Insecticides in US Streams Rarely Come Alone
Key result: Of 14,675 US stream samples tested for all four major neonicotinoids since 2015, 50.2 percent contained at least one and 26.1 percent contained two or more. In samples tested for at least 10 of 14 pest control insecticides, 35.4 percent held two or more and one held ten.
One compound at a time is not how streams work
Pesticide monitoring is usually reported compound by compound, as in our analyses of insecticides in US streams and of stream samples against EPA’s benchmarks. Benchmarks, too, are set for one compound at a time. But laboratories analyse a single water sample for many compounds at once, so the national record can show how often they occur together.
We matched every result for 14 insecticides used in pest control to its water sample, using the portal’s sample identifier, and counted how many were detected in each sample. Hidden non-detects were corrected as described in our monitoring audit.
The four neonicotinoids
| Neonicotinoids detected | Samples | Share |
|---|---|---|
| None | 7,310 | 49.8% |
| One | 3,539 | 24.1% |
| Two | 2,035 | 13.9% |
| Three | 1,351 | 9.2% |
| All four | 440 | 3.0% |
| Two or more | 3,826 | 26.1% |
Source: Water Quality Portal, US stream sites, water samples from 1 January 2015 analysed for imidacloprid, clothianidin, thiamethoxam and dinotefuran. Author calculation.
What it means. A stream sample with one neonicotinoid usually has another. Of the 7,365 samples with any, 3,826, or 51.9 percent, had two or more. The most common pairing is imidacloprid with clothianidin, in 2,331 samples, followed by imidacloprid with thiamethoxam, 1,822, and clothianidin with thiamethoxam, 1,650. 846 of 2,072 monitored sites had at least one sample with two or more.
What limits it. The four compounds are analysed together mainly by state agricultural programmes, led by Minnesota, Washington and Wisconsin, and their sampling choices shape the result.
Does it hold across programmes?
| Programme | Samples | Any neonicotinoid | Two or more |
|---|---|---|---|
| Minnesota Department of Agriculture | 3,939 | 38.4% | 16.6% |
| Washington State Department of Agriculture | 2,714 | 49.9% | 26.1% |
| Wisconsin Department of Agriculture | 1,119 | 30.1% | 13.6% |
| USGS California Water Science Center | 734 | 34.3% | 12.3% |
| Florida DEP, South District | 624 | 81.6% | 53.5% |
Source: as above, five largest programmes. Author calculation.
What it means. Every large programme finds multiple neonicotinoids in a substantial share of samples, from 12.3 percent in USGS California sampling to 53.5 percent in south Florida. Among samples with any neonicotinoid, the share with two or more ranges from 36 to 66 percent.
Across 14 insecticides
What it means. In the 2,093 samples analysed for at least 10 of the 14 insecticides, 54.0 percent had at least one, 35.4 percent two or more and 20.5 percent three or more. One sample had ten different insecticides. 29.6 percent had at least one compound above its own lowest EPA freshwater invertebrate benchmark, and 6.8 percent, 143 samples, had two or more compounds each above its own benchmark.
What limits it. Broad panels are run by few programmes; 48.6 percent of these samples come from the USGS California Water Science Center, so this result leans on California streams.
Why mixtures matter for benchmarks
EPA’s aquatic life benchmarks apply to one compound at a time. A sample in which several insecticides are each below their own benchmark is assessed as clean for each of them. Our data show that is the normal situation for neonicotinoids rather than an exception. We do not sum the compounds against a combined benchmark, because EPA publishes none and combining different chemicals that way is a scientific judgement this monitoring record cannot make.
Checks
1. Matching
Method. Results matched by the Water Quality Portal activity identifier, shared by all results from one water sample.
2. Corrected detections
Method. Detection limits stored as values were treated as non-detects, and programmes that never report a non-detect were excluded for the compounds concerned.
3. Programme robustness
Result. Multiple neonicotinoids appear in at least 12 percent of samples in each of the five largest programmes.
Download the data
The tables in this report are published as CSV files under a Creative Commons Attribution 4.0 licence. You may republish, remix and build on them, including commercially, with attribution to The Pest Control Brief and a link to this page.
- Number of insecticides detected per sample, for the four-neonicotinoid and 14-insecticide panels, and co-detected pairs (CSV, 17 rows)
How to cite this report
The Pest Control Brief, “Insecticides in US Streams Rarely Come Alone: Half of Neonicotinoid-Positive Samples Contain Two or More”, 2 October 2026. https://thepestcontrolbrief.com/insecticide-mixtures-in-streams/
References
- Water Quality Portal. Result search, narrowResult profile, siteType=Stream, from 1 January 2015, for 14 insecticides. waterqualitydata.us. Retrieved 25 September to 3 October 2026.
- US Environmental Protection Agency. Aquatic Life Benchmarks. Last updated 2 February 2026. epa.gov aquatic life benchmarks. Accessed 2 October 2026.
- The Pest Control Brief. The national pesticide monitoring record, audited. thepestcontrolbrief.com. Source of the detection rule.
How the samples were counted
Data. US stream-site water results since 1 January 2015 for imidacloprid, clothianidin, thiamethoxam, dinotefuran, fipronil, bifenthrin, permethrin, deltamethrin, cyfluthrin, esfenvalerate, chlorpyrifos, chlorfenapyr, indoxacarb and pyriproxyfen.
Panels. The neonicotinoid panel is every sample analysed for all four neonicotinoids. The broad panel is every sample analysed for at least 10 of the 14 compounds.
Limitations. Only compounds a sample was analysed for can be counted, so real mixtures may be larger. Breakdown products are not included. Monitoring is purposive.
Last reviewed: 4 October 2026.
For environmental reporters
Most quotable statistics
- 26.1 percent of US stream samples tested for all four major neonicotinoids contained two or more of them.
- Of samples with any neonicotinoid, 51.9 percent had at least two.
- 440 samples contained all four.
- In samples tested for at least 10 pest control insecticides, 35.4 percent had two or more, and one had ten.
- 143 samples had two or more insecticides each above its own EPA benchmark.
Press summary
Neonicotinoid insecticides in US streams usually travel in company, according to an analysis of the national water-quality record by The Pest Control Brief. Of 14,675 stream samples tested for all four major neonicotinoids since 2015, half contained at least one and a quarter contained two or more. Across a broader panel of 14 insecticides used in pest control, a third of samples held two or more. EPA’s aquatic life benchmarks assess each compound alone.
Headlines editors could use
- Half of neonicotinoid-positive stream samples hold more than one
- One US stream sample, ten insecticides
- The pesticide mixtures single-compound benchmarks miss
Questions about mixtures
How often do streams contain more than one insecticide?
Often. A quarter of US stream samples tested for all four major neonicotinoids had two or more, and a third of samples tested for a broad panel of 14 insecticides had two or more.
Which neonicotinoids occur together most?
Imidacloprid and clothianidin, in 2,331 samples, then imidacloprid and thiamethoxam, and clothianidin and thiamethoxam.
Do EPA benchmarks account for mixtures?
No. EPA’s aquatic life benchmarks are set for each compound individually.
Is a mixture more harmful?
This analysis does not assess combined toxicity. It shows how often compounds occur together.
Where can I get the data?
The distributions and pair counts are in the CSV above.
