Traces of pesticides found in water systems, no public health threat

Board of Water Supply

Trace amounts of pesticides have been found in two Oahu water systems, the state Department of Health confirmed Thursday.

Trace levels of the chemical dieldrin were detected in the Honolulu Board of Water Supply Pearl City Shaft. The levels of dieldrin found were well below the U.S. Environmental Protection Agency (EPA) lifetime potential cancer risk level for dieldrin in drinking water.

In addition, trace levels of bromacil were recently detected in water samples collected at the Board of Water Supply’s Waialua Wells Pump 1. Hawaii Department of Health (DOH) officials assure consumers that the water is safe to drink as levels were well below the EPA Lifetime Health Advisory Level for drinking water, and bromacil is filtered out through Granular Activated Carbon (GAC) treatment before being delivered to drinking water supplies.

“The Department of Health and the Board of Water Supply are committed to protecting the purity of Hawaii’s drinking water,” said Gary Gill, acting deputy director for Environmental Health. “We regularly test water systems for a wide range of chemical contaminants. In this case, the trace levels of contaminants are so small that there is no threat to public health. The department will continue to work with the Honolulu Board of Water Supply to ensure that tests for these chemicals are conducted regularly and that public health is not compromised.”

In accordance with state law, the Honolulu Board of Water Supply routinely tests for the presence of these chemicals and reports its findings to DOH. DOH is providing the information to the public also in accordance with state law.

The Honolulu Board of Water Supply reported very low levels of dieldrin of 0.01 micrograms per liter or parts per billion (ppb) at the Pearl City Shaft. These levels were well below the EPA one-in-ten thousand lifetime potential cancer risk level for dieldrin in drinking water of 0.2 ppb and do not represent a health threat. Dieldrin was an insecticide first licensed for use in Hawaii in 1976, primarily for subsurface treatment of termites and also for fruits and vegetables. Most uses of dieldrin were banned in 1974 except to control termites; it was discontinued for use in Hawaii in 1989 for all uses. Today, dieldrin is no longer produced or imported into the United States.

The bromacil level detected at the Waialua Wells Pump 1 was 0.45 ppb, more than one hundred times lower than the EPA Lifetime Health Advisory Level for drinking water of 70 ppb. EPA defines the Lifetime Health Advisory Level as the concentration in drinking water that is not expected to cause any adverse, non-carcinogenic effects for a lifetime of exposure. Bromacil is a broad-spectrum herbicide used for weed control for pineapple fields and citrus plants.

The EPA currently does not regulate dieldrin or bromacil in drinking water, therefore there is no enforceable standard for these chemicals on the highest concentration (the Maximum Contaminant Level) that is allowed in drinking water.

The Honolulu Board of Water Supply regularly conducts tests at sources and treatment facilities as mandated by federal and state drinking water regulations.

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