The dioxin levels found in Irish beef cattle do not pose a significant risk to consumers, writes Dr Muiris Houston, Medical Correspondent
THE NEWS that beef products have been contaminated by PCB in animal feed does not mean that there is a risk to human health.
At levels two to three times those recommended for non-dioxin, PCBs in beef will not harm anyone.
When regulatory authorities, such as the World Health Organisation (WHO) decide on actual numerical limits for toxic chemicals, they routinely build in an additional factor of 10 to 100 in order to "be sure to be sure".
As a result of this "belt and braces" approach to human toxicity, the elevated toxic levels reported yesterday in Irish beef samples can be safely ignored by consumers.
What about pork products?
While the dioxin levels in some pigmeat was up to 200 times the accepted level, this does not mean that people who consumed contaminated pork products have high levels of dioxin in their blood stream. Unlike some other substances which exert a poisonous effect within hours of ingestion, dioxin is different.
This is because it travels to the body fat of humans and remains there for a long time.
On average, dioxins have a half-life of seven years. Half-life is the time it takes one half of the dose of a substance to leave the body.
Continual exposure from contaminated food could lead in the long term to a high total amount of dioxins in the human body.
However, this body burden of dioxin is unlikely to be added to significantly by a few exposures that exceeded the accepted dietary limit by a hundred fold.
A number of pregnant women have contacted The Irish Times to express a particular fear for their unborn children.
While there is a theoretical possibility of thyroid problems from a massive acute exposure to dioxin, there is no scientific evidence to suggest that a baby could be harmed by his or her mother's recent eating habits.
There is understandable confusion among the public about the health implications of the dioxin scare.
It would be most helpful if the Department of Health and the Food Safety Authority of Ireland could quantify the risk to public health in a way that is easily assimilated.
Telling us the risk of particular consequences using absolute numbers and simple graphs would give people a ready take-home message that is personally relevant to them.
The public must be told the truth.
But it must also be helped to understand that some uncertainty will always remain when calculating any risk to public health.