It is an extraordinarily unlucky person who is poisoned from eating too many apples. While the risk does exist it is extremely remote and is hardly worth treating as a genuine threat.
The current method of measuring the possible danger is based on the worst-case scenario. The risk of consuming too much pesticide residue, for example on apples, is calculated by assuming a person is among that part of the population that eats the most apples. It is also assumed that every single apple the person eats contains a high level of pesticide.
That would be an "unfortunate person, which is not to say they can't exist, but the chance of them existing is very, very slim", explained Dr Joyce Lambe, of the Institute of European Food Studies (IEFS), based in Trinity College Dublin.
Food safety researchers in the Institute are developing a computer programme which will "scientifically introduce more realistic estimates" of food chemical intakes, Dr Lambe said.
A software programme will be developed as part of the research project. Called Montecarlo and involving seven countries, it will be co-ordinated by the Dublin team. The programme will use predictive mathematics to set more accurate and reliable probability levels for food safety. It is funded by the EU and is due to be completed by 2003.
The risk-assessment method in use now cannot encompass the enormous variability involved with food chemicals, such as the type of food consumed, the presence of the chemical in the food, and, if the chemical is present, its level.
These highly complex variables need to be modelled using powerful, previously unavailable processing potential.
At TCD's centre for high-performance computing, several very powerful computers can simultaneously analyse data, delivering the required computing power for the programme.
When developed, the software programme will ask thousands of "what-if" questions, or iterations, about the chances of any particular level of food chemical intake occurring. The possible risk at every level of consumption will be listed, not just the worst case scenario.
The assumed level of intake is compared with data from toxicologists. On food with additives and preservatives, there have been extensive toxicological tests to determine scientifically acceptable levels of exposure, below which there is no danger to consumers, said Dr Lambe.
If the level of food chemical intake found by the Montecarlo programme is less than the safe level established by toxicologists, the assumption is the food is safe. If the level is greater, however, risk managers in government, science and industry must try to minimise the exposure to consumers. This is done by careful profiling of the sector of the population assumed to be consuming too much of the food chemical.
"If there is genuinely found to be a problem, something has to be done. The consumer is always the priority," stated Dr Lambe.
Montecarlo will sift through data gathered from databases of dietary information and records of chemical concentrations in food. For the Irish input, a survey was carried out by the Irish University Nutrition Alliance, comprising food scientists in TCD, UCC and the University of Ulster.
In the first North-South food consumption survey, the alliance compiled a week's food consumption for 1,000 people in the Republic and 500 people in the North.
The possible risk of chemical intake also has to be put in context, said Dr Lambe. Not eating apples because of the risk of pesticide residue being present could have a worse effect on health then actually eating the apples with pesticide in the first place, she said.