Average Exposure Limit

Phosphine has an 8-h time-weighted average exposure limit of 0.3 ppm (13). Under alkaline conditions the rate of PH formation is high. At neutral or acidic pH, the PH generation is slow but stiU very ha2ardous if the PH is allowed to accumulate in a confined vapor space. The safest commercial handling conditions for molten phosphoms are generally considered to be from pH 6 to 8 at 45—65°C. 

Carboxyhc acid dust and vapors are generally described as being destmctive to tissues of the mucous membrane, eyes, and skin. The small molecules such as formic, acetic, propionic, butyric, and acryUc acids tend to be the most aggressive (Table 11) (83). Formic, acetic, propionic, acryUc, and methacrylic acids have time weighted-average exposure limits of 20 ppm or lower. AcryUc acid showed an LD q of 33.5 mg/kg from oral adrninistration to rats. 

Another type of time-weighted average exposure limit is the decision level (DL), which is expressed as a fraction of the OEL. In general, it is based on judgment, and it is greater than a dose of 50% and usually corresponds to one-fourth of the dose. For special substances, such as carcinogens, it should... 

The estimated ambient vapor-phase concentrations of chemicals in indoor air were, in general, below the NIOSH time-weighted average exposure limits for a 40 hr workweek. However, the authors of this study concluded that the consequences of long term human exposure to these complex mixtures of airborne... 

Figure 2. Contour plot showing the long-term average exposure, x, as a function of e, and GSD. The heavy line, where x = 0.95 PEL is the proposed Average Exposure Limit, A EL. Acceptable workplaces lie in the region to the left of the A EL. Each marks the location of one of the charts from Figure 1.

It is informative to compare the decision regions of the OSHA Compliance Criteria as shown in Figure 5, with the Average Exposure Limit Concept of Figure 2. Five of the six workplaces identified as OK in Figure 2 are likely to be declared OK by an OSHA compliance officer. However, only one of the three unacceptable workplaces of Figure 2 is likely to be declared NOT OK by the criteria of Figure 5. 

Average Exposure Limit If x < AEL, Decide OK. Action Level If x > AL, Decide OK. 

The American Conference of Governmental Industrial Hygienists (ACGIH) (1997) has not proposed any occupational exposure limit for 1,2-epoxybutane in workplace air. However, manufacturers in the United States have recommended a voluntary standard of 40 ppm [118 mg/m ] for an 8-h time-weighted average exposure limit (United States National Toxicology Program, 1988). 

The concentrations of white phosphorus levels in the atmosphere of a wet fill production line at Pine Bluff Arsenal, Arkansas, were measured in 1975 (Berkowitz et al. 1981). The levels of white phosphorus at this location exceeded the OSHA 8-hour time-weighted average exposure limit of 0.1 mg/m3. At one location, the concentration of elemental phosphorus was 0.45 mg/m3 and may have been underestimated due to poor quality control (Berkowitz et al. 

Respirable fraction of the dust. TWA, time-weighted-average exposure limit (8 h). 

Substance Notes Formula CAS Reg. No. weighted average exposure limit... 

The permissible 8 hr time weighted average exposure limit is 1 part per million parts of air [3]. Even at concentrations as high as 50 ppm, lull-face respirators with EO-approved canister are required [4). 

The American Conference of Governmental Industrial Hygienists has adopted a time-weighted average threshold limit value (TLV-TWA) for arsine of 0.05 ppm. [1] The U.S. Occupational Safety and Health Administration has established an eight-hour time-weighted average exposure limit of 0.05 ppm (0.2 mg/m ) for arsine. [2]... 

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