Toxicants threshold limit values

Caution. All operations involving the use of butyllithium and phosphine gas must be carried out in an inert atmosphere and inside a well-ventilated hood. Phosphine has a foul odor and is very toxic (threshold limit value in air is 0.3 ppm). A gas mask approved for use with phosphine should be immediately available in case of emergency. 

However, phosgene is clearly highly toxic (threshold limit value-TLV of 0.1 ppm), but acrolein, for example, has the same TLV and is produced in quantities of several millions worldwide. Acrolein is also produced at barbecue parties by roasting foods, without provoking health alarms. Clearly, a low TLV implies the adoption of special safety procedures and limited storage. On-demand production and other safety procedures, such as those discussed above, are the solution to minimizing the risk to a sustainable level. 

The toxic threshold limit value as reported by Sax (Ref 3) ia ( pm in air or 750mg/m of air, and by Plunkett (Ref 8) is lOOppm and 375mg/m. Acute poisoning from the use of toluene is the result of a small amount of benz in commercial (coal-tar) derived toluene. Table 1 presents the effects of toluene vapor (Ref 4). Plunkett (Ref 8) reports that prolonged exposure to toluene vapor can result in permanent central nervous system changes such as cerebellar degeneration, tremulousness, ataxia, emotional lability and EEC changes... 

The advantages of carbon dioxide as solvent have been well publicized it is, in fact, classified as GRAS - generally regarded as safe, it has low toxicity (threshold limit value - TLV = 5000 ppm), it is supercritical just above ambient temperature (critical temperature 31 C) and it is cheap. Also, like other supercritical fluids, it has advantageous gas-like transport properties, such as low viscosity and high diffusivity. 

Trace Components The trace components of landfill gas mainly comprise a range of alkanes and alkenes, and their oxidation products (aldehydes, ketones, alcohols and esters). Waste Management Paper 26 (DoE, 1986) lists 108 compounds, or groups of compounds found in landfill gas sampled at six different landfill sites. Many of these trace compounds in landfill gas are recognised toxicants when present in air at concentrations which exceed established toxicity threshold limit values (TLVs) or the Occupational Exposure Standards (OESs) set by the Health and Safety Executive. Anyone coming into contact with landfiU gas is therefore potentially at risk from the toxic nature of the minor components, and under the Control of Substances Hazardous to Health Regulations (COSHH, 1988), landfill operators are legally responsible for the health of employees and are required to comply with OES s and exposure limits set by the Health and Safety Executive (HSE). 

Table 23-5. Toxicity Threshold Limit Values TLV of Monomers...

OSHA, under its 29 CFR 1910.1450 (Laboratory Standard), is very specific about maintaining the face velocity of laboratory fume hoods within certain ranges, depending on the toxicity of the contaminant. The higher the toxicity (threshold limit value— TLV), the higher the face velocity required to ensure adequate protection for the worker. At a minimum, OSHA requires laboratory fitme hood face velocities of 60—100 ft/min. A list of the required face velocity levels for use with chemicals with varying levels of toxicity in fume hoods is provided in table 9.5. 

Although there is Httle toxicity information pubHshed on hydrides, a threshold limit value (TLV) for lithium hydride in air of 25 fig/has been established (52). More extensive data are available (53) for sodium borohydride in the powder and solution forms. The acute oral LD q of NaBH is 50-100 mg/kg for NaBH and 50-1000 mg/kg for the solution. The acute dermal LD q (on dry skin) is 4-8 g/kg for NaBH and 100-500 mg/kg for the solution. The reaction or decomposition by-product sodium metaborate is slightly toxic orally (LD q is 2000-4000 mg/kg) and nontoxic dermally. 

Tetrahydronaphthalene is not a highly toxic compound. A threshold limit value of 25 ppm or 135 mg/m has been suggested for Tetralin. Tetralin vapor is an irritant to the eyes, nose, and throat, and dermatitis has been reported in painters working with it (28). The single-dose oral toxicity LD q for rats is 2.9 g/kg (29). 

Table 8. Oral Toxicity and Threshold Limit Values of Nitroparaffins...

Phenol. Phenol monomer is highly toxic and absorption by the skin can cause severe blistering. Large quantities can cause paralysis of the central nervous system and death. Ingestion of minor amounts may damage kidneys, Hver, and pancreas. Inhalation can cause headaches, dizziness, vomiting, and heart failure. The threshold limit value (TLV) for phenol is 5 ppm. The health and environmental risks of phenol and alkylated phenols, such as cresols and butylphenols, have been reviewed (66). 

Threshold limit value (TLV) not estabUshed by ACGIH. Value given is an estimate of a comparable iadex based on limited or incomplete toxicity testing made by chemical producers. 

A commercially interesting low calorie fat has been produced from sucrose. Proctor Gamble has patented a mixture of penta- to octafatty acid ester derivatives of sucrose under the brand name Olestra. It was approved by the FDA in January 1996 for use as up to 100% replacement for the oil used in preparing savory snacks and biscuits. Olestra, a viscous, bland-tasting Hquid insoluble in water, has an appearance and color similar to refined edible vegetable oils. It is basically inert from a toxicity point of view as it is not metabolized or absorbed. It absorbs cholesterol (low density Hpoprotein) and removes certain fat-soluble vitamins (A, D, E, and K). Hence, Olestra has to be supplemented with these vitamins. No standard LD q tests have been performed on Olestra however, several chronic and subchronic studies were performed at levels of 15% in the diet, and no evidence of toxicity was found. No threshold limit value (TLV), expressed as a maximum exposure per m of air, has been estabhshed, but it is estimated to be similar to that of an inert hpid material at 5 mg/m. ... 

Although acetylene is considered to be a material having a very low toxicity, a threshold limit value (TLV) of 2500 ppm has been estabUshed by NIOSH. In the presence of a small amount of water carbide may become incandescent and ignition of the evolved air—acetylene mixture may occur. Nonsparking tools should be used when working in the area of acetylene-generating equipment. 

AH volatile organic solvents are toxic to some degree. Excessive vapor inhalation of the volatile chloriaated solveats, and the central nervous system depression that results, is the greatest hazard for iadustrial use of these solvents. Proper protective equipment and operating procedures permit safe use of solvents such as methylene chloride, 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene ia both cold and hot metal-cleaning operations. The toxicity of a solvent cannot be predicted from its chlorine content or chemical stmcture. For example, 1,1,1-trichloroethane is one of the least toxic metal-cleaning solvents and has a recommended threshold limit value (TLV) of 350 ppm. However, the 1,1,2-trichloroethane isomer is one of the more toxic chloriaated hydrocarboas, with a TLV of only 10 ppm. 

Toxic materials shall be at or below the threshold limit value, permissible exposure hmit, or other approved industrial hygiene guideline. 

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