Threshold Limit Values time weighted average exposures

Short-Term Exposure Limit (STEL)—The American Conference of Governmental Industrial Hygienists (ACGIH) maximum concentration to which workers can be exposed for up to 15 min continually. No more than four excursions are allowed per day, and there must be at least 60 min between exposure periods. The daily Threshold Limit Value - Time Weighted Average (TLV-TWA) may not be exceeded. 

There are three biological exposure indices (BEls) for exposure to trichloroethylene at the ACGIH threshold limit value time-weighted average (TLV-TWA) of 50 ppm (ACGIH 1996). When measured at the end of a 40-hour workweek, TCA in urine is approximately 100 mg/g creatinine when measured at the end of an 8-hour shift at the end of a workweek TCA and trichloroethanol in urine is approximately 300 mg/g creatinine, and free trichloroethanol in blood is approximately 4 mg/L. 

TIN-TWA Threshold limit value, time-weighted average for 8-h exposures, with ceiling concentrations shown as C, and with skin absorption hazard as S. The OSHA permissible exposure limit (PEL) is the lower of the TWA or the ceiling limit. 

Acetic acid was not clastogenic in Chinese hamster ovary (CHO) cells in vitro when the pH of the culture medium was neutralized. The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) for acetic acid is 10 ppm (25mg/m ) with a short-term exposure limit of 15 ppm (37mg/m ). 

Application of a 0.1M solution of yttrium chloride to the eyes of rabbits caused no injury similar exposure of eyes from which the corneal epithelium had been removed resulted in immediate slight haziness of the cornea, which subsequently became opaque and vascularized. The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) for yttrium and compounds is 1 mg/m as Y. 

Calcium carbonate is listed as a food additive and nut considered a toxic material. The exposure lo dusl is regulated and a Threshold Limit Value-Time-Weighted Average (TLV-TWA) of 10 mg/m1 is set. Both natural ground and precipitated calcium carbonates can contain low levels of impurities that are regulated. 

TLV-TWA is the Threshold Limit Value—time weighted average concentration for a conventional 8-hour workday and a 40-hour workweek, to which it is believed that nearly all workers may be repeatedly exposed, day after day, without adverse effect (ACGIH 2001). In general, TLV-TWA values are used to derive BEIs (Biological Exposure Indices). 

An example of a nonoccupational exposure is methanol, which is formed endogenously, probably as the result of the activities of intestinal flora or enzymatic processes. It is present in a number of consumer products. Methanol may be present in low concentrations in some foods, juices, and alcoholic beverages. Methanol can also be derived from the intestinal enzymatic hydrolysis of the artificial sweetener aspartame, which results in methanol absorption from the intestine (Butchko et al. 2002). It is estimated that a 355-mL serving of aspartame-sweetened beverages and of various fruit and tomato juices may contribute about 20-100 mg of dietary methanol (Butchko et al. 2002). For comparison purposes, exposure at the current Threshold Limit Value time-weighted average of methanol (262 mg/m3) would result in a daily dose of about 1,500 mg, assuming an 8-hour inhaled volume of 10 m3 of air and absorption of 57%. 

PEL (Permissible Exposure Limit) or TLV-TWA (Threshold Limit Value-Time Weighted Average). This is the maximum permitted concentration of the airborne chemical in volume parts per million (ppm) for a worker exposed 8 hours daily. 

The American Conference of Governmental Industrial Hygienists threshold limit value — time-weighted average is 0.5 mg ml for soluble barium compounds and lOmgmH for barium sulfate. The permissible exposure limit is 0.5 mg m for barium in soluble compounds. The reference dose for barium is 0.07 mg kg day and the tolerable daily intake... 

The American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value — time-weighted average (TLV — TWA) is 5000 ppm and the ACGIH short-term exposure limit (STEL) is 30 000 ppm the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) — TWA is 500 ppm (transitional limit) and 10 000 ppm (final rule limit), and the OSHA PEL STEL is 30 000 ppm the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit is 10 000 ppm (TWA). 

Conversion 1 ppm = 3.19mgm . OSHA, Occupational Safety and Health Administration NIOSH, National Institute of Occupational Safety and Health ACGIH, American Conference of Governmental Industrial Hygienists TLV - TWA, threshold limit value - time-weighted average IDLH, immediately dangerous to life or health PEL, permissible exposure limit NA, not applicable. 

The American Conference of Governmental Industrial Hygienists threshold limit value (time-weighted average) is 50 ppm (246 mg m ) based on irritation and CNS depression. The (US) Occupational Safety and Health Administration permissible exposure limit, (US) National Institute for Occupational... 

The threshold limit value — time-weighted average for chloroform is 10 ppm. The permissible exposure limit is 50 ppm. No reference concentration has been set. 

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