In January 1995, the results of a research
programme into the levels of OP and carbamate residues in individual carrot
roots indicated the occurrence of a wide variation of residue between individual
roots (see PN 27 p3). In some cases, the highest residues found meant the acute
reference dose (ARfD) was exceeded. The ARfD represents the maximum amount of a
pesticide which can be consumed on a single occasion in the practical certainty
that no harm will occur.
As a result, the Advisory Committee on Pesticides (ACP)
(which advises government ministers) made a number of recommendations to restore
the safety margins that had been eroded. One suggestion included a research
programme to established whether residue variation was also present in other
fruit and vegetables. On 14 March, MAFF published results from the first year of
such a two year programme.
Researchers tested individual units of UK apples, pears, and
tomatoes and imported apples, bananas, nectarines, peaches, oranges and tomatoes
for variation in residue levels. The ranges of variability found are
similar to those previously reported in carrots. The worst variation occurred in
nectarines where the OP propargite levels exceed the average residue level by as
much as 29 times. Carbaryl levels in imported pears and UK apples, methamidophos
and ethiofencarb in peaches, and malathion in oranges also showed wide
variations in residue levels. As a result of these findings MAFF report
suggested: "It seems that the potential for residues to vary widely between
units (of individual fruit) may be the norm rather than the exception."
The official response
ACP considered these occasionally elevated residues
were not likely to produce adverse health effects. However, given that the
potential for variable residues to occur has eroded the safety margins built
into pesticide approvals, action should again be taken to restore the margins.
This will take the form of additional research and consultation with
international experts in the field.
Both UK and imported produce contain variable pesticide
residues. Therefore MAFF has asked the Codex Alimentarius Commission (the
international food standards body) to investigate this matter further. (Pesticides
News will report later on their findings).
The government's Deputy Chief Medical Officer Dr Jeremy
Metters said fruit and vegetables remained key components of a healthy diet. He
however warned: "It is worth repeating the long-standing advice that washing
fruit before consumption is always a sensible precaution to ensure it is clean;
peeling fruit is a matter of consumer choice but it is a sensible additional
precaution when preparing fruit for small children."
Pesticides Trust [now PAN UK] comment
Credit is due to MAFF for pursuing this important
issue and for making the research public. The results should not deter consumers
from eating fresh fruit and vegetables. The risk to health from eliminating
fruit and vegetables from the diet would far outweigh the risks presented by
possible exposure to higher than usual pesticide residues.
However, there are a number of important implications to
these findings:
Although the research focused on residues of organophosphates and carbamate insecticides, the 'unit to unit variation of residues' effect can occur with any pesticide which leaves residues in a crop.
The variation in residues is not the result of illegal or inappropriate use of pesticides, but results from legitimate use.
Some pesticide residues can be washed off the surface of fruit and vegetables, although plain water is limited in its efficiency at removing pesticides. However, systemic pesticides which enter the flesh of the crop cannot be removed by washing or peeling.
This research demonstrates that enormous variations can exist in individual vegetables and fruits. Current monitoring programmes for pesticide residues in food cannot be expected to detect and report on such variations. Will extra resources be made available to develop appropriate sampling and monitoring strategies?
Current acceptable daily intakes (ADIs) are based on lifetime exposure through normal consumption of the crop containing those residue levels. The reported results suggest that we may be exposed to unexpected residue peaks which cannot be accounted for. This may significantly increase the risks of adverse health effects resulting from exposure to pesticides. It may also exacerbate the potential adverse effects resulting from cumulative exposure to pesticide residues in food. There may also be a need to address the possible acute toxic effects of exposure to pesticides through food. These are currently ignored as being too unlikely to occur in normal circumstances.
The unit to unit variation of residues is no longer within the control of pesticide regulators or users. The only viable long term strategy is one of overall reduction on the use of and reliance upon pesticides in agriculture. (DB)
Unit to unit variation of pesticide
residues in fruit and vegetables, Pesticide Safety Directorate, an executive
agency of MAFF, March 1997.
[This
article first appeared in Pesticides News No. 36,
June 1997, page 15]