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Calcimator

Aquatic Toxicology Calculator

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

Inputs

%
%

Results

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

How the result changes with Mortality at high conc (%)

Mortality at high conc (%)LC50 (mg/L)
110.01
3569.66
654.85
892.55

What each input means

Low concentration (mg/L)
Lower test concentration in mg/L.
Mortality at low conc (%)
Percent mortality observed at the lower concentration.
High concentration (mg/L)
Higher test concentration in mg/L.
Mortality at high conc (%)
Percent mortality observed at the higher concentration.
Environmental conc (mg/L)
Measured or predicted concentration of the substance in the environment.
Assessment factor
Safety factor for PNEC derivation. Typical: 1000 for single acute LC50, 100 for chronic data, 10 for field data.

What each result means

LC50 (mg/L)
Estimated concentration lethal to 50% of test organisms.
LC10 (mg/L)
Concentration lethal to 10% of organisms (low-effect threshold).
LC90 (mg/L)
Concentration lethal to 90% of organisms.
Toxic units (TU)
Environmental concentration divided by LC50. TU > 1 indicates likely adverse effects.
PNEC (mg/L)
Predicted No-Effect Concentration: LC50 divided by assessment factor.
Risk quotient (RQ)
Environmental concentration / PNEC. RQ > 1 indicates unacceptable risk.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Low concentration (mg/L) = 1, Mortality at low conc (%) = 20, High concentration (mg/L) = 10, Mortality at high conc (%) = 80 = 6 input(s) provided
  2. Calculate LC50
    LC50 = pow(10, logLC50)
    3.1623 = 3.1623
  3. Calculate LC10
    LC10 = pow(10, logLC10)
    0.5475 = 0.5475
  4. Calculate LC90
    LC90 = pow(10, logLC90)
    18.2647 = 18.2647

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