Table 4.
Acute median effect concentrations (EC50s) and 95% confidence limits (CLs; in parentheses) for 10 chemicals in the single-species study with fatmucket (Lampsilis siliquoidea)a
| Toxicant | EC50 (95% CL) (mg/L) | FAV (mg/L) | SSD percentile |
|---|---|---|---|
| 2,4-dichlorophenoxyacetic acid | >311 | NA | 76 (n = 24) |
| 4-nonylphenol | 0.099 (0.096–0.102) | 0.056 | 27 (n = 29) |
| Azoxystrobin | 0.725 (0.697–0.754) | NA | 83 (n = 5) |
| Bifenthrin | >0.0267 | NA | 86 (n = 6) |
| Carbaryl | >8.0 | 0.004 | 77 (n = 61) |
| Malathion | 23 [16–33]b | NA | 82 (n = 75) |
| Molinate | 53 (51–55) | NA | 94 (n = 17) |
| Arsenic (V) | 117 (113–122)c | 0.68 | 62 (n = 12) |
| Calcium chloride | 5383 [3862–7502]b | NA | 45 (n = 10) |
| Aluminum (total) | >54 | 1.5d | 72 (n = 17) |
Final acute values (FAVs) in the US national ambient water quality criteria and a percentile of EC50 for fatmucket in the species sensitivity distribution (SSD) for all freshwater species are presented.
An EC50 could not be calculated because of no partial mortality (Supplemental Data, Table S5). The geometric mean of the bracketing concentrations with 0% and 100% mortality was calculated to obtain an estimated EC50. The 0% and 100% effect concentrations are provided in bracket as [0–100% effect concentration].
The effect concentration was calculated in terms of assayed arsenic concentration.
The FAV in draft updated water quality criteria for aluminum at hardness 100 mg/L and pH range of 6.5 to 9.0 (D. Eignor, US Environmental Protection Agency, Washington, DC, unpublished data).
NA = not applicable.