Exposure Limits 3.53 References

Exposures require eontrol sueh that nearly all people would not suffer any adverse health effeets even if exposed to a speeifie substanee (or mixture of substanees) day after day. Eor eertain substanees there are set oeeupational exposure limits refer to page 78. 

PEL Pg pmol PHS PMR ppb ppm ppt REL RfD RTECS sec SCE SIC SIR SMR STEL STORET TLV TSCA TRI TRS TWA u.s. UF yr WHO wk permissible exposure limit picogram picomole Public Health Service proportionate mortality ratio parts per billion parts per million parts per trillion recommended exposure limit Reference Dose Registry of Toxic Effects of Chemical Substances second sister chromatid exchange Standard Industrial Classification Standardized incidence ratio standard mortality ratio short term exposure limit STORAGE and RETRIEVAL threshold limit value Toxic Substances Control Act Toxics Release Inventory total reduced sulfur time-weighted average United States uncertainty factor year World Health Organization week... 

Pg pmol PHS PMR ppb ppm ppt REL RID RTECS picogram picomole Public Health Service proportionate mortality ratio parts per billion parts per million parts per trillion recommended exposure limit Reference Dose Registry of Toxic Effects of Chemical Substances... 

The National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances (NAC/AEGL Committee) was established to develop scientifically credible short-term exposure limits for approximately 400 to 500 acutely toxic substances. These short-term exposure limits, referred to as acute exposure guideline levels, or AEGLs, are essential for emergency planning, response, and prevention of accidental releases of chemical substances. Further, it is important that the values developed be scientifically credible so that effective planning, response, and prevention can be accomplished. 

See also Occupational Exposure Limits Reference Dose (RfD) Respiratory Tract Risk Assessment, Human Health Uncertainty Factors. 

It should be remembered that all exposure limits refer to healthy adults working at normal rates over normal shift duration. In practice it is advisable to work well below the recommended value, as low as one quarter, to provide a good margin of safety. ... 

Most of the listed exposure limits refer to single substances or closely related groups, e.g. cadmium and compounds, isocyanates etc. A few exposure limits refer to complex mixtures or compounds, e.g. white spirit, rubber fume. However, exposure in workplaces is often to a mixture of substances and such combinations may, by their nature, increase the hazard. Mixed exposure requires assessment with regard to possible health effects, which should take into account other factors such as the primary target organs of the major contaminants and possible interaction between the latter substances. 

The current OSHA TLV standard for exposure to all organotin compounds is 0.1 mg of organotin compounds (as tin)/m air averaged over an 8-h work shift (192). NIOSH has recommended a permissible exposure limit of 0.1 mg/m of tin averaged over a work shift of up to 10 h/d, 40 h/wk Reference 193 should be consulted for more detailed information. Additional information on the health effects of organotin compounds is given in Reference 48. 

Toxicity Data on Af- Vinyl-2-Pyrrolidinone. Results of a chronic inhalation study in rats warrant a review of industrial hygiene practices to assure that VP vapor concentrations are maintained at a safe level. One of the manufacturers, ISP, recommends that an appropriate workplace exposure limit be set at 0.1 ppm (vapor) (9). Additionally, normal hygienic practices and precautions are recommended, such as prompt removal from skin and avoidance of ingestion. In case of accidental eye contact, immediately flush with water for at least 15 minutes and seek medical attention. Refer to the manufacturers Material Safety Data Sheets for more detailed information. Table 3 provides some toxicity data. 

Because pulp bleaching agents are, for the most part, reactive oxidising agents, appropriate precautions must be taken in their handling and use. For example, it is important to ensure that the threshold limit values (TLV) (20) in Table 2 are not exceeded in the workplace air. These are airborne concentrations in either parts per million by volume under standard ambient conditions or mg per cubic meter of air. They "represent conditions under which it is beUeved that nearly all workers may be repeatedly exposed, day after day, without adverse effect" (20). TWA refers to a time-weighted average for an 8-h workday STEL is a short-term exposure limit or maximum allowable concentration to which workers can be continuously exposed for 15 minutes. 

The Occupational Exposure Standards imposed for trichloroethylene are Maximum Exposure Limits of 100 ppm (8 hr TWA) and 150 ppm (15 minute reference period). A skin notation Sk is applicable because of the potential for skin absorption. Because of its volatility, trichloroethylene is not recommended for cold cleaning it is normally used in partially enclosed vapour degreasing equipment provided with local exhaust ventilation. 

Threshold Limit Values or Occupational Exposure Limits (preferably with reference to their interpretation, i.e. not as safe levels). 

Thus, there is a clear need to establish the relationship between the health effects of hazardous chemical agents in the environment and the level of occupational exposure to the body by means of an occupational exposure limit, in which a reference figure for the concentration of a chemical agent is set. In fact, occupational exposure limits (OELs) have been a feature of the industrialized world since the early 1950s. They were introduced, primarily in the United States, at a time when measures to prevent occupational diseases were considered more beneficial than compensating victims, and in this sense OELs have played an important part in the control of occupational illnesses. 

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