Aquatic Toxicology Calculator

Estimate LC50 from two dose-response data points using probit approximation. Calculate toxic units, PNEC, and environmental risk quotient.

Low concentration (mg/L)

Mortality at low conc (%)

High concentration (mg/L)

Mortality at high conc (%)

Environmental conc (mg/L)

Assessment factor

Tab to move between fields

LC50 (mg/L)

3.16

LC10 (mg/L)0.55

LC90 (mg/L)18.26

Toxic units (TU)0.16

PNEC (mg/L)0

Risk quotient (RQ)158.11

How to Use This Calculator

Enter the toxicant concentration in the water in mg/L or ppb.
Input the LC50 value for the target species from published toxicity data.
Set the exposure duration in hours.
Review the calculated toxicity quotient (TQ) — TQ > 1 indicates a risk of acute lethality.
Apply a safety factor of 10× below the LC50 for sub-lethal effects and sensitive life stages.

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