Vapona resin vaporizer

Research by personnel of the U.S. Public Health Service, particularly by George W. Pearce, resulted in the development of a solid formulation of 25% 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 20% dichlorvos in a resin. This formulation, known as Vapona Resin Vaporizer, is referred to hereafter as the Vaporizer. 

Table II. Cholinesterase Activity of Blood of Human Subjects During Experiment with Vapona Resin Vaporizers (11)...

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. No 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 subjects mother. 

It was concluded that Vapona Resin Vaporizers may be handled for at least 30 minutes per day without the necessity of wearing impermeable gloves. 

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. 

Table IV. Concentration of Dichlorvos in Air of Homes in which Vapona Resin Vaporizers Were Installed...

Discussion. Control of insects by the continuous vaporization of di-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. 

The exposure to Vapona Resin Vaporizers in 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. 

The handling and use of Vapona Resin Vaporizers, under the recommended conditions, are unlikely to result in adverse effects among persons so exposed. 

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