Probit functions are part of a quantitative risk assessment (QRA), used to estimate the number of deadly victims as a result of inhaling dangerous substances in an accident.

Third party risks: effects of dangerous substances

A quantitative risk assessment (QRA) is a tool for the provision of insight into the risks of the use, transport and storage of dangerous substances. The calculation methods used in the analysis provide insight into the expected number of deadly victims in an accident involving dangerous substances. The use of probit functions is prescribed for the model-based estimate of the acute lethal effects of these dangerous substances. This information is used in the granting of permits and spatial planning concerning activities involving dangerous substances.

What is a probit function?

Probit functions indicate the relationship between the concentration of a substance in the air, the exposure time and the effect on (in this case) humans. In this way, a probit function for a substance can be used to estimate the percentage of fatalities in the direct vicinity of an accident caused by exposure to the toxic substance, in any random combination of concentration and exposure time.

Probit functions are based on toxicological information of substances from animal experiments in excisting literature. This data is converted into exposure-response relationships for humans. The relevant data and the derivation of the probit function is summarized in the substance document.