What if alcohol were treated as a chemical contaminant in food?
The media never seems to tire of publicizing the chemicals, with notable exceptions such as a chemical called ethanol. The nature of the debate is often moulded more by attitudes than by any regard for facts, and there are many misconceptions about the risks of chemicals. For example, what would happen, if alcohol were to be assessed as a chemical contaminating our food? What sort of doses would be considered as dangerous, what dose would be considered as safe, and what would be the limit values for safe use?
The assessment of chemical risks is mainly performed on the basis of animal experiments. Since there is usually uncertainty in extrapolating the information to human beings, safety margins are used. These margins are usually generous to ensure that the substance is not toxic to even the most sensitive individuals.
Creating a maximum limit
The basic unit to assess the effects in organisms of different sizes is to calculate the dose as grams per kilogram body weight. In animal experiments, several different doses are usually given to animals, and the effects followed for different periods of time. The immediate effects are studied after a single dose, but long term effects need to be evaluated for several years after repeated daily doses, usually at three or more dose levels. This enables us to determine a dose-effect relationship e.g. monitoring the development of health effects in the rat population, starting in the most sensitive individuals and extending to all individuals.
The normal human being is about 200 times heavier than a rat. Many chemicals have the same effect in human beings at about a 200 times higher dose than they exert in the rat, in other words the dose per kilogram is the same. One cannot be certain that this will always be so. Differences in metabolism or other reasons can cause species-specific differences in the dose-effect relationships between rats and humans. This is why a safety margin needs to be used to guarantee that there will be no surprising unwanted effects in humans.
The most common safety margin is one hundredfold. In other words, the dose determined to be safe in animal experiments is divided by one hundred, and then one assumes that this one hundredth of the rat safe dose is certainly safe even to the most sensitive human being.
Safety margins for alcohol
The most important toxic effects of alcohol, including liver injury and developmental effects in the offspring are caused by alcohol doses of about 3–10 grams per kilogram body weight per day. No effects are seen at a dose of 1 gram per kilogram body weight. The estimated safe dose of alcohol in humans would then be about one hundredth of a gram per kilogram.
To convert this to more practical terms, this translates into one half gram of alcohol per day in a woman or a youth weighing 50 kg, in an adult male somewhat more. One dessert spoon (10 ml) of beer or one teaspoon (5 ml) of wine contains this amount. However, alcohol also can cause cancer. Even the offspring of the experimental animal may contract cancer, if they have been exposed to alcohol in the womb. Cancer is caused by approximately the same doses as other toxic effects.
Carcinogenic substances are usually managed in a much stricter manner than other toxic compounds, and this means that clearly larger safety margins are imposed; the minimum is usually one order of magnitude additional safety margin, i.e. a thousand-fold margin is required instead of one hundredfold. Therefore that would mean that the safe dose of alcohol would be about 0.1 ml (2–3 drops) per day.
Theory and practice
The rat is not a small human being. Therefore we have to accept that there is some uncertainty in our calculation. With respect to alcohol, we have plenty of direct scientific information, and we can base our estimates on human data rather than only animal data. We know that the risks start to increase after 10–20 grams of pure alcohol per day (one glass of wine or one bottle of beer).
Thus a fivefold safety margin might be sufficient instead of a hundredfold which would be the case, if the safety of alcohol had to be assessed solely on the basis of animal experiments.
We have only animal data on many chemicals. Therefore large safety margins are reasonable, but we must not forget that we are using them. If we forget this, the substances for which there are an abundance of human data seem to be less dangerous, and substances for which we have only animal data seem to be more dangerous. This in fact is turning the facts upside down, because in reality we only are certain that those substances with human data are indeed toxic to humans, while for the others we are only able to estimate that they are probably toxic to humans, because they are toxic in animals.
So the limit values reflect a degree of caution that is intended to compensate for ignorance. However, even professionals sometimes forget this fact and consider them as real boundaries between safe and toxic doses.
The human being may be a hundred times more sensitive to some chemicals than a rat; in that situation the entire hundredfold safety margin is needed, but on the average this is not the case. It is even possible that the experimental animal may be more sensitive to some chemicals than humans.
Problems of misinterpretation
If a risk is misinterpreted, then wrong prioritizations may follow. We may waste effort and money in removing exaggerated risks when our actions will have no bearing on increasing our safety. On the other hand, we may underestimate risks that have been established very well.
On the basis of many epidemiological studies it is known that air pollutants kill hundreds of thousands of people in Europe. However, the European authorities have been very reluctant to decrease the limit values of fine particulate matter down to safe levels. On the contrary, the levels of carcinogenic metals in urban air are regulated very strictly, even if they are probably not the components of urban air that are responsible for the cancers and other obvious health effects. This gives an impression that we are simply seeking a scapegoat: the true risk is seen as being so politically difficult to handle that something less important is done instead.
Even though chemical safety is an important issue, it is also important to understand the relative impact of different risks, including our lifestyle risks such as cigarettes and alcohol. Otherwise huge investments are made which really will have no meaningful consequences, and more important matters are neglected.
Effective risk management in the society requires that the conceptions on risks are true and not false.
One level up: Is man defiled by what goes to his mouth?
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