Closed-transfer systems

A modified immersion method has been used by Hamm et al.140 to obtain electrochemical cell by a closed-transfer system, and immersed in 0.1 M HCIO4 solution at various . was derived from the charge flowing during the contact with the electrolyte under potential control. For the reconstructed Au(l 11M22 X Vayo.l M HCIO4interface, =0.31 0.04V (SCE) (Table 9). Using the impedance method, = 0.34 V (SCE) for recon-... 

Closed manufacturing systems Closed transfer systems Clean-in-place systems Containment boxes or isolators... 

Studies on the Effectiveness of Closed-Transfer Systems for Mixing and Loading Toxicity Category I and II Products Containing Organophosphates and N-methyl Carbamates... 

The regulations adopted by the California Department of Food and Agriculture requiring the use of closed-transfer systems went into effect in April 1977. At that time, several types of equipment were put into use, and a series of studies were undertaken to evaluate their effectiveness in protecting workers. 

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 results indicate that the closed-transfer system reduced worker exposures below that of previously used methods. Powders are hard to handle, however, and workers must be trained to use the equipment effectively. 

The Department has developed methods for monitoring the exposure of workers exposed to organophosphate and carbamate pesticides. These methods utilize the determination of plasma and red blood cell cholinesterase activities and urinary alkyl phosphates. Studies are reported vrti ich show that these methods have proven useful in evaluating the safety effectiveness of closed-transfer systems and in determining reentry times for field workers. 

Probes have been designed that can overcome most of such risks and therefore can be regarded as closed-transfer systems, but these are relatively costly, complex and slower in operation than a simple dip probe. 

Recognising that the potential for direct operator contact with the concentrated formulation, particularly liquids, during the loading of application equipment constituted one of the highest risk factors relating to operator and environmental contamination led to the development of closed-transfer systems. The... 

Table 4.1 Types of closed transfer system developed for handling liquid pesticide formulations... 

Figure 4.2 A typical layout of a closed-transfer system using the container puncturing principle...

Figure 4.3 Valve/coupler arrangement proposed as a standard interface for closed-transfer systems using small-volume refillable containers...

In the same way that it was recognised that a poorly designed induction hopper would not reduce the risks of operator and environmental contamination (see p. 49) and that a standard relating to system specification and performance was needed (Garnett, 1993) a standard relating to closed-transfer systems for liquid plant protection products has also been produced (Anon., 1996b). This follows the same format as the standard relating to induction hoppers and indicates that in order to comply with the standard, a closed-transfer system must... 

The performance requirements specified within the British Standard for closed-transfer systems for liquid plant-protection products relate to ... 

There are now a number of complete closed-transfer systems commercially available in the UK that are able to meet the requirements of the British Standard, and yet the number of units used on farms is still relatively low. Costs, complexity and speed of operation have been cited as reasons for the slow commercial uptake of such systems. Some chemical suppliers have promoted the use of closed transfer, and the requirement to use a closed-transfer system has now been included as part of the conditions of use for some plant-protection product formulations justified by the toxicological profile of the active ingredients. It is therefore likely that the use of such systems will increase in the future. 

Felber, H.U. (1993) Closed transfer systems for small volume refillable containers. Proceedings, ANPP—BCPC Second International Symposium on Pesticide Application Techniques, Strasbourg, H, 479-486. 

Maddy (16) monitored dermal and Inhalation exposures for mlxer/loaders, flaggers and pilots associated with the aerial application of mevlnphos, using Che methods described In Peoples (15). In this study the mlxer/loaders operating closed transfer systems wore gloves but others associated with the spray operation did not. The mlxer/loaders received 74% of their total dermal exposure on Che hands, flaggers received 42% and pilots received 27%. Pilots received a considerably lower proportion of Che total exposure Co the hands Chan In the study by Peoples (15). 

---