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Dose-Response Curve Explorer

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Learning Objective

Students can analyze how the slope (Hill coefficient) and EC50 position of a dose-response curve determine the locations of the NOAEL, LOAEL, EC50/LD50, and derived Reference Dose - and explain why the linear-no-threshold (LNT) model used for carcinogens has no analogous "safe" landmark.

Bloom Level: Analyze (L4)

Specification

The full specification below is extracted from Chapter 6: Environmental Health, Toxicology, and Climate.

Type: microsim
sim-id: dose-response-explorer
Library: p5.js
Status: Implemented

Interactive dose-response curve visualization. The canvas shows a sigmoid
dose-response curve on a log-dose x-axis. Three controls govern the curve:
(1) slope steepness (Hill coefficient), (2) EC50 / LD50 horizontal position
on the log-dose axis, and (3) a model selector switching between the
classical Threshold S-curve and a Linear-No-Threshold (LNT) line used for
carcinogens.

Labeled markers appear on the curve for:
  - NOAEL (No Observed Adverse Effect Level)   - green triangle
  - LOAEL (Lowest Observed Adverse Effect Level) - orange triangle
  - EC50 / LD50                                  - red circle
  - Reference Dose (NOAEL / 100)                 - blue dashed vertical line

Hovering over any marker shows a tooltip with the definition and typical
regulatory use. A legend on the right explains every marker and the three
shaded background zones - No Effect (light green), Uncertain (light yellow),
Effect (light red) - which only appear in the Threshold model. The LNT model
shades the whole plot with a faint red wash to remind students that under
LNT there is no safe dose.

How to Use

  1. Drag the Hill slope slider to see how potency (steepness) shifts the NOAEL and LOAEL closer to or further from the EC50.
  2. Drag the Log EC50 slider to translate the entire curve along the log-dose axis - this is how more or less potent toxicants compare.
  3. Hover any marker to read its regulatory definition.
  4. Switch the model dropdown to Linear No-Threshold and notice the landmark markers (NOAEL, LOAEL, RfD) disappear - because for carcinogens modeled under LNT, those concepts do not apply.