Low level of herbicides found at pair of surface water sites

A pesticide study commissioned by the state Departments of Health and Agriculture surveyed two surface water sites on Maui and found trace levels of herbicides in concentrations much lower than state and federal health benchmarks.

“The purpose of this study was to connect how upstream land uses affect water quality,” said Fenix Grange, supervisor with the state Health Department’s Hazard Evaluation and Emergency Response Office. “We found that no standards for surface water were exceeded (on Maui), in fact most samples are between 10 and 100 times lower than the most conservative standards.”

She added that the study did find the insecticide dieldrin, commonly used for termites, exceeded state and federal water quality standards in three urban locations on Oahu. No other compound exceeded regulatory standards statewide.

In December and January, researchers collected surface water and sediment samples from 24 locations statewide – including at the mouth of a spring near Black Rock in Kaanapali and at Kealia Pond National Wildlife Refuge. The samples were sent to U.S. Geological Survey laboratories on the Mainland to be processed.

Of the two dozen sites tested, Kealia Pond had the second-highest level of atrazine at 0.182 part per billion, which is still well-below the most stringent federal water quality standards; the U.S. Environmental Protection Agency allows up to 3 parts per billion in drinking water, Grange said.

Officials said the elevated levels of atrazine at Kealia Pond may reflect current use of pesticides from farming sugar cane and seed corn farther inland, which may drain into the refuge through groundwater.

Two other herbicides were detected at the refuge – fluometuron and prometryn.

Fluometuron has not been registered for use in Hawaii, and the study said it is unknown how the herbicide got into the groundwater. Only 0.06 part per billion of the herbicide was detected, an “unimaginably small quantity,” Grange said.

Prometryn is registered for general use in Hawaii, and only 0.01 part per billion was detected (federal standards allow up to 1 part per billion).

For samples collected at Black Rock, atrazine and its breakdown products were detected at low concentrations, “possibly from turf users, wastewater and former sugar cane uses,” according to the study. Grange said that even though sugar cane has not been cultivated on Maui’s west side for more than 15 years, pesticides like atrazine have been proved to linger in the ground for many decades.

About 0.016 part per billion of atrazine was found, a much lower amount than found at Kealia Pond and below EPA standards.

Two other herbicides also were detected at Black Rock – diuron (hexazinone) at 0.03 part per billion and simazine at 0.01 part per billion.

Researchers acknowledged the study’s limitations, saying that the pilot study “is not adequate to describe exposure to human health and environment.”

“Because single grab samples were taken, data collected do not represent pesticide occurrence throughout the year and may not capture pesticides applied outside the sampling period,” a draft report said.

The study was funded with $25,000 each from the state Departments of Health and Agriculture, and an additional $45,000 from the U.S. Geological Survey.

The full report may be found after noon today at eha-web.doh.hawaii.gov/eha-cma/org/heer/.

* Eileen Chao can be reached at echao@mauinews.com.