How are TNCO values determined?
The tar, nicotine and carbon monoxide (TNCO) contents in cigarettes are determined using a smoking machine, which smokes a cigarette in accordance with an established method. In The Netherlands and the rest of the EU the so-called ISO method is used, as set out by the European Commission. This makes it possible to check that products do not exceed the maximum permissible quantities of TNCO and to compare products. Cigarette smoke is permitted to contain a maximum of 10 mg of tar, 1 mg of nicotine and 10 mg of carbon monoxide when smoked in accordance with the ISO method.
Disadvantages of the ISO method
However, the measurements taken using the ISO method do not provide an accurate picture of the amount of TNCO that smokers actually inhale. The reasons for this include the fact that in the case of the ISO method the ventilation holes are not covered, whereas smokers (partly) close these holes with their fingers or lips. The TNCO contents measured are therefore lower than the contents inhaled by smokers.
The alternative measuring method
There is an alternative method that gets closer to the TNCO contents inhaled by a smoker, namely the Canadian Intense (CI) method. Using this method the smoking machine takes puffs on the cigarette faster, with a greater volume, and the ventilation holes are taped over (see table). Measurements using the CI method produce higher TNCO values in cigarettes than measurements using the ISO method.
Figure. A test cigarette in the smoking machine.
There is a series of ventilation holes between the red lines. In the test according to the ISO method these holes remain open; in the test according to the CI method the holes are taped up.
Table. Specific characteristics of the ISO method and the Canadian Intense method, which are used to test cigarettes using a smoking machine. The bottom line provides an indication of the smoking behaviour of an average smoker.
|Duration of a puff
|Time between puffs
|Volume of a puff
|Blocking of ventilation in filter
| 0 %
|Canadian Intense method
50 %(by fingers and lips)
Difference between TNCO values with and without holes in the filter
The presence of filter ventilation thins the smoke and thus the inhaled concentration of nicotine. In order to inhale the desired amount of nicotine smokers adapt their behaviour depending on the degree of filter ventilation, for example by inhaling more deeply, for longer or more often, or they even smoke more cigarettes.
In the case of a more intense smoking method or if the ventilation holes are closed off, greater quantities of harmful substances end up in the smoke. The increase is different for each substance as the combustion process is affected by the additional air drawn in. So for each mg of nicotine smokers are exposed to higher concentrations of, for example, tar, carbon monoxide, acetaldehyde and acrolein. These substances are harmful to health as they are toxic, carcinogenic and/or addictive.
Figure. The amount of nicotine determined by a smoking machine using the ISO method, compared with the amount of nicotine that a smoker actually inhales (based on Jarvis et al. 2001). The tobacco in all cigarettes contains the same amount of nicotine, but the amount of filter ventilation affects the values that the smoking machine measures. More filter ventilation results in lower values, whereas the amount of nicotine that a smoker inhales remains the same. Smokers thus get as much nicotine from a ‘light’ cigarette as from a ‘heavy’ cigarette by adapting their behaviour.
What does this mean for your cigarette?
The RIVM database includes the TNCO values, as provided by manufacturers, for cigarettes that were available on the Dutch market in 2015. Cigarettes with low TNCO values generally have more filter ventilation and are referred to by the media as ‘cheating cigarettes’. The TNCO values give an indication of the amount of ventilation in the filters rather than the amount of harmful substances that smokers inhale.
(On-screen title: Filter ventilation in cigarettes. Voice-over:)
Filter ventilation in cigarettes
(Did you know nearly all cigarettes)
VOICE-OVER: Did you know nearly all cigarettes
have tiny holes in the filter paper?
(In some cigarettes, the holes are visible to the naked eye.)
WALTHER KLERX: In some cigarettes, the holes are visible to the naked eye.
In other cigarettes, you must use a microscope to see them.
These holes cause the smoker and the smoke machine
to inhale extra air.
(We use this smoke machine to compare)
REINSKJE TALHOUT: We use this smoke machine to compare
the tar, nicotine and carbon monoxide emissions of various products.
In Europe, we've agreed to use the so-called ISO method to do so.
The ISO method involves keeping the filter holes open during testing.
But a real smoker wants to consume a certain quantity of nicotine
because he is addicted to it.
So, he will adapt his behaviour.
The smoker will take more drags, inhale more deeply
and partially block the filter holes with his lips or fingers.
(So, this study also uses)
VOICE-OVER: So, this study also uses
the Canadian Intense protocol, in which filter holes are sealed.
(This gives a better idea of what a real smoker consumes.)
TALHOUT: This gives a better idea of what a real smoker consumes.
In the ISO method, every minute, a 35-millilitre drag is taken.
In the Canadian Intense protocol, every thirty seconds
a 55-millilitre drag is taken.
(Now, based on the filter, we can see)
KLERX: Now, based on the filter, we can see
what the effect of the different methods is.
(With the ISO method, the filter is lightest)
With the ISO method, the filter is lightest
(so fewer components were consumed)
so fewer components were consumed
(than with the Canadian Intense method. That means)
than with the Canadian Intense method. That means
(that if you take bigger drags more often and seal off the holes)
that if you take bigger drags more often and seal off the holes
(you consume more harmful components than when you don't do so.)
you consume more harmful components than when you don't do so.
(So, holes in the filter do not make a cigarette less harmful.)
So, holes in the filter do not make a cigarette less harmful.
(The Dutch coat of arms, next to: National Institute for Public Health and the Environment. Ministry of Health, Welfare and Sport. The screen turns light blue and white. On-screen text: Want to learn more about filter ventilation in cigarettes? Surf to: rivm.nl/en/tobacco. An RIVM production, copyright 2017. Tomorrow's care begins today.)
Want to know more about filter ventilation in cigarettes?
Surf to: rivm.nl/en/tobacco.