Airborne concentrations

Exposure limits (threshold limit value or TLV) are those set by the Occupational Safety and Health Administration and represent conditions to which most workers can be exposed without adverse effects. The TLV value is expressed as a time weighted average airborne concentration over a normal 8-hour workday and 40-hour workweek. 

In humans, cases of dermatitis have been described after contact with DHBs. Combined exposure to hydroquinone and quinone airborne concentrations causes eye irritation, sensitivity to light, injury of the corneal epithelium, and visual disturbances (126). Cases with an appreciable loss of vision have occurred (127). Long-term exposure causes staining due to irritation or allergy of the conjunctiva and cornea and also opacities. Resorcinol and catechol are also irritants for eyes. 

Airborne organic sihcon has been detected in samples collected at Barrow, Alaska (509). Organic sihcon levels corresponding to an airborne concentration of 8 ng/m were detected. As a comparison, these samples were deterrnined to hold approximately 20 ng/m of phthalate-based plasticizers. 

Polyurethanes. These polymers can be considered safe for human use. However, exposure to dust, generated in finishing operations, should be avoided. Ventilation, dust masks, and eye protection are recommended in foam fabrication operations. Polyurethane or polyisocyanurate dust may present an explosion risk under certain conditions. Airborne concentrations of 25—30 g/m are required before an explosion occurs. Inhalation of thermal decomposition products of polyurethanes should be avoided because carbon monoxide and hydrogen cyanide are among the many products present. 

Safe Exposure Levels. The U.S. Occupational Safety and Health Administration (OSHA) has adopted workplace exposure limits designed to keep airborne concentrations weU below the levels known to cause health problems (35) including ( ) daUy time-weighted average (TWA) exposure over an eight-hour day is not to exceed beryUium concentrations of 2 lg/m of air and (2) short-term exposure should not exceed beryUium concentrations of 25... 

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. 

ERPG-l The maximum airborne concentration below which it is believed that nearly all individuals coiild be exposed for up to one hour without experiencing other than mild transient adverse health effects or perceiving a clearly defined objectionable odor. 

Keep below LEL, e.g. chill to lower airborne concentration, use exhaust ventilation, inerting, keep air out. 

Their vapors are irritating to nasal passages and to the throat. These effects are noticeable in airborne concentrations of 2-5 ppm [43,44]. When large quantities of these materials are used, efficient ventilation is required. Because alkyl... 

With all this in mind, OELs should be regarded as an important part of the overall approach to ensuring the protection of health in the workplace, providing a criteria by which decisions can be made as to whether the airborne concentration of a given substance is sufficiently low to avoid adverse health effects. 

Action level A term describing the airborne concentration that triggers certain provisions of a regulation generally, but not always, it is S0% of the PEL value. 

Threshold limit value (TLV) The limits of airborne concentration of chemical substances that are allowed in workplaces published by the American Conference of Governmental and Industrial Hygienists (ACGIH). Also known as MAC. 

Ceiling Value (CV) The airborne concentration of a potentially toxic substance which should never be exceeded in the breathing zone. 

Short Term Exposure Limit (STEL) The time w eightcd average (TWA) airborne concentration to which workers may be e.xposed for periods up to 15 minutes, with no more than 4 such c.xcursions per day and at least 60 minutes between them. 

A 1,5-hour inhalation exposure of mixed breed rabbits to airborne concentrations of 72 ppm of hydrogen sulfide resulted in ventricular repolarization, while a 5-day, 0.5-hour/day exposure to this concentration resulted in cardiac arrhythmia (Kosmider et al. 1967). Histochemical staining of the myocardial cells revealed a reduction in adenosine tri-phosphate (ATP) phosphohydrolase and NADPH2 oxidoreductase (Kosmider et al. 1967). Cardiac arrhythmia, suggestive of a stimulus transmission disorder, was... 

For occupational measurements of airborne concentrations, NIOSH (1977a) recommended the use of a midget impinger for sampling breathing zone air and the methylene blue/spectrophotometric method for the analysis of hydrogen sulfide. The detection limit was 0.20 g/m3 (0.14 ppb). 

Brouwer, R., Van Maarleveld, K., Ravensberg, L., Meuling, W., de Kort, W., and van Hemmen, J.J. (1993) Skin contamination, airborne concentrations, and urinary metabolite excretion of propoxur during harvesting of flowers in greenhouses, Am.. Ind. Med., 24 593-603. 

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