In my last post I discussed Dose-Response and how exposure to certain
substances (be it chemical, drug, or general toxic waste), can cause an effect
on the exposed individual. In the past several decades we began to realize that
many individuals have been exposed to certain chemicals in the workplace and
that a number of these exposures have led to very serious and negative
implications on the individual’s health. One such example involves asbestos and the development of a deadly form of cancer known as
Mesothelioma in those individuals who were exposed to this material. This is merely one of many different examples and it was at this time that government
knew it was time to take action. This led to the development of several
standards geared towards protecting future generations of working class men and
women.
When referring to chemical or other hazardous substances, performance
standards for exposure limits are better known as Occupational Exposure Limits
or OEL's. There are several types of OEL's, the most typical being the Time Weighted Average. This allows for ups and downs but considers the single average concentration and number of excursions that take place during worker exposure. Other OEL's include Ceiling or Short Term Exposure Limits (STEL) and standards for Vibration, Sound, Heat/Cold, Radiation, Strain, and Biological Exposure Indices. By definition, "An occupational exposure limit is an upper limit on the acceptable concentration of a hazardous substance in workplace air for a particular material of class of materials."
The two biggest organizations created and tasked with developing
these standards are the
Occupational Safety and Health Administration (OSHA)
and the
American Conference of Governmental Industrial Hygienists (ACGIH). The
American Conference of Governmental Industrial Hygienists are known for
publishing their Threshold Limit Values or TLV's while the Occupational Safety
and Health Administration refers to their limits as permissible exposure limits
or PEL's. For more information on TLV's you can visit
here. According to OSHA's website, 4,679 workers died on the job in 2014. As previously stated, all of these limits, standards, and guidlines are created with the intention of reducing this number of accidents and deaths in the workplace.
For both TLV's and PEL's exposure is generally expressed as parts per million (ppm) for gases and vapors and milligrams per cubic meter (mg/m3) for solids. When considering the OEL you are observing airborne concentration that workers may be exposed to and you want to know how long they can be exposed to this without adverse effects considering 8 hour shifts 5 days per week.
For both TLV's and PEL's exposure is generally expressed as parts per million (ppm) for gases and vapors and milligrams per cubic meter (mg/m3) for solids. When considering the OEL you are observing airborne concentration that workers may be exposed to and you want to know how long they can be exposed to this without adverse effects considering 8 hour shifts 5 days per week. 