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COMMITTEE ON THE MEDICAL EFFECTS OF AIR POLLUTANTS Minutes of the Meeting held on 29th
February 2008
Chairman: Professor Jon Ayres Members: Secretariat:
Observers: In
attendance:
1. The Chairman introduced Dr Giles Watson (working with the Air Pollution and Toxicology Units) and Ms Sue Kennedy (Committee Administrator replacing Janice Cleverly) to the Committee. 2. The Chairman also introduced those attending the meeting for specific agenda items:
3. The Chairman welcomed the return of Ms Jackie Maud (EA) after time spent away from the Committee whilst studying for her Masters degree. 4. Apologies for absence were received from: Mr Fintan Hurley, Professor Ross Anderson, Mr Nigel McMahon. It was noted that Professor David Strachan would be arriving at about 11.00 am. 5. Members were reminded to declare interests, if any, at the start of an agenda item, and to submit their expense claim forms to Sue Kennedy.
6. Members reported no errors and the minutes were agreed as an accurate record of the meeting.
3.1 Membership 7. The Chairman reported that Professor Ken Donaldson, Professor Dafydd Walters and Mr Ben Armstrong had agreed to serve for a further three years. 3.2 Annual Air Pollution Meeting 8. The Chairman reminded Members that the Eleventh Annual Review Meeting on Outdoor and Indoor Air Pollution Research would be held at Cranfield University on 15th and 16th April 2008. Members were encouraged to attend and reminded that the meeting was regarded as a COMEAP meeting: usual expenses would be paid. 3.3 Paper by Gauderman et al, 2007 9. Dr Heather Walton introduced this item. 10. Members were reminded that Professor Laxen and Mr Armstrong had been asked to provide notes of their comments made at the last meeting. These had been received and would be circulated to the Committee. It was proposed that a letter be sent to DH by the Secretariat outlining Members' views of the paper. It was further proposed that the notes provided by Professor Laxen and Mr Armstrong should be attached as Annexes to the letter to DH. [ACTION: Secretariat] 11. Professor Laxen declared an interest in this area: in his work as a consultant he had been asked about the Gauderman paper. Those arguing against road development near housing were using it as a basis for predictions of effects on health. 12. It was agreed that the Gauderman paper should be seen in the context of other work in this area. The Chairman noted that COMEAP had a commitment to look at issues concerning "roadside" exposure and that this should take its place in the Committee's work programme. It was pointed out that some clarification of the term "roadside exposure" was needed. Members' attention was drawn to a report recently published by the Health Effects Institute on Mobile Air Toxics. 3.4 Defra Air Pollution Information Service 13. The need to amend the banding system had been put forward, by Dr Janet Dixon (DEFRA), in a paper to COMEAP at its last meeting. Dr Williamson (DEFRA) indicated that the material promised (on an explanation of the changes to the banding system suitable for members of the general public) would come to COMEAP shortly. He also flagged up some procurement issues currently being faced by the Air and Environment Quality Division at DEFRA. 3.5 Statement on Asthma and Exposure to Chlorine and Associated Reaction Products at Swimming Pools 14. This statement had been completed and placed on the COMEAP website in September 2007. 3.6 Meeting between EPAQS and COMEAP Chairmen and Secretariats 15. This meeting took place on 11th October 2007. The group discussed the merger of the two committees and agreed that the merger would not formally take place until EPAQS' current work programme had been completed. It was noted that the DEFRA Secretariat would inform the COMEAP Secretariat when this was likely to take place. It was noted that a further meeting of the respective Secretariats would be arranged. Professor Holgate (Chairman of EPAQS) reported good progress on a report on metals and indicated that it was unlikely that a further meeting of EPAQS would be needed. 3.7 COMEAP Strategy Meeting 16. The Chairman reported that he had held a meeting with the Secretariat in December 2007. Many of the items discussed figured in the agenda of the present meeting. The next Strategy meeting was planned for June.
4.1 QUARK II Mortality Report 17. An update was provided by Miss Inga Mills. 18. Members were already aware that the draft report from the mortality subgroup had been placed on COMEAP's website for comment for a period of six weeks. During this time the report was peer-reviewed by: Dr Michal Krzyzanowski (WHO), Dr Bart Ostro (USA), Professor David Coggon (UK) and Professor Philip Hopke (USA). 19. In addition to the 4 peer-reviews, 8 further comments were submitted to the Secretariat by groups including the Association of Electricity Producers and CONCAWE. Areas of the report attracting comments included:
20. The comments have been considered and the report amended accordingly; these amendments include points that are editorial in nature. An annex giving responses to the key themes had been prepared. It was noted that the amended report, response annex and comments (submitted to the Secretariat) will be circulated to the subgroup for its consideration; specific members will be asked to consider particular comments. Once the final report had been prepared, a copy would be submitted to the wider Committee for clearance. The Secretariat commented that it was hoped that the final report would be published before the summer meeting of COMEAP (20th June 2008). 4.2 QUARK II Morbidity 21. An update was provided by Miss Mills. 22. It was reported that the QUARK II Morbidity Subgroup last met on October 12th 2007 and agreed the scope and approach of its work. It was agreed that the group would focus (initially) on quantifying the effects of long-term exposure to air pollution on:
23. The Secretariat will propose that the subgroup should consider the following outcomes for each of the above groups:
24. It was noted that the subgroup agreed to approach the work by developing a series of matrices: (a) A first matrix on hazard identification showing the proposed relationships between a range of pollutants and outcomes, with an indication of the strength of the evidence. (b) A second matrix for quantifying the hazards identified in the first matrix. This would include details of the available concentration-response functions for quantification. (c) A third matrix for calculating the impact of the pollutant-outcome pairs (i.e., long-term exposure to pollutant x and the effect on health outcome y). 25. The Secretariat was currently obtaining literature on COPD/Chronic Bronchitis and writing draft chapters for Members' consideration. It was noted that this would be sent to Members of the Morbidity subgroup in March 2008. 26. Members commented that this was a challenging piece of work and agreed that the approach adopted was likely to be helpful. The Secretariat noted that producing a narrative account of published work would be feasible but that extracting coefficients (in the second matrix) in a formal or mathematical way would be difficult because the available papers use a wide range of methodologies. 4.3 Asthma Report 27. Dr Robert Maynard introduced this item. 28. It was noted that questions to be discussed in this report were:
29. Members were informed that a first paper focusing on atopic (allergic) asthma had been written by the Secretariat. It was noted that this paper discussed the role that air pollution plays in the development of this form of asthma. The Secretariat had attempted to look at the logic and assertions behind the evidence on this, for example: countries with high levels of air pollution should also be expected to have high levels of asthma - not true; or, as air pollution declines, then asthma should decline - not true. The draft report attempts to be clear about such assertions. 30. The Secretariat commented that the document also outlines the various stages (from genome to patient) at which air pollution could be playing a part. It was pointed out that the mechanistic evidence suggested that a link between air pollutants and the causation of allergic (atopic) asthma was plausible but that epidemiological evidence to support this was weak. 31. Members pointed out that this was a rapidly developing field and that the American Academy of Allergy, Asthma and Immunology had devoted time to a discussion in this area. Dr Louise Newport asked for the House of Lords report on allergy to be considered by the Committee (House of Lords (2007). Allergy. London: The Stationery Office). This suggestion was supported by Members. It was suggested that the topic of air pollution and asthma should be raised at a British Thoracic Society meeting. It was noted that the Chairman was asked by the British Thoracic Society to give a presentation at its winter meeting on whether the environment contributes to the prevalence of asthma. [ACTION: Secretariat; Chairman] 32. It was agreed that the Secretariat and Members should press on with this report - it had already been delayed for some time. Members stressed the need to raise the profile of this topic and a possible role for improved education and communication was suggested. The Secretariat pointed out that the draft report focused on trying to determine whether air pollution played a significant or substantial role in the causation of asthma. It was argued that proving that air pollution played a minor role would be very difficult. 4.4 Statement from the Subgroup on Air Pollution and Children's Health and Development 33. This item was introduced by Dr Maynard. 34. The following progress was reported: (i) A comprehensive search of the literature that had appeared since the WHO report on Air Pollution and Children's Health and Development had been undertaken. (ii) Professor Holgate had updated the chapter on mechanisms from the WHO report. (iii) Professor Vicki Stone had agreed to review recent work on neuro-behavioural effects of air pollutants. (iv) Professor Roy Harrison had agreed to review recent work on air pollutants and childhood cancer. 35. It was noted that nothing to weaken the conclusions of the WHO report had yet been discovered. Some strengthening of the evidence regarding effects in the fetal and perinatal periods of development was noted. It was agreed that an amended statement (a draft had been seen by Members) would be put to COMEAP at the June meeting. When agreed, this would be placed, along with the literature search, on the COMEAP website. [ACTION: Secretariat]
36. Members agreed with the findings of the report and stressed the need for additional resources. That COMEAP provided excellent value for a modest outlay was agreed. A response from DH to a letter drawing attention to the findings of the report from the Chairman had been received. This was disappointing regarding extra funding: providing extra funds for a specific area (extra to the DH allocation to HPA as a whole) appeared to be considered as unfeasible. An uplift of funding to HPA as a whole had been provided by DH for the financial year 2008-2009. 37. It was agreed by Members that the current approach to funding did not easily allow for rapidly expanding areas: the Chairman agreed to take this up with HPA. [ACTION: Chairman] 37a. It was noted that, despite the impression in the report of the review in paragraphs 3.2-3.3 and recommendation 4, the merger of COMEAP with the Expert Panel on Air Quality Standards (EPAQS) had not yet occurred. 38. Points regarding the COMEAP website were raised. It was agreed that these would be addressed by the Secretariat. It was also mentioned that there were plans to update the Handbook on Air Pollution and Health. Dr Tim King agreed to help with this. [ACTION: Secretariat, Dr Tim King]
39. This item was introduced by Dr Robert Maynard. Members noted the points made in COMEAP/2008/02 but disagreed with the suggestion that experts from specialised areas should be co-opted. It was felt that there was a need to involve experts from fields such as cardiology and paediatrics more deeply as full members of the Committee. It was agreed that funding in the UK was currently not sufficient to build up a significant cadre of research workers interested primarily in air pollution and health and thus Members with other mainstream interests would be needed. It was noted that interest in the air pollution field was developing in the specialties of cardiology and allergic diseases. A number of ideas for improving the level of interest in the area and thus the number of potential applicants for members of the Committee were put forward: (i) Current Members should seek to interest other members of their specialties in the air pollution field. [ACTION: MEMBERS] (ii) The MRC should be encouraged to show an increased interest in environmental issues. [ACTION: Chairman] (iii)
Active recruiting should be undertaken: it was doubted whether the current approach
of advertising vacancies was sufficient. (v) Open meetings to demonstrate the importance of the work that goes into developing COMEAP's advice might be organised. This might be of interest to both members of professional bodies (potential applicants) and to local authorities that use COMEAP advice. (vi) Outsourcing of work to experts outside the Committee should be considered. 40. Members noted that the approach being taken by universities to staff providing time, without payment, to Government work was changing. It was increasingly difficult to justify this. It was also noted that younger research workers might not apply to become members on the grounds that they might feel that they would be unlikely to be appointed. The need to encourage younger research workers to apply was agreed and Members were asked to take this up with their younger colleagues. The Secretariat undertook to consider the above suggestions and to propose ways forward. [ACTION: Secretariat]
41. Dr Pat Saunders introduced this item. It was noted that COMEAP's statement on this topic had been helpful in reassuring the public regarding their concerns. However, there were issues arising (from the public) regarding other substitute fuels that had not been previously commented on by the Committee. Dr Saunders pointed out that all cement kilns in the UK (save one) were now using refuse-derived fuels: these varied from plant to plant as did the combinations of fuels used. He noted that a large amount of data had been provided to Members and thanked Professor Roy Harrison and John Isherwood (EA) for their assistance. 42. Dr Derwent declared an interest in this area. He went on to express concern about producing generic advice on the grounds that new fuels, new combinations of fuels and proportions of new fuels to conventional fuels such as coke/coal could vary. Of these, he was least concerned about new combinations of fuels. Predicting emissions in the face of such uncertainty was likely to be difficult. He also expressed concerns regarding the processing of waste-derived material before it was used as fuel in cement kilns. A specific point regarding cadmium from batteries was raised. Batteries are, in fact, unlikely to appear in the fuel because of pre-use processing. 42a. The Committee was informed that it was unlikely that any new fuels would appear beyond the two considered in the last COMEAP statement and the three considered in the current paper. 43. Hadyn Jones (EA) addressed the point about percentage substitution. This was defined by the EC Waste Incineration Directive: up to 40% thermal substitution is allowed under the rules applying to cement kilns burning substitute fuels. It was noted that if more than 40% thermal substitution occurred, tighter limits on emissions are imposed (as per waste incinerators). This had the effect of limiting fuel substitution by operators of cement kilns. 44. A number of specific points were discussed. (i) Of the many possible substitute fuels, COMEAP was now being asked to advise on only those referred to in the papers provided. It was agreed that going beyond the data provided was not advisable. (ii) Members noted, with some concern, data on emissions of PAH compounds. It was pointed out that ground level concentrations of PAH compounds were unlikely to be significantly affected by the emissions recorded. (iii) Emissions of metals were noted.
The origin of metals appearing in the emissions was agreed to be difficult to
identify: processed household waste was seen as a possible source. Some discussion
of zinc as a potentially toxicologically active component of particles followed*
. It was noted that zinc was a cause of metal fume fever and that US work had
identified zinc as an active component of the ambient aerosol. It was agreed that
emissions of zinc and other metals at the rates specified in the data provided
were unlikely to be injurious to health. (iv) The EA had presented a paper in which they recommended compositional limits for pollutant substances and pollutant precursors in alternative fuels. There was some discussion regarding ensuring that analysis of non-homogenous waste did not miss areas of input materials with higher concentrations. The Environment Agency had standard protocols to address this and a CEN standard was being developed. (v) Members expressed some concerns about peaks in concentrations of some metals in emissions. The use of averaged concentrations was acknowledged as limited in that peaks would be lost in the averaging process. (vi) It was noted that a proportion of potentially toxicologically active materials produced in cement kilns were combined with solid material in the kiln and not released to the air. The trend towards installation of more efficient abatement plant to cement works was to be welcomed. 45. In conclusion it was agreed that: (i) The data provided in Dr Saunder's paper were reassuring. (ii) In regard to the 3 substitute fuels considered: MBM (meat and bone meal), processed sewage pellets (PSP) and refuse-derived fuel (RDF), it was agreed that as long as the thermal substitution rate was held at below 40%, no changes in emissions likely to be significant as regards effects on health were likely to occur. (iii) The above conclusion was subject to the process and inputs being effectively managed to ensure that the appropriate limits were met. 46. In answer to the questions posed in the paper provided:
Members were able to reply affirmatively to the first and second questions; the third was thus irrelevant. 47.
It was agreed that the Secretariat would draft a statement to this effect and
that this would be agreed with Members by correspondence. It was agreed that the
statement would make clear that the conclusions applied to stack emissions not
fugitive emissions and to stack emissions from the kiln not other stacks on site. 48 .Mr Richard Mohan (HPA CHaPD, London) introduced this paper. He pointed out that there had been a perception that had meteorological conditions been less favourable, the Buncefield fire could have led to significantly higher levels of pollutants in London that had actually been recorded. Modelling had been undertaken to explore this. Calculations based on ground level concentrations of particles that might have been produced under "worst case" meteorological conditions in 2005 had been undertaken: the results were given in the paper provided (COMEAP/2008/04). 49. A number of points were raised in discussion. 50. The modelling exercise used the NAME model. This was accepted as State of the Art for long range modelling but Members asked about its reliability for short-range urban dispersion modelling. It was noted that HPA (CHaPD) was undertaking work in this area. 51. Calculations of health impacts had been done for background concentrations (PM10) above 6 µg/m3, this figure being identified as the non-anthropogenic component of PM10. The Secretariat queried whether the output of the NAME model should be regarded as equivalent to gravimetric or to TEOM measurements. It was explained that modelling had led to predictions of concentrations that would equate with gravimetric measurements. The predicted particle concentrations in the paper would therefore need to be divided by 1.3 to produce values equivalent to those (TEOM) measurements that were used in the method used to calculate deaths brought forward in the QUARK I report. These functions had been recommended by Members for use in quantification of effects work in 1998. 52. The question of using coefficients based on distributed lags was raised. It was noted that the method used (single day lag structure) "picked up" effects over more than one day and that extended time periods for distributed lags increased potential uncertainties due to contributions from other factors. 53. It was accepted that had a distributed lag approach been used somewhat larger effect estimates might have been calculated. It was agreed that this should be noted in the final copy of the paper. [ACTION: Secretariat] 54. It was noted that in comparison with the effects of the London smogs of the 1950's the effects of the Buncefield fire, even under worst case meteorological conditions, were small. This was due to the Buncefield plume being notably hot in comparison with smoke from domestic chimneys and the fact that it was a single source - not a widely distributed mass of sources. It was agreed that the dispersion of a cooler plume might have been different from that of the Buncefield plume. 55. Members discussed the use of the effects on
health of cold winter days as a comparator for the effects of the Buncefield fire.
Some felt that the longer lag for the effects of cold complicated the comparison.
Others still felt it was helpful. It was agreed that, if a comparison with the
effects of cold winter days was not done, then some other comparisons to put the
results in context should be done. Suggestions included a comparison with the
normal daily fluctuations in PM10 in August and a comparison with total deaths
in the relevant period. 55a. HPA London agreed
to acknowledge COMEAP for its comments in the final version of the report. ITEM 9. PRESENTATION OF RESULTS OF PARTICLE NUMBERS PROJECT FROM DR RICHARD ATKINSON 56. Dr Richard Atkinson presented preliminary results from a large time-series study being funded by DEFRA. The study looked at a range of indices of particulate air pollutants including particle number concentrations. As expected, particle concentrations were found to be associated with health endpoints (deaths and hospital admissions). Using the interquartile range as a basis for expressing effects (per interquartile range) particle number appeared more strongly associated with health effects than mass concentrations. This provides some support for the theory that the smaller components of the ambient aerosol may be most significantly active in toxicological terms. Particle number concentrations appeared to be only moderately well correlated with mass measurements, PM10. It was noted that correlations between other indices of particulate air pollution (coarse particles (PM10-PM2.5), sulphate and nitrate) and health endpoints varied and needed further study. Another element of the work involved consideration of correlations between home indoor; home outdoor and monitoring site particle concentrations. These correlations were weaker for particle numbers than for PM2.5 or PM10. Dr Atkinson said that he would be presenting the time-series work at the Annual Air Pollution meeting in Cranfield in April and that it was intended that the work should be submitted for publication. 56a. The Committee agreed
with a suggestion to have a presentation on another DEFRA funded project (on oxidative
potential of particles) at a future meeting. The Secretariat also offered to circulate
a figure showing ST segment depression in response to exposure to diesel soot. ITEM 10. MILLER ET AL (2007). LONG-TERM EXPOSURE TO AIR POLLUTION AND INCIDENCE OF CARDIOVASCULAR EVENTS IN WOMEN - POSSIBLE REASONS FOR LARGE COEFFICIENT (COMEAP/2008/05) 57. Dr Heather Walton introduced this item, reminding Members that they had discussed the study by Miller et al (2007) at the February 2007 meeting. She explained that the study had reported a strikingly large coefficient of a 76% increase in the risk of death from cardiovascular disease (hazard ratio, 1.76; 95% CI, 1.25 to 2.47) per 10 µg/m3 increase in PM2.5 amongst women > 50 years of age. As requested, the Secretariat had produced: a list of possible reasons for the large coefficient based on the discussion at the meeting; correspondence in response to the published article; and a letter from Professor Philip Poole-Wilson. The reasons covered in the paper were:
58. Dr Walton said that as these reasons were almost all speculative, the Secretariat found it difficult to propose a ranking of the reasons although some qualitative comments had been made. The Committee was invited to comment on the collated list of reasons and on the feasibility of ranking them by likelihood. 59. Dr Walton went on to draw attention to some further material which had been provided for consideration. The Secretariat had asked the Institute of Occupational Medicine (IOM) to undertake some life-table runs using the 76% coefficient for cardiovascular mortality assuming only women aged 50-79 without heart disease were susceptible. The results were only slightly lower than the standard result using the 6% coefficient despite the fact that this covers mortality from all causes and a wider population of all adults over 30. This suggests that the first reason listed above (elderly women without heart disease are particularly susceptible) is not sufficient on its own to explain the higher coefficient. 60. In addition, a series of tables summarising separate results for men and women in the ACS study and the Six Cities study were also provided. She noted that the key points were:
Thus, Dr Walton concluded that although there was some indication from these key cohort studies that women were more affected than men, this was not entirely consistent. Members' comments were welcomed. 61. A number of points were raised in discussion. 62. The study was statistically and epidemiologically strong. The large within-cities hazard ratio for cardiovascular deaths (about 2) was reassuring as it was less likely that a hazard ratio this large could be explained by residual confounding. However, on examination of Table 2 of the paper by Miller et al (2007), it was noted that the 10th-90th percentile range of the difference between individual exposure and citywide average exposure was of the order of 3 µg/m3. The within-cities hazard ratio for cardiovascular deaths of 2.28, expressed as per 10 µg/m3 PM2.5 could thus be regarded as inflated and might be misleading regarding the possibility of the effect being explained by residual confounding. 63. Members suggested that more focus should be given to the hazard ratios for cardiovascular events as these were based on larger numbers. These hazard ratios were not as large as those for cardiovascular mortality. The lack of information on total mortality was seen as a drawback to interpretation. 64. Members noted that even within the metropolitan areas studied, monitors could be as far as 30 miles from subjects' homes. 64a. This raised concerns about local factors affecting diagnosis and it was noted that little was said of distribution of health care within metropolitan areas. 64b. It was noted that a major potential reason for the high results was chance. 65. It was agreed that the study had reported an unusually large effect but that there were a number of reasons to be cautious about accepting the findings as a basis for impact calculations, for example, in the UK. Confirmation by other workers would be welcome. It was also agreed that Mr Armstrong, Dr Atkinson and the Secretariat should clarify points regarding the discussion of 10th-90th percentile ranges and Hazard Ratios by email. [ACTION:
Secretariat] 66. Calls for research on carbon monoxide, air pollution and nanotoxicology were noted. The Secretariat noted the work of the DH colleagues in securing funding for the work. ITEM 12. DATE OF NEXT MEETING 67. The following date was noted: Annual
Air Pollution meeting in Cranfield 15-16th April 2008.
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