History of the AA45Y-1 Internal Defoliant Dispenser.

Compiled by Noel Benefield

Seven UC-123B's with the hourglass (MC-1) dispenser system were operating in Vietnam in 1965. In June 1965 the new Agent Orange formulation with 98 percent esters was introduced.

It was found that 3 gallons per acre (28 litre/hectare) was the rate which was the determined "minimum biological effective ground deposition level" (MBEGDL) when using Agent Orange or Agent Blue.

To accomplish this using the earlier MC-1 dispenser, aircraft had to fly twice over the designated area. The first of the AA45Y-1 dispensers was in use in Vietnam by mid-1965, when Orange was introduced. In 1966 ten additional aircraft were deployed and these all had the AA45Y-1 installed in them. Additional systems were sent that year to complete the modification of the original aircraft so that by the end of 1966 all aircraft had the Internal Defoliant Dispenser mounted in them.

The AA45Y-1 was a modular system. Not only were the drums color coded, but also the F-6 trailers and the tank within a given aircraft. These were installed in mission specific aircraft for each of the three agents, Orange, White and Blue.

The driver for the new defoliant dispenser was not the herbicide, but rather the rate at which the herbicide could be disseminated, and the fact that the new system had a dump value that allowed the tank to be emptied in less than 8 seconds in an emergency. The AA45Y-1 had an excellent pump system that permitted the MBEGDL to be accomplished in a single pass.

All applications of Agent Orange in Phuoc Tuy province would have been carried out using mission specific aircraft with the AA45Y-1 dispensers.

Rarely was the MBEGDL of 3 gals/acre identified in an evaluation of Traildust missions, recorded in the Australian Army Report. There is a wide range in calculated gals/acre of missions conducted in Phuoc Tuy Province with many instances of Agent Orange been applied markedly in excess of the MBEDGL. There were also wide variations in quantity applied when comparing similar sized sprayed areas.

The reason was that there were different application rates dependent on the target vegetation, facilitated by the introduction of the AA45Y-1 dispenser with its improved pump system.

Most literature confirms that relative quantities of chemicals applied in Vietnam, were much greater than domestic products, and in the case of Agent Orange, 98% esters was much higher concentration of esters than any other product. One comparison identified domestic product as 2 lbs. per acre versus 27 lbs per acre in Vietnam. The higher 27lb figure was derived from the MBEGDL, but this is not representative of the average application of Agent Orange.

In regard the contaminate TCDD in Agent Orange, the true level in all stocks will never be known. Limited data that is available suggest that during manufacture, of products that would have been applied in Phuoc Tuy Province during ANZAC troop deployment, these would have contained greater quantities of TCDD than domestic product applied elsewhere in the world.

Most histories identify the cause of this contamination, as been the result of a lack of care during the manufacture of the 245Trichlorophenol, but known data indicate that this alone could not be the cause of the gross contamination of some Agent Orange stocks.

The most likely alternative explanation is the fact that Agent Orange manufacture was a "fixed price" tender bounded by "war provisions" legislation.

To increase any return from this manufacture would require a change in manufacturing processes to reduce costs and improve margins.

The most logical change would be deleting the time consuming removal of un-reacted 245Trichlorophenol from 245T destined for Agent Orange stocks.

There are two items that suggest this occurred. The limited sampling of Agent Orange stocks, manufactured before the imposition of TCDD reduction techniques, clearly identify markedly more TCDD in Agent Orange than in domestic products. The second item of evidence is the inability of the patent holder of hexachlorophene to obtain un-reacted 245Trichlorophenol at a time when it could be expected to be readily available given the increased manufacture for domestic and defence requirements.

Given that Agent Orange aircraft were mission specific, one has to question why this tool has not been used by Ranch Hand health investigators, who have considered all members of the unit, regardless of the aircraft flown, as the only cohort for evaluation.

From the evidence available, it can be stated that the current high levels of TCDD in previously defoliated areas of Vietnam, are a result of the introduction of the AA45Y-1 dispenser to apply the specific product Agent Orange.

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