The permissible exposure limit (PEL or OSHA PEL) is a

legal Law is a set of rules that are created and are enforceable by social or governmental institutions to regulate behavior,Robertson, ''Crimes against humanity'', 90. with its precise definition a matter of longstanding debate. It has been vario ...

limit in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

for exposure of an employee to a

chemical substance A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wi ...

or physical agent such as high level noise. Permissible exposure limits are established by the

Occupational Safety and Health Administration The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...

(OSHA). Most of OSHA's PELs were issued shortly after adoption of the Occupational Safety and Health (OSH) Act in 1970. For chemicals, the chemical regulation is usually expressed in

parts per million In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they ...

(ppm), or sometimes in

milligram The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. ...

s per

cubic meter The cubic metre (in Commonwealth English and international spelling as used by the International Bureau of Weights and Measures) or cubic meter (in American English) is the unit of volume in the International System of Units (SI). Its symbol is m ...

(mg/m³). Units of measure for physical agents such as

noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...

are specific to the agent. A PEL is usually given as a time-weighted average (TWA), although some are

short-term exposure limit A short-term exposure limit (STEL) is the acceptable average exposure over a short period of time, usually 15 minutes as long as the time-weighted average is not exceeded. STEL is a term used in occupational health, industrial hygiene and toxicolo ...

s (STEL) or ceiling limits. A TWA is the average exposure over a specified period, usually a nominal eight hours. This means that, for limited periods, a worker may be exposed to concentration excursions higher than the PEL, so long as the TWA is not exceeded and any applicable excursion limit is not exceeded. An excursion limit typically means that "...worker exposure levels may exceed 3 times the PEL-TWA for no more than a total of 30 minutes during a workday, and under no circumstances should they exceed 5 times the PEL-TWA, provided that the PEL-TWA is not exceeded." Excursion limits are enforced in some states (for example Oregon) and on the federal level for certain contaminants such as asbestos. A short-term exposure limit is one that addresses the average exposure over a 15-30 minute period of maximum exposure during a single work shift. A ceiling limit is one that may not be exceeded for any time, and is applied to irritants and other materials that have immediate effects.

Regulatory agencies for occupational noise exposure

OSHA

The current PEL for OSHA standards are based on a 5

decibel The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a po ...

exchange rate. OSHA's PEL for noise exposure is 90 decibels (dBA) for an 8-hour TWA. Levels of 90-140 dBA are included in the noise dose. PEL can also be expressed as 100 percent “dose” for noise exposure. When the noise exposure increases by 5 dB, the exposure time is cut in half. According to OSHA, a 95dBA TWA would be a 200 percent dose. PEL is exceeded when TWA > 90 dBA. OSHA requires feasible engineering OR

administrative controls Administrative controls are training, procedure, policy, or shift designs that lessen the threat of a hazard to an individual. Administrative controls typically change the behavior of people (e.g., factory workers) rather than removing the actu ...

, and mandatory hearing protection when the PEL is exceeded.

MSHA

Like OSHA,

Mine Safety and Health Administration The Mine Safety and Health Administration (MSHA) () is a large agency of the United States Department of Labor which administers the provisions of the Federal Mine Safety and Health Act of 1977 (Mine Act) to enforce compliance with mandatory safet ...

(MSHA) also uses the same 5 decibel exchange rate and 90 dBA for an 8-hour TWA for their PEL. Once a miner's noise exposure exceeds the PEL, feasible engineering AND administrative controls must be in place to try to limit the noise exposure of the employees. If a mine operator uses administrative controls, procedures for such controls must be posted on the bulletin board and a copy must be supplied to all affected employees.

NIOSH

The

National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...

(NIOSH)

Recommended Exposure Limit A recommended exposure limit (REL) is an occupational exposure limit that has been recommended by the United States National Institute for Occupational Safety and Health. The REL is a level that NIOSH believes would be protective of worker safety ...

(REL) for noise exposure uses a 3 decibel exchange rate. The recommendation for occupational noise exposure is 85 decibels (dBA) for an 8-hour TWA. For every 3 dB over 85, the exposure time is cut in half. NIOSH reports exposures above this level are considered hazardous. NIOSH uses a hierarchy of control to reduce or remove hazardous noise.

References

External links