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COMMITTEE ON THE MEDICAL EFFECTS OF AIR POLLUTANTS
Minutes of the meeting held on Friday 2 November 2001 in Room 149 Richmond House, 79 Whitehall, London SW1A 2NS.
Present:
ITEM 1. OPENING REMARKS, APOLOGIES FOR ABSENCE AND ANNOUNCEMENTS
1. The Secretariat had some comments regarding appointments to the Committee. It was announced that the Department had recently finished conducting a series of interviews. The posts of Chairman and specialist posts had attracted interest from only a few people; in contrast the post of lay member had attracted 150+ applications. The Chief Medical Officer had given the Secretariat approval to announce that Professor Jon Ayres had been appointed as the new Chairman of the Committee. Professor Ayres noted that Professor Stephen Holgate, (the retiring Chairman) should be congratulated for his tireless and excellent work for the Committee. It was noted that this last remark would be noted in the minutes of the meeting held on June 21 2001. The Committee would be informed of the other appointments in due course.
2. Apologies for absence had been received from Dr Anna Gavin, Dr Paul Harrison and Mr Fintan Hurley.
3. It was noted that Dr Stephanie Coster had recently taken up a new post at DEFRA; she had made a huge contribution over the years and the Committee wished her well in her new job. Dr Janet Dixon would now be attending as an assessor on behalf of the Committee.
4. The Chairman also welcomed Ms Isabella Lindup from Imperial College who would be assisting the Secretariat.
ITEM 2. MINUTES OF THE MEETING HELD ON 21 JUNE 2001
5. The minutes were agreed as an accurate record of the meeting.
ITEM 3. MATTERS ARISING
Research Funding
6. The Secretariat commented that the call for proposals had been circulated with a deadline of 16 November. Proposals were expected to be of 4 pages or shorter if possible. The Secretariat hoped that there would be a good response to the call and that an initial sift would be made on November 26.
7. In response to a question from the Chairman it was noted that funding for the research proposals was unlikely to be available before March 2002. It was also noted that the Ł1 million pounds would be distributed in response to this call for proposals for a variety of projects lasting for an average of 3 years. An initiative to undertake literature reviews had been included in the call for proposals.
8. DEFRA representatives commented that there was a need to fund all aspects of research; therefore, research money needed to be allocated to measurement, modelling and atmospheric chemistry as well as the health effects of exposure to air pollution. DEFRA was also a new and evolving ministry and thus systems for allocation of research funds were being reviewed.
9. It was noted that an article had been published recently dealing with the cost of abatement of levels of PM10. This had indicated that Ł1 billion would potentially need to be spent in order to achieve a 1 µg/m3 reduction. Some Members thought that a Ł1 million research programme into health effects was modest in comparison, and although they welcomed that fact that the research programme had been re-established, wondered whether there were any plans for a larger programme of research at a later date. The Secretariat replied that the allocation of resources in DH was based on priorities set out by the Secretary of State for Health. The Secretariat agreed to look into this.
[ACTION: Secretariat]
ITEM 4. REVISION OF LEAFLET "AIR POLLUTION – WHAT IT MEANS FOR YOUR HEALTH" AND INTERNET DOCUMENT "THE HEALTH EFFECTS OF AIR POLLUTANTS". COMEAP/2001/12
10. The Secretariat commented that this subject had been considered several times in the past. However, DEFRA was now updating its air pollution leaflet with the aim of explaining the improvements made to its Air Pollution Information Service. It was explained that the Air Pollution Information Service had been designed to inform concerned or interested members of the public about the levels of pollutants on a particular day, make members of the public aware of the Service and provide guidance on how to use the Banding System. The other main purpose of the leaflet was to highlight effects on health. Members’ attention was drawn to COMEAP/2001/12 which outlined various questions, in particular whether text on heart disease and the effects of long-term exposure to air pollution, and on "where should I live" should be revised. Advice from Members was welcomed.
Heart Disease and Exposure to Air Pollution
11. Members noted that a new COMEAP subgroup to review the effects of air pollution on cardiovascular disease had recently been convened. Members were in agreement that it would probably be wise to wait until this review had been completed before making any change to the previous Committee view. It was suggested that it might be helpful to separate the text on the effects of exposure to air pollutants on people with lung disease from the text on effects on people with heart disease.
12. There was some discussion of the website document and the effects of long-term exposure to air pollution with regard to its effects on life expectancy. Some Members felt that the emphasis of this section should be altered in order to avoid implying that all air pollution could be removed. It was suggested that there should be a reference to the COMEAP report on long-term effects where assumptions were mentioned. It was also considered important to emphasise that the effect was small relative to the effects of smoking. Some Members wondered whether there should be any reference to radon. The Secretariat explained that radon was considered by other expert groups and that there was a separate leaflet on this issue. It was agreed that this section would be redrafted by the Secretariat and agreed with Members by correspondence.
[ACTION: Secretariat]
Long-Term Effects of Air Pollution on Health
13. With regard to the paragraphs in the leaflet describing the effects of long-term exposure to air pollutants on health, it was felt that the final sentence of the last paragraph on page 2 which stated that "the long-term effects may be more significant than the short-term effects" could be better phrased. Some Members were of the opinion that this section was not easy for the lay person to grasp and did not explain clearly what was meant by "is more significant". It was noted that whilst the effects of chronic exposure to air pollution might be to promote development of chronic disease, it was not clear that two different processes could be occurring: ie, exacerbation or promotion of disease. It was also noted that it might be sufficient to cross reference between the DEFRA leaflet and the Internet statement so as not to overburden the leaflet with details regarding long-term effects of exposure to air pollution. It was pointed out that the Committee needed to avoid publishing information only on the website since this was not accessible to all.
14. Some Members commented that air pollution levels were declining and felt that this should be emphasised to alleviate anxiety. After further comment, it was agreed that the Secretariat should redraft this section and that it would be agreed with the Committee by correspondence.
[ACTION: Secretariat, Members]
15. There was some discussion of the website document and the effects of long-term exposure to air pollution with regard to its effects on life expectancy. Some Members felt that the emphasis of this section should be altered in order to point out the benefits of lowering levels of air pollution rather than the impact of current levels. The Secretariat pointed out that the long-term effects statement was phrased in the former way; some Members felt that it might be more appropriate to link the two rather than to expand and repeat information that was already available on the website. It was agreed that this section would be redrafted by the Secretariat and agreed with Members by correspondence.
[ACTION: Members, Secretariat]
Where Should I Live?
16. It was noted that there was no information on the extent to which it was possible to change one’s exposure to air pollutants by moving to a different area of the country. It was also noted that a family might move from an urban area to a rural area, for example, only to exchange exposure to one set of pollutants to another, different, set of pollutants. For example, in rural areas levels of ozone might be much higher than those experienced in urban areas. Members were of the opinion that the title of this section should be changed from "Where should I live?" (which might imply that people should move) to "Does it make a difference where I live?" but also wondered whether this section should be included when it was difficult to give specific advice. However, the Secretariat pointed out that this was a very common question from Members of the public concerned about the effects of air pollution on the health of themselves and their families.
17. It was noted that the evidence on whether asthma symptoms were worse in proximity to roads was mixed, and that there was a body of evidence suggesting asthma could be worse in children whose families moved often. The role of air pollution was thought to be minor as a triggering factor for asthma exacerbation compared with other factors. It was agreed that this section would be redrafted by the Secretariat and agreed with Members by correspondence.
[ACTION: Secretariat, Members]
ITEM 5. IS THERE A THRESHOLD FOR THE HEALTH EFFECTS OF OZONE? DISCUSSION OF POSSIBLE APPROACHES TO THIS QUESTION. COMEAP/2001/13
18. The Secretariat introduced this item by noting that ozone had not been considered in detail by COMEAP for some time. It had also not been reviewed as a part of the air quality strategy because agreement of an EC Directive on ozone had been awaited; that directive had been very close to being finalised. However, the Secretariat went on to say that ozone was a priority at the present time because:
mean levels were not dropping and might even be rising in urban areas (due to reductions in nitrogen oxides);
there was a major uncertainty in the size of its effects according to whether or not there was a threshold of effect at 50 ppb;
if there was no threshold, then it might be perceived that ozone posed a greater problem to public health than exposure to particulate matter.
19. The Secretariat drew attention to COMEAP/2001/13, and sought Members’ views on what areas should be covered to determine whether or not there was a threshold for the effects of exposure to ozone on health. Some questions for the Committee were highlighted in paragraphs 8 to 11 of the paper. In particular Members’ views were sought on: whether it was feasible to detect a threshold for the effects of ozone in the time-series studies; what comparisons, (eg, between summer and winter or between high ozone and low ozone areas) might be useful; and what other studies, eg, chamber studies and mechanistic studies might need to be considered with regard to this issue.
20. A short introduction on the atmospheric chemistry of ozone and the trends of concentrations encountered in the UK was given. The overheads used to illustrate this introduction are appended at Annex 1.
Range of endpoints to be considered
21. The Committee was informed that research at St George’s Hospital Medical School was currently being undertaken to look at the effects of ozone on mortality and admission to hospital for respiratory disease in the over 65 age group. The effects of exposure to ozone in children with regard to hospital admissions for asthma were unclear.
22. The Secretariat asked whether it would be appropriate to look at any other specific endpoints. It was felt that if asthma was being considered then it would be appropriate to look only at hospital admissions data. Members did not think it appropriate to look at all hospital admissions as one broad category. It was suggested that it might be possible to separate chronic obstructive pulmonary disease admissions and pneumonia admissions from the overall hospital admissions data. It was acknowledged that American studies did include such distinctions. European studies, in contrast, tended to classify asthma and chronic obstructive pulmonary disease together in the elderly, mainly because of diagnostic problems which made it difficult to tell that people in the over 65 age group had asthma or "fixed obstruction" airway disease.
23. There was some discussion of whether it was possible to examine the effects of ozone on cardiovascular admissions and it was noted that this would be possible. It was also agreed that it would be helpful to have more information on cause-specific mortality.
[ACTION: Professor Anderson]
Evidence for there being a threshold of effect
24. It was noted that two different issues needed to be considered here. Firstly, it was necessary to give consideration to the metric being measured. Most studies used 8 hour averages as the metric of ozone concentration. There were not thought to be any studies which compared the coefficient for the maximum hourly average ozone concentration with that for the 8 hour average concentration within the same study. Secondly, the issue of whether there was a non-linear dose response was important. In reply to the first comment, it was pointed out that there was little difference between the results of studies that used 1 or 8 hour peaks as these were closely correlated. It was noted that ozone peaks tended to be fairly broad in the afternoon. An important point was that non-episode days were driven by different atmospheric processes from episode days.
25. The Secretariat commented that the QUARK Report should ascertain what metric was used previously. Using 1 hour or 8 hour averages would change the scale of the coefficient but would be unlikely to affect whether an association was found. APHEA had chosen to use the maximum 8 hour average concentration, since this seemed to be more biologically plausible. The AIRS database, an American database, had used 24-hour averages. However, it was pointed out that these studies were also on the St George’s database, and so the analyses could be run on studies with different averaging times if required.
26. Members went on to discuss the issue of coefficients for a dose-response effect. Members asked whether there were any studies comparing cities where the levels of ozone were always very high, such as Los Angeles, with other cities. Attention was drawn to the "bubble plot" on page 39 of Annex 2 of COMEAP/2001/13 which showed the relationship between peak 8-hour average ozone concentrations and hospital admissions and had been used in the QUARK Report. It was noted that when data above and below 100 m g/m3 were considered separately, there was no association between ozone and hospital admissions below 100 m g/m3. However, there was a small association if levels higher than 100 µg/m3 were used. It was noted that APHEA II was currently looking at these exposure response relationships, with the Greek researchers analysing the mortality data, and the UK analysing the relationship for hospital admissions. The initial results indicated that there was no consistent evidence to state categorically whether there was a threshold of effect for ozone.
27. Some Members expressed concerns about the positive correlation between ozone and nitrogen dioxide and noted that time series studies often attributed effects to nitrogen oxides as well as ozone. In winter, the sum of ozone and NO2 was constant because the scavenging of ozone by NO produced NO2. However, ozone and NO2 were positively correlated in the summer because both ozone and NO2 could be generated by photochemical reactions. Members felt that it was difficult to disentangle these effects in statistical terms, and that this might explain why an apparent threshold might be observed in, for example, London but not in other cities. It was acknowledged that it would be difficult to correct the shape of a dose response relationship for the effects of nitrogen oxides. It was also pointed out that the negative coefficients linking ozone and health effects that were sometimes found in winter might be explained by reverse confounding by particles. .
28. The Secretariat acknowledged that in the past, the Committee had come to the conclusion that the time series studies did not show a threshold effect for ozone at a population level.
29. The comment was made that though a sharp threshold of effect was unlikely to be demonstrated, some degree of non linearity of effect might be observed. This could be investigated in two ways: either by using the "bubble plot" in individual studies or by performing further meta-analyses of studies in cities with higher and lower average ozone levels. Methods developed as a part of the US NMMAPS study might be used.
30. Members were of the opinion that it was helpful to discuss the issue in terms of non-linearity rather than thresholds and agreed that it might be appropriate to look at studies of different concentrations of ozone although they were unsure what this would say about the nature of the non linear effect observed.
31. After some further discussion it was agreed that addressing these issues was feasible but difficult. It was also suggested that it might be appropriate to delay final discussions until the results of APHEA II were available. The time scale for publication of the APHEA II results was thought to be between 6-9 months, but it was thought that there would be little problem in making the initial results available to COMEAP. It was also agreed that it would be useful to investigate further the degree of non-linearity of the effects of ozone.
[ACTION: Secretariat]
ITEM 6. DISCUSSION OF PAPER BY PROFESSOR WILLIAM KEATINGE – "MORTALITY RELATED TO COLD AND AIR POLLUTION IN LONDON AFTER ALLOWANCE FOR EFFECTS OF ASSOCIATED WEATHER PATTERNS. COMEAP/2001/14
32. The Secretariat commented that the thrust of Professor Keatinge’s paper was that if temperature effects were adjusted for in a more comprehensive way than is usual in time-series studies then apparent associations between day-to-day concentrations of some pollutants and health effects would be reduced and would, in some cases, disappear. It was also suggested that low temperature days occurring as long as 20 days before the day of analysis in a time-series study might need to be taken into account. The Secretariat commented further that it was notable that even after such adjustment, associations with some indices of particles, that is PM10, remained significant. Members’ comments on the paper were welcomed.
33. Members agreed that this was an important paper and felt that Professor Keatinge continued to make an important contribution to defining the interactions between low temperatures and air pollutants in terms of their effects on health. Members made a number of specific comments:
34. It was agreed that the Secretariat should thank Professor Keatinge for his work and pass Members’ comments on to him.
[ACTION: Secretariat]
ITEM 7. REPORT ON THE AIR POLLUTION DATABASE DEVELOPED BY PROFESSOR ANDERSON AND COLLEAGUES AT ST GEORGE’S HOSPITAL MEDICAL SCHOOL
35. The Secretariat commented that a systematic review of the time-series and panel studies papers on the effects of air pollution on health had indicated that the amount of information available was too large for any one person to take on the task of trawling through this literature. Therefore St George’s Hospital had been allocated the funds to build up a database which would make this easier. The objectives of the project had been to:
(i) identify systematically all published studies on short term associations between air pollutants and health;
(ii) extract relevant data and provide numerical estimates;
(iii) Develop facilities to interrogate the database.
36. The review process involved 3 steps which began with the searching of Medline, Embase and the Web of Science and testing the search results against the body of literature already known. Secondly on the basis of the abstract, likely studies to be useful were picked out and thirdly, those to be placed on the database were chosen on the basis of a "quality screen" of the full paper.
37. There was some further explanation of how the studies had been classified and on the status of the time-series studies. The database had so far been used to aid with the report on cardiovascular admissions and air pollution, and had been used in writing a report for WHO on the global burden of disease. It was noted that much international interest had been expressed in the database. A three volume report on how the database had been developed and used had been produced and it was agreed that the first two volumes would be circulated to Members for information. (The third volume was simply a list of references.) [ACTION: Secretariat] ITEM 8. SUBGROUP ON AIR POLLUTION AND CARDIOVASCULAR DISEASE
38. The Secretariat reported that an informal meeting had been held and that it was now formally agreed that Professor Jon Ayres would be the Chairman of this group. A further meeting had been scheduled for the end of November, and it was intended that the report would be published in the summer of 2002 as a draft for comment.
Particles and Cardiovascular admissions – methods of measurement of particles. COMEAP/2001/16
39. Members’ attention was drawn to the tabled paper, COMEAP/2001/16. This included a table of the cardiovascular admission studies with a note of the methods used to measure particle levels attached. Several, only, refer to the EPA AIRS Database which is believed to include some TEOM measurements as well as data produced by the high-vol "gravimetric" method. It was commented, that the Secretariat, after discussion with some COMEAP members, had suggested that the summary estimate be left as it was, but that a description of what it was based on should be included. Therefore, a footnote had been added to the statement as in paragraph 3 of the covering note of COMEAP/2001/16. Members were in agreement that this should be included im the statement on cardiovascular effects, and the Secretariat undertook to amend the statement accordingly.
[ACTION: Secretariat]
ITEM 9. DEVELOPMENT OF GUIDANCE ON INDOOR AIR. COMEAP/2001/15
40. The Committee was reminded that this issue had been discussed at the previous meeting when Members had supported an initiative to review the provision of advice on the effects of indoor air pollutants on health. It was noted that meetings with relevant colleagues from HSE, DTLR, DEFRA, DfES, IEH and BRE and with representatives of Trade Associations with an interest in the area had been held. The meetings had been encouraging and it had been generally accepted that indoor exposure to air pollutants could damage health, and that regularly updated advice on how to avoid such danger should be provided by DH. However, as anticipated, the idea of standards for indoor air pollutants had provoked a good deal of comment. Guidelines had been seen as more acceptable than numerical standards by some, though others felt these too might present problems. It was hoped that further progress would be reported at the February 2002 meeting.
[ACTION: Secretariat]
41. The Secretariat also reported that it had been informed that flueless gas fires with catalytic converters were being introduced to the market. This had been discussed with HSE and DTI, and Melanie Griffiths, the minister at DTI had asked that the Committee look at this in the near future.
ITEM 10. DISCUSSION OF RECENT LITERATURE
42. The Secretariat drew attention to four papers which had been sent out to the Committee as items of particular interest:
HEI Perspectives: Airborne Particles and Health: HEI Epidemiological Evidence
43. It was noted that this was a very useful review of the epidemiological evidence with respect to the effects of airborne particles on health, particularly in regard to the discussion and summary of the NMMAPS study. The Secretariat commented that a striking outcome was that the association of air pollution with mortality appeared to be greatest among those with less than a high school education.
Dye et al: Acute Pulmonary Toxicity of Particulate Matter Filter Extracts in Rats: Coherence with Epidemiological Studies in Utah Valley Residents
44. The Secretariat noted that this was the final report on the change in toxicity of particles from the Utah Valley caused by the temporary closure of the steel works in 1987. The present study showed that the toxicity of the particles fell during the closure as did the particle levels in the valley and the number of hospital admission for treatment of respiratory disorders in children at the time the works were not in use. It was noted that this gave considerable support to the idea that the metal content of the particles played an important part in their toxicity. The Secretariat had written to Dr Arden Pope asking whether this was reflected in a change in the slope of the line linking particle concentrations and admissions. He had replied to say that the period of closure of the steel works had been too brief to detect any change in slope. Members agreed that this was a good and important study which indicated that the toxicity of particles was related to the bioavailability of the metals associated with those particles.
Samet et al: Effect of Antioxidant Supplementation on Ozone-induced Lung Injury in Human Subjects
45. The Secretariat commented that this paper looked at the effects of antioxidant supplementation on ozone-induced respiratory injury and found that lung injury induced by ozone was reduced suggested that dietary antioxidants could be used to protect against ozone-induced pulmonary function decrements in humans.
Basham: Application of COMEAP Dose-Response Coefficients Within a Regulatory Health Impact Assessment Methodology
46. This paper was drawn to Members’ attention as it reported the application of the published COMEAP dose-response coefficients within a regulatory framework.
Members commented that they appreciated being kept up to date with developments in the air pollution literature in this manner. The Secretariat said that it would appreciate comments from Members on such papers, and after some further discussion it was agreed that in future the Secretariat should refer particular points to individual Members of the Committed in the covering letter that went out with the paper..
ITEM 11. FUTURE WORK
47. The Secretariat noted that work on the effects of air pollutants on cardiovascular disease and on ozone would be undertaken during 2002.
48. The Secretariat also commented that at the next meeting the Committee would be required to address the issue of dust on the London Underground. This had been considered by the Committee some years ago, and the Committee’s statement on the situation at that time could be found on the website. However, a new report had recently been produced, and it was likely that this would attract some attention in the media. There was some discussion as to how Members should respond if individually approached by the media on this matter. It was agreed that Members should refer any enquirers either to the Secretariat or the DH Press Office in the first instance. They could also refer people to the COMEAP statement on the website.
ITEM 12. DATE OF FUTURE MEETINGS
49. The
following dates were agreed:
ACTION SHEET
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