The REACH regulation defines them as exposure levels beneath which a substance does not harm human health.
Correspondent to REACH legislation, the registrant (manufacturer or importer) of a substance has to indicate the DNELs for the most probable way of exposition (oral, dermal, inhalative) and the expected frequency and duration of exposure.
Depending on the way of exposure it can be necessary to specify different DNELs for affected persons (employees, consumer, children, pregnant women etc.).
[1] The GESTIS DNEL list of the German Social Accident Insurance (DGUV) makes workplace-related DNELs available that have been established by manufacturers and importers on their own responsibility and are published in this form by the European Chemicals Agency (ECHA).
The DNEL list can be used for a risk assessment of tasks involving hazardous substances, for the specification of protective measures, and for the evaluation of their efficiency.