The New Straits Times, August 8, 1997
Q: I came across a US report in the New Sunday Times (Aug 3) on the sue of ammonia to increase the release of nicotine from cigarettes. Could you elaborate on this enhancement and comment on the toxic effects arising from inhaling ammonia continuously through smoking?
A: The enhancement of nicotine absorption through the lung as achieved by treating the tobacco with ammonia can be best explained based on the physicochemical properties of nicotine.
Nicotine, in its pure form, is an oily pale yellow liquid. It is also classified as a weak base and thus, when mixed with the lung's fluid, it will be dissociated to a certain extent to form two species, the ionised and un-ionised form: (unlike salts - for example, the common salt dissociates completely in water).
This degree of dissociation would then determine the passage of nicotine through the lung membrane before being absorbed into the blood.
If the cellular environment at the site of absorption, in this case the lung, favours the formation of the more ionised species of nicotine than the unionised forms (also known as the free base), the passage of nicotine through the lung's membrane would be lessen and the amount of the absorbed nicotine would be minimal.
Upon being able to pass through the lung's membrane, the nicotine would be transported via the blood to the receptor sites to elicit their effects. It has been reported through the above study conducted in the US that the amount of nicotine to satisfy the addictive habit depends very much on the degree of nicotine dissociation which can be manipulated by changing the pH of the lung's fluid.
In the case of the co-inhalant, ammonia, the compound would change the pH of the lung's fluid to a slightly basic condition and thus alter the distribution of the ionised to the un-ionised species.
Under the slightly basic condition, the un-ionised species would be more favoured and a higher amount of nicotine would be absorbed into the body to achieve a relatively higher degree of satisfaction.
On the same note, the same principle has been applied to increases the absorption of drugs which are either weak acids or bases.
Exposure to, and inhalation of very high concentrations of 2,500-6,500 ppm - as when spillages of liquid concentrated ammonia occur in industrial accidents - causes severe corneal irritation difficulty in breathing, spasm of the bronchus, chest pain and pulmonary edema which may be fatal.
Although these effects would not be seen from inhaling ammonia through cigarette smoking, experimental studies carried out with lower concentrations of ammonia in humans have indicated almost similar patterns of respiratory problems.
In a study where various concentrations of ammonia were exposed to human subjects for five minutes, 134 ppm caused irritation to the eyes, nose and throat in nine participants while one person complained of chest irritation; at 72 ppm, several subjects reported the same symptoms while at 32 ppm, only one person reported nasal dryness.
If these findings were to be applied to smokers, then a heavy smoker consuming perhaps a packet of 20 cigarettes would be likely to inhale a higher concentration of ammonia, and may thus experience the above general problems.
The findings of the study, as expected, have been rejected by the US tobacco producers as the enhancement of the absorption of nicotine was carried in normal subjects and not smokers.
The counter-argument being put forward is that smokers are known to develop a tolerance to ammonia. A similar effect has been seen among drug addicts who tend to increase their intake of illicit drugs over time so as to achieve the same effects.
Based on this, the same extrapolation seen in normal subjects cannot be applied to smokers as the amount of absorbed nicotine would be decreased if inhaled at similar concentrations of ammonia.
Even though the tobacco producers have rejected these findings, have rejected these findings, they however have acknowledged that ammonia has been used as an ingredient in cigarettes solely for the purpose to improve product taste.
In this case, it must be highlighted that the admission of adding this ingredient into cigarettes should be accepted as an intention to further endanger the health of smokers.
