Joint Statement on Re-assessment of the Toxicological Testing of Tobacco Products
COT/04/9; COC/04/S4 & COM/04/S2 - November 2004
Introduction
1. Article 11 of the Directive 2001/37/EC of the European Parliament and of the Council1 sets out a requirement for the European Commission to submit, no later than 31 December 2004 and every two years thereafter, a report on the Directive's application. Such a report will aim to review, and advise on the development of, particular features of the Directive. Two areas of specific concern are:
"methodologies for more realistically assessing and regulating toxic exposure and harm"
and
"toxicological data to be required from manufacturers on ingredients and the manner in which they should be tested in order to allow public health authorities to assess their use"
2. The Committees (COT/COC/COM) were asked to provide advice on these areas of toxicological assessment with reference to the assessment of Potentially Reduced Exposure Products (PREPS) and in particular tobacco-based PREPS which are smoked. A brief overview of the information reviewed and approach taken by the Committees is given below.
3. The Committees agreed that it was important to state that the ideal way forward to reduce risks and hazards of tobacco smoke was to encourage smokers to stop or people not to start in the first place and any attempt to reduce toxicity should not be allowed to detract from that. Members acknowledged that the primary remit of the Committees' discussions was to provide advice based on the information provided.
Approach taken and evidence reviewed
4. The Committees considered a covering paper drafted by the secretariat (available on the Committee internet sites) and appended references. These included information from the Symposium proceedings of the 56th meeting of the Tobacco Science Research Conference2 and a number of peer-reviewed publications in scientific journals.3-9 In discussing these data members
were reminded of the recent considerations (at COT/COC/COM meetings during 2004) on toxicogenomics where a number of studies investigating tobacco smoke had been considered (See above internet sites for minutes and papers). The Committees were aware that additional studies both in the public domain and possibly held by industry could have been reviewed but noted that they had been asked to provide the best advice possible in the available time based on the information provided to members. The discussion paper and appended references were considered at the COM meeting on 7 October, the COT meeting on 26 October and the COC meeting on 18 November 2004.
Generic consideration of toxicological approaches to evaluation of PREPS.
5. The Committees commented that tobacco smoke was a highly complex chemical mixture and that the causative agents for smoke induced diseases (such as cardiovascular disease, cancer, effects on reproduction and on offspring) were unknown. The mechanisms by which tobacco induced adverse effects were not established. The best information related to tobacco smokeinduced lung cancer, but even in this instance a detailed mechanism was not available. The Committees therefore agreed that on the basis of current knowledge, it would be very difficult to identify a toxicological testing strategy or a biomonitoring approach for use in volunteer studies with smokers where the end-points determined or biomarkers measured were predictive of the overall burden of tobacco induced disease.
6. The Committees commented that, since it was not possible to define reliable end-points or biomarkers for use in in-vitro investigations (with exception of mutagenicity testing see paragraph 10 below), in-vivo studies in experimental animals or in volunteer studies using smokers, it would not be possible to compare PREPS using such approaches.
7. The Committees also noted that some weight could be placed on investigations of markers for the tobacco-specific nitrosamine NNK (4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone) and its metabolite NNAL (4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanol) as markers for exposure to a potentially relevant tobacco smoke-derived carcinogen. However, a valid investigation of carcinogenic potency of PREPS would have to examine a wide range of the 50 or so known human carcinogens present in tobacco-smoke. In addition, strategies designed to compare PREPS with regard to one chronic disease associated with tobacco smoke, such as lung cancer, may have no predictive value for other diseases such as tobacco-smoke-induced cardiovascular disease.
8. Overall, the Committees agreed that there were considerable difficulties in designing a toxicological testing strategy for the reassessment of tobacco products and that it was not possible to design a valid strategy given current understanding of the diseases associated with smoking tobacco.
Consideration of approaches currently used
9. The Committees commented on the approaches used in the information provided. When tobacco manufacturers wish to assess the influence of any design changes on the overall toxicity of a product, a tiered testing regime has been advocated which currently consists of one or more of the following:
1) A bacterial test for gene mutation (eg the Ames test)
2) A test for clastogenicity and for indications of aneugenicity
i) In vitro metaphase analysis
ii) In-vitro micronucleus test
3) Mammalian cell mutation assay (preferred choice is the mouse lymphoma assay)
4) Cytotoxicity as assessed using the Neutral Red uptake assay
5) In-vivo studies in experimental animals to investigate biomarkers of disease
6) Studies in smokers (volunteers) to examine effects on smoking and biomarkers following switching from one tobacco product to a PREP.
Advice from COM on mutagenicity
10. The COM considered the available information and agreed that, using suitable protocols, it was possible to compare mutagenicity in-vitro of different PREPS which could be useful to assess hazard. However, the results of such in-vitro tests had no predictive value for risk of in-vivo mutagenicity or cancer. No conclusions could be drawn on the approaches using toxicogenomic methods. The available biomonitoring approaches were too limited to draw any conclusions regarding a comparison of PREPS.
Advice from COT on Toxicology testing
11. The COT concluded that in-vitro cytotoxicity testing could be used as part of an overall approach for comparing PREPS but the data could not be extrapolated to the in-vivo situation and the outcome measured in such tests had no predictive value with regard to tobacco-smoke associated diseases. The COT considered that studies in smokers (volunteers) to investigate tobacco-based PREPS should take account of changes in smoking behaviour in addition to investigation of biomarkers of disease. The COT concluded that there were currently no adequate biomarkers for tobacco-smoke induced diseases and no conclusions could be reached on the available data. The COT concluded that smoke chemistry could not be used to compare PREPS.
Advice from COC on carcinogenicity
12. The COC commented on the complexity of tobacco induced cancer and noted that the mechanism(s) and information on the chemical agents responsible for tobacco induced cancer in humans had not been fully elucidated. In addition members noted the importance of the interaction between chemical carcinogens and susceptibility factors regarding the pathogenesis of tobacco-induced cancer. The COC concluded there is no strategy which could be used to compare PREPS for carcinogenic potency and that the approaches used are not informative on the risk of tobacco induced carcinogenicity. The COC agreed that it was not possible to draw conclusions on the carcinogenic risk of tobacco-based PREPS on the available biomarker studies reviewed.6-9 The COC commented on the need to examine a wide range of biomarkers for carcinogenicity and their interaction with susceptibility factors.
Overall conclusions of the Committees
13. The Committees agreed that analysis of tobacco smoke constituents was not useful in comparing tobacco-based PREPS or predicting risks associated with tobacco smoking.
14. The Committees agreed that the current in-vitro tests and in-vivo approaches used in experimental animals to evaluate the toxicity of tobacco products and tobacco-based PREPS are not informative on risk of diseases induced by tobacco-smoke.
15. It was noted that comparative assessments between PREPS can be undertaken for data generated in some in-vitro mutagenicity tests, but the data cannot be extrapolated to in-vivo mutagenicity.
16. The Committees agreed that the available biomonitoring studies in volunteer smokers are too limited to draw any conclusions regarding comparisons of tobacco-based PREPs.
17. The Committees cautioned that biomonitoring studies which focused on the risk of one disease (such as cancer) in volunteer smokers have no predictive relevance to other tobacco smoke-induced diseases such as cardiovascular diseases.
18. The Committees advised that future progress on the proposed approach to reduce tobacco-smoke induced disease by modification of tobacco products could only be made when detailed mechanistic information on tobacco-induced diseases is available.
November 2004
COT/04/9; COC/04/S4 & COM/04/S2
References
1. Directive 2001/37/EC of the European Parliament and of the Council on the approximation of the laws, regulations and administrative provisions of the Member States concerning the manufacture, presentation and sale of tobacco products, (2001).
2. Recent Advances in Tobacco Science, Toxicological Evaluation of Tobacco Products, Symposium Proceedings, 56th Meeting of the Tobacco Science Research Conference, (2002). September 29-October 2, 2002, Lexington, Kentucky, USA.
3. Andreoli C et al Toxicology In-vitro, 17, 587-594, (2003).
4. Gebel S, Gerstmeyer B, Bosio A, Haussmann H-J, Van Miert E and Müller T, Gene expression profiling in respiratory tissues from rats exposed to mainstream cigarette smoke, Carcinogenesis, 25(2), 169-178, (2004).
5. Obot CJ et al Characterisation of mainstream cigarette smoke-induced biomarker responses in ICR and C57Bl/6 mice. Inhalation Toxicology, 16, 701-719, (2004).
6. Breland et al Acute effects of Advance™: a potential reduced exposure product for smokers. Tobacco Control vol 11, 376-378, (2002).
7. Breland AB et al Tobacco specific nitrosamines and potential reduced exposure products for smokers: a preliminary evaluation of Advance™. Tobacco Control, 12, 317-321, (2003).
8. Hughes JR et al Smoking behaviour and toxin exposure during six weeks use of a potential reduced exposure product: Omni. Tobacco Control vol 13, 175-179, (2004).
9. Hatsukami DK et al Evaluation of carcinogen exposure in people who used "reduced exposure" tobacco products. JNCI, 96, 844-852, (2004).