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Data is sparse on how pesticides migrate into Hawaii’s waterways from commercial farms and ranches, but a new study of water from 31 streams, ditches, canals and a wetland on Oahu and Kauai found at least one pesticide present — at very low levels — in all but one of the samples.
All told, 61 pesticides were detected at least once, but nearly all were at trace levels at least 10 times lower than the federal benchmark to protect human and aquatic life.
Fenix Grange, an environmental toxicologist at the state Department of Health, said the results are reassuring because none of the pesticides exceeded federal or state water quality standards.
“But we don’t wash our hands of it and say, ‘OK, there’s not a problem,’ because we still want to understand more about how pesticides might be moving in the environment and how they might be associated with different land uses,” Grange said.
Department of Agriculture Director Scott Enright said in a statement that the results of the U.S. Geological Survey study can be viewed as early evidence that pesticides in Hawaii are being used properly.
But Carl Berg, senior scientist of the Surfrider Foundation’s Kauai Chapter, said he found the results anything but encouraging. The main takeaway, he said, is that pesticides in local waters are prevalent.
“What we have here looks like a chronic toxic stew in nearly all of our waters,” Berg said. “Although any one thing may not have reached the level that is of concern for humans, we have no idea how toxic these things are in combination.”
On Oahu, the insecticide flubendiamide was detected during storm events at concentrations that exceed the lowest federal aquatic-life benchmark. After finding that flubendiamide can kill mussels and other invertebrates, the EPA has moved to cancel the sale of products in which the chemical is the active ingredient.
The study also found low levels of chlorpyrifos, a chemical that the state is currently in the process of reclassifying for restricted use, in two Honouliuli stream samples collected during the same storm event.
The study, which was funded by the state health and agriculture departments, concluded that there were no violations of state or federal water quality standards for pesticides that are currently used.
The water was not tested for the presence of glyphosate, an herbicide better known by its trade name, Roundup. The state doesn’t generally test for glyphosate because of the high cost.
The report is more comprehensive than a similar study released in 2014 that analyzed water from 24 streams and found that the areas with the greatest number of pesticides were not near large farms but rather in urban Oahu.
In the most recent analysis, surface water samples were collected for testing at periods of low flow during dry weather as well as periods of high flow during storm events. The prior study merely analyzed surface water for pesticides at a particular point in time, rather than exploring how heavy rain events alter the type and amount of pesticides present in the water.
The earlier study, however, did test for glyphosate, which was found in surface water at three locations.
Another round of testing is already underway at sites where detections were near the benchmark levels. The next iteration of the study has also been expanded to include site monitoring on Maui and the Big Island.
The studies are helping to build a historical resource for state regulators to draw on as they address concerns over exposure to toxic chemicals used to control pests in agriculture.
Milton Clark, a former senior health and science advisor for the U.S. Environmental Protection Agency, cautioned that the study results are not cause for celebration.
“You can’t conclude that pesticides are being used safely just because you see trace levels in the water,” said Clark, a former professor of environmental and occupational health sciences at the University of Illinois School of Public Health. “That doesn’t take into account what might be in the soil or the air or even in people. We have a total lack of information.”’
Last week, Clark submitted testimony regarding a bill that would establish a pilot program to create a vegetative buffer zone around 10 Hawaii schools near commercial agricultural production areas.
The legislation, which would also require the Department of Agriculture to develop and implement a pesticide drift monitoring study, is a good start, Clark said. He urged lawmakers to restore some of the original language that had been removed from the bill, such as a provision that would require that schools and daycare centers be notified prior to any nearby spraying of restricted use pesticides.
But on Thursday, the House Finance Committee recommended the bill for deferral.
Another bill set to be heard by the Senate this session would require the disclosure of commercial agricultural pesticide use under specified conditions. It would also appropriate funds to study the effects of exposure to the pesticide chlorpyrifos on pregnant mothers.
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