Field compliance tests for pesticide containers

WASTE MANAGEMENT, Vol. 13, pp. 285-287, 1993 Printed in the U.S.A. All rights reserved.

0956-053X/93 $6.00 + .00 Copyright © 1993 Pergamon Press Ltd.

TECHNICAL NOTES

FIELD COMPLIANCE TESTS FOR PESTICIDE CONTAINERS A Summary of Studies Performed Under Cooperative Agreement No. CR813936-03-0 With Wright State University T. David Ferguson U.S. Environmental Protection Agency, Risk Reduction Engineering Laboratory, Cincinnati, OH, 45268, U.S.A.

I. INTRODUCTION

atrazine (a triazine herbicide) and 2,4-D amine (a chlorophenoxy herbicide). The pesticide containers which were purchased for the present study were constructed of plastic and had a capacity of 2.5 gallons.

The U.S. EPA estimated that during 1986 a total of 223 million empty pesticide containers were generated in the United States. Federal statutes regulate the handling and disposal of pesticide wastes, which include empty containers, equipment rinsate and excess or unwanted pesticides. Under the Federal I n s e c t i c i d e , F u n g i c i d e and R o d e n t i c i d e Act (FIFRA), the EPA promulgated procedures for the disposal of pesticides and pesticide containers. This document summarizes current work performed in this area by Wright State University under Cooperative Agreement No. CR813936-03-0 with the U.S. EPA.

IV. THE EFFECTIVENESS OF THE TRIPLE-RINSE PROCEDURE The initial group of experiments was designed to evaluate a defined triple-rinsing procedure which could be implemented by pesticide applicators. Within these experiments, additional water and organic solvents were performed to test the effectiveness of the triple-rinse procedure. While the organic solvents may not be appropriate for use by pesticide applicators, they could potentially be employed by reusers or recyclers of emptied containers who processed these at a central location. Following the rinsing experiments, sections of the containers were removed and thoroughly extracted by a rigorous procedure in order to quantify any residual pesticide in the container, and to identify those areas of the container in which the pesticide was localized. The first experiment was performed with a pesticide container of atrazine (PST9-1) and consisted of three consecutive water rinses followed by three methanol rinses. The second experiment was conducted with another pesticide container of atrazine (PST9-2) and involved the six consecutive water rinses of the container. Following the water rinses, the container was rinsed four times with chloroform. While chloroform is not an acceptable solvent for container rinsing by pesticide applicators, chloroform is a better solvent than water for atrazine and can be used to evaluate the effectiveness of a stronger solvent in the rinsing procedure, in order to more reliably

II. OBJECTIVES OF THE WRIGHT STATE STUDY 1. Evaluate the effectiveness of the triple-rinse procedure for the different pesticides to determine if additional decontamination procedures are required. 2. Evaluate additional rinsing using organic solvents. 3. Develop or identify tests which evaluate the effectiveness of pesticide-applicator rinsing procedures.

III. PESTICIDES USED IN STUDY A limited number of pesticides were identified for the used-container decontamination studies. They were malathion (an organophosphate insecticide), RECEIVED 2 FEBRUARY 1993; ACCEPTED 26 APRIL 1993. TECHNICAL NOTES is a section for concise, peer-reviewed papers containing useful, albeit sometimes narrowly focused, technical information.

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quantify the amount of residual atrazine in the container. In the third experiment, an emptied container of malathion (PST9-5) was rinsed with five consecutive water rinses. While malathion is only slightly soluble in water, it is miscible with many organic solvents. Four acetone rinses were therefore accomplished following the water rinses to determine if additional malathion could be recovered from the container upon completion of water rinsing. In the fourth experiment, an emptied container of 2,4-D amine (PST9-6) was rinsed with five consecutive water rinses followed by four chloroform rinses. In experiments, 1 through 4, it was determined that the triple-rinsing process significantly reduces the quantity of pesticide in the rinsed container. The quantity of pesticide removed in the third water rinsate is more that 1500 times lower than the quantity of pesticide removed in the first water rinsate for each of the three pesticide formulations tested in these experiments. The quantities of pesticides removed by additional water rinses (beyond three rinses) is not as significant as those removed by the first three water rinses.

had been completed was 30.8 mg. Approximately 2% of the 30.8 mg of residual pesticide was associated with the sidewall and 22% was associated with the handle. The most significant portion of atrazine, not removed by the rinsing (87%), was deposited on the threaded surfaces and the cap liner. These experiments have also shown that pesticides are present on the exterior of the container as a result of spillage during filling and emptying and around the cap. These experiments indicate that the quantity of pesticide on the exterior and threaded surfaces of a container may exceed the quantity of pesticide which remains inside the triple-rinsed container. Moreover, the pesticide on the exterior of the container represents a more significant potential exposure hazard to the applicator who is handling the container. The present study has demonstrated that the triple-rinsing procedure significantly reduces the quantity of pesticide which remains in an emptied pesticide container, at least for the three pesticides tested thus far. These experiments have also demonstrated that pesticides deposited on the exterior of the container must be considered when developing procedures for container decontamination.

V. FURTHER EXAMINATION OF THE RINSED CONTAINERS

VI. TESTS TO EVALUATE THE USE OF FIELD MONITORABLE CHEMICAL TRACERS AS INDICATORS OF PESTICIDE RESIDUES IN CONTAINERS

Following rinsing of the containers, experiments were conducted to quantify any pesticide which was still present in the rinsed containers. Such residual quantities of the pesticides could be retained in cavities in the molded plastic container, held within the structure of the plastic itself, or bound on the surface. A Soxhlet extraction apparatus was used to rigorously extract portions of containers PST9-2 and PST9-5 in order to quantify any pesticide which remained associated with the container following the rinsing experiments. A review of the quantity of the pesticide which was found to be associated with pesticide container PST9-2 illustrates several significant points. The total amount of pesticide remaining in this container after the initial emptying was found to be 188892.3 mg. The first three water rinses removed approximately 18787.3 mg or 99.4% of the pesticide which remained after emptying the container. These results show that the triple-rinsing procedure is indeed very effective in reducing the amount of atrazine in the emptied container. The fourth, fifth and sixth water rinses and the four chloroform rinses removed an additional 74.2 mg or 0.4% of the total atrazine from the container. Approximately 92% of the 74.2 mg was removed in the first chloroform rinse. The amount of atrazine remaining with the container after all the water and chloroform rinses

Preliminary experiments have been conducted to investigate the use of an easily detected chemical tracer in order to determine if pesticide containers have been properly cleaned by the pesticide applicator following removal of the pesticide. Ideally, this tracer or indicator would be added to the pesticide during formulation and would permit easy tracking of the pesticide during its transport, application and disposal. The indicator used in the present set of experiments was the sodium salt of fluorescein. This widely used indicator compound is freely soluble in water and its yellow-green fluorescence can be detected at concentrations as low as approximately 0.02 ppm when it is subjected to UV light. Fluorescein has been previously used to find connections between bodies of water, determine the source of drinking water contamination and monitor wastewater infiltration of soil. Fluorescein is also approved for use in externally applied drugs and cosmetics and is therefore not a hazardous substance. A bottle containing 100 g of fluorescein sodium, which is also known as D and C Yellow No. 8, was purchased from a chemical supplier at a cost of l0 cents/gram. This is a modest cost in terms of potential incorporation of this material into pesticides.

FIELD COMPLIANCE

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Experiments with fluorescein were conducted to determine if the indicator could be detected in the rinsates which would be removed from a pesticide container during the triple-rinsing procedure. Test solutions of atrazine, malathion and 2,4-D in tap water were prepared to correspond to the first water rinsates (that is, these were prepared at concentrations appropriate to the first water rinsate in each case). Dissolving one gram of fluorescein in a 2.5 gallon container of pesticide produces a concentration of approximately 0.1 mg of fluorescein per gram of pesticide formulation. Based on the concentration of pesticide formulation in the test mixture, the appropriate quantity of fluorescein was added to each test mixture. Control mixtures containing only pesticide and water were also prepared. The test mixtures containing atrazine and 2,4-D appeared greenish under normal light and bright yellow-green fluorescence was visible under UV light. The test mixture containing malathion and fluorescein did not appear different from malathion control under either normal or UV light. The addition of 201xL of 20% KOH solution to the malathion test mixture produced a greenish solution under normal light and the yellow-green fluorescence was easily visible under UV light. Fluorescein does not fluoresce when the solution is made acidic. These tests demonstrated that fluorescein could be detected in the test mixtures at concentrations which are typical of the first rinsate for the three pesticides evaluated here. The second rinse of the pesticide container reduces the concentration of the pesticide in the rinsate by a factor of 100-200. Therefore, the test mixtures for each pesticide and the control were each diluted by a factor of 100 to represent the concentration which would be present in the second rinsate. In this case, none of the fluorescein test mixtures appeared different from its control under normal light. Under UV light, however, the yellow-green fluorescence was visible in all three test mixture when the mixtures were compared to the controls. As a preliminary test of the applicability of the fluorescein tracer to detect residues in emptied pesticide containers, 45.6 grams of water containing 4.56 milligrams of fluorescein was added to an unused 2.5-gallon natural color plastic container. This is the quantity of liquid and the concentration of fluorescein which would be expected to remain in an atrazine container following the initial emptying of the pesticide formulation. The liquid containing the fluorescein was easily visible through the plastic. When the UV light was held over the inside surface of the container, the entire container ap-

peared to glow under the UV light. The 2.5-gallon container was then rinsed with 1000 ml of tap water according to the defined rinsing procedure. After the rinsing, the rinsate was drained from the container in the normal manner and this first rinsate was drained from the container in the normal manner and this first rinsate was examined. The fluorescein in the first rinse was visible in normal light, and the solution glowed rightly under UV light. The liquid remaining inside the pesticide container was clearly visible through the wall of the container under UV light. This liquid was also visible through the mouth of the container. A second rinse of the container with 1000 ml of water was performed. The rinsate which was removed following the rinsing was clear in normal light but yellow-green in UV light. The residual liquid which did not drain from the container was visible through the mouth and through the wall of the container. The yellow-green fluorescence of the residual liquid was most easily seen when the light was held near the bottom of the container and the container viewed from the bottom. The threads of the cap and mouth appeared wet but clear in normal light. There was an intense fluorescence from the threads under the UV light which demonstrates that this area of a container is not effectively cleaned in the triple rinsing procedure. The third rinse of the container was performed with 1000 ml of tap water. The liter of water in the container at the end of the rinsing could not be distinguished from tap water under UV light. The small amount of liquid remaining in the container did not show any fluorescence under UV light when viewed from the outside. The intense fluorescence of the liquid on the threads of the mouth prevented detecting any fluorescence of the residual liquid through the mouth of the container. While still more experiments need to be performed, these preliminary results suggest that the addition of one gram of fluorescein to 2.5 gallons of pesticide may be sufficient to validate that the container has been rinsed and the pesticide removed. Additional experiments are needed to determine if such an indicator can be incorporated into the pesticide formulation. Once the indicator is in the formulation, experiments will be required to determine if the indicator is removed from the container at the same rate as the pesticide. These experiments will involve correlation of the indicator response with the concentration of the pesticide and must verify that the indicator response remains detectable until the quantity of pesticide inside and outside the container is below an acceptable limit.

Open for discussion until 29 October 1993.