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Mixed Exposure Index Calculator

Work out mixed exposure index instantly with clear inputs, formula shown and shareable results.

About Mixed Exposure Index Calculator

Where substances act on the same target organ their effects are treated as additive: each concentration is divided by its own limit and the fractions are summed. An index above one means the mixture is over-exposed even when no single substance exceeds its individual limit, which is the situation this calculation exists to catch.

Formula

Additive mixture index

Index = C1/L1 + C2/L2 + ... , must not exceed 1

Worked example

With the default values below, Mixed Exposure Index Calculator returns Mixed exposure index of 0.7000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Concentration of the first substanceminimum 0 ppm
20 ppm
Exposure limit of the first substanceminimum 0.001 ppm
50 ppm
Concentration of the second substanceminimum 0 ppm
30 ppm
Exposure limit of the second substanceminimum 0.001 ppm
100 ppm

Results

Mixed exposure index
0.7000
First substance contribution
0.4000
Second substance contribution
0.3000
Assessment
Above the action level for the mixture

Step by step

  1. 1Values used
  2. 2Additive mixture index
  3. 3Mixed exposure index= 0.7000
  4. 4First substance contribution= 0.4000
  5. 5Second substance contribution= 0.3000
  6. 6Assessment= Above the action level for the mixture

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Mixed exposure assessment requires a qualified occupational hygienist to establish whether additive, independent or synergistic treatment applies.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Mixed exposure assessment requires a qualified occupational hygienist to establish whether additive, independent or synergistic treatment applies.

Frequently Asked Questions

How is the Mixed Exposure Index figure worked out?

Index = C1/L1 + C2/L2 + . , must not exceed 1. Where substances act on the same target organ their effects are treated as additive: each concentration is divided by its own limit and the fractions are summed.

When does the additive rule not apply?

When the substances act on different organs by different mechanisms, in which case each is assessed independently. Where there is synergy the additive rule under-estimates the risk and specialist advice is needed.

What values do I need to enter?

This calculator takes 4 inputs: Concentration of the first substance, Exposure limit of the first substance, Concentration of the second substance, Exposure limit of the second substance. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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