Since long, St. John's wort has been recognized by people for the health benefits possessed by the herb. For instance, it possesses wonderful anti-viral as well as antiseptic characteristics and is also effective when used as an analgesic.
Occupational Exposure Limits (. s) restrict the amount and length of time a worker is exposed to airborne concentrations of hazardous biological or chemical agents.here are. s for over 725 substances under R.R.O. 1990, Regulation 833 (Control of Exposure to Biological or Chemical Agents) and Ontario Regulation 490/09 (Designated Substances) under Ontarioâs Occupational Health and Safety Act.
1 the time-weighted average (TWA) exposure limit-the maximum average concentration of a chemical in air for a normal 8-hour working day and 40-hour week; 2  the short-term exposure limit (STEL) - the maximum average concentration to which workers can be exposed for a short period (usually 15 minutes);he legal basis for the preparation of occupational exposure limits and biological limits in the European Union is contained in Directive 98/24/EC on chemical agents and Directive 2004/37/EC on carcinogens and mutagens.