Effects from copper were reported at concentrations slightly above 1 mg/L from acute freshwater exposures, although effects at this low range were rare. The 10th percentile value for all species derived from the freshwater acute copper toxicity database was 8.3 mg/L. Similar freshwater acute 10th percentile values (6.9 to 10.8 mg/L) were reported among the various trophic groups. The 10th percentile value for all species in the freshwater chronic database was 3.8 mg/L copper. This value is approximately half the 10th percentile value for the acute freshwater data
These data are supportive of the very low ACR for copper previously documented. The 10th percentile value for all species exposed to acute saltwater copper exposures was 6.3 mg/L. This concentration is similar to the acute copper freshwater 10th percentile value (8.3 mg/L) reported above. Saltwater chronic data with copper were limited to four species; a 10th percentile value of 6.4 mg/L was determined from these data.