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May 1991, Volume 41, Issue 5

Letter to the Editor

LEAD - AN ESSENTIAL TRACE ELEMENT

Madam,

I have failed to understand what Dr. Manser is trying to communicate in his Editorial note “Lead - an essential trace element” which appeared in the March, 1991 issue of this Journal. Is he retracting his previous Editorial note "Plumbum - Karachi Quo Vadis” the data referred to by him to prove that lead is an essential trace element is indirect and hypothetical. The fact that some other trace elements have been found to essential. As far as I know, no one has yet shown that lead participates in a biochemical reaction of physiological importance and that the particular reaction will not take place in its absence. Till, that is shown, the labelling of lead as essential is hypothetical. The closing sentence of the note which states there is probably no clear cut distinction between essential and non essential or between toxicity and non toxicity in life process’, is controversial. The distinction between essential and non essen­tial is very clear. To be essential a substance has to be shown to be required for a physiological function. The fact that the list of essential elements is not yet final, does not mean that everything is labelled essential till proven otherwise. Again the fine cut off point below which an element is harmless may not be known in all cases but the levels at which the substances cause toxic symptoms are known. If the purpose of the note was to bring attention to the possibility that many elements in nature are required in very minute quantities by the body then the title and thrust of the note should have been on that. The present title and the bulk of the note lam afraid is liable to misuse by vested interests and prevent efforts to restrict lead levels in the environment.

NA. Jafarey

Journal of the Pakistan Medical Association has agreed to receive and publish manuscripts in accordance with the principles of the following committees: