New EPA Guidelines Means Synthetic Pesticides in Boulder Creek Exceed National Benchmarks

The Environmental Protection Agency (EPA) has decreased its aquatic life benchmarks for neonicotinoids, which is a group of insecticides that are linked to the decline of bees and are commonly used in agriculture, urban yards and for termites and flea prevention in pets.

IMG: Rella Abernathy Integrated Pest Management Coordinator City of Boulder at Boulder Creek. The EPA has revised its benchmarks for imidacloprid found in water. The new benchmarks means the levels of the pesticide found in Boulder Creek in 2016 now exceed EPA guidelines.

These stricter guidelines align with a growing body of scientific literature that demonstrates harm to both terrestrial and aquatic ecosystems by these insecticides even at low levels. The City of Boulder banned the use of neonicotinoids on city properties in 2015. In 2016 the city tested the water in Boulder Creek for the presence of these pesticides.



Water samples were taken at Boulder, Four Mile and Wonderland Creeks and found imidacloprid, a neonicotinoid, at all sites except Eben G. Fine Park. The 2016 samples did not reach the former thresholds of concern for imidacloprid. However, under the revised EPA benchmarks, the 2016 samples exceed the new limits by an average of nearly 5 times.

Rella Abernathy, Boulder’s Integrated Pest Management Coordinator says that it is likely that imidacloprid originated from residential and commercial uses of the insecticide, which is incredibly water soluble.

“When it rains or when we water it ends up in the storm system and when it’s in the storm water it ends up in the creeks, so they actually run off into the stream system.”

Neonicotinoids are highly water soluble and easily move from sites where they were applied into waterways, where they can kill or harm aquatic invertebrates, such as mayflies, caddisflies and dragonflies. This indirectly affects fish, amphibians, birds and mammals that feed on these insects.

Based on the new EPA guidelines and past results, city staff is examining options for implementing more frequent testing of the urban creek system.

The City of Boulder is offering a free workshop on Monday, Jan. 29, from 5:30 to 7:30 p.m. at the Canyon Theater of the Boulder Public Library, to provide information about ways to avoid using synthetic chemicals, such as neonicotinoids, and caring for lawns in ways that are safe for families, neighborhoods and the environment.