Banned pesticide 'Dieldrin' discovered in Guam's drinking water

A banned chemical has been discovered in Guam’s drinking water causing the Guam Environmental Protection Agency (EPA) to investigate. 

A recent Guam EPA Board of Directors meeting revealed traces of Dieldrin was flagged in 80 Guam Waterworks Authority (GWA) entry points after an inspection by the US EPA National Enforcement Investigation Center back in March.

Dieldrin is an organic chemical once used as a pesticide in crops and to control termites.

It was banned by the US EPA in the late 1980s for its environmental hazards and potential carcinogenic effects. The chemical is not regulated by the US EPA so there is no maximum contaminant level.

Following Florida and Hawaii guidelines, Guam EPA plans to mandate a public notification and advisory at 0.002 micrograms per liter and a “do not drink without treatment” advisory at 0.2 micrograms per litre. 

Environmental Health Specialist II, Juliana Mendoza said, “Guam EPA will be working with the Guam public water systems to ensure that samples are analyzed at lower minimum recording levels at 0.002 micrograms per litre to ensure public safety. Furthermore, Guam EPA is in the process of acquiring instruments to test dieldrin.”

80 GWA entry points have sample results of over 0.01 micrograms per litre. Three GWA production wells are above the threshold for EPA’s “acceptable risk range.” 

Military water wells do not currently have a report of dieldrin results, leaving the agency unsure where the banned chemical is coming from. 

“There’s been studies that have shown that if you leave it in soil, exposed to the environment, it will all be gone in 20 to 25 years. So that’s why it’s puzzling to us why we’re still seeing it. But it’s not unusual. Other states have seen the same thing.”

Chief Engineer Captain Brian Bearden has a working hypothesis that the increase in dieldrin in our drinking water may be due to demolition of old buildings around the island.

He believes the materials are hauled to hardfills, exposed to rainfall and end up washing into the aquifer.  

He said, “That's something that’s going to require a whole Guam EPA approach. So from pesticides, to green parcels, to hazardous wastes, all branches of Guam EPA are going to have to be mobilizing to figure this out now and find out why it's increasing and try to stop this.”

Once EPA leaders are ready to propose action levels, there will be a public comment period and a hearing.