OSHA Exposure Limits

The first compilation of health and safety standards promulgated by the Department of Labor s OSHA in 1970 was derived from the then existing federal standards and national consensus standards. Thus, many of the 1968 TLVs established by the ACGIH became federal standards or PELs. In addition, certain workplace quality standards known as maximal acceptable concentrations of the American National Standards Institute (ANSI) were incorporated as federal health standards in 29 CFR 1910.1000 as national consensus standards. These PEL values for general industry were subsequently updated in 1989. 

Unlike the TLVs, OSHA s PELs are enforceable by law. Employers must keep employee exposure levels below the PELs of regulated substances. As with TLVs, there are three types of PELs. The most common is the 8 h TWA. The others are the STEL and the ceiling limit (C). 

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Benzene can have both chronic and acute toxic effects. The risk of acute effects is low, since acute symptoms occur only at 1000 ppm or higher. Chronic vapor inhalation at the level of 25 to 50 ppm can cause changes in blood chemistry, and co/ rmoa7 exposure at 100 ppm can cause severe blood disorders. The OSHA exposure limits for benzene vapor are 1 ppm as an 8-hour time-weighted average and a ceiling of 50 ppm for no more than 10 min. In order to reach the level of 10 ppm in a laboratory of 750 m volume, 23 g of liquid benzene would have to evaporate into a closed atmosphere. Thus the hazards associated with the infrequent use of liquid benzene in a well-ventilated laboratory are very low. 

Acting under the authority of the Occupational Safety and Health Act of 1970 (Public Law 91-596), the NIOSH develops and periodically revises recommended exposure limits (RELs) for hazardous substances or conditions in the workplace. These recommendations are then published and transmitted to OSHA for use in promulgating legal standards. NIOSH may identify numerous chemicals that it believes should be treated as occupational carcinogens even though OSHA has not yet identified them as such. Generally, where OSHA has adopted the NIOSH recommendations as OSHA standards, the OSHA PELs and NIOSH RELs are equal. In cases in which the NIOSH recommendations have not been formally adopted by OSHA, the NIOSH RELs may be different from the OSHA PELs. For example, the NIOSH exposure limit for trichloroethylene (25 ppm) differs from the OSHA exposure limit (50 ppm). 

The NIOSH thresholds for carcinogens were not designed to be protective of 100% of the population. NIOSH usually recommends that occupational exposures to carcinogens be limited to the lowest feasible concentration. This perhaps is the reason that the NIOSH exposure limit for vinyl chloride is the lowest reliably detectable concentration and the OSHA exposure limit is 1 ppm. 

OSHA exposure limits for 8-hr weighted average. fFor 20.25-m cell. 

The first line in the entry indicates whether the NIOSH or the OSHA exposure limit is used on which to base the respirator recommendations. The more protective limit between the NIOSH REL or the OSHA PEL is always used. NIOSH/OSHA indicates that the limits are equivalent. 

Concentration of substances (and conditions) under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse effects. American Conference of Governmental Industrial Hygienists (ACGIH) limits are called threshold limit value and Occupational Safety and Health Administration (OSHA) exposure limits are referred to as permissible exposure limits (PEL). See also Permissible Exposure Limit (PEL). 

T is derived from an expansion of the OSHA exposure limits (Table 23-2) and is computed as... 

In the United States there are no OSHA exposure limits for cold working environments. It is often recommended that work warm-up schedules be developed. In most normal cold conditions, a warm-up break every 2 hours is reconunended, but, as temperatures and wind increase, more warm-up breaks are needed. 

Chlorine Dioxide Shghtlyless destructive to membranes Must be site generated Chlorite toxicity Toxic gas/OSHA exposure limits May generate some free chlorine also ... 

Material Safety Data Sheets (MSDS) issued by suppHers of acetone ate requited to be revised within 90 days to include new permissible exposure limits (PEL). Current OSHA PEL (54) and ACGIH threshold limit values (TLV) (55) ate the same, 750 ppm TWA and 1000 ppm STEL. Eot comparison, the ACGIH TWA values for the common mbbing alcohols are ethyl, 1000, and isopropyl, 400 ppm. A report on human experience (56) concluded that exposure to 1000 ppm for an 8-h day produced no effects other than slight, transient irritation of the eyes, nose, and throat. 

Air Contaminants—Permissible Exposure Limit," Title 29 Code of Federal Regulations Part CFR 1910.1000, OSHA, 1989, p. 3112. 

Exposure limits for siHcon carbide and powders of zirconium compounds (including zirconium dioxide) have been estabHshed by ACGIH. TLV—TWA s are 10 mg/m and 5 mg/m, respectively. OSHA guidelines for zirconium compounds call for a PEL of 5 mg/m. There are no exposure limits for siHcon nitride powder, but pmdent practice suggests a TLV—TWA of 0.1 mg/m. The soHd ceramics present no apparent health hazard. In machining such ceramics, however, care should be taken to prevent inhalation of respirable particles in amounts in excess of estabHshed limits. Disposal should be in approved landfills the materials are inert and should pose no danger to the environment. 

The OSHA permissible exposure limit (11) and the American Conference of Governmental Industrial Hygienists (ACGIH) estabHshed threshold limit value (TLV) (12) for fluorides is 2.5 mg of fluoride per cubic meter of air. This is the TLV—TWA concentration for a normal 8-h work day and a 40-h work week. 

Stannous fluoride is used in dentifrices and dental preparations. The OSHA permissible exposure limit (44) and ACGIH (45) estabUshed TLV for fluoride is 2.5 mg/m of air. 

Handling and Toxicity. Tungsten hexafluoride is irritating and corrosive to the upper and lower airways, eyes, and skin. It is extremely corrosive to the skin, producing bums typical of hydrofluoric acid. The OSHA permissible exposure limits is set as a time-weighted average of 2.5 mg/kg or 0.2 ppm (22). 

Colorado has a monthly mean. The OSHA permissible exposure limit (PEL) for lead is 50 at an action level (local authorities must investigate) of... 

However, if air sampling estabHshes that the lead exposure concentration is excessive, engineering controls (such as improved ventilation), adrninistrative controls (such as job rotation), and work practices (such as improved personal hygiene of workers) have to be appHed to comply with the permissible exposure limit (PEL) of the OSHA standard. 

Mg(OH)2 powder is classified by OSHA as a nuisance dust. ACGIH categorizes the powder form as particulates not otherwise classified. Exposure limits are as follows (108) ACGIH 10 mg/m , OSHA 5 mg/m (respirable), and 15 mg/m (total). Magnesium hydroxide is reported in the EPA TSCA inventory (109). 

It is good practice to keep concentrations of airborne nickel in any chemical form as low as possible and certainly below the relevant standard. Local exhaust ventilation is the preferred method, particularly for powders, but personal respirator protection may be employed where necessary. In the United States, the Occupational Safety and Health Administration (OSHA) personal exposure limit (PEL) for all forms of nickel except nickel carbonyl is 1 mg/m. The ACGIH TLVs are respectively 1 mg/m for Ni metal, insoluble compounds, and fume and dust from nickel sulfide roasting, and 0.1 mg/m for soluble nickel compounds. The ACGIH is considering whether to lower the TLVs for all forms of nickel to 0.05 mg/m, based on nonmalignant respiratory effects in experimental animals. 

PPS dust should be treated as a nuisance particulate. The OSHA permissible exposure limit for respirable dust is 5 mg/m for dust containing no asbestos and less than 1% siUca. The principal decomposition products released during mol ding of PPS and their permissible exposure limits are given in Table 10. Sulfur dioxide and carbonyl sulfide are the most significant off-gases for production of mucous membrane irritation. 

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