Additional notes on the published presentation.

Speculating about prevention we suppose that a risk factor contributes to the development of
disease. We can derive our knowledge from epidemiological studies: the cohort studies allow us to
express results in the form of the relative risk. However, the concept of risk can also be seen in
a more general level.


The risk is in general the probability. It expresses the chance of a biological, chemical or
physical agent to cause an adverse change in health.

Health risk has both an objective and a subjective aspect: despite all objective results and
observations, each risk can affect specific people in an emotional way. The emotional component of
health risk is often greatly underestimatedand, which, as a result, leads to a disruption of
communication and mutual trust.   In his practice, the doctor encounters this phenomenon in the
interpretation of the side effects of drugs, antivaccination campaigns, etc..

The labelling procedure known as a health risk assessment is a sequence of steps to be followed:
the first step is determination of health or social importance of risk factor. It should be
replaced later by an effort to express the "strength of harmfulness" of the factor, more precisely
the dose-response relationship. In many cases, a detectable harmful effect can only happen when the
effective (threshold) dose is exceeded. We also know the stochastic effects of an agent, but even
here, when the dose is decreasing, the probability of the disease is reduced up to a certain basal
value given genetically.


Exposure assessment is the most difficult part of the process: We have to determine an effective
dose, which is expected as harmful. The size of effective doses in the target organs is estimated
by indirect and by direct methods.


Indirect methods are easier but less accurate: if we know theamount of hazardous substance in food
or water and if we can estimate the amount of food or water that is consumed, using simply
multiplying the both values, we get a probabilistic estimate of exposure.

To distinguish the subtle differences in exposures, direct methods of estimating exposure based on
individual measurements, polling and tests have been developed. However, individual measurement is
always time-consuming and financially demanding.

Only when we gather information on harmfulness and quantitative exposure we can conclude an overall
impact on health (characterize the risk). The whole procedure can also be expressed graphically as
the risk matrix: the health impact in relation to the likelihood that we will encounter a risk
factor to a sufficient extent.

Honesty of any scientific work, incl. health risk assessment cannot be done without a discussion of
uncertainties. When using indirect methods of exposure assessment, we work with an "average
individual". Nevertheless, individual measurements can be affected by random fluctuations, the
body's response to the attack is also strictly individual. Epidemiological methodology brings
further inspiration to work, from a scientific point of view, with uncertainties in health risk
assessment.

A pioneer in this area was british epidemiologist Austin Bradford Hill, who has expressed several
postulates, suitable for discussing our conclusions about the size of the risk.


Some of Hill's causality criteria have been partially exceeded, others revised.  Perhaps the most
important thing is the postulate of the effect temporality: only such a consequence, which had been
proven to occur after known exposure only, it could be responsible for an adverse change in health!


In recent years, some elements of the qualitative research have penetrated the field of the health
risk assessment. Quantitative research and qualitative research should form indivisible unity. The
complex of health and risk factors that threaten health cannot be  summarised in the result
formally expressed as "p<0.05". Questioning public attitudes and including public attitudes in
objective decision-making of authorities should gradually become a matter of course in the
protection of public health.