5.1.9 EH40 (2005): The health and Safety Executive (UK) Guidance on Occupation Exposure Limits.
5.1.10 Hazardous substances include:
(1) Substances used directly in work activities ( e.g. adhesives, paint, cleaning agents);
(2) Substances generated during work activities ( e.g. fumes from soldering and welding);
(3) Naturally occurring substances ( e.g. grain dust);
(4) Biological agents such as bacteria and other micro-organisms.