Initial Data Released on Pesticides in Surface Water

Posted on Mar 14, 2018 in Main

March 14, 2018

Six-Month Monitoring Levels Meet State & Federal Water Quality Standards

HONOLULU –  The Hawaii Department of Agriculture (HDOA) and the Hawaii Department of Health (DOH) have announced the release of data collected during an initial six-month period of monitoring for pesticides in surface water on Oahu and Kauai. The U.S. Geological Survey (USGS) is conducting the study which collected 32 water samples at 31 sites between November 2016 and April 2017 and produced 7,200 test results.

The USGS tests screened each sample for 225 pesticides and all the results were within state and federal regulatory water quality standards. Thirty-one of the 32 samples detected one or more pesticides; however, a large majority of the detections were at trace levels that were at least 10 times lower than the federal benchmark to be protective of human health and aquatic life. Sixty-one different pesticide compounds (37 pesticides and 24 pesticide degradates) were detected at least once. (Degradates are chemicals found as pesticides break down and degrade).

The study was ordered in 2016 by HDOA and DOH in a $520,000 joint funding agreement with the USGS to provide a science-based water monitoring program and was part of Gov. Ige’s statewide pesticides initiative to help to address community concerns about pesticide use in the state. The leadership of the Hawaii State Senate and the House have also been supportive of this effort. The full report may be viewed at:

“This multi-year surface water study goes a long way towards assuring the citizenry of Hawaii that pesticides are continuing to be used properly,” said Scott Enright, chairperson of the Hawaii Board of Agriculture.

During the monitoring period, water samples were taken during various water flow conditions, including low-flow (dry weather conditions) and high-flow (storm) conditions. Sampling areas included agricultural lands, urban and developed lands, and mixed land use.

The second year of the study is already underway with pesticide monitoring being expanded to sites on Maui and Hawaii Island. In addition, USGS will retest sites on Oahu and Kauai where detections were near the benchmark levels.

Other noteworthy findings during the study period:

  • Chlorpyrifos was detected in two Honouliuli stream samples collected during the same high-flow storm event. The highest concentration of 23.3 ng/l is below the state water quality standard of 83 ng/l and the strictest acute benchmark of 50 ng/l for the protection of freshwater invertebrates. HDOA is currently in the process of restricting the use of chlorpyrifos by reclassifying it to a restricted-use pesticide (RUP) which will allow its use by only state-certified applicators. The proposed restrictions will mirror what California has done and includes required buffer zone. These rules are anticipated to be finalized by this summer.
  • Concentrations of flubendiamide in high-flow samples collected at two sites on Oahu exceeded the lowest Federal aquatic-life benchmark. Flubendiamide is an insecticide that the U.S. Environmental Protection Agency (EPA) is currently in the process of cancelling its use due to the risk to aquatic invertebrates and aquatic environments.
  • Atrazine, an herbicide and established groundwater contaminant, and an RUP was detected in low-flow samples at three sites, at concentrations more than 100 times lower than the EPA maximum contaminant level for drinking water and the strictest aquatic life benchmarks. This represents a significant drop compared to the 75 percent detection rate in a 2013-14 study. The decline likely reflects the decrease in current atrazine applications and sales statewide after 2015, during the time that saw the closure of a large sugarcane plantation.
  • Bromacil is an herbicide and established groundwater contaminant used almost exclusively on pineapple in Hawaii. Bromocil was detected in two areas, one of which is known to have grown pineapple.

The full USGS report may be found at:

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