sec - BUTYLAMINE JMPR 1978
In 1975 the Joint Meeting (FAO/WHO 1976b) evaluated
sec-butylamine. A temporary ADI was allocated and some temporary
MRLs were recommended. In 1977 information on the fate of
sec-butylamine in livestock when citrus pulp and molasses containing
residues are used as components in their ration was evaluated (FAO/WHO
Of the remaining work or information required, some information
on uses on fruits other than citrus was considered in 1977. Since
then, information has been supplied from Scotland and Ireland on the
use and fate of sec-butylamine applied to potatoes: this is evaluated
in the following monograph addendum.
EVALUATION FOR ACCEPTABLE DAILY INTAKE
No toxicological data bearing on the concerns expressed by the
1975 Meeting were received. A re-evaluation of the long-term
rat-feeding study, including a microscopic examination of tissues, was
made to consider the suggestion of an incidence of thyroid light-cell
adenoma. The Meeting was also made aware of similarities between
light-cell tumours in rats and thyroid tumours in humans. Although
there was no evidence from that re-evaluation to suggest a
carcinogenic potential for sec-butylamine, it was felt that the
study was of borderline value for an adequate carcinogenic bioassay.
The Meeting felt that further information on the carcinogenic
potential was needed. No bioassays for mutagenic activity which would
bear on this question and which were requested by the 1975 Meeting
were reported. Concern was raised on the potential for the formation
of a nitrosated derivative. As a result of these concerns, the Meeting
estimated a temporary ADI at a lower level.
Level causing no toxicological effect
Rat: 686 ppm base (1250 ppm acetate salt) in the diet
equivalent to 35 mg base/kg bw (63 mg acetate salt)
Mouse: 69 mg base/kg bw/day (125 mg acetate salt) kg bw/day
Estimate of temporary acceptable daily intake for man
0 - 0.1 mg base/kg body weight
RESIDUES IN FOOD AND THEIR EVALUATION
Since 1971 sec-butylamine has been widely used in Scotland, and
more recently in Ireland, for treatment of seed potatoes, giving good
control of gangrene caused by Phoma exigua var. FAVEATA and skin
spot due to Oospora pustulans. Some control of silver scurf disease
(Helminthos porium solani) is also obtained (Graham and Hamilton,
1970; Graham et al., 1973, 1973b, 1975; Quinn et al., 1976; Graham,
Recently, limited approval was extended to allow the sale of
those treated potatoes which are too small or too large for seed
purposes for human consumption and animal feed.
Potato-tubers are fumigated with sec-butylamine generated as a
vapour from the base. The rate is 200 mg/kg and application should be
made within 14 days of harvest. Air is charged with the vaporised
sec-butylamine while it is re-circulated through the potatoes for 30
minutes and then re-circulation of the charged air continued for a
further two hours.
In general, fumigation does not have any substantial effect on
the growth pattern or the yield of the crop obtained from treated
seeds. However the use of sec-butylamine greatly reduces the loss of
seed potatoes during storage. Without treatment the loss can exceed
60% with some varieties (Quinn at al., 1976).
Although sec-butylamine has been used experimentally on
commodities other than citrus and potatoes there was no evidence that
any of these treatments has been accepted commercially.
RESIDUES RESULTING FROM SUPERVISED TRIALS
Having demonstrated effectiveness against gangrene and skin spot
Graham and Hamilton (1970) carried out trials in which 3 varieties of
potatoes were fumigated in a specially constructed chamber holding
5000 kg of potatoes, treatment being carried out within 2 days of
harvest and care being taken to ensure good distribution throughout
the stack. The air/fumigant mixture was blown through the perforated
floor of the chambers.
The potatoes were sampled from the top and bottom of the stacks
(1.5 m high). The samples were analysed by the gas-chromatographic
method of Day et al., (1968) but without a carbon tetrachloride wash.
Considerable variation was found in the residues in individual
potatoes, even in adjacent tubers. This was almost certainly due to
the condition of the skin since higher residues were found in immature
tubers and in those whose skin was damaged. To reduce this variation,
sound quarters were taken from each of four tubers of fairly uniform
size for each analysis.
Typical residues in potatoes treated in the 5-tonne chambers
where the fumigant was introduced over 30-40 minutes and re-circulated
for a further 2 hours are shown in Table 1. Good distribution with a
dosage of 200 mg/kg was achieved, but at 50 mg/kg most of the residue
was confined to the lower tubers indicating this dose to be
insufficient for equal distribution.
Commercial potato stores of large capacity fitted with internal
re-circulation systems are adaptable for fumigation and Graham et al.,
(1975b) reported trials in which 35 tonne lots were fumigated in such
a store. The degree to which equal distribution of sec-butylamine
throughout the bulk of tubers took place was determined by residue
analysis. Results are given in Table 2. The residue levels in samples
taken at the end of fumigation (Nos. 1-17), showed there was good
horizontal distribution at the top of the bin. Vertical distribution
also seemed to have been satisfactory because samples taken from
various positions at the top of the bin had a mean residue level of
161 mg/kg whereas 196 mean level of 196 mg/kg was found on samples
taken from the bottom near the duct.
Samples in mesh bags were buried in the bulk at the time of
filling the store. These were recovered 5 months after fumigation and
analysed. Some reduction in the residues had occurred but the mean
levels of 111, 88 and 100 mg/kg in the top, middle and bottom
confirmed that the gas distribution had been satisfactory.
Graham at al., (1973a) recognized that the decline in
effectiveness of fumigation which occurs when the treatment is delayed
following harvest was due to the skin and damaged areas becoming
increasingly impervious to the gas as a result of physico-chemical
changes after lifting. It was also suggested that the fungus might
have penetrated to depths in the tuber which the sec-butylamine
could not reach in sufficient concentration to kill the organism.
However, the need to treat tubers so soon after lifting presents
practical problems, especially when chemicals that many only be
applied to seed potatoes are used because separation of seed and ware
(table) potatoes has then to be done quickly, often while growers are
still lifting crops. Growers prefer to store the mixture of seed and
ware, separating them up to several months later. Another reason for
delaying sorting is that latent infections associated with the tuber
become activated by damage during grading. Fumigation after grading
was shown to be much less effective than a similar treatment carried
out on the freshly lifted tubers.
TABLE 1. Residues of sec-butylamine in potatoes fumigated within 2 days
of lifting in a 5-tonne prototype fumigation chamber
Cultivar Dose (mg/kg) Same position Residue (mg/kg)
Redskin 1 200 top 194
Majestic 1 200 top 103
Redskin 2 200 top 92
King Edward 1 200 top 92
Kind Edward 2 50 top 12
Redskin 3 50 top 2
TABLE 2. Residues in a 35 tonne bulk fumigated soon after lifting
(Pentland Crown tubers) (Graham et al., 1973b)
Range of Mean
Sample Position Time of sampling residues residue
no. in bin 4 (mg/kg) (mg/kg)
1-2 top layer after 50% of dose applied 2.3-6.8 4.6
3-4 top layer after 100% dose applied 57-114 86
5-6 top layer after 1 h further recirculation 103-112 108
7-8 duct below bin at end of fumigation 156-236 196
9-17 top layer at end of fumigation 124-184 161
18-21 top layer at unloading of bin 95-122 111
22-23 middle layer at unloading of bin 64-113 88
26-30 bottom layer at unloading of bin 58-130 100
Graham et al., (1975) in the course of experiments to determine
the feasibility of delaying fumigation until the ware potatoes had
been sorted from the bulk determined the residue of sec-butylamine
in tubers after hand and mechanical sorting. The data are summarized
in Table 3. These potatoes had been fumigated at the rate of
Graham (1978) provided information on residue levels measured in
several other trials in which sec-butylamine was applied in the
vapour phase at the rate of 200 mg/kg. There results are summarised in
Eades et al., (1978) reported results of the analysis of samples
taken from 50 kg jute sacks fumigated at the rate of 200 mg/kg. These
are given in Table 5. Some analyses were done in triplicate. The
variation between individual samples is noticeable.
FATE OF RESIDUES
In 1968, potatoes which had been grown from seed tubers treated
at 140 mg/kg three days after lifting in 1967, were harvested. In 1969
crops were harvested from seed treated at levels of 200, 500 and 1000
mg/kg three days after lifting in 1968. In 1970, crops were harvested
from seed treated at 200 mg/kg three and fourteen days after lifting
in 1969. Results of the analysis of all these crops and untreated
material from the same source are given in Table 6 (Graham et al.,
1973). Eades et al., (1978) reported from 0 to 0.36 mg/kg in the
progency of single tubers fumigated at 200 mg/kg. This value had been
corrected for background contamination.
The residues found crops grown from treated seed are very small
and are generally not greatly different from those found in untreated
material, even when the mother tubers had been treated at five times
the recommended dosage. There is, therefore, no significant
translocation of the chemical to daughter tubers, so that there is no
hazard to consumers from crops grown from treated seeds.
General studies designed to evaluate the effect and fate of
sec-butylamine fed to dairy cows as a residue in their ration were
evaluated in 1977 (FAO/WHO 1978b).
Graham et al., (1973a) reported that there was some reduction in
residue when potatoes were stored under ventilated conditions, such as
in oven trays. However, the variation between individual tubers made
it difficult to establish this with certainty. Substantial residues
were still present after many months storage.
Graham et al., (1973b) showed that some reduction occurred in
large stacks held for 5 months but the average concentration was still
about 100 mg/kg.
Graham et al., (1973a) found that 44-75% of the residue was
removed by peeling potatoes in the usual manner, which removes 10-12%
of the weight of the whole tuber. The distribution of the residues
between whole tuber flesh and peel is given in Table 7. When the
treatment is delayed until the potatoes have been in store for a
longer period there is less penetration: 50-84% of the residue was
removed by peeling potatoes stored for periods up to 14 weeks before
fumigation (Graham et al., 1975; Table 3).
Graham et al., (1973a) found that 24-45 of the residues in potato
flesh were removed by boiling and slightly more by crisping (Table 8).
There are significant losses converting unpeeled potatoes into
part-cooked potato chips (Graham 1978). Data are given in Table 9.
RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION
No residue figures are available on samples taken at the point of
retail sale but some of the figures given in Tables 4 and 9 are from
potatoes intended for consumption following processing.
When treated potatoes are sorted to remove tubers which are
either too small or too large for use as seed only about 10% of the
bulk is normally diverted for ware (table) use. This greatly reduces
the likelihood of significant quantities of treated potatoes being
used as human food.
METHODS OF RESIDUE ANALYSIS
These residue data involving the experimentation of more than
1000 samples, were all obtained by the method of Day et al., (1968) as
modified by Graham et al., (1973). The latter modification consists of
omitting the carbon tetrachloride wash. It gave a recovery greater
than 95% and a limit of determination of 0.05 mg/kg (Graham 1978).
Results were from the analysis of a sample comprising one quarter
from each of four sound tubers of uniform size. The potatoes were not
washed or peeled before analysis, but any surplus adhering soil was
NATIONAL MRLs REPORTED TO THE MEETING
The Meeting is not aware of any national MRLs having been
established for sec-butylamine residues in potatoes.
For a number of years the use of sec-butylamine has been
approved in Scotland and Ireland for the treatment of seed potatoes
against a number of fungal diseases. Recently limited approval was
extended to allow the sale for human consumption and animal feed of
those treated potatoes which are too large or too small for seed
purposes. The fungicide is applied by fumigation within 14 days
Extensive studies in Government research stations have followed
the distribution of the fungicide among potatoes in storage, the
effects of various factors on the retention of residues and their fate
following processing and cooking. The bulk of the residue is in the
outer layer and is removed by peeling. Up to half of that remaining is
removed by cooking.
The method of analysis used for citrus is applicable to potatoes
as well as citrus and has been used successfully in monitoring
programmes. The limit of determination is 0.05 mg/kg.
Because of the limited need to use sec-butylamine on potatoes
and the limited distribution of treated potatoes in international
trade, no recommendation is made.
FURTHER WORK OR INFORMATION
Required (by 1981)
1. Further studies to resolve the question of carcinogenic risk.
1. Quantitative metabolic studies to determine if metabolites in
test animals are the same as those in food plants and animals.
2. Information on the formation and, if found toxicity of potential
3. Mutagenicity studies with techniques currently available.
4. Clinical and metabolic observations in humans.
TABLE 3. Residues in 5 tonne bulks fumigated after periods of storage of up to 14 weeks
(Graham et al., 1975)
Cultivar Grading Number of Residue Residue Calculated Residue
method days elapsed in flesh in peel residue in removed
between (mg/kg) (mg/kg) whole tuber by peeling
grading and (mg/kg) (mg/kg)
1. Bintje hand 1 1 37 5 75
riddle 1 7 71 14 54
riddle 7 5 41 9 50
2. Marie Peer hand 1 5 109 22 79
riddle 1 10 184 31 70
riddle 7 7 82 15 59
spool 1 8 173 30 74
spool 7 5 67 13 66
3. Pentland hand 1 3 89 13 80
Squire riddle 1 12 189 30 66
riddle 7 2 57 9 84
spool 1 7 139 22 75
spool 7 4 75 10 68
TABLE 4. Residues of sec-butylamine measured in potatoes from various trials
Type of storage Quantity No of samples Range of Mean
(tonnes) residues residue
Bulk 250 20 2-96 34
Bulk 150 31 1-138 30
Bulk 100 25 2-107 32
Bulk 150 20 2-142 57
Bulk 80 42 1-256 83
Pallet Boxes 30 30 1-133 42
Pallet Boxes 11 12 45-170 101
Pallet Boxes 20 20 70-242 117
Bulk 30 15 2-44 21
Bulk 30 26 1-137 33
TABLE 5. sec-butylamine levels in fumigated seed potatoes (Eades et al., 1978)
Sample no. sec-butylamine, mg/kg
3 24, 16, 5 (mean 15)
8 158, 80, 179 (mean 139)
10 255, 161, 132 (mean 183)
TABLE 6. Residues of sec-butylamine in crops grown from fumigated seed tubers
Year Treatment of seed Number of Number of Range of Mean
tubers cultivars stocks residue residue
used used (mg/kg) (mg/kg)
1968 140 mg/kg 2 2 0.05 0.05
Nil 2 2 0.05 0.05
1969 200 mg/kg 3 4 0.04-0.12 0.08
500 mg/kg 1 1 0.09-0.16 0.14
1000 mg/kg 1 1 0.05-0.11 0.08
Nil 3 4 0.03-0.11 0.07
1970 200 mg/kg (3 days) 2 2 0.01-0.10 0.05
200 mg/kg (14 days) 2 2 0.01-0.06 0.03
Nil 2 2 0.01-0.04 0.03
Limit of detection 0.01 mg/kg
TABLE 7. Residues in 5-tonne bulks fumigated soon after lifting (Graham et al, 1973)
Cultivar Residue in Residue in Calculated Residue
flesh (mg/kg) peel (mg/kg) residue in removed by
whole tuber peeling (%)
Redskin 1 8 193 28 73
Majestic 13 294 48 75
Redskin 2 24 374 53 58
Kind Edward 1 28 508 66 60
King Edward 2 63 688 130 57
Redskin 3 16 365 45 66
King Edward 3 33 244 55 44
King Edward 4 22 192 40 50
Pentland Crown 1 24 471 62 64
Pentland Crown 2 23 420 56 70
TABLE 8. Effect of cooking on residues of sec-butylamine in fumigated potatoes
(Graham et al., 1973a)
Treatment and Residue in Residue in Residue removed
cultivar uncooked flesh cooked flesh by cooking (%)
Cooking by boiling
Redskin 1 18.8 10.3 45
King Edward 1 42.4 26.1 39
Majestic 1 53.0 37.0 30
Majestic 2 20.0 15.3 24
King Edward 10.0 5.9 41
Pentland Crown 1 24.0 15.1 37
Pentland Crown 2 14.1 8.4 40
Cooking by crisping
King Edward 1 63.0 38.0 40
King Edward 2 39.0 16.5 58
Redskin 1 7.8 4.2 46
Redskin 2 16.5 10.1 39
TABLE 9. Effect of industrial processes on the level of sec-butylamine
residues in potatoes and potato products
Description of sample Trial 1 Trial 1
Unpeeled potatoes 76 32
Peel potatoes 19 24
Peel 48 79
Waste pieces 60 6.8
Chips - freshly cut 1.2 5.7
Chips - blanched 6.8 6.0
Chips - part fried 8.4 7.2
Day, E.W., Holzer, F.J., Tepe, J.B., Echert, J.W. and Kolbezen,
(1968) M.J. Determination of sec-butylamine residues in
fruit. J. Ass. Off. Anal. Chem. 51: 39-44.
Eades, J.F., Neville, C., Rice, B. Residues of sec-butylamine in
(1978) fumigated seed and the progeny of fumigated seed.
Report of the Agricultural Institute, Carlon, Ireland.
FAO/WHO sec-butylamine. 1975 evaluations of some pesticide
(1976) residues in food AGP:1975/M/13 FAO Rome or WHO
Pesticide Residue Series No. 5. WHO Geneva P. 59.
FAO/WHO sec-butylamine.1977 evaluations of some pesticide
(1978) residues in food. AGP:1977/M FAO Rome.
FAO/WHO 1977 evaluation of some pesticide residues in food.
Graham D.C. Submission of residues of sec-butylamine in potatoes.
(1978) Letter from Department of Agriculture and Fisheries for
Scotland, Edinburgh (22 Aug. 1978).
Graham D.C. and Hamilton, G.A. Control of potato gangrene and skin
(1970) spot diseases by fumigation of tubers with
sec-butylamine. Nature, London 227: 297-298.
Graham, D.C., Hamilton, G.A., Quinn, C.E. and Ruthven, A.D. Use of
(1973a) 2-aminobutane as a fumigant for control of gangrene
skin spot and scurf diseases of potato tubers. Potato
Res. 16: 109-125.
Graham, D.C., Hamilton, G.A., Nash, M.J. and Lennard, J.H. Fumigation
(1973b) of bulk-stored potatoes with 2-aminobutane for control
of gangrene, skin spot and silver scurf diseases.
Potato Res. 16: 234-243.
Graham D.C., Hamilton, G.A., Quinn, C.E. and Ruthven, A.D. Control
(1975) of potato gangrene by fumigation of tubers with
2-aminobutane after periods of storage. Potato Res.
Quinn, C.E., Harper, P.C. and Graham, D.C. Effect of fumigation of
(1976) potato seed tubers with 2-aminobutane on plant growth
and yield. Potato Res. 19: 147-155.
Rice, B. Res. Rep. Pl. Sci. Crop Husb. An Foras Taluntais (The
(1973) Agricultural Institute) Dublin pp. 80.