Table 1 Characteristics (90th percentile concentration, detection frequency, and potential toxicity) of fipronil compounds detected in 444 wadeable streams across the continental United States by region (35).

*Compounds used in the mesocosm experiment. †ΣTUFipronils, median of the sum of toxic units [observed field concentrations for four fipronil compounds/hazard concentration for the fifth percentile of affected species from the SSDs (Fig. 4) for each compound] for fipronil(s) calculated for weekly samples from the last 4 weeks of pesticide samples collected at each site. ‡Number of sites where pesticides were measured. §The 90th percentile was derived from the site maximum observed concentration during the last 4 weeks of pesticide sampling. ║Percentage of samples with detections. ¶The 95% CIs for HC5 values (Fig. 4 and table S3, mesocosm-only) were used to calculate CIs. Dechlorofipronil was analyzed in all regions and never detected. ND, not detected.

Fipronil*Desulfinyl
fipronil*
Fipronil
sulfide*
Fipronil
sulfone*
Fipronil
amide*
Desulfinyl
fipronil
amide
Fipronil
sulfonate
Mean ΣTUFipronils% Sites >
ΣTUFipronils = 1
Number of
sites
All regions,
90th
percentile
concentration
(ng/liter)§
6.32.22.04.210.8NDND
All regions
(year)
22%11%13%20%18%1%0.1%0.62 (0.27–1.62)16% (9–20%)444
Midwest
(2013)
14%9%6%9%5%1%0.3%0.32 (0.14–0.96)5% (4–9%)100
Southeast
(2014)
51%30%40%57%56%3%ND1.82 (0.80–4.92)51% (32–55%)77
Northwest
(2015)
9%3%4%14%2%NDND0.13 (0.06–0.28)6% (0–9%)87
Northeast
(2016)
19%10%11%17%21%0.3%ND0.62 (0.27–1.56)14% (8–16%)95
Coastal
California
(2017)
19%4%8%11%14%NDND0.40 (0.18–0.85)12% (6–18%)85