Peak limitation – revised definition of the peak limitation categories: MAK Value Documentation, addendum – Translation of the German version from 2024

TL;DR

A German commission updated how peak exposure limits for chemicals are categorized, focusing on the time it takes for health effects to occur.

Contribution

The paper introduces a revised definition of peak limitation categories based on effect development time.

Findings

The MAK Commission updated peak limitation categories to prioritize the time needed for health effects.

The revised definition aims to improve the categorization of chemical exposure risks in the workplace.

Abstract

The German Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) revised the definition of the peak limitation categories to emphasize that the time required for an effect to develop is decisive for the categorization.

Tables

Tab. 1. Excursion factors, duration, number per shift and interval between the peaks

Category	Excursion factor	Duration	Number per shift	Minimum intervalc)
I  Substances with immediate effects (irritants) or which cause sensitization of the airways	1a)	15 minutes, average valueb)	4	1 hour
II  Substances with delayed effects (systemic effects or effects in the lungs after repeated exposure)	2a)	15 minutes, average value	4	1 hour

Full text

Revised definition

The previous definition (Hartwig and MAK Commission 2017) distinguished between irritants (Category I) and substances with systemic effects (Category II). It was implied that substances in Category I have rapid effects while those in Category II require a certain amount of time to have an effect as they must first be absorbed. The time required for effects to develop is decisive; to make this clear, the categories have been re-defined (Table 1). The uncertainty whether substances which affect the lungs as the target organ should be classified as systemic agents, although they in fact have local effects, is thus avoided. If the effect is manifest only after a longer period of time, Category II applies. Also in the past, substances were classified in this way. Substances which have sensitizing effects on the airways were classified in Category I, as the peak concentrations are decisive for their effects. Because the MAK value does not offer protection against the induction and elicitation of sensitization, or only does so to a certain extent, such peaks must be limited. This is guaranteed by an excursion factor of 1, which Category II does not have.

Tab. 1: Excursion factors, duration, number per shift and interval between the peaks