Posted on: Tuesday, June 22, 2004
Dozens of chemicals found in O'ahu streams
By Jan TenBruggencate
Advertiser Science Writer
A three-year federal study of O'ahu's water supplies has found that groundwater and streams throughout the island are laced with chemicals as a result of decades of agricultural, industrial and residential pest-control activities.
The island's streams also turned up some of the highest levels of termite-control pesticides in the nation.
In most drinking-water resources, the dozens of detected chemicals are at levels well below those that raise federal or state caution flags. Notable exceptions are Kunia wells tainted with pesticides used by the pineapple industry and a Schofield Barracks well that has high levels of solvents used in aircraft and auto shops. These wells have been closed and are not being used for human consumption.
But there is continuing concern for streams, where bottom sediments and fish tissues displayed significant concentrations of pesticides, notably organochlorines such as DDT, dieldrin and chlordane. The compounds have all been banned, but were once commonly used to kill insects around homes.
The positive news for streams is that after more than two decades of regulation, the levels of these compounds appear to be dropping.
"One of the good pieces of information is that some concentrations are lower now than they were in the past. It suggests that regulation works," said Stephen Anthony, project chief of the U.S. Geological Survey study, "Water Quality on the Island of O'ahu, Hawai'i, 1999-2001." The study was part of the National Water-Quality Assessment Program, which studied water in 52 sites across the nation.
Anthony said federal money to continue the study is not available.
But the state Department of Health is following up where it has the money to do so and expanding the areas being tested to include Neighbor Island sites and O'ahu ones not addressed by the USGS study, said David Penn of the state's Environmental Planning Office.
"One issue is that we haven't looked at very many places yet," Penn said.
The study found what many people already knew — that the chemicals used on land during the past century have been finding their way into the water. Most of the island's drinking water comes from wells tapped into underground aquifers, and although dozens of chemicals were detected, the concentrations were low, typically less than one part per billion, Anthony said.
Although streams continue to display high levels of organochlorine chemicals — within the highest 25 percent of waters sampled nationwide — the amounts of those banned pesticides is dropping significantly.
The study found the level of DDT in fish in Manoa Stream had dropped 62 times, from 1,870 micrograms per kilogram in the 1970s to 30 at the most recent testing. The termite-treatment chemical chlordane dropped from 6,360 to 885 and dieldrin from 9,100 to 885.
At Waikele Stream, the chlordane and dieldrin figures were lower than at Manoa, but DDT remained higher.
Penn called these chemicals "legacy pollutants" because their impact continues to be detected long after their use is halted.
The study also found that many chemicals that residents use in their home gardens, such as carbaryl, diazinon, chlorpyrifos and malathion, are ending up in streams. These chemicals have not been found in significant levels in wells, either because they break down fairly quickly or because they are not very soluble in water.
The message for people who fish in streams is that you shouldn't be bringing the catch home to the dinner table.
"In some of these urban streams, it should be catch and release. You don't want to be eating the fish," Anthony said.
Anthony said that another finding of the report is that many urban streams have been degraded as habitats for native species, often by flood-control programs that cut streamside vegetation and replace native streambeds with concrete channels.
In many streams, native species such as the edible 'o'opu have been replaced by alien streamlife that can survive the stream alterations.
Both streams and groundwater in many cases had excess levels of nutrients, often because of fertilizer runoff and fertilizer flow into groundwater.
The water report is available online at water.usgs.gov/nawqa/nawqa_sumr.html. Reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808) 245-3074.
