[Setting limit values for chemical substances in the workplace: DNEL(INH) setting according to REACH principles following the example of 2-butyne-1,4-diol].

Derived No Effect Level (DNEL(inh)) has been set for occupational exposure to but-2-yno-1,4-diol according to REACH principles. Maximum allowable concentration (MAC) and DNEL(inh) have been compared. Experimental data from two inhalation studies on rats and three oral studies have been used to calculate DNEL. Estimated DNEL(inh) values show significant differences and fall within the range of 0.33-0.02 mg/m3, depending on the chosen experiment and critical effect. It seems that a 30-day inhalation study best reflects the penetration of xenobiotic to the human organism. This experiment has been used to set MAC value of but-2-yno-1,4-diol of 0,25 mg/m3 and it is close to local DNEL(inh)--0.10 mg/m3. Both values have been estimated on the same starting point NOAEC(loc)--0.5 mg/m3, but different assessment factors have been applied. A general feeling is that because of the differences in methodologies for calculating DNELs versus those used for calculating health-based OELs, the DNEL will tend to be lower than any corresponding health-based OEL for that chemical. This indicates that the OEL does not provide the appropriate level of protection required by REACH. The calculation leads to a new value (DNEL) that requires different risk management measures and operational conditions.