british american tobacco p.l.c. sustainability report 2009 - Addressing the scientific challenges around combustible 'PREPs'


We have progressed our understanding of how to measure exposure to smoke toxicants. We have shown good correlation between exposure measured using cigarette filter analysis and the levels of biomarkers (metabolites of toxicants) in smokers’ body fluids. Filter analysis techniques should, therefore, be useful for studying exposure in large populations.
Scientific challengesWe have begun a study to determine whether this is the case by using the filter analysis techniques to observe smoking behaviour and exposure to some tobacco smoke toxicants in large numbers of smokers (1,000) over a number of years (up to five).

Short term changes in smoking behaviour, as a result of switching between products with different ISO tar yields, have been studied previously by others. However, our study is different because it is the first study, to our knowledge, to observe smoking behaviour at regular intervals in a large smoker population that is free to switch products or to quit smoking at any time over a number of years. This means that in addition to providing more data, the study situation is closer to real life as the smokers are free to choose if and when to switch or to quit.

The study subjects are smokers of the same conventional 10mg ISO tar yield product for more than six months who regularly smoke eight or more cigarettes daily. Over the study period, a reasonable number of subjects are expected to decide to switch to another conventional product, either of the same or lower ISO tar yield (10mg ISO tar yield is the maximum permitted by regulation in the European Union). By using filter analysis techniques, and by measuring certain biomarkers of exposure in smokers’ urine, it should be possible to determine how switching or quitting affects the levels of biomarkers in smokers’ urine, and therefore to determine the smokers’ levels of exposure to some smoke toxicants.

For more information on this study, please see the Current Controlled Trials website, where the study is registered, at Opens in new window.


‘Metabolites of toxicants’

Metabolites of toxicants refer to the substances produced in the body when smoke toxicants are broken down by the metabolic process. These metabolites can be measured in blood, urine and saliva. In some cases, the measurements obtained can be used to provide an indication of what an individual has been exposed to in terms of smoke toxicants.

We are also developing a range of in vitro models of disease, which seek to mimic in the laboratory, parts of the disease process for the smoking-related diseases of cancer, cardiovascular disease and chronic obstructive pulmonary disease. Once validated, we will use these models to see if there are differences in the response of cells between exposure to the smoke of conventional cigarettes and the smoke of prototype products with reduced toxicant levels. We are also investigating biomarkers of exposure and of biological effect with a view to generating a baseline biomarker signature for smokers, former smokers and never-smokers, which might then be used in a clinical study for assessing prototype combustible products. In 2009, we undertook our first clinical study of prototype products to determine whether the reduced levels of toxicants in the smoke, as observed using machine smoking, equate to reduced levels of exposure in the smoker.



The term ‘potential reduced-exposure product’ (PREP) was introduced by the US Institute of Medicine (IOM) in its 2001 report ‘Clearing the Smoke: Assessing the Science Base for Tobacco Harm Reduction’. In this report, the authors called for research to develop tests to assess the effect of different types of products in reducing tobacco-related exposure and to determine biological markers of effect that could be used for product evaluation. The report also recommends approaches to informing the public about PREPs that include utilising scientific research, market surveillance and regulation.

Addressing scientific challenges: what’s next?

We will analyse and submit for publication the results of our scientific research, including our first clinical study of a range of modified combustible prototype products. We will also continue to look for new and innovative ways of reducing tobacco smoke toxicant exposure levels from our products, and will develop and validate new methods for studying how people smoke, what they are exposed to in terms of smoke toxicants and how this relates to the development of disease.