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COMMITTEE ON MUTAGENICITY OF CHEMICALS IN FOOD, CONSUMER PRODUCTS AND THE ENVIRONMENT
Minutes of the meeting held on Thursday 4 February 1999 at 10.30 am, in
Room 136/7B, Skipton House, 80 London Road, Elephant and Castle, London SE1 6LH
Present:
Chairman:
Professor J M Parry
Members:
Professor J Ashby
Dr P E Bryant
Professor D Davies
Professor MHL Green
Dr S Venitt
Secretariat:
Dr R J Fielder (Scientific)
Mr J Battershill (Minutes)
Mr K N Mistry (Administrative)
Assessors:
Mr A Browning (VMD)
Dr J Sims (MCA)
Dr A Smith (HSE)
Dr JP Tromans (Welsh Office)
In attendance
Miss J Andrews (DH)
Professor A Boobis (ICSTM)
Dr C Boyle (DH)
Dr A Davies (MAFF-JFSSG)
Dr J Greig (DH-JFSSG)
Mr G Kowalcyzk (DH)
Mr D Renshaw (DH-JFSSG)
CONTENTS
| Item |
|
Paragraph |
| 1. |
Apologies for absence Announcements |
1-2 |
| 2. |
Minutes for meeting held 15th October 1998 |
3 |
| |
2.1 Conclusions from meeting on 15th October 1998 |
4-5 |
| 3. |
Matters arising not covered by later agenda items |
|
| |
3.1 In-Vitro Micronucleus test |
6 |
| |
3.2 CS Spray |
7 |
| |
3.3 Openness: Press Release |
8 |
| 4. |
Malachite Green |
9-14 |
| 5. |
TCDD |
15-18 |
| 6. |
MCPD (3 Monochloro propane 1,2 diol) |
19-22 |
| 7. |
Ozone/mutational signatures |
23-25 |
| 8. |
Conduct and interpretation of genotoxicity assays 1994-1998 |
26 |
| 9. |
Annual Report 1998 |
27 |
| 10. |
Role of CMO Advisory Committees |
28-29 |
| 11. |
Guidance document for members |
30-31 |
| 12. |
Revision of guidelines |
32 |
| |
12.1 Implications for carcinogenesis |
|
| |
12.2 Genetic diseases in humans |
|
| |
12.3 Monitoring human populations |
|
| |
12.4 Members views on relevant new assays |
|
| |
12.5 Recommended test systems/strategies |
|
| 13. |
Any Other business |
33 |
| 14. |
For Information |
34 |
| |
13.1 Expert Panel report on significance of DNA adducts |
|
| |
13.2 DH paper on Communicating risks to the public on health matters |
|
| |
13.3 Article on flawed statistics |
|
| |
13.4 Improved arrangements for Openness |
|
| |
13.5 Mouse Lymphoma Assay |
|
| 15. |
Date of next meeting: 20th May 1999 |
35 |
ITEM 1: APOLOGIES FOR ABSENCE
1. Apologies for absence were received from Professor Cooper and Professor
Newbold, Dr Shillaker (PSD) and Dr C Fisher (MAFF-JFSSG).
Announcements
2. Members were reminded of the need to declare any interests. The Committee
welcomed back Dr Andrew Smith as the HSE assessor who had spent a period of secondment at the Chemicals Directorate
at Ispra, Italy. Members asked for a short presentation of his work at a future COM meeting.
ITEM 2: MINUTES OF MEETING HELD ON 5 OCTOBER 1998- MUT/MIN/98/3
3. The minutes of the meeting held on 10 October 1998 were agreed subject
to a number of minor typographical amendments.
DRAFT CONCLUSIONS FROM MEETING HELD ON 5 OCTOBER 1998
Comet Assay (Item 5)
4. The conclusions were agreed subject to revision of conclusion iii)
"useful supplementary data on a case by case basis to provide data to complement the in-vitro..."
5. Members heard that a major investigation had recently been completed by a Japanese research group and agreed
to review the results when published in the scientific literature.
ITEM 3: MATTERS ARISING NOT COVERED BY LATER AGENDA ITEMS
In-vitro Micronucleus Assay
6. Members heard that a common position had been reached by the EEMS regarding
the draft protocol for this test. It was hoped that the document would be submitted to the OECD in the very near
future
CS Spray
7. Members were told that the COT had endorsed the COM conclusions at
their meeting of 27 October 1998. The COT would undertake further discussions regarding CS spray during 1999 before
finalising its conclusions.
Openness
8. Members were told that Professor Donaldson (CMO) had issued a press release on the 26 January 1999 announcing
changes to the procedures of the COT/COM/COC which would result in greater openness of Committee business including
the publication of agendas, minutes, conclusions and statements subject to arrangements for dealing with confidential
data. Arrangements had also been put in hand to appoint a lay member to the COM and COC.
ITEM 4: MALACHITE GREEN AND LEUCOMALACHITE GREEN: USE IN FISH FARMING (MUT/99/1)
9. Members heard that malachite green was produced by a number of manufacturers
for use in several industries including the ceramics, paper and pulp and fish farming industries. No interests
were declared.
10. Members noted that malachite green was a cationic triphenylmethane dyestuff and that commercial products often
contained poorly defined mixture. Regarding its use in fish farming, Members observed that malachite green is widely
used in freshwater fisheries for the treatment of various external fungal infections and infestations, its main
use being to stop fungal growth on the eggs. No products containing malachite green have been granted marketing
authorisation by the VMD. However, as malachite green had a long history of use in the fish industry it is permitted
to remain in use unless it could be shown to pose a unacceptable risk to human health. The COT had begun its consideration
of the potential health effects of low level residues of malachite green, and its major conversion product, ie
in trout, leucomalachite green, at its meeting in December 1998. Members of the COT had expressed concerns about
the potential mutagenicity of malachite green and leucomalachite green, particularly in respect of results from
recent NTP 32P post-labelling studies (sub acute) carried out as part of range-finding studies prior to initiating
carcinogenicity bioassays on malachite green and leucomalachite green in rats and mice. The COT have referred the
question of the mutagenicity of malachite green and leucomalachite green to the COM before finalising its advice
on the public health implications of residues in fish.
11. The Committee commented on the paucity of the available mutagenicity data, particularly in respect of leucomalachite
green and agreed it was important to evaluate the potential mutagenicity of both malachite green and its lipophilic
metabolite leucomalachite green. Members noted that results from the 1997 surveillance investigations conducted
for VMD which presented results for leucomalachite green for the first time suggested that, when found, residues
of this chemical were higher in fish than residues of malachite green.
12. Members agreed that the structure of both malachite green and leucomalachite green contained groupings which
were structurally alerting for potential mutagenicity. A positive result was obtained for in-vitro studies using
Salmonella typhimurium TA 98 in the presence of exogenous metabolic activation using S-9. Members agreed that gene
deletions had been reported in Aspergillus nidulans. It was difficult to assess the studies to investigate potential
clastogenicity of malachite green in mammalian cells as the standard of reporting was poor and non-standard protocols
had been used. Members noted that clastogenicity in Chinese hamster lung cells had been documented in the absence
of exogenous metabolic activation at a single high concentration tested of 4 mg/ml, and agreed that this provided
some evidence of mutagenic activity in mammalian cells.
13. The in-vivo micronucleus assay in mice conducted using oral administration of malachite green had been poorly
reported and it was difficult to draw any conclusions. Members agreed that the high dose level of 37.5 mg/kg was
adequate, but it was difficult to assess the value of the negative results in the absence of appropriate information
on systemic toxicity or data to show that malachite green and metabolites reached the bone marrow. Members considered
the recent 32P post-labelling investigations undertaken during 28 day feeding studies in rats and mice, and agreed
that an appropriate enrichment protocol had been used for these studies. The chromatograms available to the committee
provided good evidence that malachite green and leucomalachite green formed DNA adducts in rat liver and evidence
for DNA adducts in mouse liver in animals fed malachite green. Members agreed that no definite conclusions could
be drawn from the results of studies in fish and the cell transformation assays presented to the committee.
14. Members agreed that a statement for the COT should be drafted and circulated to members for comment with agreement
through Chairman's action. The statement would be needed for the COT meeting on the 24/2/99.
ITEM 5: TCDD (MUT /99/2)
15. Members recalled that there were 75 possible chlorinated polychlorinated-para-dioxins
(PCDDs) and 135 possible polychlorinated-para-dibenzofurans (PCDFs), and that a number of these congeners might
be present in small amounts as contaminants in food. The toxicological properties and potencies of PCDDs and PCDFs
could all be related to the known effects 2,3,7,8-TCDD or TCDD (2,3,7,8-tetrachlorodibenzo[b,e][1,4]dioxin) through
the use of toxic equivalency factors (TEFs). The IARC concluded in 1997 that TCDD should be regarded as a known
human carcinogen. Previously it had been classified as 2A (probable human carcinogen). This change in view prompted
the Department of Health to request the COC to review their earlier conclusion. The COC concluded in 1998 that
there were insufficient epidemiological and toxicological data on TCDD to conclude a causal link with cancer in
humans, but it would be prudent to consider TCDD as a 'probable weak human carcinogen'. The IARC working group
concluded that the "experimental data indicated that 2,3,7,8-TCDD and probably other PCDDs and PCDFs are not
direct-acting genotoxic agents and that TCDD is considered a non-genotoxic substance." The previous COM evaluation
of TCDD was completed in 1987 and it is therefore timely for the committee to reconsider its previous conclusions.
The discussion paper Annex 2 to MUT/99/2 presented a review of genotoxicity studies published since 1987 but did
not include investigations on inter-cellular communication and tumour promotion studies. Studies of particular
note had been appended as Annexes 3 and 4 to MUT/99/2.
16. Members agreed that negative results had been obtained in the in-vitro mutagenicity tests conducted in Salmonella
and in L5178Y tk+/tk- cells mouse lymphoma cells. However TCDD induced micronuclei formation had been reported in one study using human lymphocytes
and the cytochalasin B technique. The same research group had also noted sister chromatid exchange (SCE) in a subsequent
publication. Members commented that it was not possible to draw any conclusions based on these results particularly
in view of the unusually long incubation period of 71 hours prior to harvesting the cells. The Committee agreed
that a repeat test would be desirable in order to validate the method used in these investigations.
17. The Committee agreed that negative results had been obtained in mouse hepatocytes following dosing of animals
with up to 150 µg/kg (i.p). No increase in SCE in peripheral blood lymphocytes was noted in Rhesus monkeys
2 years post administration of a diet containing 25 ppt TCDD for 4 years. However, a small, but statistically significant
increase in SCEs in peripheral blood lymphocytes had been documented in a limited study in rats given weekly gavage
doses of 5 µg/kg for 2 weeks but not at 0.5 µg/kg . Evidence of TCDD induced single strand DNA breaks
in peritoneal lavage cells was found in rats given an oral dose of up to 100µg/kg. In addition a positive
result had been reported in deletion recombination spot test but not in a separate study which used a similar dosing
regime. Members considered that no weight could be attached to this investigation in view of the limited study
design and the negative findings reported in a mouse spot test by a separate research group.
18. The Committee agreed that the new information did not alter the position adopted in 1987, namely that weight
of evidence from the large amount of data indicated that TCDD was not genotoxic. The Secretariat were asked to
draft a short statement to this effect.
ITEM 6: 3-MONOCHLORO PROPANE 1,2 DIOL (IN DRINKING WATER) (MUT/99/9)
19. 3-monochloro propane 1,2 diol (3-MCPD) can arise as a contaminant
in the use of polyamine flocculants to treat drinking water. It can also be present in certain savoury foods as
a contaminant of acid hydrolysed vegetable protein. No interests were declared.
20. Members noted that the CEC's Scientific Committee for Food had considered 3-MCPD and concluded that in view
of the clearly demonstrated in-vitro mutagenicity and the tumourigenic effects in rats, it should be regarded as
a genotoxic carcinogen and steps have been taken to minimise exposure in food. However industry had submitted a
review prepared by CANTOX Inc on behalf of the International Hydrolysed Protein Council which had proposed that
3-MCPD was not mutagenic in-vivo and that the tumours seen in rats did not suggest a hazard to humans. The COM
was asked for advice on the available mutagenicity data.
21. Members commented that a number of key test reports (eg mouse lymphoma assay and bone-marrow micronucleus test
in mice) had been submitted in confidence to the SCF and asked if it were possible to obtain these reports. The
Committee agreed that 3-MCPD was mutagenic in Salmonella typhimurium in the absence of metabolic activation. The
addition of S-9 mix did not increase the mutagenic response observed. Members noted that a positive response had
been reported in the mouse lymphoma assay using the tk locus. The Committee concluded that the available information
suggested that 3-MCPD should be considered an in-vitro mutagen. Members noted that there was insufficient information
available to draw any conclusions regarding the in-vivo mutagenicity studies with 3-MCPD and agreed that it would
be prudent to assume that 3-MCPD may have mutagenic potential in-vivo.
22 The Committee considered the summary arguments presented by CANTOX Inc and agreed that there was no evidence
to support the view that differences in the metabolism of 3-MCPD in bacteria and mammals and the formation of bacterial
specific mutagens was a valid explanation for the documented mutagenicity results. The Committee noted that the
COC would also review the CANTOX document in respect of the interpretation of animal carcinogenicity tests.
ITEM 7: OZONE: MUTATIONAL SIGNATURES (MUT/99/3)
23. Ozone was considered by the COM in 1998 when it was concluded that
it should be regarded as a potential in-vivo
mutagen. Much emphasis was placed on the specific A-T transversion of codon 61 of K ras seen in tumour tissue derived from the mouse lung, the target site for carcinogenicity.
The COC had not reached agreement regarding the interpretation of the carcinogenicity data on ozone, particularly
as to whether the lung tumours arose as a result of a genotoxic mechanism. The COM had therefore been asked to
further consider the significance of the mutations found in lung tumours
in the light of a discussion paper prepared by Imperial College of Science Technology and Medicine (ICSTM). The
secretariat had asked ICSTM to specifically present proposals on the minimum data regarding mutations in tumours
which would be required in order to draw conclusions on mutagenicity of chemicals.
24. Members considered the generic arguments outlined in Annex 2 to MUT/99/3
and agreed that it was theoretically possible that selection of spontaneous mutations with particular effect, or
in particular genes could give rise to differences between treated and control animals with respect to mutational
signatures of tumours. The proposal outlined in the paper to establish whether a compound could induce specific
mutations in neutral situations, ie where there is no selection through growth advantage as occurs in a tumour,
was acceptable, although Members considered that it would be difficult to conduct such experiments with ozone.
There were a number of uncertainties to be resolved in developing a suitable methodology, for example whether the
use of specific reporter genes (such as lac
Z) would be selective resulting in important effects being missed.
25. Regarding ozone, Members considered that additional data from in-vitro studies of mutation signatures could provide valuable information but agreed that it would
still be prudent to assume that ozone may have in-vivo genotoxic potential.
ITEM 8: CONDUCT AND INTERPRETATION OF GENOTOXICITY ASSAY 1994-1998 (MUT/99/4)
26. Members noted that this paper outlined some of the general principles
for evaluating genotoxicity assays drawn from the Committees discussions 1994-8 and updated the previous paper
agreed in 1997. The document was primarily intended to assist Government Departments in the interpretation of mutagenicity
data. Members and assessors were asked to comment on the paper by the end of March.
ITEM 9: ANNUAL REPORT 1998 (MUT/99/5)
27. Members were asked to comment on the text by the end of February 1999.
It was noted that in future some items would be agreed during the year under the new arrangements for greater openness
of Committee business.
ITEM 10: ROLE OF CMO ADVISORY COMMITTEES (MUT/99/6)
28. Members were informed that all advisory committees dealing with food
safety issues had been asked to comment on their role with respect to risk assessment and risk communication. MUT/99/6
had been drafted to outline the current practise of the COM and also present a paper on this issue circulated to
the COT last autumn.
29. Members agreed that the role of the COM related to providing expert, specialised scientific advice across many
chemical sectors and in response to requests from various parts of DH and from other government departments/agencies.
The COM did not advise directly on policy or on risk management issues, but the scientific advice provided by COM
would be used by DH and other Government Departments in informing policy decisions.
ITEM 11: GUIDANCE DOCUMENT FOR MEMBERS (MUT/99/7)
30. The draft guidance document on procedures and standards was being
submitted to COM, COC and COT at their next meetings. It was based on the Cabinet Office model code of practice
for board members of advisory non-departmental bodies. The document presented information on areas of committee
procedures that had already been agreed with CMO and Ministers (eg the sections on committee openness and the introduction
to CMO's advisory committees). Other aspects were new to members, eg appointment procedures but the advice followed
the guidelines issued by the Office of the Commissioner for Public Appointments in this regard. There was some
flexibility in other aspects with regard to adopting the code to specialist committees such as COM. Members were
informed that comments would be considered, together with the comments from the COT and COC before preparing a
submission to CMO.
31. Members commented that the requirement to declare direct commercial interests of personal partners and children
as currently worded was impracticable and needed to be amended to make it clear that the general principle that
Members were not under any obligation to seek out knowledge if they would not normally expect to be informed would
apply in this instance. The Committee agreed the document subject to this amendment.
ITEM 12: REVISED GUIDELINES
32. Members submitted a number of draft sections (Implications for carcinogenesis
and Monitoring of human populations). These documents would be circulated for comment at the next meeting. The
Chairman asked all Members to submit their draft chapters to the secretariat in time for circulation for the May
1999 meeting. The Chairman also requested that members consider the range of available test systems that might
be considered in the revised guidelines.
ITEM 13: ANY OTHER BUSINESS
33. There were no other items of business.
ITEM 14: FOR INFORMATION ONLY PAPERS
34. The following 5 papers were circulated for information only.
14.1 Expert Panel Report on Significance of DNA adducts MUT/99/8
14.2 DH paper on risk communication MUT/99/12
14.3 Paper on flawed statistics MUT/99/13
14.4 Improved arrangements for openness MUT/99/14
14.5 Review papers on the Mouse Lymphoma Assay MUT/99/15
ITEM 15: DATE OF NEXT MEETING
35. The next meeting would be held on 20th May 1999. The meeting ended
at 3.05 pm
ACTIONS
| Item |
Action |
Responsibility |
| 4. Malachite Green |
Finalise conclusions for February COT |
Secretariat |
| 5. TCDD |
Draft statement for circulation by post |
Secretariat |
| 6. 3-MCPD |
Consult COC |
Secretariat |
| 8. Interpretation of studies |
Amend in light of Members and Assessor comments |
Secretariat |
| 9. Annual Report |
Amend in light of Members and Assessor comments |
Secretariat |
| 11. Guidance document |
Collate COM/COC/COT views |
Secretariat |
|
12. Guidelines document (revision)
|
Members to draft sections for May meeting |
Members |
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