Before a probit function is included in the calculation method, a step-by-step process of derivation, evaluation and formalisation is followed.

The probit function has a certain status in the various stages of this process:

  • The ‘proposed’ status:
    The probit function has been derived by the author of the substance document and published for external comment. A probit function with this status may be used in a QRA only if no formalised probit relation is available for the substance in question yet. Because the probit function has not yet been evaluated by the probit functions expert panel, its use is the responsibility of the user, in consultation with the competent authority.
  • The ‘interim’ status:
    The expert panel on probit functions has approved the probit function on scientific grounds. A probit function with this status can be used in a QRA only if no formalised probit function is yet available for the substance in question.
  • The ‘established’ status:
    The probit function has been formalised by the Ministry of Infrastructure and the Environment and is or will be included in the calculation method. The use of a probit function with this status in a QRA is obligatory.

For a current overview of the status of probit functions, see the Probit Functions Status Overview.


The derivation of a probit function takes place using an established methodology based on information from literature. The methodology is described in the RIVM report Method for derivation of probit functions for acute inhalation toxicity (2015).

This new methodology for the derivation of probit functions has been developed over the past number of years by the expert panel on probit functions under the responsibility of RIVM. There is not always a large quantity of data available, so a conservative approach was used in the development of the derivation methodology, where the elaboration of the precautionary principle was reduced to a manageable minimum. In general, toxicological information about substances lies mainly with the chemical industry. The intended plan of work of the expert panel is therefore made public in an early stage. Because the industry has the opportunity to provide relevant information, it is able to fulfil its responsibility and contribute knowledge.

The methodology for the derivation has been reviewed by an international panel of experts and approved, stating some recommendations for adaptation. A report of this international review can be found on this page.

The derivation of a probit function is described in a substance document, which is drafted according to a template provided. This results in a transparent, verifiable, robust and valid, technical substance document that provides a consistent, uniform approach and quality.

The most recently updated version of the template can be found at the Helpdesk Externe Veiligheid (NL).

External public comment

After a check for completeness, concept substance documents are assigned the status ‘proposed’. The documents are published on this website in order to provide interested parties with the opportunity to comment or provide additional information. A minimum term of 6 weeks applies. Interested parties are informed of the publication of new substance documents via e-mail.


The proposed probit functions and any comments received arescientifically evaluated by a scientific expert panel. The expert panel consist of 6 members:

  • A. (Anneke) Wijbenga MSc, Ministry of Health, Welfare and Sports (chair)
  • Dr Doctor . J.H.E. (Josje) Arts MSc, AkzoNobel
  • Dr. P.J. (Peter) Boogaard, Shell
  • P.M.J. (Peter) Bos MSc, RIVM
  • Dr. H. (Hans) Muijser, TNO
  • Dr. M. (Marc) Ruijten MSc, CrisisTox Consult

The expert panel evaluates whether a proposed probit function has been derived correctly and in conformity with the methodology for the derivation. The expert panel provides advice based on scientific grounds about proposed probit functions. The expert panel’s approval of a probit function results in the status ‘interim’.

Consequence analysis

After the conclusion of the scientific process, a consequence analysis is carried out under the direction of RIVM. The technical consequences in dealing with a new probit function are mapped out, and the social impact of the possible implementation of a probit function in the calculation method is considered. In conjunction with the industry, RIVM draws up a plan to ensure that all stakeholders involved receive the opportunity to provide input for the process and the execution of the analyses.


RIVM presents the scientific advice from the Expert panel and the results of the consequence analysis to the Ministry of Infrastructure and the Environment. The Ministry weighs the societal feasibility and affordability and establishes whether, and if so, in what time frame and under which conditions a probit function will be implemented and fits into the legally prescribed calculation methods. By the compulsory prescription of a probit function, the Ministry of Infrastructure and the Environment raises the status of a probit function to ‘established’. The establishment of a probit function ultimately results in an update of the Bevi calculation methodology in the form of an updated list of established probit functions in the Reference Manual Bevi Risk Assessments (NL, Module B, section 3.5).

Additional information

The procedure has been described in detail in the Evaluation and assessment of probit functions document. Further information about the derivation of proposed probit functions can be obtained at our helpdesk (NL) as required.