Exposure limits for

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 toxicological problems associated with asbestos have been widely pubHshed and asbestos has been banned from most uses by the EPA. However, modem diaphragm cell chlorine plants have not had difficulty meeting the required exposure limits for asbestos fibers, and, as of 1990, the chlorine industry had an exemption allowing the continued use of asbestos as a diaphragm material. 

Fig. 5. Long-term magnetic field exposure limits for general public exposures in uncontrolled environment, where A is the 50/60 Hz window, according to B, IRPA C, VDE (Germany) D, NRPB (U.K.) and E (IEEE C95.1, 1991). To convert T to G, multiply by 10/...

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. 

The National Institute of Occupational Safety and Health (NIOSH), under the Department of Health and Human Services, works with OSHA. It is NIOSH s responsibihty to determine safe exposure limits for chemical substances and to recommend to OSHA that these limits be adopted as standards. 

Succinic anhydride is extremely irritating to the eyes. It causes skin, mucous membranes, and respiratory tract irritation. It may be a sensiti2er. There is no evidence of carcinogenic activity in male or female tats given 50 or 100 mg/kg succinic anhydride (186) the Ames test is negative (187). LD q in rat 1510 mg/kg. There ate no estabflshed exposure limits for ACGIH TLV or TWA. 

Talc is considered a nuisance dust and subject to regulation in the workplace by both the Occupational Health and Safety Administration and the Mine Safety and Health Administration. Eight-hour exposure limits for talc dust are two milligrams of talc per cubic meter. 

OSHA and ACGIH have not estabhshed specific airborne exposure limits for PVB and PVF resias however, some products may contain sufficient fines to be considered nuisance dust and present dust explosion potential if sufficient quantities are dispersed ia air. Unformulated PVB and PVF resias have flash poiats above 370°C. The lower explosive limit (lei) for PVB dust ia air is about 20 g/m. ... 

A recommended exposure limit for antimony compounds of 0.5 mg /m (as Sb) has been given (2). Disposal may be effected by washing residues down the drain at very high dilution unless prohibited by local regulations. 

The handling of arsenic in the workplace should be in compliance with the Occupational Safety and Health Administration (OSHA) regulations the maximum permissible exposure limit for arsenic in the workplace is 10 p-g/m of air as deterrnined as an average over an 8-h period (33). 

In accordance with demonstrated differences between the various asbestos fiber types, the workplace regulation in many countries specifies different exposure limits for chrysotile and the amphiboles (45). Moreover, to alleviate estabHshed, or apprehended, risk from substitute fibers, the regulation often specifies maximum exposure limits for synthetic fibers (46) values of exposure limits adopted in leading industrial countries are coUected in Table 8. 

Table 8. Exposure Limits for Asbestos Fibers, Synthetic Mineral Fibers (SMF) and Nuisance Dust in the Workplace ...

Country Asbestos exposure limits Fiber type Exposure limits for SMF and nuisance dust... 

Workplace exposure limits for benzene have been regulated to levels as low as 0.5 ppm (43). Industrial emissions affecting the pubHc ate now low enough that the EPA considers that a greater hazard exists from mosdy indoor sources such as smoking, automobile exhausts, and consumer products (44). 

Other toxicological effects that may be associated with exposure to benzyl chloride based on animal studies are skin sensitization and developmental embryo and/or fetal toxicity. A 1980 OSHA regulation has estabhshed a national occupational exposure limit for benzyl chloride of 5 mg/m (1 ppm). Concentrations of 160 mg/m (32 ppm) in air cause severe irritation of the eyes and respiratory tract (68). 

Safety. Chlorosulfuric acid is a strong acid and the principal ha2ard is severe chemical bums when the acid comes into contact with body tissue. The vapor is also ha2ardous and extremely irritating to the skin, eyes, nose, and respiratory tract. Exposure limits for chlorosulfuric acid have not been estabhshed by OSHA or ACGIH. However, chlorosulfuric acid fumes react readily with moisture in the air to form hydrochloric and sulfuric acid mists, which do have estabhshed limits. The OSHA 8-h TWA limits and ACGIH TLV—TWA limits are sulfuric acid = 1 mg/m hydrochloric acid = 5 ppm or 7 mg/m (ceiling limit). 

The NIOSH recommended exposure limit for carcinogenic hexavalent chromium is 1 lg/m Cr(VI) as a 10-h TWA, and for noncarcinogenic Cr(VI) the 10-h TWA is 25 lg/m Cr(VI), including a 15-min maximum exposure of 50 lg/m Cr(VI). According to NIOSH, the noncarcinogenic Cr(VI) compounds are chromic acid and the chromates and dichromates of sodium, potassium, lithium, mbidium, cesium, and ammonia. NIOSH considers any hexavalent chromium compound that does not appear on the preceding Hst carcinogenic (145). 

Inhalation. The threshold limit value of HCN is 4.7 ppm. This is defined as the maximum average safe exposure limit for a 15-min period by the Occupational Safety and Health Administration. Exposure to 20 ppm of HCN in air causes slight warning symptoms after several hours 50 ppm causes disturbances within an hour 100 ppm is dangerous for exposures of 30 to 60 min and 300 ppm can be rapidly fatal unless prompt, effective first aid is adininistered. There is always a small concentration of cyanide (0.02 to 0.04 mg/L) in the blood, and the body has a mechanism for continuous removal of small amounts, such as from smoking, by converting it to thiocyanate, which is discharged in the urine. 

Oeeupational exposure limits for airborne eontaminants are reviewed annually in the UK by the Health and Safety Exeeutive. They are published as Guidanee Note EH 40/-. The two types of exposure limit are ... 

Control of Substances Hazardous to Health Regulations (COSHH). Guidance on Exposure Limits for Mixtures (Regulation 7). Revised (1993)... 

International Labor Office, 1991. Occupational exposure limits for airborne toxic substances. Occupational Safety and Health Series, No. 37. International Labour Office, Geneva. 

Health hazard due to exposure to contaminants by inhalation is the most important issue. International or national health and building regulations or codes and recommendations are used as basis for the discussion of what requirements should be used for design. In regulations, worker exposure limits for airbctrne gases are normally expressed as... 

Short term exposure limit (STEL) T he permissible exposure limit for a given contaminant averaged out over any 10-minute period during an 8-hour working shift. See also Occupational exposure limit (GEL) and Long-term exposure limit (LTEL). 

Professional society of persons conducting research in occupational safety and health or responsible for implementing industrial hygiene programs in governmental and industrial organizations. Establishes exposure limits for toxic chemicals used in the workplace. 

Process Applications 259 TABLE 8.3.2 Exposure Limits for Anhydrous Ammonia ... 

Process Applications TABLE 8.4.1 Exposure Limits for Hydrogen Cyanide 265... 

TABLE 8.5.2 Chapter 8 Exposure Limits for Hydrogen Fluoride... 

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