Loaders California

Assume 100% respiratory absorption of chlorpyrifos except for mixer-loaders, applicators, and cleanup workers in California who wore respirators which blocked 100% of the respiratory exposure. 

In California, mixer-loaders and spray applicators who work with toxicity category I and II organophosphates or N-methyl carbamates more than 30 hours per 30-day period are required to have medical supervision. Supervision consists of an interview and a medical examination to determine if a medical condition exists which would make the worker unusually susceptible to poisoning due to cholinesterase inhibition, and to caution the individual about the use of certain drugs such as the pheno-thiazine tranquilizers vdtich potentiate the effects of cholinesterase (ChE) inhibition. Two blood samples, taken several days apart, are analyzed to determine the individual s preexposure plasma and red blood cell (RBC) ChE activity (baseline value). The physician arranges a routine ChE testing program and provides for extra ChE tests should the worker be accidently exposed to OP s. If ChE activity is depressed to 50 percent of the baseline value, the physician may ask the employer to place the worker on... 

In one study (2), plasma and RBC ChE activities were followed from May to September in two mixer-loaders (ML) who used a Swampmate closed-transfer system (Cherlor Manufacturing Co., Salinas, California), and in three mixer-loader applicators (MLA) who used a Model SS 12-4 closed-transfer system (Soil Serv, Salinas, California). The results shown in Fig. 1 indicate that the activities of plasma and RBC ChE were depressed during the application season, but returned to normal by the middle of September. The MLA showed less plasma and RBC ChE depression. It is interesting to note that the plasma ChE showed the "rebound effect," recording levels way above baseline. 

The use of closed systems has been required in California for transfer of toxicity category one liquid pesticides from the manufacturer s container into the mix tank and then into the application vehicle tank. It appears that this process has considerably reduced both dermal and inhalation exposure. The use of probes that are inserted and then removed from containers reduces dermal exposure up to ten-fold it also appears that the use of built-in probes further reduces exposure to the mixer-loader by up to another ten-fold factor in some cases. 

Krieger, R.I., C. Blewett, S. Echniston, H.R. Fong, D.D. Meinders, L.P. O Connell, F. Schneider, J. Spencer, T. Thongsinthusak and J.H. Ross (1990). Gauging pesticide exposure of handlers (mixer/loader/applicators) and harvesters in California agriculture. 

C. Conrad, D. Cooper, C. Monitoring of Potential Exposures of Mixer-Loaders, Pilots, and Flaggers During Application of tributyl phosphorotrlthloate (DEF) and trlbutyl phosphorotrithl-olte (FOLEX) to Cotton Fields in the San Joaquin Valley of California in 1979. California Department of Food and Agriculture, 1981. 

Appendix One Dermal Exposure Monitoring of Mixers, Loaders, and Applicators of Pesticides in California... 

California regulations require daily provision and use of clean coveralls or other clean outer clothing to mixers, loaders, flaggers, and applicators of any pesticide in toxicity Categories I and II (12). These requirements serve to reduce the potential dermal exposure of workers to pesticides by decreasing the area of bare skin available for contact with the chemicals. 

Krieger R (1990) Gauging pesticide exposure of handlers (mixer/loaders/applicators) and harvesters in California agriculture. Proceedings of the Pesticide Workshop. Milan... 

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