Work out mixed exposure index instantly with clear inputs, formula shown and shareable results.
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.
Additive mixture index
Index = C1/L1 + C2/L2 + ... , must not exceed 1
Preliminary estimate only. Mixed exposure assessment requires a qualified occupational hygienist to establish whether additive, independent or synergistic treatment applies.
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 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.
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.