Excessive residues
In September each year
the Working Party on Pesticide Residues (WPPR)
(soon to be renamed the Pesticides Residues
Committee) publishes its annual report. This
year's results showed 25% of food analysed
contained pesticide residues at levels below the
maximum residue levels (MRLs) and 1.4% of samples
exceeded the MRL (see table 1). These figures
should be treated carefully, as the percentage of
food samples that contain pesticides will depend
on what foods are sampled and what pesticides are
sought.
| Table 1. Recent sampling results | ||||
| 1995 | 1996 | 1997 | 1998 | |
| No. of samples | 3230 | 2263 | 1878 | 2200 |
| Containing residues (%) |
31 | 34 | 29 | 25 |
| Exceeding MRLs (%) | 1 | 1 | 1 | 1.4 |
A large proportion of the
excess residues were found in yams, sampled for
the first time. Twelve out of 16 samples
contained car-bendazim technically in excess of
MRLs. This is because no MRLs have been applied
for by the importers, so any residue found is
treated as exceeding the MRL.
More serious exceedances of
MRLs occurred in pears with high levels in
imports from Belgium and Holland, and evidence of
illegal use of pesticides by UK growers (see
end).
The illegal use of certain
fungicides on lettuce has been a problem for the
past six years. This year two out of 99 samples
contained chlorothalonil, and six out of 11
iprodione, neither of which are approved for use
on winter lettuce.
Unpredictable results
Chlorothalonil is a
fungicide that is difficult to analyse
accurately. This is because it is unstable and
degrades during analysis. It now seems the
problem is wider than just chlorothalonil. Tests
run in 1999 on four representative
commodities-apples, lettuce, oranges and
tomatoes-and spiked with over 100 pesticide
residues, showed that residue 'loss' occurred
during processing (see table 2). The 'loss' of
residues means that results may understate the
amount of pesticide actually in the sample.
These results are highly
significant. It is not clear why different
laboratories are getting different results, why
different pesticides behave differently, nor why
the losses occur in the first place. One idea is
that either the temperature at which the sample
is analysed (from frozen, or at room
temperature), or the fineness with which the
sample is mashed for analysis may be important.
Clearly, the interpretation of residue analysis
needs to be taken with a pinch of salt, and there
may be more pesticides in food than we think.
| Table 2. Loss of pesticide residues from spiked samples during analytical processing | ||||
| No. of pesticides sought | No. of pesticides | with loss | > 20% | |
| Lab 1 | Lab 2 | Lab 3 | ||
| Apple | 105 | 16 | 33 | 69 |
| Lettuce | 104 | 81 | 86 | 13 |
| Orange | 106 | 12 | 17 | 8 |
| Tomato | 106 | 14 | 5 | 3 |
Naming the guilty parties
In accordance with the
policy of 'openness' espoused by government
Ministers, this report names the retail outlets
where samples containing residues in excess of
MRLs are bought. This policy requires the
Pesticides Safety Directorate (PSD) to notify the
retail outlet, which has the opportunity to
reply. The gist of the replies are then
published. For example, five samples of imported
spinach had residues in excess of the MRLs. One
sample from Sainsbury, and one from ASDA
contained excess levels of the insecticide
permethrin; and one sample each from Safeway,
Sainsbury and Tesco, had levels of the fungicide
iprodione above the MRL.
Choosing the samples
Until recently,
samples were bought at the front of the shop, to
ensure that the food chosen was the same as the
consumer would actually buy. If offending brands
are now going to be named, then sampling should
now be 'at the back of the shop' where
lots-particularly of fruit and vegetables-from
different suppliers come in, in labelled boxes,
and are mixed: this is the point at which
traceability can be demonstrated.
What's next?
WPPR tries to target
its resources at a combination of regular dietary
staples, rolling programmes of food samples, and
new areas that have not previously been looked
at. New areas in the future will include fast
food burgers, bottled water and pasta, and more
emphasis will be put on monitoring fruit and
vegetables commonly given to children. And how
much reliance can we put on the results?
Annual Report of the WPPR 1998, Ministry of Agriculture Fisheries and Food/Health and Safety Executive, MAFF Publications, London, 1999, 100pp. WPPR results are also available on: www.maff.gov.uk/aboutmaf/agency/psd/wppr97/wppr1.htm
| Pesticides in your pears High levels of the pesticide chlormequat (a growth regulator, which helps to swell pears, and ensure that most of the crop on the tree ripens ready to drop at the same time) have been found in pears imported from Belgium and Holland, indicating large scale overuse. Chlormequat has also been found in UK pears where it is not approved for use. Four out of five samples of these pears contained chlormequat at levels well below MRLs. Another sample contained the pesticide tolylfluanid, which is also not approved for use on pears. These findings indicate illegal use of both chlormequat and tolylfluanid. There has been concern since 1995 that chlormequat was being used illegally by UK growers. Six out of 36 samples of imported pears contained chlormequat above the MRL of 3 mg/kg. It is heavily used in Belgium and Holland. The Pesticides Safety Directorate (PSD) notes that: "assurances have been received that the authorities have begun a more rigorous screening programme with the aim of ensuring that future imports to the UK will fall within statutory MRL limits." PSD states that at the highest level of chlormequat residue found (11 mg/kg - or nearly four times the MRL) there should be no health risk to consumers, even in the 'worst case assumption' (a toddler consuming large quantities of pears); and that 'adverse health effects are most unlikely although the safety margins could be eroded.' Regulators are now concerned not just about long-term low doses, but also by short-term higher doses. Research shows that the Acute Reference Dose (acuteRfD)-the safe dose at one meal or on one day for the most vulnerable population group (probably children) based on toxicological data-is about 0.05 mg/kg/body weight. So for an 'average' adult weighing 70 kg, the lifetime safe dose would be 3.5 mg. Anyone eating more than one pear a day with high residues may be vulnerable. It is difficult to assess what the chances of this may be: but clearly pears are not as safe as we thought they were. This is another instance of too many chemicals in fruit. |
[This article first appeared in Pesticides News No. 45, September 1999, page 6]