Some substances are UVCBs: substances of Unknown or Variable composition, Complex reaction products or Biological materials. Examples include paraffin wax and petroleum fractions. For such substances, a molecular formula, molecular weight, melting and boiling point, and vapour pressure do not describe a discrete molecule but a range of compositions. The numbers are therefore approximate.
DOHSBase Online now makes this explicit:
- A neutral UVCB chip appears next to the substance name, with a tooltip explaining what it means.
- On the physical and chemical properties tab, molecular weight, melting point, boiling point and vapour pressure carry a ~ sign, with an explanatory note above the panel.
- In DOHSBase Compare, Cmax, TIX and RAS for a UVCB are shown in italics with a ~. The limit value (OEL) is deliberately not marked as approximate: limit values are regulatory and do not depend on molecular composition.
UVCB is a normal regulatory category, not a warning. The cue is therefore neutral (a grey chip, a ~ sign) and is only meant to make clear what the displayed numbers mean.