you end up with highly annoyed.

MR. LEO TURNER: I guess the point that I wanted to make was that the previous graph indicated that fewer people were highly annoyed by six runways. It just didn't seem to be possible.

DR. STEPHEN BLY: I know, it seems extraordinary. The reason is that if you take a constant factor, which is this 20 per cent highly annoyed, and multiply it by 100,000 and multiply it by 70,000 people under the six runway in 2011, this 6 here in brackets means it's the six runway scenario. The three runway scenario says 100,000 people. Those are Transport Canada's predictions and they explained to us just now why they believe what the source of those predictions is.

The 60 to 65 contour is the determining contour, I mean the most of the highly annoyed come from that 60 to 65 contour. So this number is bigger than this number, so that's how it works.

MR. LEO TURNER: So you have the same three and the six, so you would take the 100,000 from the three and add it to the other people that are affected by the six. So the number has to to--

DR. STEPHEN BLY: No, no, we keep adding the threes -- the threes all add up together and the sixes all add up together, each one being multiplied by their own number.

MR. LEO TURNER: Thank you for your attention.

THE CHAIRMAN: I saw one other question there?

MR. ALBERT HUARD: Mr. Chairman, my name is Albert Huard.

The question I have is, Dr. Bly, you kept repeating that assuming an average response time of the population, average response criteria for the -- this population, assuming that the population around LBPIA has the average response criterion that is found as an average of the response criteria that came out of a number of community surveys already done at different airports and at LBPIA.

MR. ALBERT HUARD: There is a study which points out that that assumption is not valid and led to the Hall curve; it was a study specific to the people around Lester. B. Pearson Airport; it was done by qualified people on a scientific basis. It pointed out that there were significantly higher response times and I believe Dr. Von Gierke was convinced enough to shift his graph closer to the Hall curve.

But my point is 1) does the Hall curve not tend to indicate that for our community we are more effected. Secondly, since the noise affects the very old and the very young, with the Canadian population aging, would this not tend to indicate that this will increase in the future?

DR. STEPHEN BLY: The first part of the question -- I guess it is difficult to say what the response criterion is right now or will be in the future, so that's why I took the average. The shift that Dr. Von Gierke cited, and which I used, was actually based more on the results of Fidell and Green than on the Hall curve, although as it turns out, it's a nice compromise.

If you want to assume that the response criterion around LBPIA is the same as it was 12 years ago -- you see, I'm thinking insulation may be different in the homes and so the actual noise exposure may not be as high as it was back then. So there is no guarantee that that response criterion is the same actually.

But let's say it is. You could just multiply everything here as -- it's really amazing that you can, but you can, I checked it, by about a factor of 1.8. So if you want to assume that, if you want to base your impact on that you could do that, but as I said, it is hard to know that the response criterion is going to be the same.

There have been mixed studies in other areas looking at how the per cent highly annoyed change iwht time and some places find that it is pretty stable and other places find that it varies. There are these factors of whether the homes are better insulated as time goes on, whether the airport is -- you know, non-acoustical factors is the airport angering the residents or is it making them feel like they are doing something about it and so they aren't as sensitive to saying they're highly -- they aren't as likely to say they are highly annoyed.

So that is why the safest thing to take is the average because you don't really know how things are going to change. But as I said, if you want to multiply it by 1.8 you can. That is up to the Panel, I guess, to decide.

MR. ALBERT HUARD: Thank you.

THE CHAIRMAN: Are there any other questions?

Mr. Neeb?

MR. MARK NEEB: I will be really quick, Mr. Chairman, I promise.

Is there any way in the world that you believe -- and this is just an opinion on your part, forget Ldns, the whole nine yards -- do you believe that for the north-south runway, the new north-south runway, given that it is being proposed to operate 420 hours a year, is there any way that we will ever be able to measure -- not long therm, but simply when the actual runway is operating those 420 hours a year -- is there any way we will be able to determine how annoyed or highly annoyed residents are going to be when the actual runway is in operation? I means is there any way of measuring that? Have you got some kind of guess?

DR. STEPHEN BLY: Well, I mean one could design -- somebody would have to fund another community survey study, as was done 12 years ago. If you are lucky maybe it could even be stratified so that you could actually pick out areas and get good enough statistics within different areas.

Is that what you are asking?

MR. MARK NEEB: So the best measure then to try to determine that annoyance level is by survey in terms of how annoyed do you think youare going to be if the runways go in, and the best method is if the runways go in is to measure it after the fact by survey.

DR. STEPHEN BLY: Yes, the best method -- the method that I would choose, that I would recommend for predicting, for want of anything better right now, would be the average one which is like the shifted Schultz curve and then for actual measurements -- I mean for actually determining what you've got, sure you measure it later. There is a problem in that -- I mean I'm not a social scientist, I'm not going to pretend to be, but I could foresee a problem after having a highly charged situation like this, attempting to do a community survey in the future.

I mean just intuitively you asked my opinion, off the top of my head that is what I would say.

I mean Dr. Taylor has done these sorts of things. What do you think about the possible bias of a future population?

THE CHAIRMAN: Mr. Neeb, if the City of Mississauga is comtemplating commissioning such a survey they will have the added problem, of course, of how to determine in advance when to take the survey so that the anger will be active at the time that the weather mandates the use of that runway.

MR. MARK NEEB: That's an outstanding point, Mr. Chairman.

THE CHAIRMAN: I think we are all getting tired and I think -- you're not tired, Dr. McCoomb?

DR. LLOYD MCCOOMB: I think it's an important point, just to ensure I don't erode in any way the credibility of the Dr. because I didn't intend to.

You have a graph that Peter did show you on the relationship between the three runway and six runway case and it does definitely confirm that Dr. Bly's calculations are quite correct; his plot is quite correct.

THE CHAIRMAN: Thank you.