1,3-Dichlorobenzene – Evaluation of a biological guidance value (BLW)

In 2025, the German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has evaluated a biological guidance value (BLW) for 1,3‑dichlorobenzene 541-73-1. Relevant publications were identified from a literature search. For the derivation of the BLW, an experimental study was available that demonstrated a good correlation between the concentration of 1,3-dichlorobenzene in the air and 1,3-dichlorobenzene in blood as well as the urinary metabolites 3,5‑dichlorocatechol, 2,4‑dichlorophenol and 3,5-dichlorophenol. The data of the experimental study conducted with resting volunteers for 6-hours were extrapolated to account for an exposure of 8 hours and an increased respiratory volume at the work place. At the level of the MAK value of 2 ml/m3, an average value of 40 mg 3,5-dichlorocatechol (after hydrolysis)/g creatinine can be expected and was set as BLW. Sampling time is at the end of the shift, after several previous shifts.