RESEARCH

     Chlorophenoxyacetic acid herbicide, 2,4,5-Trichlorophenoxyacetic acid (2,4,5-T), was developed in the late 1940s and was determined to be toxic. An intake rated of 10 mg/kg /day of 2,4,5-T can cause adverse alterations in organisms. In addition, the manufacturing process for 2,4,5-T can contaminate this commercial herbicide with unknown amounts of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD is an unanticipated contaminant created during the manufacture of the herbicide 2,4,5-T. TCDD has a very long half-life and does not degrade easily. TCDD is not water soluble and can adhere to leaf surfaces, organic material, fine soil particles and sediments which can be carried downstream by runoff water flow into wetlands, ponds and lakes such as Lake Gatun. Dioxin TCDD can bio-accumulate in aquatic species and become bio-magnified throughout the food chain. In most waters, TCDD particles attach to and are deposited with sediment, but can be returned to the water when sediment is re-suspended. Panama lake and river waters, which are shallow and easily churned by wind and wave action, results in sediment re-suspension, preventing elimination from the aquatic system.

     On military bases in the Panama Canal Zone and around the world, the United States’ decision to use 2,4,5-T has also impacted the local environment and human health. The chemical manufacture, transport, disposal and storage of 2,4,5-T herbicide has affected human health. The civilian and military workers, who handled and moved this commercial 2,4,5-T herbicide around the world, including Panama, have been affected. Between 1948 and 1999, the United States military base commanders around the world had the ability to order and use commercial herbicides containing dioxin TCDD. The herbicide 2,4,5-T, with unknown amounts of dioxin TCDD, was transported, according to shipping records, to Panama Canal Zone ports, including Balboa and Cristobal, and distributed to the US military bases in Panama Canal Zone by rail or truck.

     Since the construction of the Panama Canal, in the 1910s, pesticides, herbicides and chemicals, including arsenic, have been essential for controlling wetland vegetation, including hyacinth, which blocked rivers, lakes, and the canal as well as managing mosquitoes. Pesticides and chemicals flowed into Lake Gatun (reservoir) either attached to sediment or in solution during the monsoon season. Lake Gatun was the drinking water source for most of the people living in the Panama Canal Zone. 

     Commercially available white arsenic was purchased to eliminate the floating

plants. The arsenic desiccated and killed the water plants and the arsenic

rich residues fell to the bottom of Panama Canal and Lake Gatun. Bottom

feeding fish could feed on the decomposing vegetation and bio-accumulate the

arsenic. Bigger fish and birds ate these bottom feeding fish and then humans ate

the fish and birds. It was later shown that organic arsenic, which is not toxic, can be transformed into deadly inorganic arsenic through metabolization in animals.

     Arsenic-based cacodylic acid was a specific pesticide used against narrow-leaf grasses. It was the active ingredient in Agent Blue. In the 1960s and 1970s the US military tested tactical herbicides in the Panama Canal Zone. The most likely herbicides tested were probably cacodylic acid, 2.4-D and 2,4,5-T with unknown amounts of dioxin TCDD). Cristobal and Balboa ports were the port destinations in the Panama Canal Zone which received herbicide shipments for testing and use on military base grounds.

     During the last 50 years, the Panamanians living in the Panama Canal Zone have continued to ingest and bio-accumulate arsenic (natural and manufactured) via their food supply and drinking water. However, not all of the ingested arsenic remains in the human body.  Arsenic is transported by blood to different organs in the body and can bio-accumulate in humans and animals. The routes of entry of cacodylic acid into the human body are ingestion, inhalation, absorption through the skin and eye contact.

     Arsenic does not have a half-life and once added to the Panama Canal Zone environment, since 1914, was not destroyed. The present public health concern to human exposure to arsenic was linked with the consumption of drinking water rich in arsenic.

     The arsenic levels, including both natural and anthropic sources, in the surface and groundwater of the Panama Canal Zone, need to be reduced to meet WHO drinking water standard (10 ug/L). The canal and groundwater is the drinking water source for the millions of people living in the Panama Canal Zone and Panama City. High arsenic levels in the water used for agriculture can also contribute to the contamination of the food supply, including seafood. Some of the arsenic can bio-accumulate in animals and humans. Arsenic levels in the Panama Canal Zone hotspots, surface water and groundwater need to be mitigated. The arsenic rich ground water on the US military base perimeters remained in the saturated soil root zone, runoff or was leached into the groundwater. The arsenic  levels in anthropic sources, from herbicides (cacodylic acid, ANSAR 138 (powder) and PHYTAR 560 (liquid)) applications, spilling, spraying and dumping hotspots in Panama Canal Zone, are more concentrated than the natural arsenic concentration in the alluvial sediments and soils. Systematic sampling of the Lake Gatun or the Panama Canal sediments and soil sampling of former military bases, chemical disposal sites, and sediment is needed to determine if restoration and mitigation are required.

Seven Royal Thai Air Force bases in Thailand were used by the United States

Air Force (USAF) during the Vietnam War as staging hubs for operations in Laos and Cambodia.... an eighth Royal Thai Air Force base was used by the United States Marine Corps air operations starting in 1972. Two herbicides, Agent Purple and Agent Orange containing 2, 4, 5-T contaminated with dioxin (TCDD—2, 3, 7, 8 tetrachlorodibenzodioxin) and a third herbicide, the arsenic-based Agent Blue, were routinely received at these Thailand airbases in support of air missions and to keep airbases and perimeter fences clear of vegetation. The USAF at Udorn was under the command of the United States Pacific Air Forces (PACAF) Thirteenth Air Force and was used to temporarily store and distribute Agent Purple, Agent Orange and Agent Blue to Laos’s airfields for spraying of the Ho Chi Minh Trail.... In this study, we document the use of Agent Orange, Agent Purple and Agent Blue on Royal Thai Air Force base perimeters and grounds during the Vietnam War, potential active-duty service personnel exposure to these toxic herbicides and health impacts of the contaminant dioxin TCDD and arsenic on U.S. Vietnam Era Veterans and Vietnam Veterans. This documentation is important evidence in the “assumption of exposure” for health claims to the US Veterans Administration (VA) by veterans that served in Thailand between 1962 and 1976.  [Some striking similarities exist between the DOD's relationship with the truth about toxic herbicide use in Panama and toxic herbicide use in Thailand:] ... Records suggest the movement of herbicides to and from Thailand was not exclusively associated with [specific herbicide spraying] missions and that herbicides were used at US Air Force bases throughout Thailand. Despite this evidence, VA’s position, with the support of the DOD, was that [herbicide spraying] aircraft and herbicides were either temporarily staged, or never staged, on Thailand bases. Further documentation and sworn statements contradict that claim.