Occupational exposure limits (OELs) are intended to set the airborne concentrations of substances to which workers can be exposed, on a daily basis without significant risk of material adverse effects. OELs are normally set for an 8 hour day and are expressed as an 8-hour time-weighted average. In many cases, a short-term (15-minute) exposure limit is also established. Occupational exposure limits can be called by different names such as: threshold limit values (TLV); permissible exposure limits (PEL) and short-term exposure limit (STEL) in the United States; maximale arbeitplatzkonzentrationen (MAK) in Germany; and indicative and binding limit values (ILV) in the European Union.
OELs for the majority of hydrocarbon and oxygenated solvents are set between 10 and 500 parts per million (ppm) depending on the individual substance's volatility and toxicity. Where solvents are used in combinations, additional precautions may be appropriate.
For most oxygenated solvents, OELs have been set by the Occupational Safety and Health Administration (OSHA) and/or the American Conference of Governmental and Industrial Hygienists (ACGIH). Determining OELs for hydrocarbon solvents has been made more difficult due to their complex composition. An industry task group has published guidelines for recommending a uniform methodology for calculating OELs for complex hydrocarbon solvents and blends.
Worker safety is important to the Solvents Industry Group. Many tools are available to monitor worker exposure. For example, organic vapor analyzers can be used to monitor the level of exposure on the spot. And monitoring badges, worn by individual workers, can be used to assess the level of personal exposure and help to ensure that safe exposure limits to airborne solvents are being met.
