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FOR MEMBERS' USE ONLY COMEAP/MIN/2002/1
COMMITTEE ON THE MEDICAL EFFECTS OF AIR POLLUTANTS
Minutes of the meeting held on Friday 8 February 2002 in the Dorchester Library, The Royal College of Physicians, 11 St Andrews Place, Regents Park, London NW1 4LE.
Present:
Chairman: Professor J G Ayres
Members: Professor H R Anderson
Secretariat: Dr R L Maynard Assessors: Dr J Dixon (DEFRA)
In Attendance: Ms I Lindup (DH)
ITEM 1. OPENING REMARKS, APOLOGIES FOR ABSENCE AND ANNOUNCEMENTS
1. Apologies for absence were received from Professor Ken Donaldson, Professor Bill MacNee and Lord Toby Harris.
2. The Chairman welcomed and introduced three new members to the Committee: Mrs Alice Lambert, Dr Virginia Murray and Professor Anthony Frew. It was agreed that the Secretariat should prepare a short document of bibliography outlining the work and interests of each Member of the Committee.
[ACTION: Secretariat]
3. The Chairman also welcomed Mr Richard Harris (DTI), Mr Peter Ridgway (HSE) and Mr Allyn Jones (HSE) who were attending for the discussion of Item 5. It was noted that Dr Olivia Carlton and Dr Chris Beach (London Underground) and Dr Leslie Hawkins (Robens Institute) were also attending for the discussion of Item 9.
ITEM 2. MINUTES OF THE MEETING HELD ON 2 NOVEMBER 2001
4. It was noted that Dr Paul Harrison had not attended the meeting.
5. Subject to this amendment, the minutes were agreed as an accurate record of the meeting.
ITEM 3. MATTERS ARISING COMEAP Leaflet "Air Pollution – What it Means for Your Health"
6. It was noted that DEFRA were aiming to have this leaflet printed and ready for publication by the end of March 2002.
COMEAP Statement and Report on Long-Term Effects of Particles on Mortality
7. The Secretariat commented that the report had been proof read and approved for formal publication by officials. A few minor alterations, such as the addition of a Membership list had been made since its informal publication on the COMEAP website. The report was being printed by the Stationery Office as a priced publication which would be listed as part of the COMEAP report series. COMEAP Statement on Particles and Effects on Cardiovascular Health
8. The Secretariat informed Members that this should be made available on the COMEAP website in the near future.
ITEM 4. IS THERE A THRESHOLD FOR THE EFFECTS OF OZONE ON HEALTH? INITIAL ASSESSMENT OF EFFECT OF MORTALITY AND RESPIRATORY HOSPITAL ADMISSIONS. COMEAP/2002/1 9. Public Availability: There was some initial discussion of the public availability of this paper. Members were informed that St George’s Hospital had been instrumental in providing much of the data used to produce COMEAP/2002/1. However, the data were initial, interim data provided early to start the process of informing policy; research was not yet fully complete. It was further commented that it might be confusing if information initially placed on the COMEAP website was subsequently changed in light of further analysis of data. Other Members considered that this was acceptable provided it was clearly explained that the data were provisional.
10. This led to some discussion of public availability of papers in light of the policy of openness and the Code of Practice both of which government advisory committees were expected to adhere to.
11. The Secretariat noted that within the Code of Practice there was a section that related to reports that included incomplete analysis of data: this stated that an exemption from the requirements for openness was acceptable if the results were incomplete. Therefore, the Secretariat suggested that in the present case, the introduction (paragraphs 1-3), summary (paragraphs 16-18) and next steps (paragraphs 19-22) could be made publicly available on the website with an explanation that the rest of the paper contained incomplete data. This was agreed.
[ACTION: Secretariat]
12. Some Members felt that work might not be brought before the Committee if researchers felt that future publication was being jeopardised. There were also questions raised about what the requirements were for holding open meetings. The Secretariat replied that open meetings were encouraged but were not compulsory. It was also agreed that a list of acronyms would be placed on the website and regularly updated and that the Secretariat would produce a further paper on openness for the June meeting.
[ACTION: Secretariat]
13. Introducing COMEAP/2002/1, the Secretariat informed Members that, as proposed at the last meeting, the paper considered two issues, namely whether the overall literature supported a positive association between ozone and all-cause mortality, respiratory or cardiovascular mortality or respiratory hospital admissions; and if so, whether there was any indication that the coefficients or their statistical significance varied according to ozone concentration. It was noted that this paper constituted a progress report and that there was further work to be completed before the Committee would be expected to come to any firm conclusions on these questions. However, the Secretariat noted that the Committee’s views and advice on the work so far and on the planned next steps would be helpful. 14. The Secretariat went on to say that the results so far had suggested the following:
15. It was commented that these results were tentative at present because the plots represented coefficients from only single pollutant models and with mixed lag times and averaging times. The Secretariat suggested that if the Committee agreed that there was sufficient indication of a positive association between ozone concentrations and the various health indicators outlined, views on further work suggested in paragraphs 20 to 24 of COMEAP/2002/1 would be welcomed.
16. Members felt that this was an excellent paper. A query was raised as to how many of the studies analysed were mathematically capable of showing a threshold? It was replied that some of the studies did this graphically, but these were in the minority. However, there had been insufficient time to go through all the studies in detail to look at this issue; all the studies were thought to have the potential to estimate an exposure-response relationship. It was suggested that in reality, thresholds were difficult to identify and that there was likely to be only very indirect evidence for a threshold effect of ozone.
17. Some Members noted that there were different trends of peak and mean concentrations of ozone and agreed that it was useful to answer the policy-orientated question of what level of threshold would make a difference in terms of effects on public health. It was commented that the paper gave a very useful of the health effects of ozone. In quantitative terms if no effects were demonstrated, then there would be no need to look for a threshold. It was also noted that there would be a level at which it would be futile to look for one.
18. In relation to Figure 2 of COMEAP/2002/1, a question was raised about the sensitivity of the methods of measuring levels of ozone, particularly at low levels. It was replied that measurement at fixed points was very precise. However, it was also pointed out that fixed point measurement was not representative of personal exposure of populations across a city particularly for ozone since levels were low indoors and close to traffic due to scavengers by nitric oxide. It was also suggested that the variation in Figure 2 might be dependent on the different atmospheric conditions in different cities and at different times of the year. Some Members thought that the spread of data in Figure 2 might have more to do with study design and the epidemiological methods used. The Secretariat commented that a mixture of averaging times had been used, some being 24-hour averages, thus giving low overall levels.
19. Members commented that at first sight, there was little evidence of a population threshold for the effects of ozone which led to the question of whether there was a real public health issue to be considered. However, it was acknowledged that there would almost certainly be a threshold at an individual level. It was suggested that it might be useful to investigate whether adjustment for the effects of particles made any difference to the outcomes and that the most important information might be gained from multi-pollutant models. It was noted that there was some evidence of a stronger association in summer rather than winter in some cities.
20. It was commented that, in using this kind of epidemiological evidence to look for thresholds, there were other reasons why differences in estimates might be found and that these should be looked at carefully. For example, one of the London based estimates was based on data taken from one monitoring site at London, Victoria. This would certainly underestimate levels in suburban areas. Thus, when a time-series analysis was conducted there might be estimates of similar precision but different coefficients which might result in some bias. It was further commented that in summer personal exposure to indoor ozone concentrations correlated more closely to outdoor levels since not only were people more likely to spend time outdoors, but also housing was more ventilated (by leaving windows open, etc). Therefore, it was agreed that any higher coefficient of effect would not necessarily be due to greater effects at higher levels of ozone. The point was made that it was also necessary to integrate into the analyses what else was known about the effects of ozone on the lung, from, for example, clinical and experimental studies. It was, for example, established from volunteer studies (chamber studies) that individuals became tolerant to the effects of ozone after a few days, ie adaptation took place.
21. It was remarked that ozone was a pollutant which had a baseline level that was going up all the time and therefore the population was not ever unexposed to this pollutant. Thus, the Committee thought that it might never be possible to come to a firm conclusion with regard to exposure-response relationships. However, it would be possible to undertake sensitivity analyses which would result in a suggested range of impacts on health.
22. Some Members pointed out that in some cities ozone levels would correlate well with those of other pollutants, for example, nitrogen dioxide, whilst in other places there would be anti-correlation. This all added to the complications of interpreting single-pollutant models.
23. With regard to further analysis of the data it was noted that many of the studies reported demonstrated wide confidence intervals. The reasons for this were many and varied, and included parameters such as size of city, length of time series. It was also noted that publication bias needed to be taken into account, and it was acknowledged that this could be examined.
24. After some further discussion it was thought that it might be needed to organise the final report slightly differently and that the issue warranted a working group to meet informally with the aim of producing the final report. This was agreed and the Secretariat undertook to produce some further papers for consideration for the next meeting.
[ACTION: Secretariat]
ITEM 5. UNFLUED GAS FIRES: REQUEST FOR ADVICE FOR HSE AND DTI. COMEAP/2001/2
No interests were declared in this item.
Public Availability: It was agreed that Annex 1 of COMEAP 2001/2 without the last paragraph could be made publicly available.
It was further noted that paragraphs 26-39 should not be made publicly available at the present time since these paragraphs referred to work that was currently in progress and not in the public domain.
40. It was concluded that a further paper should be produced which would be discussed by the Committee at its meeting in June. After this a definitive statement would be produced. Members were asked to feedback their views on low oxygen levels to the Secretariat as there had not been a chance to discuss this.
[ACTION: Secretariat, Members]
ITEM 6. APRED DATABASE – IEH 41. Members were given a short presentation about the database recently established by IEH – Air Pollution Research Databases (APRED). This database had been produced by the MRC Institute for Environment and Health with support from DH and DEFRA. Members were told that this database enabled up-to-date information on researchers in the United Kingdom working in the field of air pollution to be accessed. In particular their fields of expertise and areas of interest were highlighted. Other details included that could easily be accessed were of their organisations and research projects. It was also noted that whilst the focus of the site was on UK-based researchers, the database also contained some information on international collaborators and funders. 42. It was noted that the search facilities incorporated into the database would allow a user to:
43. It was commented that government bodies and other funding organisations might find this resource particularly useful when planning research calls and seeking experts for consultation. Researchers were encouraged to submit information to the database in order for it to function effectively. Further information could be found at the following website address: http://wads.le.ac.uk/ieh/apred/welcome.htm ITEM 7. PAPERS FOR INFORMATION 7.1 Dominici et al. COMEAP/2002/3 44. This paper was circulated for information. Members were reminded that mention was made of this study during the discussion of the CONCAWE report on APHEA studies at the meeting held in February 2000. A prepublication copy of the paper was circulated to Members at the June 2000 meeting, and later that year the paper was formally published in the Journal of the Royal Statistical Society, along with a discussion section and response from the authors.
7.2 Tabled papers for information
45. The following papers were tabled for information:
Guidelines 2000 Implementation Report. COMEAP/2002/6
46. It was noted that this report mentioned COMEAP as a good example of a Committee that adhered to the guidelines.
Code of Practice for Scientific Advisory Committees
47. It was noted that this had been circulated to the Committee on previous occasions: this final version was very little changed.
ITEM 8. ORAL REPORTS
8.1 Update on progress with call for research
48. The Secretariat informed Members that the new call for research had been put out last October. A subsequent sift of 71 submitted proposals had taken place. Of these, 40 had been asked to submit further details the deadline being 30th January 2002. It was intended that a final selection process would be undertaken during March 2002.
8.2 Update on COMEAP membership
49. It was noted that four members were due to retire from the Committee in June: Professor Ross Anderson, Professor Roy Harrison, Professor Roy Richards and Professor Anthony Seaton.
8.3 COMEAP 5 year review
50. The Secretariat commented that this was currently being discussed with officials elsewhere in the Environment Branch who were undertaking to find a suitable independent person to conduct the review.
8.4 Update on EPAQS future work programme
51. DEFRA officials commented that there was a much wider range of compounds emitted by industry than those covered by the current list of air quality standards, and noted that the Environment Agency had said that it would appreciate clear advice on the levels of these compounds that might constitute a risk to health. This would assist the Agency in assessing IPPC applications. Therefore, it had been suggested that EPAQS should look at a list of compounds that frequently came up in IPPC applications. It was noted that these included halogens and halides, heavy metals such as antimony and beryllium and some organic compounds such as phenol and xylene.
8.5 Update on WHO Work Programme
52. The Secretariat commented that WHO had been commissioned to review particles, ozone and nitrogen dioxide in order to assist with the EC review of limit values for particles and nitrogen dioxide in 2003 and ozone in 2004. A first meeting had been held in January and some subgroups were being set up. It was noted that particles would be the first pollutant to be addressed.
8.6 Subgroup on Air Pollution and Cardiovascular Disease
53. The Secretariat told Members that a framework for the report had been produced. It was also noted that a discussion website was currently being set up. This would enable Members of the subgroup to interact directly with each other online.
ITEM 9. LONDON UNDERGROUND TUNNEL DUST. COMEAP/2002/4 Mr Hurley declared an interest in this item.
Public Availability: It was agreed that this document and paper could be made publicly available: the London Underground report had already been published in full on the following website address: http://www.thetube.com where it can be found under press releases for October 2001.
54. The Secretariat reminded Members that they considered the possible effects on health of exposure to particles found in the air in the London Underground at their meeting on 16 October 1998 after which a COMEAP statement was produced (see Annex 1 of COMEAP 2002/04 or COMEAP website).
55. However, the Committee was informed that recently, the Director of Safety, London Underground (Mike Strzelecki) had asked DH for advice and comments on a further report prepared for London Underground by Dr Leslie Hawkins of the Robens Centre of Occupational Health and Safety at Surrey University (Annex 2 of COMEAP/2002/04). It was noted that this report was already publicly available in full on the following website address: http://www.thetube.com where it could be found under press releases for October 2001.
56. The Secretariat commented further that three main areas of the report should be considered: (i) the use of epidemiological time-series studies and cross-sectional cohort studies as a basis for predicting the effects on health of exposure to particles in the London Underground;
(ii) the risks of silicosis as a result of exposure to silica in the aerosol; (iii) the possible toxicological effects of metals found in the particles – possibly acting via a free radical generating pathway. 57. Members’ comments were invited on these and other points, and it was commented that Members might wish to consider further evidence before coming to a final view. Therefore, the Secretariat suggested that the discussion at the present meeting should be regarded as exploratory; that held in June would be definitive.
58. A short resume of the report was given by the author. Members were informed that the report comprised a short look at the issues concerning the RMT Union which had issued a request to investigate further, various claims that exposure of London Underground employees, and the travelling public, were exposed to an unacceptable risk to their health from exposure to airborne dust in the tunnel network. Data from 1979 onwards had been made available, but it was noted the report quoted data which went back many years further than this. The report presented a broad brush picture of exposure. Another purpose of the report had been to examine the chemical composition of London Underground tunnel dust and to examine the effects of exposure to this particular dust on health. It was acknowledged that most of the information available related to occupational exposures, and that whilst this did not fall under the remit of COMEAP, it would be valuable to have an idea as to what extent ambient air quality standards might be applied to the London Underground. Members comments and questions were invited.
59. It was noted that, in the mid 1990’s, a study of personal exposure of London taxi drivers to manganese was compared to the personal exposure of Central London office workers. It had been found that those exposed to the highest levels of manganese were amongst a subgroup of office workers and that those who used the London Underground were exposed to approximately twice the levels of taxi drivers. After undertaking measurements of manganese levels in the London Underground, it had been found that these were well in excess of the WHO Air Quality Guideline Value for manganese.
60. It was remarked that that it might be the case that there was a relatively high proportion of individuals who spent much of their time travelling on the Underground. Thus, it might be useful to look at pattern of use in order to put the levels of exposure into context.
61. Representatives from London Underground commented that a report by the Institute of Occupational Medicine (IOM) published in 1991 had reported levels of manganese and that it had repeated its monitoring during 1999. These levels had not seemed particularly high. They also noted that the present report on London Underground dust had not been asked to look at patterns of passenger use in any detail. However, if the Committee was interested, London Underground commented that extensive detail was available and could be distributed to members. It was agreed that this would be useful.
62. Some Members of COMEAP felt that the report had not clarified clearly the difference between fine and ultrafine particles, noting that the report attributed effects on health to PM2.5 when in fact the evidence was based on studies of ultrafine particles. The author replied that the proportion of PM10 made up of fine particles (PM2.5) on the London Underground was high (Table 7 on page 37 of the report). Members noted that the study had measured TSP rather PM10 levels; the comment was made that about 40% of the TSP was made of PM2.5 and so was less than levels measured in ambient atmosphere. London Underground replied that much depended on where the measurement were made; for example, at the platform level there were higher levels of coarse particles present when a train arrived. The Committee further commented that that 60-70% of PM10 in London was made up of PM2.5 particles. Thus the "high proportion of fine particles" was really quite low. London Underground felt that these levels had been high given that they were not combustion-derived fine particles. It was suggested that it would be interesting to compare the situation on the London Underground with that of the Glasgow Underground where conditions were wetter.
63. There was some discussion of the ‘potential’ toxicity of dust in terms of particle size. Members commented that resuspended dust was usually in the coarse fraction and that there was debate as to how toxic this fraction actually was. EPAQS had discussed this at some length and had concluded that whilst effects on health of exposure to coarse particles could not be excluded, there was more concern in relation to combustion-related particles; data on these particles were not included in this report. It was noted that the fine particles in the London Underground were probably from abrasion. In response to a query about the relative toxicity of abraded and resuspended particles Members of the Committee commented that freshly abraded quartz was more toxic than other forms of quartz.
64. Members commented that the levels of iron measured in the dust presumably arose from abraded particles, but queried the source of the silica levels observed. London Underground said this was unclear but that one possible source was from structures containing concrete. Levels of silicon in brakes had been found to be low.
65. Attention was drawn to Tables 1 and 2 of the London Underground report. It was pointed out that the breakdown of levels of iron, quartz and calcium did not add up to 100%. It was replied that the remainder could include components from street level particles, and peoples’ "personal clouds" ie, levels of particles arising from people moving around. London Underground also remarked that the concentrations were expressed as a percentage by weight and the iron and calcium would have associated anions that were included in the tables. It was noted that silica occurred in the PM10-PM2.5 range as described in paragraph 2.3.
66. Members asked about the rate of generation of new particles and of the effect of periodic cleaning regimes. London Underground replied that one cleaning train was in existence which travelled periodically around the deep tunnels. London Underground was currently looking at how much the levels of respirable dusts were reduced by this regime. DEFRA wondered to what extent the Underground was acting as a sump for ambient particles. The author of the report replied that it was clear that particle concentrations had been accumulating up to 1990 but then had started going down again.
67. Members asked whether there had been any evidence (anecdotal or formal) over the past 100 years that any London Underground worker had been seen to experience any adverse effects on their health. It was felt that it would be easy to embark on an enormous programme of research but that this might be inappropriate if no one had ever previously suggested that workers’ health had been harmed. It was also thought to be unlikely that any worker (with the possible exception of drillers) would be diagnosed with silicosis or Parkinson’s disease given the levels of silica and manganese present. It was recommended that it might be appropriate to look for evidence from large mortality studies before taking this issue any further. London Underground agreed that there had not been much research in this area, and that the report represented all that had been identified.
68. Members were of the opinion that to undertake health studies as recommended in paragraph 10.4 of the London Underground report would be a huge undertaking that could not be justified if there was no evidence that workers’ health was being affected by the levels of particles experienced in tunnels. The money spent on a large study might be better spent on reducing the levels of particles. However, London Underground representatives replied that the major worry at the present time was the fact that there was much interest in the effects of exposure to particles on respiratory and cardiovascular health and that the Government targets for this pollutant in London Underground tunnels were not being met by some way. There were also other concerns about the effects upon health of exposure to free radicals, which had also being receiving media attention recently.
69. Members felt that the important question was whether the standards for ambient air particles could be said to be applicable to those encountered in the tunnels or platforms of the London Underground. This in turn related to the composition of the particles which appeared to be so different that extrapolation of ambient standards might not be appropriate. Other Members agreed with these comments. It was felt that if any estimate of health effects were to be made, then it would be inappropriate to use the time-series studies. It was suggested that long-term exposure studies of other work forces with analogous exposure should be used. Levels of particles had been declining since 1990. In addition, smoking was no longer allowed on the Underground, which might have had some bearing on the improved particle levels.
70. However, some Members expressed concern that the Committee should claim that there was no cause for concern despite the differences in the chemical composition of the particles in the Underground as compared to those in the ambient air. It was felt that the particles were of similar size ranges, those underground were much higher than those above ground, and it was not clear that the only problem was with combustion-related particles. Members further remarked that there was likely to remain immense media interest in this issue. The Committee queried whether the 1994 study of track workers mentioned in paragraph 8.6 was currently followed up. If so, publication of these data might provide some reassurance to both members of the public and occupational groups.
71. It was felt that it would be possible to make judgements on the basis of other studies. It was further commented that information on vulnerable groups (which did not usually tend to be occupationally exposed groups) and pattern of use, eg, the age of people who use the London Underground (not usually the aged) would be useful. This might give some insight into the issue of acute effects which might have hitherto gone unnoticed. Some Members thought that this was mainly an occupational health rather than a public health issue.
72. It was commented that COMEAP had published a very clear statement on the health effects of exposure to dust on the London Underground in 1998 and tjere were no new data in this report. Whilst it was acknowledged that there had been changes in public perception of the risks to health, this did not necessarily mean that a large research programme should be undertaken at the present time
73. Some Members were concerned about the lack of clarity regarding the classification of particles. For example, the report had failed to make clear the difference between combustion/abrasion, fine/ultrafine particles. It was also felt that the report had not advanced understanding of the effects of London Underground particles on health because it focused more on hazard rather than risk. It seemed likely that London Underground would prefer to know more about the latter.
74. The Committee felt that the main issue to consider in this case was whether the potential hazard constituted a real risk. This could not be determined from the available data and it was noted that appropriate data might prove difficult to obtain unless an analogous occupational exposure situation could be identified. Informed judgement tended towards a view that there was not a significant risk to health, but it was acknowledged that it was understandable that people would be concerned. Careful presentation of the Committee’s view would therefore be required.
75. Members addressed the questions presented in paragraph 4 of COMEAP/2002/4 and concluded:
(i) time-series studies and cross sectional cohort studies should not be used as a basis for predicting the effects on health of exposure to particles in the London Underground;
(ii) there was no evidence of a risk of developing silicosis as a result of exposure to the aerosol;
(iii) basic information on toxicology of metals was easily obtained. However, it would be useful to know the form of the iron in the dust as this might affect the likelihood of production of free radicals. It was noted that the emphasis on free radicals in the report had been disproportionate.
76. The Committee agreed that comments would be sought from some particle experts on the Committee who had not been able to attend for the present discussion and that a draft statement would be produced by the Secretariat for comment and discussion at the next meeting.
[ACTION: SECRETARIAT] ITEM 10. ANY OTHER BUSINESS 10.1 Infectious Diseases Strategy 77. It was noted that a report: "Getting ahead of the Curve" had recently been published by the Chief Medical Officer. An extract from this report relating to chemicals had been circulated for information. No further details beyond those stated in the strategy were yet available. It was intended that the new structure should be in place by 1 April 2003.
78. Some Members felt that this had given some thought to the importance of the effects upon health of environmental chemicals. However, others expressed concerns that there were many excellent procedures already in place to deal with, for example, chemical incidents, and feared that some of these might be unnecessarily dismantled. The Secretariat undertook to keep Members informed of developments.
[ACTION: Secretariat]
ITEM 11. DATES OF FUTURE MEETINGS
79. The following dates were noted:
80. The following dates for 2003 were proposed:
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