LC50 and Aquatic Toxicity
Lethal concentration of a substance in water causing death in 50% of exposed aquatic organisms, used to regulate water pollutants.
Formula
LC50 (mg/L) = lethal concentration causing 50% mortality over 96-hour aquatic exposure
Real World
The 2000 Baia Mare cyanide spill in Romania released 100,000 m³ of cyanide-contaminated water into the Tisza River; cyanide's aquatic LC50 for fish is below 0.1 mg/L, and the spill caused near-total fish death along 400 km of river.
Exam Focus
Specify the test organism and exposure duration (96-hour fish LC50) when quoting LC50 values; omitting these details is penalised in mark schemes.
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