UK Ministry
Concerns over Fungicide Residues in Lettuce
“Recent findings
suggest that about 10% of UK lettuces contain residues indicative of misuse of
pesticides” according to a leaked memo from a senior official in the Ministry
of Agriculture (MAFF) which found its way to the environmental group the SAFE
Alliance(1).
Specific
concerns centred around fungicide application. Chlorothalonil “which has never
been approved for use on lettuce and vinclozolin for which the approval is
suspended appear to be used on a significant number of samples. Residues of
tolclofos-methyl suggest that this pesticide is being used after pre-planting
out, but it is only approved for use up to planting out. Excessive use of
dithiocarbamate fungicides also remains a problem” the memo says. These data
and other pesticide residue analysis are due to be published in the autumn.
Vinclozolin
Many
approvals of vinclozolin were withdrawn in 1991, including on lettuce, when it
was shown that high doses in rat studies reduced reproductive capacity and
produced birth defects. MAFF acted by restricting approved uses “to ensure
that an adequate margin of safety is observed for consumers and operators”(2).
This misuse suggests that the safety margin may be affected if vinclozolin is
used on lettuces. Not so according to MAFF. At the levels found they say
residues do not constitute a health problem, merely an indication that growers
are not sticking to the detailed rules for pesticide use.MAFF will discuss ways
of improving growers' awareness with the National Farmers Union and the Health
and Safety Executive.
Chlorothalonil
Chlorothalonil
use is permitted on several food crops, and in conjunction with other
fungicides, but not on lettuce. It is listed by the US Environmental Protection
Agency as a probable human carcinogen.
Tolclofos-methyl
An
organophosphorus fungicide, whose use after the pre-planting stage may cause
significant residues.
Dithiocarbamates
This
widely used group of fungicides caused public concern when studies showed they
could break down into potentially toxic residues in selected foods.
Dithiocarbamates includes the group of EBDC fungicides.
Previous
studies show similar results
Specific
concerns over dithiocarbamate residues in lettuces have been published in MAFF
data. Residue samples taken between 1988 and 1989 showed that of 77 samples, 21%
contained detectable residues of which were above the maximum residue limit (MRL).
Residues below the MRL are indicative of good agricultural practice. One sample
contained 225 mg/kg dithiocarbamates which exceeded the MRL by 45 times.
Tolclofos-methyl, which has no MRL, was found in 38% of samples, up to 33 mg/kg
in one case(3). In 1991 47% of samples contained residues of tolclofos-methyl,
for which no MRL has been set(4). Of 106 samples collected in 1990 and
tested for dithiocarbamates, 9% contained residues above the proposed MRL. On
average, for most UK fruit and vegetables, 2% of residues are found to be above
the relevant MRL(5).
References:
1.
SAFE press release 29 July 1993.
2.
Ministry of Agriculture, Evaluation on Vinclozolin April 1991, No. 34. 56pp.
3.
Ministry of Agriculture, Report of the Working Party on Pesticide Residues:
1988-1989, 86pp.
4.
Ministry of Agriculture, Report of the Working Party on Pesticide Residues:
1991, 95pp.
5.
Ministry of Agriculture, Report of the Working Party on Pesticide Residues:
1989-90, 98pp.
[This article first
appeared in Pesticides News No.21,September 1993, page 15]
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