Traces of a toxic defoliant were found in groundwater in Camp Carroll, a U.S. military camp in Chilgok, North Gyeongsang Province, where three American veterans claimed they dumped drums containing chemicals presumed to be Agent Orange in 1978, Korean investigators said Friday.

Korean officials on the Korea-U.S. joint probe team found 0.161 micrograms of the defoliant substance 2,4,5-T per liter in five groundwater wells within Sector 41 of the base. The amount is not harmful to humans as the World Health Organization allows up to 9 micrograms per liter in potable water, the joint investigation team said.

The 2,4,5-T was not detected, however, in the U.S. investigators’ sample study.

The two sides agreed to conduct a reexamination of the groundwater in Sector 41.

The Korean team’s analysis found other dioxin-containing substances in four out of the five monitoring wells, whereas the U.S. officials found infinitesimal amount in only one of the monitoring wells.

In an additional study of samples taken from 10 groundwater wells along the boundaries of Sector D, negligible amount of 2,4-D (0.00088 micrograms) and 2,4,5-T (0.00178 micrograms) were detected in one of the wells.

Some cancer-causing pollutants such as trichloroethylene, perchloroethylene and volatile organic compounds, unrelated to Agent Orange, were also found at exceeding the WHO standards both inside and outside the base. The recorded level of volatile organic compounds found in the water near the camp exceeded 900 times the standard level for drinking water.

The joint team said they will take action to stop residents in nearby areas from drinking the water and will further examine the contamination in order to locate its exact source.

The team didn’t find irregularities in the helipad area where U.S. veteran Steve House claimed that he helped bury drums believed to be containing the highly toxic defoliant decades ago.

House testified on the alleged burial of Agent Orange at the Camp Carroll at National Assembly in July and investigation has undertaken to verify his claim.

By Kim So-hyun (sophie@heraldcorp.com)