Acute toxicity modeling of rainbow trout and silver sea bream exposed to waterborne metals

Of three proposed acute toxicity models, the uptake-depuration (UD) model, the time-integrated concentration (TIC) model, and the concentration-time ( CT) model are derived and verified with acute toxicity data to estimate the internal residues of waterborne metals in fish as a function of a few cons tants and variables. The main factors are the exposure time, the external e xposure concentration, the bioconcentration factor (BCF), and the depuratio n rate constant (k(2)). The UD model is based on the concept of residue lev els at the cell membrane well correlating with the whole-body concentration s, whereas the TIC and the CT models are based on the idea of irreversible inhibition of the enzyme acetylcholinesterase (AChE) governing the metal ac ute toxicity in that metals in the entire fish or in the aqueous phase can be described by the critical area under the time-concentration curve that i s associated with a critical TIC of toxicant in the target tissue. A highly significant correlation (r(2) > 0.9) was found between predictions and LC5 0(t) data for both the TIC and the CT models, indicating successfully descr ibe 4- to 18-d LC50(t) data of arsenic (As), cobalt (Co), copper (Cu), and Co/Cu mixture in rainbow trout (Oncorhyuchus mykiss) and of Cu in fingerlin gs and subadults of silver sea bream (Sparus sarba). The time-dependent let hal internal concentration at the site of action that causes 50% mortality is also predicted for a given compound and species. It concludes that the T IC and the CT models can be applied to regulate the acute toxicity and to e stimate incipient LC50 values and internal residues of waterborne metals in fish. (C) 2001 by John Wiley & Sons, Inc.