Richard Ha writes:
The State of Hawai‘i tested 24 sites throughout the islands for pesticide residue, and the Big Island tested the lowest. Of all the islands, we had the lowest amount of pesticide residue.
It’s interesting to note that “the USGS laboratory methods used for this study measure compounds at trace levels; commonly 10 to 1,000 times lower than drinking water standards and aquatic life guidelines.”
From the executive summary (there’s lots more detail within the study itself):
Surface water samples collected from 24 sites statewide were analyzed for a total of 136 different pesticides or breakdown products. All locations had at least one pesticide detection. Only one pesticide, a historically used termiticide exceeded state and federal water regulatory limits. Five other pesticide compounds were detected at levels exceeding the most conservative EPA aquatic life benchmark. All other pesticides detected were lower than the most stringent aquatic or human health guideline value.
These findings represent a snapshot in time from a single sampling event within watersheds with multiple upstream inputs. While they provide useful information about pesticide occurrence across different land uses, they may not be representative of typical conditions or identify specific sources.
- Every location sampled had a trace detection of one or more pesticides; however, the majority of these represented minute concentrations that fall below state and federal benchmarks for human health and ecosystems.
- Land use significantly impacted the number and type of pesticides detected. Urban areas on Oahu showed the highest number of different pesticides.
- Oahu’s urban streams had the highest number of different pesticides detected. Manoa Stream at the University of Hawaii showed 20 different pesticides and breakdown products.
- Dieldrin, a termite treatment that has been banned from sale in Hawaii since 1980, exceeded State and Federal Water Quality standards in three urban locations on Oahu.
- Fipronil detected in Manoa Stream and Waialae Iki Stream exceeded aquatic life benchmarks for freshwater invertebrates. Fipronil is an insecticide commonly used in residential settings and applied by commercial pest companies to treat soil for termites.
- Atrazine and metolachlor, two restricted use herbicides, were detected on Kauai at agricultural sites downstream of seed crop operations. One location had levels that exceed aquatic life guidelines, but remain below regulatory standards.
- The number of pesticides detected in water samples on Hawaii Island was lower than that of Kauai and Oahu.
- Atrazine, a restricted use pesticide, was the most commonly found pesticide in the study. Of the sites tested, 80 percent had atrazine detections. Only two sites, one on Kauai, and one on Maui, reflected elevated concentrations suggestive of current use of atrazine. All of the remaining detections were trace level concentrations far below state and federal benchmarks.
- The pilot study tested stream bed sediment at seven sites and found glyphosate, in all samples. Glyphosate (trade marked as Roundup) is widely used for residential, commercial, agricultural and roadside weed management.