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APPENDIX VI
PESTICIDE RESIDUES IN FOOD. PROPOSED PUBLIC HEALTH CONTROL MEASURES
(Extracted from "Pesticides Abstracts and News Summary", Section A, 1962)
H. AMPHLETT WILLIAMS, Ph.D., A.C.G.F.C., F.R.I.C., F.R.S.H., Public Analyst, City of
London Laboratories, King's Head Yard, Borough High Street, London, S.E.1.
The possible occurrence in foodstuffs of residual traces of insecticides, fungicides and
other agricultural chemicals that might constitute a danger to public health presents a problem of
increasing difficulty to Food & Drugs and Port Health Authorities.
The problem, which arises from the continuing production and use of an immense variety of
new and highly complext pesticides, affects three fundamental aspects of food administration
which may conveniently be dealt with under Sampling, Analysis and Enforcement.
Sampling
Until quite recently a non-volatile insecticidal spray applied to fruit could be relied upon to
leave a visible residue when it dried. If the spray happened to be too strong or applied too near
harvesting time the residue would be sufficiently noticeable to be seen by a food inspector, and
the fruit could be sampled and tested for toxic substances. Many of the newer insecticides, however,
might leave little or no residue when applied to fruit or vegetables. Visual evidence can
therefore no longer be relied upon, and the absence of such a useful guide renders the job of the
sampling officer, whether at the port or in the market, haphazard and wasteful.
Analysis
It has to be admitted that small, but possibly toxic, proportions of many of the new pesticides
would escape detection in fruit and vegetable products in a general analysis of the kind
hitherto carried out for the purposes of the Food & Drugs Act.
Although methods for the analysis of residues of some of the new pesticides have, indeed,
been worked out and published by the manufacturers they are usually difficult, lengthy and
unsuitable for routine control in a general food laboratory. Moreover, the necessity for carrying
out control determinations on similar plant material to that under test, with and without the pesticide
for which the sample is to be tested, considerably increases the time required. The main
difficulty, however, is that the analyst will not know which method to adopt unless he is informed
which pesticide has been used.
In the case of food sampled upon importation, the disposal of which may be held up for a time
not exceeding 48 hours, it would be difficult for one such method of analysis to be completed
satisfactorily within the time allowed; in the case of other samples perhaps two or three such
methods could be completed. Unless, therefore, the analyst happens to select the appropriate
method a toxic residue of one of the complex new pesticides might well be missed. No information
is made available to the public analyst as to which insecticides are currently in use in the
district where it was grown for the kind of produce of which he may have a sample. But, to take
apples as an example, tolerances for no less than 45 different pesticides are mentioned in the
Current Food Additives Legislation of the U.S.A., according to the F.A.O. Bulletin No. 34 of
15/5/60.
Enforcement
Although the toxicity of some of the new organic pesticides would appear from their literature
to be as high as that of the most poisonous of the older inorganic insecticides, no safe limits for
their residues in food have been laid down, nor even suggested, by either of the Ministries concerned,
for the use of Local Authorities.
Neither the analyst, nor any of the other officers of a Local Authority is usually in a position
to ascertain by trial what is a safe limit for a chemical in food. Little useful information on
toxicity to human beings is available in the literature, for there is not as yet sufficient case
history of poisoning by the new products on which their minimum toxic dosage could be assessed.
Limits for residues have, indeed, been published in the U.S.A. and elsewhere, but they are said
to be based rather upon how much remains when the spray has been correctly applied than upon
toxicity data.
In the absence of official limits it would obviously be difficult to establish in a Court of Law
that a residual trace of an insecticide was injurious to health. Hence, even if a sampling officer
happened to procure a sample of contaminated produce, and the Analyst to detect the contaminant,
the Local Authority might still be in no position to assess the danger, if any, nor to take suitable
action.
Proposed Remedies
Consideration of the problems outlined above leads inevitably to the conclusion that they
can only be solved by some measure of Government control of the use of potentially toxic pesticides.
Three measures are suggested below, which, taken together, would seem to offer a possible
solution: