In the absence of an international standard for analysing tobacco heating products, scientists at British American Tobacco have adapted an existing method to test the composition of the main aerosol.
Tobacco heating products (THPs), also known as heat-not-burn, form aerosol by gently warming tobacco but do not burn it. This process releases nicotine, glycerol and tobacco flavourings. Without combustion, the aerosol produced contains mostly water and glycerol and far fewer and lower concentrations of the toxic substances usually found in cigarette smoke.
Currently, the commercial development of THPs has outpaced regulatory standard activities. Different laboratories around the world are left to adopt cigarette-based methods for THPs with varying procedures and different terminologies. To ensure consistency and accuracy across different laboratories globally, the International Organization for Standardization (ISO) defines methods and parameters for analytical purposes, for example, the ISO4387 standard is used to determine the main constituents in cigarette smoke.
Currently, there are no ISO standards for THPs, so scientists at BAT adapted this cigarette standard to make it more appropriate for evaluating THPs. Rather than developing a new method for THPs, this enables most of the regulatory laboratories practicing the ISO4387 to easily adopt the new procedures.
Using ISO4387 for smoke analysis involves puffing a cigarette on a smoking machine using a set of standardised puffing parameters. The smoke produced passes through a Cambridge filter pad, which is housed in a standardised pad holder. The pad traps particles from the smoke, including nicotine. A fixed part of the holder is swabbed for water that condenses out of the smoke, allowing the amount of nicotine-free dry particulate matter (NFDPM) or “tar” to be calculated.
BAT scientists introduced additional measures to cater for the higher volume of water produced by THPs compared to cigarettes, and this made working with the ISO4387 standard much more effective for THPs. For example, water collection on the pad holder was improved by swabbing areas that would not normally be swabbed. This simple improvement proves to be effective in identifying sources behind some of the erroneously reported “THP tar” values in the literature.
“The proposed modification of additional wiping of specific areas is readily adoptable by laboratories already using ISO4387 for cigarette smoke analyses, enabling a satisfactory evaluation of NFDPM for THPs,” said Chuan Liu, Head of Tobacco Futures at BAT.
"As well as avoiding cumbersome alterations in procedure or having to make custom components, these extra steps will, in effect, purpose the ISO4387 into a new standard for THPs until THP-specific standards are set by international agencies.”
The experimental results, published in Regulatory Toxicology and Pharmacology, also substantiate previous findings that THP aerosols differ fundamentally from cigarette smoke. As a result, BAT’s scientists said the terminology used for cigarettes and the residue that they produce was not appropriate for THPs, and they proposed calling the aerosol condensate from a THP ‘distillate’ rather than ‘tar’.
Further cross-laboratory tests are needed to establish the method’s repeatability and reproducibility.