Removal of DDT and Parathion Residues from Apples, Pears, Lemons


Mechanical removal was sought by using emulsifying agents, detergents, pressure sprays, and scrubbing brushes. Solvent removal attempts included the u...
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Removal of DDT and Parathion Residues from Apples, Pears, Lemons, and Oranges F. A. GUNTHER, M. M. BARNES, and G . E. C A R M A N

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University of California Citrus Experiment Station, Riverside, Calif.

Alkaline and halogen-carrier media, such as sodium silicate, trisodium phosphate, ferric chloride, sodium carbonate and bicarbonate, and alkaline soaps were used for chemical removal of DDT deposits. Me­ chanical removal was sought by using emulsifying agents, detergents, pressure sprays, and scrubbing brushes. Solvent removal attempts included the use of kerosene, mineral oil, xylene, and polymethylated naphthalenes. With apples and pears, sodium sili­ cate frequently proved superior, removing as much as 90% of the residual surface DDT, and an alkaline soap effected significant removal from oranges. No experimental treatment has afforded significant re­ moval of parathion from treated fruits.

T h e widespread commercial use of D D T and the anticipated use of parathion indicated the practical value of investigating the feasibility of removing their harvest residues without injury to the fruits. A distinction has been drawn (1) between "harvest" and " u l t i m a t e " residues. The former term is being defined as the surface or penetrated residue of insecticide at the time of harvest, whereas the latter designation refers to the residues i n or on the foodstuff, whether fresh or processed, at the time of consumption. Thus, there exist harvest sur­ face and penetration or harvest total residues, as well as ultimate surface, penetration, and total residues. Where necessary, component parts of the foodstuff m a y be specified to delimit this concept further. Begun i n 1944 with D D T and i n 1947 with parathion, the present report includes analytical data secured from certain chemical, mechanical, and solvent actions on apples, pears, lemons, and oranges. I n the absence of established tolerances for these two insecticidal materials, i t is hardly possible to interpret the significance of many of these data with respect to consumer hazard. Although there are a number of published reports of the magnitude of [harvest] D D T residues, particularly on apples (4, 5, 7, 8, 14, 15, 18, 19), grapes (β), oranges (10), and pears (2, 5,18), and of terminal residues i n canned products (15,17), only a few publica­ tions have been concerned either with the nature of the residual deposits (6, 7,11,16) or with their removal (2,14,18) prior to consumption. Hough (14), for example, reported that 1.3% hydrochloric acid solution, and dilute solutions of sodium silicate, trisodium phosphate, IN-181-P (a powder containing 5 0 % sodium lauryl sulfate, as supplied b y Ε. I . d u Pont de Nemours & Company, Inc., Wilmington, Del.), and a Santomerse a l l failed to remove readily the D D T deposits on mature apples. (The Santomerses are the 137

AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.

ADVANCES IN CHEMISTRY SERIES

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salts of a homologous series of substituted aromatic sulfonic acids, supplied b y the M o n santo Chemical Company, St. Louis, M o . ) Similarly, Borden et al. (2) recorded the conclusion that D D T applied w i t h spray oils is not removed easily. So far as the authors are aware, there have been no published results of attempts to remove parathion residues from harvested fruits. Because D D T is readily dehydrohalogenatable, chemical expedition of deposit removal was sought through the use of alkaline and halogen-carrier media, such as sodium silicate, trisodium phosphate, ferric chloride, sodium carbonate and bicarbonate, and strong soaps. Mechanical removal was sought through the use of a variety of emulsifying agents, detergents, pressure sprays, and scrubbing brushes. Solvent removal attempts included the use of kerosene, mineral oil, xylene, and a mixture of polymethylated naphthalenes. F o r purposes of coherence and clarity, methods and results with apples and pears are presented separately from those with oranges.

Methods with Apples and Pears Apples. T h e Rome Beauty apples used i n the wash tests were sampled from trees that had received varying amounts of D D T mixtures i n as many as six cover sprays. Duplicate or triplicate samples of 30 apples each were taken at random for the residue analyses from the fruit passed through each experimental wash mixture. Additional lots of 30 washed apples each were placed i n cold storage for subsequent examinations. U n less otherwise indicated, all washing tests were r u n i n a flood-type washer of recent design (a B A D D washer with a heated prewash tank unit, a n unheated main tank unit, a water rinse tank unit, and a velour roller dryer unit, manufactured b y the Bean-Cutler Division, Food Machinery Corporation, San Jose, Calif.). Surface deposits of D D T were determined as described (10, 12) on samples taken just before and immediately after the washing treatments. Pears. Triplicate samples of 20 Bartlett pears each were used and a fourth sample was placed i n cold storage for subsequent examination, as with the apples. Washing trials were performed i n a standard type washer (an Ideal fruit washer with an unheated main tank unit and a water rinse tank unit, M o d e l W K A , manufactured b y the Ideal Grader and Nursery Company, H o o d River, Ore.).

Results with Apples and Pears D D T on Apples. E x p l o r a t o r y investigations i n 1944 w i t h the flood-type tandem washer indicated t h a t D D T surface residues of from 3.3 to 9.5 p.p.m. could readily be reduced 82 to 9 8 % b y a number of materials, b o t h alone and i n combination. These materials included sodium silicate solution (70 to 82 pounds of the 58.5° Baume solution per 100 gallons), hydrochloric acid (1.25%), ferric chloride solution (1 ounce per 100 gallons), sodium hypochlorite solution (3 pints of 4 % per 100 gallons), M e r m a i d Soap (a proprietary, buffered sodium salt of the fatty acids i n cottonseed oil foots, as supplied by the Los Angeles Soap Company, Los Angeles, Calif.) (4 pounds per 100 gallons), t r i sodium phosphate (4 pounds per 100 gallons), and IN-181-P (1 ounce per 100 gallons). Solution temperatures ranged from 50° to 110° F . i n a variety of wash sequences. A l though combinations of IN-181-P washes and sodium silicate washes appeared to be the most efficient, all the washes reduced the residues appreciably. I n some instances, slight visible deposits remained i n the blossom and stem ends following the washing treatment. Washing tests subsequent to 1944 were designed to evaluate more precisely the efficiency of the sodium silicate solution, but other materials were considered sufficiently promising to be included. I n Table I are summarized the data for the sodium silicate washes, at 80 pounds per 100 gallons, with water only i n the main tank, for a variety of types of spray deposits. I n practically all cases the residual D D T was reduced to less than 1 p.p.m. fresh weight. However, some of the apples used i n the 1944 tests carried as high as 9.5 p.p.m. of D D T as surface residue, whereas subsequent deposits prior to washing averaged about 2 p.p.m. F r o m these and supplemental tests i t would seem that such small harvest residues of D D T AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.

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GUNTHER, BARNES, AND

CARMAN—REMOVAL OF

DDT

AND

PARATHION RESIDUES

139

can readily be reduced by at least 5 0 % with a number of washing materials including so­ dium silicate (80 pounds per 100 gallons, 65° to 100° F . ) , trisodium phosphate (4 pounds per 100 gallons, 108° F . ) , and IN-181-P (1 ounce per 100 gallons, 65° F . ) . Tennessee ball clay was the only extending material which when i n composition with D D T appeared to interfere appreciably with the removal of D D T surface residues by sodium silicate washes. None of these washing treatments occasioned apparent fruit injury or decreased storage life. D D T on Pears. E a r l y experiments indicated t h a t the conventional hydrochloric a c i d b a t h , as used for the r e m o v a l of lead arsenate residues, afforded p a r t i a l D D T residue r e m o v a l b y v i r t u e of mechanical action o n l y — f o r example, a surface residue of 1.0 p . p . m . was reduced to 0.6 p . p . m . b y such treatment, but the residue i n the calyx o n l y was untouched (15 p.p.m., fresh weight of calyx o n l y ) . Supplemental wash tests w i t h other materials afforded the residue data collected i n T a b l e I I . Table I.

Removal of DDT Surface Residues from Rome Beauty Apples with Sodium Silicate Washes Dosage

c

Spray Treatments 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

n

6

Sprays, Lb.

D D T (c.p.)-amorphou8 silica (35-65) D D T (aerosol)-amorphous silica (40-60) D D T (tech.)-amorphous silica (50-50) D D T (tech.)-amorphous silica (25-75) D D T (tech.)-amorphous silica (121/2-871/2) D D T (tech.)-amorphous silica (50-50), remilled D D T (tech.)-calcium silicate (50-50) D D T (tech.)-ball clay (50-50) D D T (tech.)-kaolin clay (50-50) Gesarol A K - 4 0 a

Wettable powder with 40%

Table II.

1.

9. 10. 11. 12.

75 59

0.3

85

89 80 65 89 70

0.7 0.4 1.0 1.1 0.4

0.2 0.2 1.2 0.6 0.6

65 87 38 59 76

90 94 25 78 65

0.6

0.5

68

75

0.9 2.0 1.7 1.8 2.0

0.5 0.7

1.4 1.4 1.4 1.4 1.4

2.0 3.1 1.6 2.7 1.7 1.9

DDT.

Wash Tests for Removal of DDT Surface Residues from Bartlett Pears Materials

2. 3. 4. 5. 6. 7. 8.

D D T Surface Residue Removed 80° F . 100° F .

0.1 0.4 0.6 0.2 0.6

1.4 1.4 1.4 2.8 5.6

Av. α

D D T Surface Residues on Fruits, P . P . M . Wet Weight Washed Unwashed 80° F . 100° F .

Trisodium phosphate Trisodium phosphate Triton X - 1 0 0 IN-181-P Ivory soap Mermaid soap Sodium silicate Ferric chloride C.P. Hydrochloric acid Mineral seal oil Triton X-100 Treatment 9 followed by 7 • Xylene Triton X-100 Treatment 11 followed by 7 c

Lb./100 Gal. e

16 8 1.67 ounces 1 ounce 2 6 80 4 ounces 5 quarts 1 gal. 0.5 ounce 2 quarts 0.5 ounce

....

D D T Surface Residues, P . P . M . & Unwashed Washed

«

'Pi

Residue Removed

7.2 7.2 7.2 7.2 7.2 7.2 7.2 7.2

1.9 3.3 2.3 2.4 2.4 2.8 3.2 3.0

74 54 68 67 67 61 56 58

7.2

2.7

62

7.2 7.2

2.7 2.6

62 64

7.2

2.8

61

Fruits exposed to wash for approximately 20 seconds. & Each figure represents average of 3 analyses, except 1, 5, and 9 where figure represents one analysis only. Liquid, anhydrous nonionic emulsifier, Rohm & Haas Co., Philadelphia, Pa.

α

c

The xylene emulsion wash caused injury i n the lenticel areas of the fruits. Fruits washed i n the mineral seal oil emulsion retained a considerable oil deposit even when washed subsequently with sodium silicate and exhibited considerable shrinkage while i n storage. Further wash tests with apples and pears have not been extensive because the magni­ tudes of typical D D T harvest residues suggest that no appreciable difficulty will be en­ countered i n bringing fruits sprayed with the lower dosages under the provisional toler­ ance for D D T residues on these fruits. Parathion on Apples and Pears. A l t h o u g h parathion deposits appear to be less AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.

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ADVANCES IN CHEMISTRY SERIES

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persistent t h a n those f r o m D D T , the ready sorption of p a r a t h i o n b y certain fruit metabolites indicates t h a t late seasonal a p p l i c a t i o n on early harvested varieties of apples a n d pears could result i n measurable amounts of p a r a t h i o n as ultimate resi­ dues. Washing tests for these trials were made i n a flood-type washer with one wash and one rinse chamber. T h e results presented i n Tables I I I and I V suggest that parathion residues (from wettable powders) are not readily removed with the materials and equipment e m ­ ployed; support is thus secured for the authors* contention that with many substrates parathion residues are actually subsurface and exist i n situ i n close association with the oily and waxy constituents of the plants. Of these materials, kerosene and mineral oil decreased the storage life of the fruits. Table III.

Wash Tests for Removal of Parathion Residues from Rome Beauty Apples* Materials

Gal./100 Gal.

Trisodium phosphate Velsicol A R - 6 0 (0.1% Triton X-100) Mineral seal oil Blood albumin spreader Triton X-100 IN-181-P* Kerosene Blood albumin spreader

61b. 1 1 1 ounce 1 ounce 3 ounces 1 1 ounce

e

Parathion in Total Fruit&, P . P . M . Unwashed Washed 2.5 2.5 2.5 1.0 '2.5 2.5 2.5

% Removed

1.5 1.5 1.7 0.8 1.9 2.0 2.4

40 40 32 20 24 20 4

Temperature of wash water 50° F . wash 25 seconds, rinse 10 seconds. b Entire fruits macerated for analysis representing total parathion. Mixture of polymethylated naphthalenes. Added in maximum amount without excessive foaming.

β

t

c d

Table IV.

Wash Tests for Removal of Parathion Residues from Bartlett Pears and? Rome Beauty Apples*'* Parathion Surface Residues Series l Series 2 Series 3/ Bartlett Bartlett Green Rome Pears Pears Beauty Apples Re­ Re­ Re­ moved, moved, moved,. P.p.m. P.p.m. P.p.m. % % % 0.07 0.32 0.27 15 0.23 0.03 57 0.30 7 0.04 43 0.25 0.28 12 0.04 43 0.17 37 0.30 6 0.21 22 57 0.03 0.33 15 57 0.03 0.23 0.30 26 0.03 57 0.20 57 0.21 22 0.03 120.28 22" 0.04 43 0.25 0.25 7 60.04 43 33 0.30 0.18 0

e

d

Lb./100 Gal.

Material No treatment (unwashed) Trisodium phosphate Trisodium phosphate Santomerse 1 Trisodium phosphate Trisodium phosphate Santomerse 1 Sodium triphosphate Sodium acid pyrophosphate Sodium acid pyrophosphate Tetraeodium pyrophosphate Tetraeodium pyrophosphate Tetrasodium pyrophosphate Santomerse 1 Trie odium phosphate Triton X-100 Tetraeodium pyrophosphate Tetrasodium pyrophosphate Santomerse 1 Sodium silicate

8

>io

J 2 ounces?J 16 16 ) 2 ounces/ 8 8 8

4 4

Approxi­ mate p H

>10 >10 >10 9 4 7 9 9

\

2 ounces/

\ 36 m l . / 8

8 8

\

2 ounces/ 80

>10 10 10 >10

0.23 0.22 0.28 0.20

15 19 26

0.03 0.04 0.05 0.03

57 43 29 57

0.22 0.24 0.27 0.21

31 25 16 34

Temperature of wash water 68° F . , wash 35 seconds, rinse 25 seconds. & Surface residue values reported to second decimal largely because of close agreement between duplicateanalyses and because amount of parathion in each sample was within range for maximum accuracy of analytical method. Therefore, ratios reported retain possible significance. « Each figure represents average of 2 analyses. Fruits of this series sprayed with 4 ounces of actual parathion per 100 gallons specifically for this test. * Fruits of this series sprayed with 2 ounces of actual parathion per 100 gallons July 18 and Aug. 10, sampled! Aug. 26. / Fruits of this series sampled after fourth cover of 4 ounces of actual parathion per 100 gallons. ι Maximum amount without excessive foaming. α

d

Methods with Lemons and Oranges D D T . W i t h both the Eureka lemons and the Valencia oranges, trees were sprayed i n a conventional manner with conventional high pressure equipment, and with the follow­ ing mixtures: AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.

GUNTHER, BARNES, AND C A R M A N — R E M O V A L

O F DDT AND PARATHION RESIDUES

141

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I . T e n pounds of A K - 2 0 (a wettable powder with 2 0 % D D T ) and 4 ounces of a casein spreader per 100 gallons of water. I I . A light-medium oil containing 4 grams of technical grade D D T per 100 m l . used at 1.67%, plus 4 ounces of a blood albumin spreader, emulsified i n 100 gallons of water. I I I . A kerosene containing 4 grams of technical grade D D T per 100 m l . used at 3 % , plus 4 ounces of a blood albumin spreader, emulsified i n 100 gallons of water. Three field boxes of each fruit for each treatment were picked at random from the treated trees 2 days after spraying. One box of each sample was stripped with the washbottle technique and the D D T obtained thereby was estimated b y the dehydrohaiogenation method (10). T h e remaining boxes of treated fruit were subjected to the normal citrus packinghouse treatments, which include a thorough machine scrubbing with M e r maid soap (at Ontario, Calif., by-products plant of the California F r u i t Growers E x change). After having been so processed, these fruits were stripped and analyzed as before. Parathion. T h e available evidence suggests t h a t parathion is soluble i n m a n y p l a n t oils a n d waxes. W i t h citrus fruits, i t is clear t h a t t o p i c a l l y applied parathion preparations q u i c k l y lose a part of their parathion essentially b y a transfer into the surface waxes a n d then into the o i l gland containing tissues of the fruits. F o r example, samples stripped either b y the wash-bottle technique (10) or b y a machine technique (18) 24 hours after treatment always exhibit little or no parathion, whereas total peel values for the same fruits may be relatively high i n parathion content (see also 1,8). O i l expressed from the peel of parathion-treated oranges may contain from 65 to 9 0 % of the parathion originally present i n that peel. Prescrubbing of treated citrus fruits with warm 1 0 % trisodium phosphate solution does not alter appreciably the amount of parathion obtainable b y surface stripping (10). I t is concluded that there is no true measurable extrasurface residue of parathion on fruits such as citrus shortly after application, and that surface stripping, b y either laving or brief steeping techniques, merely extracts some of the insecticide from subsurface regions. T h e fact that citrus waxes are completely miscible with benzene lends credence to the postulate that the parathion does not linger i n the wax layers but migrates rapidly through the cuticle. T h i s migration and a t tendant further redistribution of subsurface parathion are under investigation. I t would seem, therefore, that particularly with o i l - and wax-soluble insecticides the older concepts of surface residues on plant tissues should be revised i n terms of extrasurface—i.e., above the cuticle—and subsurface—i.e., within or below the cuticle— residues. The latter would i n turn be subdivided into cuticular residues and various i n t r a carp residues.

Results with Lemons and Oranges D D T . I n T a b l e V are shown the results of attempts to remove D D T surface residues f r o m treated lemons and oranges b y the standard packinghouse processing. F r o m these data i t is apparent t h a t such D D T surface residues are readily removable. T h e ultimate fates of penetrated D D T (8) or field-decomposed surface residues of D D T (1,12) have not been determined, but work along these lines is being continued. Table V. Removal of DDT Surface Residues from Lemons and Oranges with Standard Packinghouse Processing D D T Surface Residue before Processing P.p.m. 7 / s q . cm.

D D T Surface Residue after Processing P.p.m. 7&/sq. cm.

Fruit

Treatment*

Lemons

I II III

12.5 1.0 4.6

19.3 1.4 4.8

0.4 0.5 1.9

0.4 0.5 1.9

Oranges

I II III

9.1 2.5 2.3

8.4 2.1 2.0

0.0 0.0 0.3

0.0 0.0 0.3

6

See text for explanation of field treatments. à Each value represents average of duplicate determinations.

a

AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.

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ADVANCES IN CHEMISTRY SERIES

Parathion. A t present i t has not been found possible to remove p a r a t h i o n f r o m the peel of citrus fruits.

Acknowledgment Besides companies specifically mentioned i n the text, the authors are indebted for donations of materials to the American Cyanamid Company, the Geigy Company, and t h e Pennsylvania Salt Manufacturing Company. T h e y also wish to express indebtedness to W . E . Baier, of the California F r u i t Growers Exchange, for arranging to process the D D T treated lemons and oranges, and to M . E l l i o t M i l l e r and R . C . B l i n n of these laboratories for most of the analytical work..

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Summary Because D D T is readily dehydrohalogenatable, chemical expedition of deposit r e ­ moval was sought through the use of alkaline and halogen-carrier media, such as sodium s i l i ­ cate, trisodium phosphate, ferric chloride, sodium carbonate and bicarbonate, alkaline soaps, and others. Mechanical removal was sought by using a variety of emulsifying agents, detergents, pressure sprays, and scrubbing brushes. Solvent removal attempts included the use of kerosene, mineral oil, xylene, and polymethylated naphthalenes. W i t h apples and pears, sodium silicate frequently proved superior, removing i n some cases 9 0 % of the residual surface D D T , and a n alkaline soap (standard packinghouse treatment) effected significant removal from oranges. None of the experimental treatments has afforded significant removal of parathion from treated fruits. A satisfactory chemical attack on parathion residues has not been achieved, possibly because these residues are actually subsurface.

Literature Cited (1) Barnes,M.M.,Carman, G. E., Ewart, W. H . , and Gunther, F .A.,ADVANCES IN CHEMISTRY SERIES, 1, 112 (1950).

(2) Borden, A. D., Hoskins, W. M . , and Fulmer, Ο. H . , The Blue Anchor, 24, 19 (1947). (3) Carman, G. E . , Ewart, W. H., Barnes, M . M . , and Gunther, F. Α., ADVANCES IN CHEMISTRY (4) (5) (6) (7) (8) (9) (10) (11) (12)

SERIES, 1, 128 (1950).

Carter, R. H., J. Assoc. Offic. Agr. Chemists, 30, 456 (1947). Carter, R. H., and Hubanks, P.E.,Ibid., 29, 112 (1946). Ebeling, W., J. Econ. Entomol., 38, 689 (1945); 40, 628 (1947). Fahey, J. E . , and Rusk, H . W., J. Assoc. Offic. Agr. Chemists, 30, 349 (1947). Fleck, Ε. E . , Ibid., 30, 319 (1947). Frear, D. Ε. H . , and Cox, J. Α., Food Packer, 27, 64, 78 (1946). Gunther, F. Α., Hilgardia, 18, 297 (1948). Gunther, F. Α., J. Econ. Entomol., 41, 895 (1948). Gunther, F. Α., Mimeo, Univ. of Calif. Citrus Experiment Station, February 1948.

(13) Gunther, F . Α., and Blinn, R. C., ADVANCES IN CHEMISTRY SERIES, 1, 72 (1950).

(14) (15) (16) (17) (18) (19)

Hough, W. S., Virginia Fruit, 33, 1 (1945); 34, 128 (1946). Manalo, G. D., Hutson, R., and Benne, Ε. J., Canning Trade, 68, 9, 22 (1946). Parkin, Ε. Α., and Green, Α. Α., Nature, 155, 668 (1945). Tressler, C. J . , J. Assoc. Offic. Agr. Chemists, 30, 140 (1947). Walker, K . C., Proc. Am. Soc. Hort. Sci., 51, 85 (1948). Wichmann, H . J . , Patterson, W. I., Clifford, P. Α., Klein, A . K., and Claborn, Η. V., J. Assoc. Offic. Agr. Chemists, 29, 188 (1946).

PAPER 623, University of California Citrus Experiment Station, Riverside, Calif.

AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.