Potential Hazard in Using Dichlorvos Insecticide ... - ACS Publications

14 Potential Hazard in Using Dichlorvos

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on May 15, 2018 | https://pubs.acs.org Publication Date: June 1, 1966 | doi: 10.1021/ba-1966-0060.ch014

Insecticide Resin M I T C H E L L R. Z A V O N and E . A. K I N D E L , Jr. The Kettering Laboratory, University of Cincinnati College of Medicine, Cincinnati, Ohio 45219

Dichlorvos, an organic phosphate insecticide, has been incorporated in a resin for continuous vaporization. The hazard in handling the resin strips and in home use of the resin strip vaporizer has been evaluated under simulated or actual use conditions. Use conditions included observations for as long as 6 months of persons using the vaporizers in their homes. Cholinesterase activity of the plasma and red blood cells of those exposed was determined serially. No significant degree of cholinesterase inhibition resulted either from handling the resin strips under the conditions of the experiment or from using them in the home over a 6-month period.

Dichlorvos ( D D V P , dichlorovinyldimethyl phosphate) was first synthesized in the late 1940's, but active investigation of its insecticidal properties was not initiated until 1954. Investigations at that time revealed that low concentrations of the vapor of dichlorvos were toxic to adult mosquitoes and flies and that there appeared to be a relatively wide margin of safety between the insecticidal dose and the concentration required to affect man. Research by personnel of the U.S. Public Health Service, particularly by George W . Pearce, resulted in the development of a solid formulation of 2 5 % dichlorvos in montan wax, which when open to the air, released the vapor of dichlorvos continuously, in small quantities, over a prolonged period of time. This development led to a search for other, more stable formulations and eventually to the development of a formulation of 2 0 % dichlorvos in a resin. This formulation, known as Vapona Resin Vaporizer, is referred to hereafter as the Vaporizer. 177 Rosen and Kraybill; Organic Pesticides in the Environment Advances in Chemistry; American Chemical Society: Washington, DC, 1966.


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It is a strip of resin, 4% by 10 inches, flexible, but tougher than leather, developed originally and primarily for use in controlling malaria by the W o r l d Health Organization. This particular formulation has gained wide acceptance in the United States for controlling flies and mosquitoes, and to a lesser extent, cockroaches in homes, offices, factories, barns, and other establishments. The series of investigations described was initiated to evaluate the degree of hazard involved in handling and using this formulation of dichlorvos. The studies were designed to simulate as closely as possible the most severe conditions of actual use, while maintaining some degree of control of the subjects. Prior to these investigations, a thorough review of all relevant experiments involving animals and men had i n dicated the improbability of any significant effect from the procedures to be followed (1-10,12,15). A major concern throughout has been to make these experiments as meaningful as possible, without undue inconvenience to volunteer subjects. Handling of Vapona Resin Vaporizers

To determine the effect on the skin and on the cholinesterase activity of the blood of persons engaged in handling the Vaporizers, 10 volunteers were selected for investigation: six men and four women. Before they handled the Vaporizer, blood was drawn by venipuncture from each subject, and the cholinesterase activity of the plasma and erythrocytes was determined. Two of the volunteers were used i n a preliminary trial, one i n handling the Vaporizer for 30 minutes, and the other by having the Vaporizer fixed to the volar aspect of the forearm for 30 minutes. Another sample of blood was drawn 24 hours after the experimental procedures (Table I ) . Personal D a t a on Subjects Subject 1 4 6 8 10 12 14 15 20

Sex

Age

F F F F F F F F F

23 27 23 25 42 35 46 23 13

Subject 2 3 5 7 9 11 13 16 17 18 19 21

Sex

Age

M M M M M M M M M M M M

24 29 25 25 41 39 48 25 2 14 12 52

Rosen and Kraybill; Organic Pesticides in the Environment Advances in Chemistry; American Chemical Society: Washington, DC, 1966.

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Dichlorvos Insecticide Resin

Table I. Cholinesterase Activity of Two Subjects in Preliminary Experiment α

Cholinesterase

Activity, ΔρΗ Units


Before Exposure Subject

Plasma

1 4

0.89 1.06

a

After

Erythrocytes

Exposure

Plasma

0.68 0.79

Erythrocytes

1.06 1.10

Cholinesterase activity determined by Michel method

0.63 0.73

(11).

The subjects were divided arbitrarily into two groups, A and B. Members of group A handled the Vaporizer for 30 minutes each day i n the manner required for household or farm use. A portion of Vaporizer, 2V2 by 5 inches, was affixed with adhesive tape in direct contact with the bare skin of the volar surface of the forearm of each member of group B, for 30 minutes of each of 5 successive days. Fresh Vaporizers were applied on the first and third of the 5 successive days. Cholinesterase activity was determined before the first period of contact and after the second and fifth ( Tables I and II ). Table II. Cholinesterase Activity of Blood of Human Subjects During Experiment with Vapona Resin Vaporizers ( 1 1 ) Cholinesterase

Subject

Age

Sex

Pre-experimental Plasma

1 2 3 4 5 6 7 8 9 10

52 21 23 30 24

F F F

0.89 1.57 0.99

F

47 45 29 32 31

M M M M M

1.06 1.45 0.93 1.66 0.88 1.04 1.18

M

Activity, àpH Units

After 2nd period of contact

Erythrocytes

Plasma

0.68 0.90 0.81 0.79 0.77 0.85 0.79 0.90 0.82 0.69

1.78 1.46 1.88 0.99 1.32 1.98 1.62 0.90 0.90 1.12

Erythrocytes 0.69 0.88 0.74 0.78 0.78 0.77 0.72 0.83 0.83 0.61

After 5th period of contact Plasma

Erythrocytes

0.92 1.57 1.01 0.96 1.21 0.91 1.79 1.00 0.91 1.03

0.70 0.89 0.78 0.81 0.78 0.69 0.71 0.91 0.83 0.69

The brief periods of exposure and the close contact with the skin, whether of hands or forearm, made percutaneous absorption the most likely route of absorption. Inhalation, though possible, was certainly less significant, according to what is known of the rate of vaporization of the Vaporizer (14).



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The results of this investigation indicate no detectable inhibition of the cholinesterase activity of either plasma or erythrocytes as a result of handling Vapona Resin Vaporizers under the conditions of this experiment or of maintaining Vaporizers in direct contact with the skin for 30 minutes per day on 5 successive days. The fluctuations in cholinesterase activity were well within the normal range of day-to-day variation. The second determination of the cholinesterase activity of the plasma of subject 6 was unusually high. N o explanation can be offered for this unusually high value, except to note that the specimen was "very milky" (the probable result of lipemia) and that it was taken on the day following the death of the subject's mother. It was concluded that Vapona Resin Vaporizers may be handled for at least 30 minutes per day without the necessity of wearing i m permeable gloves. Use of Vapona Resin Vaporizers

in the Home

The use of Vapona Resin Vaporizers in the home poses the possibility of an adverse effect upon persons subjected day-in and day-out to the inhalation of the vapor of dichlorvos. In order to determine the extent of this hazard, the following investigation was undertaken. Procedure. Initially, two families volunteered to have the Vaporizers installed in their homes in the recommended number of one per 1000 cubic feet of air. The members of the two families were observed regularly and tested for changes i n the cholinesterase activity of their blood. They kept daily accounts of the amount of time spent i n the house and maintained a continuous record of temperature and humidity. A l l were encouraged to report any hint of an adverse effect. These observations were made over the 6 months the Vaporizers were used in the homes. During the first 4 months of observation, new Vaporizers were installed monthly. Those installed at the beginning of the fourth month of observation remained, without change, during the fifth and sixth months of observation. Just before and at intervals during the 6 months of the experimental regimen, blood was drawn from the subjects to determine cholinesterase activity. Table III presents the results over the entire period. Subjects 1 and 2 live in an air-conditioned apartment of 5 rooms (5088 cubic feet), in which air-conditioning equipment operated intermittently during the period of observation. In effect, it is one big room since the doors to the two bedrooms are rarely closed and there are no doors between the living room, dining room, and kitchen. Five Vaporizers were installed in this area and changed at the frequency indicated above.


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Insecticide

181

Resin

Table III. Cholinesterase Activity (ΔρΗ Units) in Blood of Persons in Homes in which Vapona Vaporizers Were Installed Over Period of Six Months a

Before

Installing


Subject

Vaporizers,

4/15/64

Erythrocytes

Plasma

1

0.74

0.76

2

0.62

0.83

3

0.68

0.96

4

0.57

0.79

Mean

0.65

0.83

After 4/16/64

Installing

Vaporizers

4/22/64

Erythro

4/29/64

Erythro

cytes

Plasma

0.83

0.74

0.78

0.71

0.78

1.06

0.66

0.79

M e a n 0.76

0.83

5/6/64 Erythro

Erythro

Plasma

cytes

Plasma

cytes

Plasma

0.65

0.92

0.75

0.85

0.62

0.68

0.61

0.81

0.84

0.70

0.59

0.75

— —

0.65

0.87

0.61

0.91

0.66

0.82

0.53

0.78

0.87

0.73

0.81

0.56

0.78

cytes

— —

0.63

5/13/64

6/24/64

6/10/64

5/27/64

0.56

0.45

0.57

0.57

0.68

0.61

0.67

0.58

0.56

0.62

0.58

0.62

0.72

0.62

0.70

0.76

0.74

0.65

0.88

0.63

0.90

0.60

—

0.45

0.50

0.43

0.73

0.59

0.74

0.57

0.76

M e a n 0.57

0.56

0.55

0.66

0.64

0.74

0.62

0.73

—

7/8/64

10/16/64

9/16/64

8/5/64

0.63

0.55

0.42

0.68

0.65

0.79

0.60

0.79

0.60

0.70

0.43

0.73

0.54

0.82

0.55

0.71

0.60

0.98

0.65

1.01

0.53

1.16

0.50

0.74

0.43

1.05

0.47

0.73

0.43

0.89

M e a n 0.58

0.74

0.43

0.82

0.58

0.84

0.53

0.89

a

—

—

Fresh Vapona Vaporizers installed 4/16/64, 5/13/64, 6/16/64, 7/10/64.

Subjects 3 and 4 live i n a detached, frame house which is not airconditioned. The area lived i n , approximately 8000 cubic feet, required eight Vaporizers. In this two-story house, Vaporizers were placed u p stairs and downstairs. Results. Samples were collected from the air of both residences on the morning of August 19, 1964, about one month following the latest replacement of new Vaporizers. A l l doors and windows were shut tightly


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at the time of sampling, and in each case the sample was collected in the middle of the living room, the largest room i n each residence. T w o Greenburg-Smith impingers, i n series, containing together about 250 ml. of 0.13M phosphate buffer solution ( p H 7.2), were used to collect each of the samples. One cubic foot of air per minute was drawn through the impingers b y means of a Willson vacuum pump. Subjects

Period of Sampling

1 and 2 3 and 4

9:40 to 10:20 10:40 to 11:20

Temp., °F.

Relative Humidity

76 70

50 59

A . M . A . M .

Both samples of buffer solution were packed in dry ice, for transpor tation, and were received frozen and i n good condition at the analytical laboratory. The results of the analyses are shown in Table I V . Table IV. Concentration of Dichlorvos in Air of Homes in which Vapona Resin Vaporizers Were Installed Source of Sample Residence of subjects 1, 2 Residence of subjects 3, 4 Modesto Laboratory

Vol. of Sample, Buffer Solution Cu. Ft. Volume, Ml.

Vapona Found ", μ«. Per Cu. Ft. Air Per Liter Air

40

239

2.75

0.097

40

240

2.45

0.087

—

1

—

"Analyses performed by Agricultural Chemical Laboratory, Shell Development Corp., Modesto, Calif. (13).

The diaries indicated that subjects 1 and 2 spent considerably more time at home than subjects 3 and 4. The two couples lived i n the same community and were subjected to the same ranges of temperature and humidity. During the period of these observations, there were wide variations i n the out-of-doors temperature, which reached 100°F. on at least one occasion. Inside temperatures ranged between 60° and 82°F., with a tendency toward the higher end of the range i n the non-airconditioned dwelling during the summer months. The range of humidity was from 30 to 9 0 % , with the air-conditioned dwelling having a lower humidity. To extend the information concerning the use of Vaporizers to addi tional families under varying conditions of use, six additional volunteer families were enlisted, and the observations were initiated i n September 1964 (Table V ) . The procedure followed was similar to that previously described, except that the periods of-exposure were shorter. Three pre-experimental


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Table V . Cholinesterase Activity in Blood of Persons in Homes in which Vapona Vaporizers Were Installed Over Period of Two Months Cholinesterase Activity before Installation of Vaporizers, ΔρΗ Units


9116164

9/17/64

Subject

Erythrocytes

Plasma

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

0.63 0.58

0.74 0.73

0.93 1.09 0.74 0.59 0.70

0.74 0.66

0.57 0.56

0.66 1.04

Mean

0.71

Erythrocytes

0.95 0.92

0.81

9/18/64

Plasma

Erythrocytes

0.76 0.62 0.86 0.82 0.89 0.89 0.68 0.95 0.79 0.89 0.52 0.91

0.75 0.66 0.66 0.75 1.16 0.79 0.60' 0.85 0.58 0.65 0.81

0.78 0.95

0.88 0.91

0.77

0.81

Plasma

0.58 0.57 0.61 0.59 0.78 0.68 0.67 0.60 0.60 0.64 0.69 0.79 0.54 0.59

0.76 0.85 0.89 0.72 1.04 0.80 0.89 0.92 0.82 0.98 0.58

0.64

0.85

0.79 0.98

Cholinesterase Activity after Installation of Vaporizers, ΔρΗ Units 9/28/64

10/9/64

10/15/64

10/23/64

10/30/64

Erythro Erythro Erythro Erythro Erythro cytes Plasma cytes Plasma cytes Plasma cytes Plasma cytes Plasma 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

0.64 0.45 0.73 0.69 0.40 0.56 0.52 0.52 0.58 0.46

0.76 0.45 0.54 0.59 0.78 0.78 0.65 0.11 0.65 1.08

xMean 0.56

0.64

0.57 0.61 0.74 0.61 0.85 0.58 0.64 0.61 0.63 0.65

0.52 0.68 0.53 0.35 0.64 0.75 0.65 0.60 0.55

0.67

0.95

0.65

0.62

0.59 0.54 0.70 0.67 0.85 0.59 0.59 0.59 0.56 0.62 0.51 0.67 0.58 0.54 0.55 0.62

0.61 0.43 0.75 0.45 0.46 0.63 0.76 0.78 0.65 0.58 0.53 0.85 0.66 0.65 0.80 0.58

0.73 0.69 0.61 0.82 1.04 0.70 0.78 0.96 0.57 0.78 0.62 0.77

0.73 0.53 0.76 0.48 0.58 0.71 0.83 0.75 0.74 0.78 0.64 0.89

0.64 0.58 0.59 0.83 1.05 0.72 0.61 0.73 0.58 0.70 0.61 0.74

0.57 0.50 0.66 0.38 0.36 0.60 0.82 0.74 0.74 0.80 0.56 0.69

0.61

0.64

0.76

0.70

0.70

0.62


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determinations of the cholinesterase activity of the blood of the subjects were made. The temperature and humidity in two of the homes was recorded throughout the experiment and at two others during a portion of the time. The results of the cholinesterase determinations are recorded in Table V . The temperature and humidity were similar to those in the non-air-conditioned apartment noted above. Discussion. Control of insects by the continuous vaporization of d i chlorvos within enclosed spaces in which persons are housed intermittently or continuously constitutes a potential threat of the absorption of significant quantities of the material dispersed as vapor in the air. Despite extensive toxicological investigation of dichlorvos, which has included observations of human beings (4,5,6,8,12,15), no work had been done to evaluate the hazard of Vapona Resin Vaporizers under actual conditions of use. The observations described in this report were designed to reveal the significance, if any, of such hazards. Handling the Vaporizers does not appear to cause any significant decrease in cholinesterase activity among those doing the handling, nor is the cholinesterase activity affected by the prolonged contact of the Vaporizers with the skin of the forearm. In the ordinary day's work, the householder or the pest control operator would not be expected to handle the Vaporizer as much as 30 minutes each day even under the most unusual conditions. Under ordinary circumstances, the contact of the resin vaporizer with the skin would not persist for 30 minutes in any one day and would not be continued day after day. The exposure to Vapona Resin Vaporizers i n the general environment poses a somewhat different problem. Here, the potential hazard involves the combined effects of the absorption of the material through inhalation, through the skin, and from the alimentary tract (if swallowed). The observations made on two families over the period of 6 months, and of six other families over the period of 2 months, were designed to determine whether any adverse effect could be demonstrated. Inhibition of the cholinesterase activity of the blood is the most sensitive means now available, with the possible exception of the inhibition of the esterase activity of the liver, for detecting the absorption of an organic phosphorus compound that is known to be capable of inducing this effect. The values indicative of cholinesterase activity are shown in Tables III and V . A l l subjects were exposed to the recommended dosage (one Vaporizer per 1000 cubic feet) except subjects 15 and 16, who were exposed to resin strips that contained no dichlorvos. The data obtained were examined initially by plotting the cholinesterase activity of the erythrocytes and plasma against the day of exposure of each individual subject and summarizing the results obtained from



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each of the three test groups. These graphs revealed no consistent trend in any of the groups. The data were examined more closely for possible trends by fitting linear equations to each group. In all three cases, the slope of the best equation, determined by the method of least squares, was not significantly different from zero, indicating that the variations in the cholinesterase activity of the erythrocytes and plasma were not a function of the duration of the exposure of the subjects. Dichlorvos is a known inhibitor of cholinesterase, and it is likely that under certain conditions of use, a significant degree of inhibition might occur. However, under the conditions of these experiments, no such effect appears to have occurred. The subjects indicated no adverse effects. In addition to the human residents, two dogs and three cats were residents of the homes. None of the animals exhibited any difficulty dur ing the period of exposure. In these experiments the vaporizers were replaced at much shorter intervals than those normally recommended. Conclusion

The handling and use of Vapona Resin Vaporizers, under the rec ommended conditions, are unlikely to result i n adverse effects among persons so exposed. Literature

Cited

(1) Casida, J. E., McBride, L . , Niedermeier, R. P., J. Agr. Food Chem. 10, 370-7 (1962). (2) Durham, W . F . , Gaines, T . B., McCauley, R. H . , Jr., Sedlak, V . Α., Mattson, A . M . , Hayes, W . J . , Jr., A.M.A. Arch. Ind. Health 15, 340-9 (1957). (3) Durham, W . F . , Hayes, W . J . , Jr., Mattson, A . M . , Ibid., 20, 202-10 (1959). (4) Funckes, A. J . , Miller, S., Hayes, W . J . , Jr., Bull. World Health Org. 29, 243-6 (1963). (5) Gaines, T . B., Toxicol. Appl. Pharmacol. 2, 88-99 (1960). (6) Gratz, N . G., Bracha, P., Carmichael, Α., Bull. World Health Org. 29, 251-70 (1963). (7) Hayes, W . J., Jr., Ibid., 24, 629-33 (1961). (8) Hayes, W . J., Jr., "Clinical Handbook on Economic Poisons: Emergency Information for Treating Poisoning," U.S. Dept. Health, Education & Welfare, Public Health Service, 1963. (9) Hodgson, E., Casida, J. E., J. Agr. Food Chem. 10, 208-14 (1962). (10) Kettering Laboratory, "The Immediate Toxicity of Various Formula tions Containing Vapona Insecticide," Aug. 24, 1962. (11) Michel, H . O., J. Lab. Clin. Med. 34, 1564-8 (1949). (12) Rasmussen, W . Α., Jensen, J, Α., Stein, W . J., Hayes, W . J., Jr., Aero space Med. 34, 593-600 (1963).


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(13) Shell Chemical Co., "Method for the Determination of Vapona Insecticide in Crops and Animal Products. Enzyme Inhibition Spectrophotometric Method," MMS-30/64 (July 1964). (14) Shell Chemical Co., personal communication. (15) Witter, R. F . , A . M . A . Arch. Ind. Health 21, 7-9 (1960).


RECEIVED November 1, 1965.


Potential Hazard in Using Dichlorvos Insecticide ... - ACS Publications

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