Species Sensitivity & Dose-Response (LC50) Lab

Pollutant concentration

Concentration – mg/L

Species response (this concentration)

Most sensitive

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Most tolerant

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LC50 spread (max/min)

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Species >50% affected

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How it works

Each species here has its own dose-response curve: expose a population to a range of concentrations and plot the fraction affected against concentration (on a log axis) and you get a characteristic S-shaped (sigmoid) curve — almost nobody affected at low doses, a steep transition zone, then almost everybody affected at high doses. The LC50 is the concentration at the curve's midpoint, where exactly half the population is affected — a single number that summarizes how sensitive that species is.

response(C) = 100% / (1 + (LC50 / C)^slope)

A lower LC50 means a species is more sensitive — it succumbs at a lower dose.
A higher LC50 means a species is more tolerant — it can withstand a much higher dose.
Click any species row to jump the slider straight to that species' LC50 and see the other curves at that exact same concentration.

Because different species — even close neighbors in the same pond — can have LC50 values spanning orders of magnitude, a single regulatory threshold that is comfortably safe for a tolerant fish can already be deep in the lethal zone for a sensitive invertebrate living in the very same water.

Dose-response curves–

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