Chairman: Professor J G Ayres
Members: Ms A Baker, Prof P Matthiessen, Prof C Brown, Dr M McPherson, Prof G Hawksworth, Prof C Ockleford, Ms R Howell, Dr D Osborn, Dr A Leake, Prof J Parry, Prof L Maltby, Dr H Rees
Assessors: Ms G Asbury (FSA), Dr S Jess (AFBINI/DARDNI), Mr D Bench (PSD), Mr M Williams (WAG), Dr C Griffiths (SASA)
Advisers: Mr R Davis (PSD), Mr B Maycock (FSA), Dr L Hetherington (HPA), Dr R Turner (HSE)
Secretariat: Ms J Wilder (PSD) Secretary, Mr P Fisher (PSD) Minutes secretary, Ms A MacGregor (PSD) Secretariat
Visitors: Prof David Kirkland (Covance Laboratories Ltd). For agenda item 4, minutes section 6, Dr Peter Batten (JSC International Ltd). For agenda item 4, minutes section 6, Dr Alan Buckle Reading University. For agenda item 7, minutes section 9
Other attendees: Dr R Brown (PSD), Dr D Stenhouse (CASU), Mr H Dawick (PSD), Mr S Swinton (PSD), Mrs E Jenkins (PSD), Mr M Tilbrook (PSD), Mrs J Smith (PSD), Mr A Warburton (PSD)
1.1 Apologies were received from: Dr J Cherrie, Prof C V Howard, Dr W Parker, Dr A Povey, Dr D Ray, Mr S Dyer (DH), Mr J Battershill (HPA), Dr T Boucard (EA), Dr M Camlin (AFBINI/ DARDNI), Dr K Wilson (PSD).
2.1The Chairman reminded Members of the confidentiality of the papers and their discussions. If Members believed that they had a commercial or financial interest in any of the items being discussed, they should declare their interest as soon as the meeting moved on to that agenda item. They would then not take part in the discussion, nor would they be involved in any decision taking, unless invited to do so by the Chairman.
2.2 The Chairman welcomed Mr Bench attending his first meeting as the Defra assessor
3. Agenda item 1:
3.1 a) 331st Meeting: Minutes [ACP 1 (333/2008)]
3.1.1 Agreed subject to a punctuation change.
3.2 b) 331st Meeting: Detailed record of discussion [ACP 2(333/2008)]
3.2.1 Agreed subject to minor amendments.
4. Agenda item 2: Secretary’s report [ACP 3 (333/2008)]
4.1The Secretary to the Committee reported that Ministers had accepted the advice given since the previous meeting.
5. Agenda item 3: Matters arising
5.1 Other Matters Arising [ACP 5 (333/2007)]
5.1.1 Members noted the progress on other matters arising from previous meetings. The Secretary added that since drafting the paper, agreement had been reached on a referral statement for aclonifen to be considered by the Committee on Mutagenicity.
5.1.2 Members clarified that the questionnaire on access to ACP information was to be updated and re-distributed at the next open meeting and on the website
5.1.3 Members heard that Ministerial agreement to the publication of the 2007 annual report was still awaited.
6. Agenda Item 4: Ethaboxam [ACP 10 (333/2008)]
6.1 Members recalled that ethaboxam is a new fungicide proposed for use in control of downy mildew on grapes. The Committee had first considered an application for approval in September 2005 where a number of issues had been identified. These had all been discussed and resolved during meetings held in 2005, 2006 and 2007. The paper for consideration at this meeting presented the outstanding data required to address the outstanding questions about aneugenicity. Aneugenicity was an important matter for consideration in risk assessment.
6.2 Members confirmed that ethaboxam had been shown to be an aneugen with clear positive findings in both in vitro and in vivo studies. Tests for chromosome breakage were negative. Aneugenicity was known to be subject to a dose response and there would therefore be possible to identify a no observed effect level.
6.3 At present the data available on aneugenicity were all in somatic cells. However there was good evidence that ethaboxam reaches the germ cells because there were effects in the testis and on sperm in the multigeneration data. Leydig cell tumours were also formed. The Committee’s initial thoughts were that a no effect level would also be required for germ cells, as there were no data on the possible effect on meiosis.
6.4 Members also noted that the no effect level for non-disjunction had been estimated by a calculation based on the ratio of no effect levels for non-disjunction and aneugenicity from in vitro data.
6.5 Finally members noted that there is some evidence in the literature that humans may be more sensitive to some aneugens than rodents.
6.6 Members observed that the company had suggested that an assessment factor of 40 could be supported in this case because there was evidence that the toxico-dynamics did not differ between species. Although the Committee considered that assessment factors could be reduced from the standard 100 where appropriate data were available, the data available for ethaboxam would not usually be considered sufficient to support a reduced assessment factor.
6.7 A further point of possible uncertainty had been highlighted in that the NOEL for aneugenicity identified in the two in vitro studies differed, with the more recent study suggesting the higher value. The reason for the difference was not clear from the papers.
6.8 Members noted that the in vivo studies for aneugenicity were in the mouse rather than the rat because rats can suppress micronuclei via a different mechanism involving the spleen.
6..9 The Committee having identified these points to clarify with the applicants, the company representatives were invited to join the meeting.
6.10 The company summarised the original genotoxicity package where structural aberrations had first been identified, but where the impact of toxicity on the cells had been unclear. During the next stage of investigation, micronuclei had been induced in human lymphocytes at low concentrations and the positive centromere probing confirmed the presence of whole chromosomes in the micronucleus and thus provided clear evidence for aneugenicity. The applicant therefore set out to try and identify a NOEL.
6.11 The company explained that at low concentrations of aneugens such as ethaboxam, there is no damage to the spindle, so cell division proceeds normally. As the concentration increases modest damage occurs to the spindle and chromosomes might thus move to the wrong pole resulting in uneven distribution of the chromosomes to the two nuclei, but no micronucleus formation. This is known as non-disjunction or malsegregation. At yet higher doses the spindle is damaged more severely and as a result the chromosomes cannot attach properly, resulting in the formation of micronuclei. Thus the company had concluded that non-disjunction was the more critical effect for which to seek a NOEL.
6.12 The company had also noted that the literature suggested that there were other physiological effects that could also result in formation of micronucleus in vivo. For example, haematotoxicity could induce micronuclei in bone marrow, but they were seen at a later sampling time. It was thus important to demonstrate that the in vivo effects were caused by the same aneugenic mechanism as had been demonstrated in vitro.
6.13 The NOEL for non-disjunction was identified as 6-7µg/ml and the threshold for micronucleus induction was identified as 8-9µg/ml in the new in vitro study.
6.14 The new bone marrow micronucleus study included more doses. The need to repeat the high dose known to induce micronuclei in vivo required specific permission, because this dose was also known to be lethal to a proportion of the mice. The number of animals in each dose group was increased to give the study greater statistical power and samples were taken at both 24 and 48 hours. Micronuclei in blood were identified using flow cytometry. Both plasma and bone marrow were sampled, body temperature measured and samples were checked for possible effects from erythroprotein (EPO) to identify the possibility of micronucleus formation due to haematotoxicity. Micronuclei were increased in the 300 mg/kg dose group in the 24 hour sample, but not in the 48 hour sample and there were no significant body temperature changes, so the company were able to rule out possible physiological causes of the micronuclei. The NOEL was identified in this study as 250 mg/kg .
6.15 In order to determine whether the micronuclei seen at 300 mg/kg were the result of toxicity (as that dose was known to be lethal to mice), positive controls were included in the study; a known aneugen and a known clastogen. These samples were tested using a centromere probe. Positive responses were found in ethaboxam samples very similar to those found in the aneugen samples. The clastogen control delivered clearly different responses, thus enabling a conclusion that the micronucleus effects in the bone marrow micronucleus study were likely to be caused by the same aneugenic mechanism as shown in the in vitro studies. The ratio between NOELs for non-disjunction and micronucleus induction determined in the in vitro studies were therefore used to calculate a NOEL for non-disjunction from the in vivo NOEL for micronucleus induction.
6.16 The ACP noted the toxicity seen at the high dose tested in vivo and commented that a spermatogonia study that had just arrived but had not yet been evaluated used a higher dose without the same level of toxicity. The Committee sought clarification as to whether that study had used the same sample of ethaboxam. The company responded that they didn’t have that information. There were however a number of possible variables that could affect the results of studies such as these.
6.17 The ACP asked whether there was an explanation for the finding that in about 20% of cells where micronuclei were found, non-disjunction had not been demonstrated. The company explained that the centromere probe is specific for a gene sequence in the centromere. It was therefore possible that a whole chromosome could be present without that sequence and hence not be found. It was also known that micronuclei do occur spontaneously. The precise cause of the finding was therefore not known but was not considered significant for the risk assessment.
6.18 The Committee then asked whether it can be assumed that the responses seen in somatic cells are transferable to germ cells. The company considered this likely if the doses of aneugen reaching the germ cells were high enough. The company confirmed that it was not known whether there might be a lower threshold for an effect on meiosis, but there did not seem to be an obvious biological reason why the meiotic spindle should be more sensitive than the mitotic spindle. The Committee therefore asked whether the company had considered doing a micronucleus study using spermatids. They confirmed that ideally it should be done but they were not aware of any laboratories capable of doing such a study.
6.19 Having clarified these points the Committee thanked the company for their presentation and the company representatives left the meeting.
6.20 The Committee agreed that it was unlikely to be possible to obtain a clear NOEL for non-disjunction in vivo. However it would be helpful to have a study similar to the mouse bone marrow micronucleus study but considering spermatids to see whether there was any difference in NOELs between somatic and germ cells. Although the concern would be greater for critical effects in the embryo from female germ cells it was accepted that it was easier to study the male germ cells where effects would be multiplied. Whilst this was by no means a standard study, it should be possible to identify someone who could undertake the work. It would also be useful for the company to check the published literature to see whether there was any evidence of greater sensitivity to aneugens in germ cells. If it was clear from this further work that the germ cells were not more sensitive than somatic cells it would be possible to use the threshold currently identified for regulatory purposes.
Action: PSD to check the regulatory data provided for the known aneugens benomyl, carbendazim and thiophanate methyl
6.21 Members confirmed that there was no reason to reduce the standard 100 assessment factor in this case. In the absence of further clarification on sensitivity of germ cells a safety factor could not be agreed. Members commented that a safety factor greater than 100 maybe required (depending on the results from the germ cell study). Members noted that the estimates of exposure provided to date indicated exposures would be above the acceptable level for table grapes if a 100 assessment factor were used, although it was accepted that there might be some further scope to refine the exposure estimates with further data.
6.22 Members therefore confirmed that approval could not be recommended at this stage for ethaboxam.
7.Agenda item 5: HSE Report into operator and worker exposure arising from the use of Alpha C 6ED [ACP 11 (333/2008)]
7.1 Members heard that this paper summarised the results of an HSE study of forestry contractors which had been set up following reports of ill health (including paraesthesiae) in forestry workers involved in treating or planting alpha-cypermethrin treated saplings. Members heard that this is the sole treatment approved in the UK for electrodyne treatment of saplings to control insect pests, specifically Hylobius abietis and Hylastes spp.
7.2 Paraesthesia is a well known effect of acute exposure to pyrethroid insecticides. Members confirmed that there are no known long term effects arising from exposures that result in paraesthesia.
7.3 Members noted written comments on the exposure study. These identified that as both an electrodyne operator and planters experienced the same symptoms it was suggestive that hand to face contact played some role in the exposure. Thus the suggestion of a visor to prevent splash-exposure was unlikely to prevent the problem. Similarly the suggestion of adding a coloured dye to the formulation would rely on an operator noticing the colouration and washing promptly. One of the major problems in the forestry planting environment was the difficulty in supplying appropriate washing/welfare provision in these remote environments. It was noted that oral absorption of alpha-cypermethrin may have been important in producing paraesthesia, but the study had not included any measures of urinary metabolites, so the contribution of this mode of absorption remained unknown.
7.4 Members noted that the formulation was solvent-based and suggested that there should be adequate ‘drying’ time allowed after the bags were opened before the treated saplings were handled. HSE noted that the working practice guidance notes already required such a ventilation period, but the nature of the work, essentially piece-work, put pressure on compliance with this guidance. Further written comments suggested using biodegradable wrappers to avoid the need to handle the saplings directly, but members concluded that as trees were not wrapped individually this would be impractical.
7.5 HSE commented that the nature of forestry work, planting trees as ‘piece-work’ was heavy and strenuous meaning the workers were often sweaty, which would increase absorption from contaminated skin. The locations were remote so there were often no facilities for workers to wash before eating etc. Also, the workforce turned-over relatively quickly, making training difficult.. These conditions indicated that there was potential for poor work practices, continued skin exposure and adverse effects. It is important to make further efforts to deliver appropriate supervision and training and to improve working practices.
7.6 Members agreed that approvals for this use could continue unamended, but that the need to comply with good working practices needed to be re-enforced to the industry. The Chairman therefore agreed to write to the Forestry Commission and to private Forestry companies to re-enforce the importance of compliance with the current guidance on forestry working practices to improve operator protection.
Action: Chairman to write to the forestry industry
8. Agenda item 6: Thiamethoxam Monitoring Data [ACP 9 (333/2008)]
8.1 Prof Brown declared a non-personal specific interest in this item and took no part in the discussion.
8.2 Members heard that two wildlife monitoring studies had been completed as requested by the Committee at their meeting 319 held on 9 May 2006.
8.3 Members agreed that there was no need for further data on birds. However weather conditions had led to planting of the fields due to be used for the mammal monitoring out of time with the planned monitoring programme. As a result few mammals had been found. Members agreed that this monitoring study should be repeated. If any dead mice were found in the trial they should be analysed for thiamethoxam.
8.4 Members commented that relatively few birds had been analysed and the criteria for decisions on analysis were not particularly clear. They recommended that for future such trials consideration should be given to requiring analysis of a defined sample. Members recognised that this might increase costs slightly but felt that the major overheads for such trials were involved in searching for any carcasses and in setting up the analysis. Additional samples would therefore not be expected to add significantly to the overall cost.
9. Agenda item 7: An application for an experimental efficacy trial involving outdoor use of Brodifacoum in an area of second-generation anticoagulant resistance [ACP 19 (333/2008)]
9.1 Members heard that this application had been sent by email ahead of the meeting to environmental members of the committee who had concluded that it needed to be considered at this meeting. Brodifacoum is an approved rodenticide in the UK, but is restricted to indoor use due to the risk to non-target wildlife. As such this experimental trial which would use brodifacoum outdoors required a specific approval.
9.2 Members confirmed first that an experimental approval does not have to fulfil a particular regulatory need as a pre-requisite.
9.3 Members noted that open bait boxes were proposed for use in the trial, where possible and they asked whether this would pose a particular risk to any children that were in the area. HSE confirmed that the boxes were to be covered using natural cover, so that the rodents were not inhibited from accessing the bait, and this type of baiting did not pose any increased risk to children beyond that posed by other approved anti-coagulant rodenticides that have approval for this type of use.
9.4 Dr Buckle, representing the applicant, then joined the meeting. He explained that this proposed study was one of a series being undertaken across Europe. The key aim of the study was to address the relationship between practical resistance to rodenticides in the field and resistance factors. The Berkshire population to be targeted in this trial was of particular interest because the resistance factors of that population were the highest yet identified in the world. He explained that resistance factors are determined by the ratio of LD50s of the resistant strain to the susceptible strain. If the resistance factor of a population exceeds about 5 or 7 there is practical resistance experienced under field conditions.
9.5 Whilst the resistance factors were based on laboratory data, there were additional factors in the field that were important in determining efficacy. These included potency, bait palatability and ‘take’, and the use pattern of the rodenticide, all of which interacted in determining the practical outcome. Less potent second-generation anticoagulants are surplus baited to ensure a lethal dose was consumed over a period of bait take, but brodifacoum is made available in small quantities in pulsed baiting. Pulse baiting makes use of the increased potency of brodifacoum and at the same time reduces the quantity available to non-target organisms. Rats were likely to take a lethal dose of brodifacoum in a single feed.
9.6 Members asked whether this type of work could be examined in a pen or cage trial which would not carry the same environmental risk as a field trial. The applicant responded that it is difficult to undertake this type of work in caged trials. It would require a very large cage, and they were aware of only one that would be suitable in the UK. It was difficult to get replication and it was difficult to be sure that rats exhibited natural behaviour in a caged environment. The trials proposed were efficacy trials that complied with the latest EU guidance for trials with rodenticide baits and with current HSE guidance. The wildlife surveillance included in the trial was not designed to provide robust data on the non-target impact that might stem from outdoor use of brodifacoum, but rather as a means of alerting the operators to any developing environmental problems before they become serious. The relative risk to the environment from use of brodifacoum in this trial might not be greater than that from the use of other rodenticides as a lower dose was used.
9.7 Members noted that this was an efficacy trial and sought clarification as to whether rats could determine whether the bait used included the rodenticide and thus avoid it. The applicant confirmed that all rodenticides are supported by palatability trials before approval and thus in the field trial bait takes should be acceptable.
9.8 Members next asked whether the type of bait was the same for all three rodenticides included in this series of trials. The applicant confirmed that the trial was using approved products so there were some slight differences. For example the difenacoum product was a pelleted bait but these were a different colour to the brodifacoum pellets. The trials proposed using products that had been selected to be a similar as possible.
9.9 Members clarified whether the same baiting method was to be used for all of the rodenticides in the trial. The applicant confirmed that baiting practice would be in line with approved label directions, with the exception of the use outdoors of brodifacoum. Thus brodifacoum would be pulse baited whilst the other anti-coagulants being used would be surplus baited if this were the current label advice.
9.10 Members concluded that it was already known that there was resistance in the test population, and that rats would take the poisoned bait, so the efficacy of the application would depend upon how much bait needed to be taken in order to estimate a critical level for control. This information was already available without the need for this trial. The applicant clarified that as efficacy in the field was a combination of factors, this was as yet unknown. Members suggested that a non-poisoned feeding trial might provide the missing information without any risk to non-target organisms. The Applicant explained that such a trial would result only in a plateau in rat numbers feeding from the non-poisoned bait being provided. Since there would be no mortality resulting from the trial, nothing useful would be learnt.
9.11 Members then sought clarification as to how the trial could determine the number of rats taking from each bait station. The applicant clarified that bait was weighed and tracking was used around the bait stations so as to monitor activity. Bait take and activity was compared before and after the trial and in a small trial of this type it was hoped that 100% mortality would be achieved. Members concluded that it was not possible to determine from this approach how much bait per rat had been required to kill the rats.
9.12 Returning to the known data on resistance factors members clarified that both Hants and Berks rats had the Leu120Glu mutation, which was assumed to be a functional mutation of vitamin K reductase. The applicant confirmed this and added that it was suspected from the difference in resistance factors between the two strains that the Berks rats also had another mutation, but this had not yet been identified. Members commented that as it was not yet possible to clearly distinguish the genetics of the two strains it would be advisable to clarify this aspect before progressing to field trials.
9.13 Members noted that resistance has been a problem in the Berkshire/Hampshire area for many years and wondered if there were other compounding factors peculiar to this region, such as poorer than normal husbandry. Members suspected that using brodifacoum outdoors in this area could ultimately result in resistance to this compound as well. There was concern about the trial going ahead at infested sites that were subject to poor husbandry. The Applicant explained that the trial would seek discrete sites but would not improve husbandry before treatment so as to reduce the risks of scattering the resident rat population and reducing bait take. The Applicant added that in order to secure adequate results from an efficacy field trial, the infestation present at the start must be sufficiently high. The Applicant noted that it was always the case that rats are present in any environment for a reason and that good husbandry would always reduce populations. It was thus planned to do the trial in an area with a relatively high population and then advise the occupier on how to clear and maintain the area to reduce reinfestation. Members asked about the rate of baiting proposed for the trial. The applicant confirmed that the trial was to use only label recommended levels of the rodenticide.
9.14 Members noted written comments expressing some concern about the statistical power of the trials proposed. The applicant explained that restricting the trial to two sites was an attempt to both minimise the possible environmental concerns and to meet the European Commission guidance that 2-3 sites were required. They were anticipating findings would demonstrate failure of control for the compound to which the rats were resistant and 100% control from the brodifacoum. Members concluded that the issue of the statistical power of the study would be well addressed in this case by the consideration of the University ethics committee.
9.15 Having explored these questions the ACP thanked the applicant and he left the room.
9.16 Members observed that brodifacoum was not approved for use outdoors in the UK and despite the steps taken to mitigate the risk to non-target wildlife it was clear that some risk would remain. Members agreed that the potential environmental damage from the trial was likely to be localised and small-scale, but species likely to be affected might well raise public concern. It was clear that a cage or pen trial with resistant rats would be difficult, but it was not clear what additional scientific benefit could be gained from the field trial. There has been a historical concern about control of rodents in the Hants/Berks area, and members agreed that brodifacoum would be expected to offer control of the rats, but it was the Members' view that there was a likelihood of consequent impact on non-target wildlife.
9.17 The Committee accepted that this application was for a small scale trial only and should not be seen as a preliminary to an application for more general outdoor use. However, they concluded that the likely scientific benefit of the trial did not seem sufficient to justify the risk to the local environment. Alternative approaches such as exploring the resistance genetics further and possibly using a cage or pen trial seemed to offer an alternative way forward in understanding the difficult issue of control of the resistant rats in this area. If the applicant wished to pursue a cage trial, members agreed that there was no need for them to consider that application which could be evaluated by CASU staff.
9.18 Members agreed that approval could not be recommended for the outdoor trial of brodifacoum.
10. Item 8: Revision of ACP Publications Scheme [ACP 6 (333/2008)]
10.1 The Secretary explained that the proposed revision of the ACP Publications Scheme was designed to ensure that the scheme was compliant with the model publication scheme approved by the Information Commissioner.
10.2 Members agreed the proposals subject to minor change.
Action: Secretary to amend and arrange publication
11. Item 9: Human Health Strategy Meeting [ACP 7 (333/2008)]
11.1 ACP Members who attended the first Human Health Action Plan Implementation Group meeting held on 23rd July 2008 reported to the Committee on discussions held. Members heard that future meetings are expected to be held about twice a year and an outline programme of activity has been prepared. One area of particular difficulty for this group was expected to be the identification of appropriate indicators as appropriate monitoring data are not readily available. Members noted that this might be an area where the ACP could play an important role in this group.
11.2 Discussion had considered membership of the group and the large numbers of possible sources of input resulted in a conclusion that the group would be best served by a smaller ‘core’ membership with the ability to call on particular specific expertise as required.
11.3 There had been discussion of current residues issues noting both the supermarkets’ own policies which are implemented in addition to the statutory Maximum Residues Levels (MRLs), and attention was drawn to the recent changes in EU arrangements for MRLs which would introduce a large number of new MRLs.
11.4 Results of the pilot access to information study had been discussed and it was likely that this study would be followed up through this group.
11.5 The ‘grandfather rights’ provision for spray operators had recently been the subject of consultations in both England and Wales and Scotland. Respondents to the Scottish consultation had highlighted a possible greater cost associated with the proposed removal of these rights due to the large number of small crofters currently reliant on this approach.
11.6 The Chairman hoped to be able to attend the next meeting.
12. Report from the Medical and Toxicology Panel [ACP 12 (333/2008)]
12.1 The Chair of the Medical and Toxicology Panel gave a verbal report of discussions of the Meeting held on 15th September 2008. The panel had considered the annual overview of published literature for 2007, and noted a possible focus on non-Hodgkins lymphoma. Members had also heard a progress report for the biomonitoring literature survey, noting that only a few papers included both biomonitoring and exposure data. The latest quarterly report from the national poisons information centre had been considered and members had again noted the high proportion of reports relating to amateur uses. They had suggested following these up with the relevant pesticides strategy action plan working groups.
13. Plans for ACP Open Meeting 2008 [ACP 8 (333/2008)]
13.1 Members received a paper outlining proposals for the ACP Open Meeting to be held on 10th November 2008. This was agreed subject to a minor timetabling change, and the extension of the remit for one of the afternoon working groups to include cost-effectiveness.
14. Date of Next Meeting
14.1 ACP 9th Annual Open Meeting Monday 10th November 2008 followed by ACP 334 on Tuesday 11th November 2008, commencing 10.00am, both at the Monk Bar Hotel, York.
15. Any Other Business
15.1 Members considered the items for information received since the last meeting.
J G Ayres