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COMMITTEE ON THE MEDICAL EFFECTS OF AIR POLLUTANTS Minutes of the meeting held on Friday 16 June 2000 Present:
ITEM 1. APOLOGIES FOR ABSENCE AND ANNOUNCEMENTS 1. Apologies for absence had been received from Professor Peter Blain, Lord Toby Harris, Professor Anthony Seaton, Professor David Strachan, Dr Sarah Walters, Dr Tim Carter (DETR), Dr David Dixon (SEHD), and Dr Angela Cooper (MRC). 2. The Chairman went on to announce that five members would be retiring from the Committee after the present meeting. These were Professor Anne Tattersfield, Professor Anthony Dayan, Dr Allan Gibbs, Professor David Purser, and Dr Michael Burr. On behalf of the Committee, The Chairman thanked these members for their untiring work on behalf of COMEAP and hoped that it would remain possible to seek their expert advice when necessary. 3. The Chairman proceeded to introduce five new members who were attending a meeting of COMEAP for the first time, these being: Dr Ben Armstrong, Professor Ken Donaldson, Professor William MacNee, Dr John Pritchard and Professor Dafydd Walters. He also noted that Professor David Phillips was attending the meeting on behalf of Professor Peter Blain. Finally, the Chairman noted that Dr Michael Holland and Dr Kate Leverton were attending the meeting for items 5 and 8, respectively.
4. The minutes were reviewed page by page and the following amendments were agreed: (i) The heading for Item 4 was corrected to read: "Methyl-Tertiary….". (ii) It was agreed that in paragraph 10 it should be emphasised that the review of MTBE for the Existing Substances Regulations was currently in draft form. This was done by underlining the word draft. (iii) The second sentence of paragraph 11 was amended to read: "…that since the composition of petrol was not currently regulated with regard to all its components the Department had, on occasions, been approached…..". (iv) The sixth sentence of paragraph 18 was amended to say: (It was noted later in the discussion that proven allergy to oil seed rape pollen was relatively rare - the symptoms might also be due to direct chemical irritation.) (v) A final sentence was added to paragraph 23: "It was also mentioned that the introduction a new plant to Kuwait, the mesquite tree, had been associated with an increase in asthma". (vi) A final sentence was added to paragraph 26: "It was agreed that the paper should not be publicly available - it contained views under development which would be superceded by the final statement". (vii) The third sentence of paragraph 28 became: "Air pollution is generally perceived to be a problem in London: the report's conclusion on this was counter-intuitive", and the following sentence amended to read: "It was also felt that it was very poor science to produce imprecise summaries….". (viii) The third line of paragraph 29 was amended to say: "…when it was clear that the report from ……". (ix) The penultimate sentence of paragraph 43 became: "…the Committee should not suggest that there was….". (x) The penultimate sentence of paragraph 45 was reworded to say: "…was likely to reach a final position in the next few months." Subject to these amendments,
the minutes were agreed as an accurate record of
5. It was noted that there were no matters arising from the minutes that would not be dealt with under later agenda items.
Public availability: The Secretariat commented that this paper would be made publicly available when the draft statement was finalised. 6. Members were reminded that MTBE had been discussed at the previous meeting where a number of points were raised, in particular with respect to metabolism, carcinogenicity, concentrations of MTBE in air in the UK and compounds formed as MTBE took part in the combustion process in vehicle engines. Further information had been provided to Members as requested, and a note from DETR on the concentration of MTBE in UK ambient air circulated. Attention was drawn to COMEAP/2000/8 which provided further information on the carcinogenicity of MTBE at Annex A and a short summary of the aspects with respect to drinking-water at Annex B. A revised draft statement has also been provided at Annex C. The Secretariat also noted that since the last meeting, the EPA had recommended the reduction or elimination of the use of MTBE. This decision had been based on the effects of MTBE leakage on water quality, and had increased interest in the UK regarding MTBE. The Secretariat felt that there was a possibility that the COMEAP statement might be taken as the UK equivalent of the EPA announcement. However, it was noted that COMEAP had not considered the water aspects since this was not within their remit. The draft COMEAP statement therefore clarified the point that it related only to the air quality aspects of the use of MTBE. Members' comments on the additional information were welcomed and the Committee was asked whether it could now agree the revised statement. 7. With regard to the metabolic aspects, the Committee felt that MTBE per se was not a cause for concern. It was a very small molecular weight compound that immediately entered the blood stream. Of more concern was whether any of its metabolites formed via the cytochrome P4502B pathway might be carcinogenic. Of the mettabolites produced, t-butanol was not felt to be of concern as it was removed from the tissues quickly and eliminated efficiently in urine. Formaldehyde, which was formed in equal quantities, was also found to be eliminated very quickly. However, it was noted that there was little information on the metabolism in brain, kidney, lung or olfactory tissues. 8. With regard to genotoxicity, it was commented that published studies that the COM had been made aware of on MTBE had been conducted to a good standard. It was noted that induction of hepatic adenomas in mice were often seen after exposure to many compounds and was not generally regarded as a risk in humans. The finding of renal tumours in male rats involving binding to to a2u-globulin was also not thought to be relevant to the human situation. Members therefore, supported the conclusions of Annex A. 9. There was some comment on human challenge studies involving exposure to MTBE. It was noted that although high doses were used, exposure to the lowest concentrations (1.7 ppm) gave rise to an increase in neutrophils in nasal lavage fluid. (This increased was not sustained and could therefore be a defensive rather than harmful mechanism.) At higher concentrations, up to 50 ppm, a significant reduction in vital capacity was observed. The studies had only involved healthy volunteers, and therefore it was felt to be of concern that there was no information on the effects of exposure to MTBE on possibly susceptible individuals. 10. Members proceeded to discuss the draft statement at Annex C of COMEAP/2000/8. It was felt that the statement needed to explain more clearly why MTBE was used as an additive to petrol. Members felt that paragraph 2a was unclear and that it should be explained clearly that the listed effects had been observed in only one particular community in the US. It was also suggested that the second sentence of paragraph should be reworded to read: "Whilst there is evidence that large doses can produce cancer in animals, there is no indication that this occurs by mechanisms relevant to humans; effects are unlikely to be mediated by a genotoxic process." 11. The Secretariat undertook to amend the draft statement in light of the above discussion, and to finalise the statement by correspondence. It would then be placed on the COMEAP website. [ACTION: Secretariat] ITEM 5. TOWARDS ASSESSING AND COSTING THE HEALTH IMPACTS OF AMBIENT PARTICULATE AIR POLLUTION IN THE UK. COMEAP/2000/9, COMEAP/2000/9 ADDENDUM AND COMEAP/2000/14 Public availability: It was agreed that papers COMEAP/2000/9, COMEAP/2000/9 Addendum and COMEAP/2000/14 would be made available on request. The report would be made available on request once the results had been published. 12. It was explained that this project had been undertaken as a collaborative venture overseen by the Institute of Occupational Medicine (IOM) as part of the DH, MRC, DETR Joint Research Programme. The main aim of the project was to assess the feasibility of quantifying and costing the adverse health effects of particulate air pollution in the UK. The work had taken a different approach from that of the COMEAP 1998 Quantification Report. The latter report had only used outcomes for which the evidence was robust and could be quantified with reasonable confidence. Some key points from the report concerned: the potentially large impact of the long term effects on mortality; the fact that less severe effects on large numbers of people might be as significant as more severe effects; the potentially large, but very uncertain effects on chronic bronchitis; the need for relevant baseline rates for an outcome in the UK population; and, the approach to representation of uncertainty. It was noted that some of the exposure-response functions used in the report were dated, and that although the impact of this on the results was probably small, it would be important to update these before they could be used in cost-benefit analysis work. General comments on the IOM report were welcomed. The Committee was asked its opinion on what could be learnt from the report and whether it would allow COMEAP to update any of its views on quantification as expressed in the Quantification Report published in 1998. Long-term effects 13. Members' attention was drawn to COMEAP/2000/9 and COMEAP/2000/9 Addendum. COMEAP/2000/9 set out the potential impact on health of long-term exposure to current levels of particles in the UK might have, if quantified, and indicated that the effects on loss of life expectancy might be substantial. The assumptions underlying the calculations used were discussed and the paper also included a section examining the overlap between the effect of exposure to particulate air pollution on chronic and acute effects. It was noted that there might be some double counting if both effects were quantified and added together. The analysis undertaken by the IOM had produced an average loss of life expectancy due to particles, but there were many uncertainties surrounding this result. COMEAP/2000/9 Addendum gave further details of the different answers that might arise from analyses of this kind, and attention was drawn to the conclusions and questions at paragraphs 6 and 7. 14. The Committee congratulated the authors on the extensive report and felt that the issues had been considered with great care. Members considered that it deserved thorough consideration and it was suggested that a small subgroup should be set up to look at the section on the effects of long-term exposure to particulate air pollution. The IOM report itself would be considered again at the next meeting of the Committee to be held in November. These suggestions were agreed by the Committee. [Action: Members, Secretariat] 15. In response to a query as to the overall purpose of this work, the Secretariat replied that DETR were committed to reviewing the particle objectives in the Air Quality Strategy by the end of the year in order to ascertain whether this could be tightened up. Cost-benefit analysis so far had included nothing about chronic effects on health apart from a short sentence noting that these might be substantial.
17. The Secretariat stated that it would be helpful if the Committee could give its opinion of the minimum and maximum possible size of the effect along with the assumptions needed to make these estimates. This information could be used in cost-benefit work as a sensitivity analysis to demonstrate the possible impact of long-term effects, if they applied in the UK. It was agreed that the conclusions reached by the IOM report were useful and a good basis to work from, but deserved more detailed consideration, and it was concluded that these issues should be discussed further by a subgroup and that the report would be considered again at the next meeting. [ACTION: Secretariat]
18. There was a brief discussion of COMEAP/2000/14 which outlined some points of interest from other parts of the IOM report. It was noted that panel studies often used a group of patients attending a clinic but it was unclear how these patients related to the type of patients defined in the population baseline rates. For example, a panel study of mild asthmatics could not be used to predict the effects on all asthmatics in the population. In addition, these population rates were not necessarily easily available as routine statistics although it was felt that more information might be available in population research studies. It was noted that the accuracy of this baseline data could vary from place to place and suggested that the absolute rather than multiplicative approach might be more appropriate. These issues would come up again in the discussion of the COMEAP Update report.
Public availability: It was noted that this paper will be made publicly available once the statement is agreed. 19. The Secretariat explained that COMEAP/2000/10 had arisen as a result of a request for advice from the Environment Agency regarding the applicability of time-series coefficient to small areas around industrial processes. The Secretariat felt that the key question was whether the coefficients linking levels of air pollutants and effects on health- derived from city and town based time-series studies and used in the QUARK report - could be used to predict the effects of industrial emissions. Attention was drawn to the potential problems surrounding this issue as set out in COMEAP/2000/10. 20. The Secretariat went on to say that since the paper was written, an HEI report (which the Secretariat had seen) had been published on the methodological aspects of the NMMAPS study. It was noted that this included some extensive discussion of the relationship between concentrations measured at ambient monitoring sites and personal exposures and the likely impact of this on the results of time series studies. It was felt that it might be helpful to get clear views on this before finalising the present statement. Members were asked to consider the questions set out at paragraph 10 of COMEAP/2000/10 and also to give an initial consideration to draft statement. 21. Members felt that in general, the coefficients reported in the time-series studies linking concentration of air pollutants and effects on health could be used to estimate the effects of air pollutants emitted by industrial processes the people living near them. However, Members stressed that it must be made clear that there were many uncertainties associated with this approach, and that the extent of these uncertainties was at present unknown. These included, for example, the fact that the spatial distribution of air pollutants from an industrial source was likely to be different to that of a typical urban area. There were also differences between the distribution of socio-economic conditions in small areas near industrial sites as compared with whole towns or cities, and differences in patterns of personal exposure to the air pollutants emitted. In addition, the composition of industrial emissions in different places, was not likely to be the same. 22. Some Members remarked that there was likely to be a greater proportion of short-term peaks of exposure to air pollutants in the small area situation, and that it was not clear what this would mean in terms of effects on health. Furthermore, the statistical distribution of concentrations of pollutants was likely to be different compared with a typical urban situation. It was noted that, since it was generally assumed that the effects of common air pollutants studied by the time-series approach had no threshold, it might be appropriate to work with annual average concentrations of pollutants rather than day-to-day concentrations. 23. Members went on to make some comments regarding the feasibility of performing studies in such areas. It was suggested that the study populations would be much smaller than those usually taking part in epidemiological studies, and that therefore the numbers of health outcomes observed might be too small to allow meaningful conclusions to be drawn. It was noted that in Scotland, day-to-day data on health outcomes were available. Members commented that the Small Area Health Statistics Unit was well equipped to undertake studies of postulated linkages between the industrial sites and health effects such as cancer for which routine statistics were available. 24. After some further discussion, it was agreed that Members should submit further detailed comments to the Secretariat in writing, who would then revise the draft statement and circulate for agreement by correspondence as soon as possible. The outcome of the discussion would also be made available to the Environment Agency. [ACTION: Members, Secretariat]
Public availability: The Secretariat informed Members that this paper would be made publicly available. 25. Introducing this item, the Secretariat commented that COMEAP/2000/11 contained what was a near-final version of the Guidelines amended in the light of comments received during the consultation period, together with an analysis of the comments received and a list of respondents. Apart from taking any further drafting suggestions from members at the meeting, the Secretariat noted that Members would also be asked to let the Secretariat have any further detailed comments by the end of June. Members were also asked to comment on the flow chart which was tabled. It was intended that a final version would be published later in the summer. 26. Members felt that this was an interesting and valuable document. In particular it would be of great help to those public health professionals who dealt with many queries of this nature. It was suggested that it might be helpful to say more about chronic effects. Some Members felt that the document was unwieldy; it was commented that the appendices were much longer than the actual guidance. It was also pointed out that the section dealing with burdens of disease did not mention air pollution at all. Members further suggested that on page 52, the Health and Safety Executive and other appropriate European bodies should be mentioned. The Secretariat undertook to amend the Guidelines in light of these and any further comments submitted by Members, and it was agreed that this document would then be finalised with the Chairman by correspondence. [ACTION: Members, Secretariat] Public availability: The review paper could be made publicly available given the agreement of the DH Toxicology Unit at Imperial College and once the Committee's consideration was complete. 27. The Secretariat explained that this review had been commissioned from the DH Toxicology Unit at Imperial College, and noted that Dr Kate Leverton, who wrote the review was present to answer any questions. 28. A short summary of the main findings of the review was given. It was noted that the review covered only formaldehyde, acetaldehyde and acrolein in detail and that the information summarised had been taken entirely from published sources including WHO and IARC publications and reviews. It suggested that although these compounds could cause irritancy, this was unlikely at levels likely to be encountered in ambient air. The author of the review noted that the unsaturated aldehydes, such as acrolein and crotonaldehyde had the most potential to cause irritancy. The studies of acrolein reviewed had been found to be limited. It was noted that the combined effects of the aldehydes were probably less than additive. The review had also noted that although formaldehyde and acetaldehyde had been classified as probable and possible carcinogens by IARC, the compounds were not likely to present a carcinogenic risk below levels which were known to cause irritancy. Some information had been made available on ambient levels, and this was described in an addendum supplied by DETR. 29. Attention was drawn to the recent research undertaken by Andrea Venn at City Hospital, Nottingham, which suggested that formaldehyde might worsen symptoms of asthma at relatively low levels found indoors (median 22 µg/m3; interquartile range 16 to 32 µg/m3). This had not been suggested by earlier studies in the literature, and the Secretariat suggested that the Committee might wish to comment on the possible reasons for this difference. 30. The Secretariat commented that the review did not cover other aldehydes in detail but noted that it did consider structure activity relationships for aldehydes, the effects of mixtures and gave a brief summary of the information available. It was further commented that the DETR paper indicated that other simple aldehydes were generally present at lower concentrations than formaldehyde and acetaldehyde. Members were asked whether any further information on other aldehydes was required, and their comments on the DH Toxicology Unit review welcomed. 31. Members commented that the review was an excellent piece of work which had made an extensive evaluation of a very complex area. It was agreed that there was a clear relationship between chain length and irritancy and that of the unsaturated aldehydes, acrolein exhibited the most potential to cause an irritant effect, although its levels in air were low. 32. The Secretariat was informed of a study of the toxic effects of acrolein in baboons which had not been covered in the review. Acrolein produced severe lung damage in this study but the concentrations used were very high. Some members pointed out that the review had focused its attention on sensory irritation; the situation with regard to eye irritancy might be different, and the additivity theory might not apply here. It was also suggested that another issue that might be considered further was that of the effects of occupational exposure to aldehydes, the main concern here being that exposure to glutaraldehyde, a related aldehyde, was known to cause occupational asthma [1]. Members felt that more research on this issue was required before the biological mechanisms underpinning the onset of occupational asthma were fully understood. 33. Members commented that the review of the carcinogenic effects of aldehydes was good. The covering paper had suggested that the carcinogenic effects observed arose as a result of the cytotoxic effects of the aldehydes. However, some members advised that it might not be appropriate to say that formaldehyde was non-genotoxic; formaldehyde was genotoxic but it was only in the presence of cytotoxicity that this led to cancer. 34. After some further discussion it was agreed that any further comments should be sent in writing to the Secretariat. The Secretariat also undertook to produce a statement based on the summary of the report which would be circulated to Members for consideration. [ACTION: Members, Secretariat]
Public availability: this paper will be made publicly available on request. 35. The Chairman informed Members that he had recently attended a meeting of DH Advisory Committee Chairmen convened by the Chief Medical Officer (CMO) to discuss the communication of risk. The CMO had expressed great interest in this issue. The degree of independence of Advisory Committees was discussed - for example, the COMEAP website could be separate from the DH website. It was also suggested that some Members could be especially trained to deal with the issues of risk communication. It was noted that Advisory Committees should bring potential problems before the Department for consideration if necessary. 36. Members' attention was drawn to COMEAP/2000/13. The Secretariat commented that the issue of communicating with the public had been discussed at several previous meetings. COMEAP/2000/13 comprised the amended draft text of a short document describing the health effects of air pollutants which had been agreed by the Committee as a result of these previous discussions, subject to a few outstanding drafting points. The document was now simpler and easier to follow, and it was felt that placing the Executive Summary at the beginning of the document would allow users to quickly identify the main points in the text. The Secretariat noted that there were one or two points that required further resolution, namely: the issue of advising people with asthma about adjusting their treatment, especially in relation to air pollution forecasts; what to say to people with heart disease; and the overall length of the document. The Secretariat felt that once these issues were resolved, it should be possible to place the document on the Committee's website within one or two weeks. Members' comments were welcomed. 37. Some Members felt that the document dwelt heavily on the effects of air pollution in relation to asthma, and that effects in relation to other "airway diseases", such as chronic obstructive pulmonary disease (COPD) needed to be addressed further. It was agreed that there was an overemphasis on the effects of air pollution and asthma in the document, probably because there was a large body of literature dealing with this subject. 38. It was noted that it might be appropriate in paragraph 1.1 to rank sources in order of importance, and this was agreed. It was also noted that "it" should be replaced by "loss of life expectancy" in paragraph 4.2. 39. There was some discussion as to the statements in the document with regard to the concept of reduction of life expectancy as a result of exposure to air pollutants and their effects on health being as much as 1 year. Some Members were concerned that this would be seen by the media and subsequently quoted as the considered opinion of COMEAP on this matter. The Secretariat explained that this was only quoted as "one suggestion" of the size of the effect based on a paper by Brunekreef. 40. Some further minor alterations to the document were suggested. Members queried whether the potential role of antioxidants and diet had been specifically linked with respiratory disease. The Secretariat replied that there was a small literature on this issue which, whilst not conclusive, could not be ignored. It was noted that the wording in paragraph 5.3 with regard to exposure to air pollution and concentration of air pollutants seemed to be contradictory, and there was some concern about the advice given in paragraph 5.4 with regard to asthmatic patients and exercise. The Secretariat agreed to amend these paragraphs in light of the Committee's concerns. Finally, it was suggested that the document should be placed on the website in a format that enabled people to obtain the information they specifically required without having to look through the document as a whole in order to facilitate access. The Secretariat undertook to amend the document in light of the above discussion and to make it publicly available on the COMEAP website within the next few weeks. [ACTION: Secretariat] 41. Attention was drawn to COMEAP/2000/16, a paper which had been circulated to Members by E-mail. The Committee was informed that DETR was planning a consultation paper on proposed changes to the air pollutant banding system in order to take into account the EC Alert thresholds. The Secretariat requested that members submit comments on this paper in writing by July 7, after which some suitable advice to describe the health effects that occur when these threshold are exceeded would be agreed. [ACTION: Secretariat]
43. The Committee was informed of the progress of work being undertaken by the team at St George's Hospital Medical School for the COMEAP update report. Work on inputting the relevant data into the relational database was progressing very satisfactorily, and it was intended that summaries of the results available in particular categories would be available over the summer. It was noted that a meeting of Members who would be writing chapters updating the Committee's views on each pollutant was being planned for early September.
44. The following papers were circulated/tabled for information:
12.1 Terms of Reference of the Committee. COMEAP/2000/15 45. Attention was drawn to COMEAP/2000/15. This detailed an updated version of the Committee's terms of reference in order to reflect the fact that COMEAP is now a UK Committee which also advises the devolved administrations. The following terms of reference were agreed: "To advise the UK Health Departments on the effects of health of both outdoor and indoor air pollutants on the basis of data currently available; to assess the need for further research; and to liaise as necessary with other Government bodies to assess the effects of exposure and the associated risks to human health."
46. The following dates were noted: Friday 3rd November 2000; Friday 16th February 2001. [1] The review notes that early concerns that formaldehyde was related to occupational asthma have not been confirmed by more recent studies.
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