PESTICIDE RESIDUES IN FOOD - 1981
Sponsored jointly by FAO and WHO
EVALUATIONS 1981
Food and Agriculture Organization of the United Nations
Rome
FAO PLANT PRODUCTION AND PROTECTION PAPER 42
pesticide residues in food:
1981 evaluations
the monographs
data and recommendations
of the joint meeting
of the
FAO panel of experts on pesticide residues
in food and the environment
and the
WHO expert group on pesticide residues
Geneva, 23 November-2 December 1981
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome 1982
TECNAZENE
Explanation
Tecnazene was reviewed at the 1974 Meeting and further studied
at the 1978 Meeting when a temporary ADI was recommended and a few
temporary MRLs were proposed. Further data on residue levels in
potatoes have been received and are reviewed in this monograph
addendum. No additional toxicological data has been received.
RESIDUES IN FOOD
USE PATTERN
The use pattern for tecnazene on stored potatoes was reviewed at
the 1978 Meeting (FAO/WHO 1979)*. A 3% dust formulation is applied at
the rate of 10 lb product per ton (4.5 g product/kg), to reduce
sprouting during storage and to control dry rot. This recommendation
produces a theoretical initial loading on the potatoes of 134 mg/kg.
Tecnazene displays the additional merits of not inhibiting wound-
healing in freshly-clamped potatoes and of controlling dry rot,
Fusarium caeruleum.
RESIDUES RESULTING FROM SUPERVISED TRIALS
Data reviewed by the 1978 Meeting showed that when potatoes were
treated at 4.5 g/kg with 3% tecnazene dust and then stored for 4 to 5
months, mean residues on the tubers were approximately 2 to 3 mg/kg.
Increasing the storage period to six months caused a further reduction
to approximately 1 mg/kg. The original concentration applied
(134 mg/kg) was reduced mainly by handling, both before and after
storage, but losses by evaporation were also shown to occur during
storage. Washing reduced residues still further, to below 1 mg/kg
(mean approximately 0.4 mg/kg) (FAO/WHO 1979).
Residues resulting from different methods and rates of
application have been examined. Potatoes were treated with a 3% dust
formulation at 2.3 g/kg (50% of recommended rate) or 4.4 g/kg at the
time of loading into store. The residue levels resulting from
application by a vibrating device fixed over a loading elevator were
compared with those resulting from the traditional method of
application by shovel. Samples were removed for residue analysis after
5 to 6 days, 1, 2, 3 and 4 months and were deep frozen, without
airing, pending analysis. Results were as shown in Table 1.
* See Annex II for FAO and WHO documentation,
TABLE 1. Residues of tecnazene in potatoes treated with 3% 'Fusarex' dust
Interval Store Rate of Method Residues (mg/kg) in potatoes
between number application of
application (kg dust/ten. application Unwashed Washed Washed and peeled
and potatoes)
sampling range mean range mean range mean
1 2.265 Applicator Not analysed 2.7-3.9 3.6 Not analysed
2 4.43 3.9-5.1 4.3
5-6 days 3 2.265 Standard Not analysee 1.0-5.1 3.3 Not analysed
4 4.43 shovel 3.4-6.6 4.7
1 2.265 Applicator 6.0-16.4 11.9 1.7-2.5 2.0 0.25-0.39 0.32
2 4.43 4.9-23.6 12.6 1.4-2.2 1.8 0.49-0.83 0.66
1 month 3 2.265 Standard 2.3-16.1 6.3 1.6-2.8 2.4 0.53-0.67 0.55
4 4.43 shovel 2.6-30.8 14.4 1.5-2.2 1.8
1 2.265 5.1-16.5 10.5 1.5-2.3 2.0 0.17-0.23 0.21
2 4.43 Applicator 10.4-16.2 12.1 1.8-2.3 2.1 0.10-0.26 0.15
2 months 3 2.265 Standard 10.7-34.9 18.3 1.7-3.4 2.7 0.15-0.30 0.22
4 4.43 shovel 13.9-38.2 26.1 2.7-3.2 2.9 0.16-0.27 0.19
1 2.265 4.8-23.6 10.8 3.2-4.6 4.0 0.27-0.54 0.45
2 4.43 Applicator 16.0-36.1 25.7 4.4-5.1 4.6 0.49-0.69 0.59
3 months 3 2.265 Standard 5.9-34.2 18.6 4.5-5.5 5.0 0.44-0.90 0.64
4 4.43 shovel 11.6-50.9 24.6 2.6-6.4 5.3 0.49-0.89 0.73
1 2.265 2.8-17.2 8.0 2.1-3.0 2.4
2 4.43 Applicator 9.2-22.8 17.4 3.4-4.3 3.8 Not analysed
4 months 3 2.265 Standard 4.0-20.5 13.1 2.7-3.7 3.0
4 4.43 shovel 15.6-56.5 29.2 4.1-4.8 4.5 Not analysed
The vibratory application device yielded a marginally more even
distribution of residues than that provided by the traditional shovel
technique. In unwashed potatoes the mean residues at the 2.3 g/kg
treatment rate were consistently smaller than those obtained at the
recommended rate, to a degree overall that might have been anticipated
from a knowledge of the application rates. However, in potatoes washed
before analysis the difference in residues between the two rates,
although still present, was notably less marked (Table 1). In washed
potatoes, mean residues were generally in the range of 2 to 5 mg/kg.
These values are marginally higher than those reviewed at the 1978
Meeting; however, they are also probably higher than those that would
usually reach the consumer, as the potatoes were deep frozen on
removal from the store without the airing that would normally occur
during handling in commerce (Bullock and Cole 1980).
Hamilton (1981) has commented that some of the available residues
data was obtained during studies of the efficacy of tecnazene as a
fungicide and sprout suppressant rather than to obtain data for safe
use assessments. Hence, often no consideration was given to the amount
of soil adhering to the tubers, which would provide a rough surface
assisting the retention of the fungicidal dust. Some tubers have
visible amounts of adhering dust, though sometimes unexpectedly low
residues of tecnazene are observed from such samples, the tecnazene
having already volatilized, leaving in place the filler which
constitutes 97% of the formulation applied. The amount of adhering
soil will be very variable and depend on many factors, such as soil
type, wetness of soil and tubers at time of lifting, amount of
subsequent handling and aeration, etc. after storage and before
analysis. Washing the tubers certainly reduces this variability, as
Table 1 shows.
RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION
Data reviewed at the 1978 Meeting showed that washing, peeling
and cooking potatoes all cause considerable reductions in tecnazene
residue levels. When potatoes treated at 4.5 g/kg with 3% tecnazene
dust were stored commercially for 4 to 5 months, mean tecnazene
residues on tubers with adhering soil were approximately 3 mg/kg.
Washing the potatoes reduced residues to below 1 mg/kg (mean
approximately 0.4 mg/kg). After peeling, residues in uncooked edible
flesh were normally below 0.1 mg/kg (mean approximately 0.04 mg/kg).
Boiling reduced the level of tecnazene in peeled edible flesh by 50%
or more (FAO/WHO 1979).
In the further studies referred to above, washed potatoes were
also peeled using an abrasive peeler, which possibly removed less of
the residue than would occur during domestic peeling. Under these
circumstances, tecnazene levels in uncooked edible flesh were of the
order of 0.5 mg/kg, i.e. approximately an order of magnitude smaller
than levels in corresponding washed, but unpeeled, potatoes (Table 1).
Residue levels in uncooked edible flesh were not affected by
withdrawing the potatoes after an abnormally short storage period (one
month) as compared with the more representative period of four months
(Bullock and Cole 1980).
Lindsay (1981) also studied losses of tecnazene residues on
washing, peeling and cooking. Owing to the uneven distribution of
residues of fungicides and sprout suppressants between tubers, and
even between quarters of tubers, the following steps were taken to
establish the amount of these materials removed by washing, peeling
and cooking. To reduce the effects of this variation 12 tubers of a
similar size were taken and were divided into two sets of six. The
potatoes were then quartered and two quarters from different potatoes
were used for each test as shown below.
The trial thus covered washing, peeling and a range of types of
cooking. Each analysis was done in duplicate by GLC with EC detection
after appropriate clean-up of a hexane extract of dried macerated
sample. The results in Table 2 show that washing removed most of the
tecnazene and peeling removed most of the remainder. Residues were low
in cooked potatoes.
Hamilton (1981) has reviewed and collected some data on residues
of tecnazene on potatoes, 'as received' and after washing, from
various sources, including known treated material from farms and
retail purchases. Tables 3 and 4 show the results reported, which
illustrate the variability of removal efficiency.
TABLE 2. Tecnazene residues (mg/kg) - cv. Maris Piper
Samples analysed 1 2 3
As received 24.0 23.0 13.3 3.2 18.1 24.2
Washed 5.3 1.8 1.9 2.2 - -
Peeled 0.8 1.0 1.3 0.3 0.8 0.8
Boiled unpeeled (washed) 0.06 trace nd nd 1.5 0.7
As received 17.0 26.0 3.9 12.0 36.1 19.8
Boiled peeled 0.04 0.4 0.04 0.09 0.14 0.05
Chipped 0.15 0.4 0.1 0.7 0.04 nd
Crisped 0.23 0.15 0.1 0.9 trace1 trace
Percentage removed (mean of two analyses)
Washing 85 75 -
Peeling 96 90 97
Boiling unpeeled >99 100 95
Boiling peeled 99 99 99
Chipping 99 96 99
Crisping 99 95 99
1 trace = < 0.005 mg/kg)
TABLE 3. Residues of tecnazene in unwashed potatoes from various
sources
No. of Tecnazene (mg/kg)
Source samples Range Mean
Market 61 0.1 - 19.3 3.6
Various 26 0.1 - 20.5 5.4
Various 5 2.0 - 7.7 4.0
Farms 6 2.8 - 33.7 10.1
Market 5 0 - 5.1 1.5
Farms 16 0.1 - 23.7 5.8
TABLE 4. Residues of tecnazene in potatoes before and after washing
Source Cultivar Tecnazene (mg/kg) % Removed
As received Washed by washing
Farm 1 Record 9.5 6.4 33
Farm 1 Maris Piper 7.1 6.8 4
Farm 2 Maris Piper 3.6 3.8 -
Farm 2 Maris Piper 33.7 5.8 83
Farm 3 Pentland Hawk 3.6 3.6 0
Farm 4 Croft 2.8 2.6 7
Shop 1 - 2.3 2.0 13
Shop 2 - 0.02 0.01 50
Shop 3 - 0.05 0.02 60
Shop 4 - <0.01 0.02 -
Shop 5 - 5.1 3.7 28
Very variable levels of tecnazene have been found at every point
of analysis of treated potatoes. The reasons for the wide variation of
residues in potato flesh after washing and peeling are not known. The
condition of the skin due to maturity of the potato and choice of
cultivar may well be factors affecting penetration into the flesh. The
time of application after lifting and the temperature of storage, both
during the short curing period and the lengthy storage period, may
also be contributory factors. There appears to be an increase in the
residue levels in flesh related to the length of storage time, but
again this finding is not always consistent. The residues found in the
flesh of peeled potatoes are all below 1 mg/kg, but there are reports
of levels of over 1 mg/kg being found in boiled (after peeling)
potatoes, although it is unlikely that any allowance had been made for
loss of water in cooked potatoes.
Washing potatoes removed adhering soil and tecnazene dust, but
the percentage removed is very variable and can be small, as shown by
Bullock and Cole (1980) and Hamilton (1981).
Residues in excess of 1 mg/kg were found on all of the 6 samples
taken from farm stores after 6 months storage (Table 4) and on 2 out
of 5 shop samples (Table 2), which were analysed about 6 months after
harvest. The samples, ex farm, were analysed within 3 days after
removal from store, but it is unlikely that the two shop samples were
analysed that soon.
EVALUATION
APPRAISAL
Tecnazene is used on potatoes as a post-harvest sprout
suppressant and to control dry rot. The further residues data that are
now available on potatoes broadly confirm the data reviewed by the
1978 Meeting. The new data from Bullock and Cole (1980) involved
alternative means of application and also incorporated a 'Worst case'
evaluation, as the potatoes were deep frozen immediately on removal
from the store. Thus the potatoes did not receive the handling and
airing at ambient temperature that is known to reduce residue levels
by evaporation once the tubers are removed from storage. In addition,
peeling was by abrasive peeler, which can be expected to remove less
residue than normal domestic peeling. In these extreme circumstances,
tecnazene levels in uncooked, peeled edible flesh were of the order of
0.5 mg/kg, which is somewhat higher than the levels reported to the
1978 Meeting. However, when due account is taken of (i) the reduction
of residue levels which can be expected to occur during cooking and
(ii) the extreme circumstances in which the residue data were
generated, this information is reassuring. The data confirms that
residue levels in washed potatoes are reduced by approximately an
order of magnitude by peeling.
The data reviewed at the 1978 Meeting indicated that in washed
and peeled potatoes residues will normally be below 0.1 mg/kg (mean
0.04 mg/kg) and that this residue is reduced by 50% or more on
cooking. On this basis, residues in boiled potatoes would rarely be
likely to exceed 0.05 mg/kg. However, the work of Lindsay (1981) shows
that these figures may be low in some circumstances, although the
reduction due to washing and cooking is confirmed.
Toxicology
None of the required or desirable data specified by the 1978 JMPR
(FAO/WHO, 1979a) were available, However, the present Meeting again
discussed the relevance of the tumour-initiating activity observed in
a study where tecnazene was painted on the skin of mice. It was agreed
that this had little relevance to the evaluation of pesticides
residues in food especially when acceptable oral carcinogenicity
studies in rats and mice were taken into account. Because of this
reduced concern regarding the mouse skin painting study, the Meeting
agreed that the temporary ADI allocated previously (FAO/WHO, 1979) be
extended for 2 years.
The Meeting confirmed the necessity for an adequate reproduction
study on tecnazene.
Level causing no toxicological effect
Rat : 750 ppm in the diet equivalent to 38 mg/kg bw/day
Mouse : 1500 ppm in the diet equivalent to 200 mg/kg bw/day
Dog : 15 mg/kg bw/day
Estimate of temporary acceptable daily intake for man
0 - 0.01 mg/kw bw
RECOMMENDATIONS OF RESIDUE LIMITS
Although there are indications that the temporary MRL of 1 mg/kg
on potatoes (washed before analysis) proposed in 1978 may be too low,
available relevant data are insufficient to recommend any replacement
figure. The future data on losses due to washing, peeling and cooking
are reassuring.
FURTHER WORK OR INFORMATION
Required (by 1983)
An adequate study on reproduction.
Desirable
1. Clarification of the tumour-initiating activity observed in a
skin painting experiment on mice.
2. Short-term tests on mutagenicity.
3. Metabolism studies in different mammalian species.
REFERENCES
Bullock, D.J.W. and Cole, M.C. "Tecnazene"; Residues in potatoes
1980 following application of 'Fusarex' by shovel and by
applicator methods" ICI Plant Protection Division Report No.
TMJ 1794A. (Unpublished)
Hamilton, G.A. Information on tecnazene from the United Kingdom.
1981 (Unpublished)
Lindsay, D.A. Information on tecnazene from the United Kingdom.
1981 (Unpublished)
See Also:
Toxicological Abbreviations
Tecnazene (EHC 42, 1984)
Tecnazene (HSG 12, 1988)
Tecnazene (WHO Pesticide Residues Series 4)
Tecnazene (Pesticide residues in food: 1978 evaluations)
Tecnazene (Pesticide residues in food: 1994 evaluations Part II Toxicology)