Exposure mixer-loaders

Applicator and Mixer/Loader Exposure to Pesticides During Ground Boon Spraying Operations," Environnental Protection Agency, 1984. 

Brandes, Gordon A. "Applicator, Mixer/Loader Exposure Studies, Mancozeb (Dithane M-45)." Unpublished preliminary report for NCRPIAP Project Nos. 129 (132-NC-MN-F), 130 (133-NC-MI-P), 131 (134-NC-OH-F) and 132 (135-NC-OH-F) by H. L. Blssonette F. Tschirley and H.S. Potter J. Farley and C.C. Powell, respectively, and WRPIAP-Oregon Project by J.M. Witt and F.N. Dost. 1981. 

Applicators, mixers, loaders, and others who mix, spray, or apply pesticides to crops face potential dermal and/or inhalation exposure when handling bulk quantities of the formulated active ingredients. Although the exposure periods are short and occur only a few times annually, an estimate of this exposure can be obtained by quantifying the excreted polar urinary metabolites. Atrazine is the most studied triazine for potential human exposure purposes, and, therefore, most of the reported methods address the determination of atrazine or atrazine and its metabolites in urine. To a lesser extent, methods are also reported for the analysis of atrazine in blood plasma and serum. 

The purpose of this article is to present a detailed description of the current field methods for collection of samples while measuring exposure of pesticides to farm workers. These current field methods encompass detailed descriptions of the methods for measuring respiratory and also dermal exposure for workers who handle the pesticide products directly (mixer-loaders and applicators) and for re-entry workers who are exposed to pesticide dislodgeable residues when re-entering treated crops. 

Current field methods for measuring mixer-loader and re-entry worker exposure to pesticide residues... 

Both inner and outer whole-body dosimeters are common tools to measure successfully dermal exposure to pesticide workers and are employed in a variety of ways in mixer-loader/applicator or re-entry studies. 

Hand exposures of mixer-loader/applicator and re-entry workers have been measured using a variety of techniques in the past. The most common methods are using gloves as dosimeters and washing the hands with various solvents post-exposure. 

Another consideration when planning field fortification levels for the matrices is the lowest level for fortification. The low-level fortification samples should be set high enough above the limit of quantitation (LOQ) of the analyte so as to ensure that inadvertent field contamination does not add to and does not drive up the field recovery of the low-fortification samples. Setting the low field fortification level too low will lead to unacceptably high levels of the analyte in low field spike matrix samples if inadvertent aerial drift or pesticide transport occurs in and around where the field fortification samples are located. Such inadvertent aerial drift or transport is extremely hard to avoid since wind shifts and temperature inversions commonly occur during mixer-loader/re-entry exposure studies. 

The calculation of potential total dermal exposure of mixer-loaders and re-entry workers using dosimetry data and calculation of the internal dose using biological monitoring data is complex but will be discussed briefly. 

Observations of the test subjects during the course of the field portion of the worker exposure or re-entry study are extremely important in order to interpret the data that are gathered at the field site and to interpret the final analytical data. There are two schools of thought when making observations of field workers during mixer-loader/applicator worker exposure or re-entry studies. 

D.R. Hackathorn and D.C. Eberhart, Database proposal for use in predicting mixer-loader/applicator exposure, in Dermal Exposure Related to Pesticide Use Discussion of Risk Assessment, ed. R.C. Honeycutt, G. Zweig, and N.N. Ragsdale, ACS Symposium Series 273, American Chemical Society, Washington, DC, pp. 341-355 (1985). 

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. 

Table 3 Chlorpyrifos Mixer-Loader, Applicator Exposure Study Parameters...

The results from the several studies that have been conducted to measure exposures associated with the use of chlorpyrifos are summarized in Tables 1 and 2. Table 1 summarizes results from mixer-loader and applicator studies reported by Honeycutt et al.1 Listed for each work description are the number of replicates, the arithmetic mean, and the geometric mean for the replicates from both the passive dosimetry measurements and the biomonitoring tech-... 

When the data in Table 4 were given full evaluation, it was recommended that the 50W formulation of chlorpyrifos no longer be marketed in bags that allowed significant exposure for mixer-loaders of this product. This product was removed from the marketplace and was replaced with one in which the wettable powder (WP) is in water-dissolvable packets. Exposure data on other active ingredients have clearly demonstrated reduced exposure with this type of packaging. The other uses were deemed to present a minimal hazard to users, and only minor protective measures have been recommended to workers. 

Table 6 Comparison of Exposure and Risks for Greenhouse Mixers/ Loaders/ Applicators...

Nigg and Stamper (1983) conducted potential exposure and actual exposure measurements during three weekdays over three consecutive weeks for applicators and mixer-loaders, one week using normal work clothes, the second week disposable coveralls in addition to their work clothes, and the third week disposable coveralls and NIOSH-approved respirators. In conjunction, urinary excretion of a metabolite of the active ingredient was... 

Chester, G., Loftus, N.J., Woollen, B.H., and Anema, B.P. (1990b) The effectiveness of protective clothing in reducing dermal exposure to, and absorption of, the herbicide fluazifop-P-butyl by mixer-loader-applicators using tractor sprayers, in Book of Abstracts, Seventh International Congress of Pesticide Chemistry, Vol. Ill, Freshe, H. and Kesseler-Smith, E., Eds., Conway, Hamburg. 

Nigg, H.N. and Stamper J. (1983) Exposure of spray applicators and mixer-loaders to chlorobenzilate miticide in Florida citrus groves, Arch. Environ. Contam. Toxicol, 12 477-482. 

Generally speaking, the equipment that workers use and the type of agricultural work performed while handling pesticides or pesticide-treated commodities have a major impact on the level of exposure a worker receives. Neat work habits generally lead to lower exposure for agricultural workers who handle pesticides. The current Pesticide Handlers Exposure Database (PHED), which is used to predict exposure to mixers/loaders/applicators, is based on this concept. 

Dermal Exposure Levels. Setting acceptable maximum dermal exposure levels to specific pesticides has been difficult. This is primarily due to a lack of specific data on dermal transport rates for specific pesticides as related to adverse effect levels and presumed no-effect levels. We are now requiring such data from the registrants, and our Department has a suggested protocol (1) that is offered to registrants that will provide such information from animal exposure studies. This dermal transport rate information is important in setting minimum field reentry intervals for field workers as well as in evaluating exposure levels of mixers, loaders, and applicators. 

Mixer, Loader, Applicator Exposure Studies. A major difficulty in making hazard assessments for mixers, loaders, and applicators is the lack of information on how much of the pesticide may be inhaled or may reach the skin under a typical use situation. 

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. 

Comer et al. (2) therefore evaluated the effect of exposure to carbaryl (1-naphthyl methylcarbamate) on formulating plant workers and on workers applying carbaryl to fruit orchards with a tractor-drawn air-blast sprayer. However, information was still needed on the persistence of carbaryl in apple orchards and on the resultant exposure of workers who re-enter treated orchards. Further, no studies had been done on other types of crops. The present study was undertaken to determine the exposure of agricultural workers to carbaryl as a function of type of formulation, application equipment, application method, and type of work performed (i.e., mixer-loader, applicator, flagman, bystander, and apple thinners). 

Mixer-loaders. The mixer-loader operation was not inherently different for ground, aerial, or handgun applications. Several factors affected the hourly dermal exposure (HDE) to these workers (Table II). These included (1) the formulation used, (2) whether or not the worker wore gloves, and (3) the method of removing the powdered insecticide from its container prior to mixing. 

The techniques the mixer-loader used to handle powdered formulations also affected the exposure level. In experiments 2 and 9 the worker (without gloves) scooped the formulation from the container, whereas in experiments 1, 7 and 8 the worker (without gloves) poured the formulation from the container. These precedures produced average total HDE s of 176 and 38 mg/h, respectively. 

Applicators. The workers involved in the ground applications of carbaryl received considerably less exposure than the mixer-loaders. Most of the exposure was to the hands and was attributed to adjusting the nozzles on the spray equipment. Thus, for the ground application of the 80S formulation, the total HDE was 1.6 mg/h and the HDE to the hands was 1.5 mg/h. For a similar application of Sevimol-4, the total HDE was 2.8 mg/h and the HDE to the hands was 2.7... 

Avg exposure when mixer-loader was not wearing gloves. 

The aerial applicators also had considerably less exposure than the mixer-loaders. Again, most of this exposure was to the hands and was acquired from adjusting nozzles on the spray equipment. For the 80S and the XLR formulations, the total HDE s were 7.4 and 3.4 mg/h, respectively, and almost 100% of the exposure was to the hands in both cases. Here, as for the ground application, the highest HDE was obtained from Sevimol-4 because of the more frequent plugging of the spray nozzels. Thus the total HDE for Sevimol-4 was 26.5 mg/h, and the HDE on the hands was 25.7 mg/h. 

Exposure of workers (applicators and mixer-loaders) to 2,4-D [(2,4-dichlorophenoxy)acetic acid], when applied to wheat under normal use, was determined by measuring urinary excretion of... 

D. The participants included 26 ground applicators in North Dakota after a single exposure and 17 aerial applicators in Washington during intermittent exposure. The objective was to ascertain worker exposure base-levels of 2,4-D under normal use conditions. Mean daily urinary excretion of 2,4-D by workers involved in aerial applications was 0.006 mg/kg body weight for pilots and 0.02 mg/kg for mixer/loaders from intermittent exposure. Workers involved in ground applications had maximum mean one-day 2,4-D urinary excretion of 0.002, 0.003, and 0.004 mg/kg, respectively, for applicators, mixer/loaders, and mixer/loader/applicators from a one-time exposure. The Ej/2 (half-elimination time for total... 

---