Solvent maximum permissible concentration

MAK maximum permissible concentrations for components 1, 2,n The maximum eoncentrations for short exposure is the most frequently limit specified for an exposure of 15 min with a maximum of 4 sueh occurrences per day eaeh oeeurring at least 60 min apart from each other. These values are 0-4 times larger than TLVs. They are selected based on the risks associated with an individual solvent. 

Central to the type of assessment is a definition of an environmentally acceptable concentration of each contaminant. These acceptable levels were defined as Maximum Permissible Concentrations (MPC), and were based on the toxicological assessments of solvents in drinking water by George and Siegel. These MPC levels (Table 17.2.1) are not the same levels as the current Maximum Contaminant Levels (MCL) that were promulgated by the U.S. Environmental Protection Agency for drinking water. 

Table 17.2.1. The six groups of solvents discussed in this section, their corresponding Maximum Permissible Concentrations (MPC), the largest reported concentrations in leachate (LC), and the assigned half-lives from Roy et al. ...

Because of differences in the solvents and chemical agents in CAIS materials and recovered chemical munitions, the RRS and MMD use different neutralization chemistries and produce different liquid waste streams—collectively referred to in this study as neutralent wastes or neutralents. A summary of nonstockpile CWM that will be treated by the RRS and MMD, as well as the major constituents of their neutralent waste streams, is given in Table ES-1. According to the Army, the maximum permissible concentration for blister agents in a neutralent stream is 50 parts per million (ppm) (although in practice the actual concentration is more likely to be about 1 ppm). The maximum for nerve agents is 20 to 30 parts per billion (ppb). RRS neutralents may contain arsenic, a toxic heavy metal that must be captured and immobilized. 

In a solution, the concentration of solids —i.e., material which will remain in the final adhesive layer—is usually under 30% for organic solvents but may be higher with water as the solvent, and especially in latexes. For a solution, too great a solids content results in such high viscosity that the dope has poor wetting characteristics. The higher the molecular weight of the dissolved polymer, the lower is the maximum permissible concentration. 

The numerical value shows the threshold limit value, which is defined as the maximum permissible vapor concentration that the average person can be exposed to for 8 h/day, 5 days/week without harm, in ppm (cm of solvent per 1 m of air). The mark T shows the solvent has Hsted in Title 111 of the Clean Air Act (42 U.S.C. 7401-7626 Public Law 159 from July 14,1955 69 Stat. 322) and the Amendments of 1990 as a hazardous air pollutant. Source Compton, S. and Brownlee, R., Biotechniques, 6,432-440,1988. With permission. 

Toxicity. Acetone is one of the solvents abused in glue-sniffing . Severe toxic effects have been associated with blood concentrations of 200 to 300 xg/ml a blood concentration of 550 pg/ml has been reported in a fatality. The maximum permissible atmospheric concentration is 1000 ppm. Exposure to 1600 ppm for about 15 minutes causes irritation to the eyes and nose. Up to 20 ml has been ingested without ill-effect. 

Toxicity. The estimated minimum lethal dose is 30 g but a single oral dose of 10 mg/kg may produce toxic symptoms the maximum permissible atmospheric concentration is 1 mg/m and the maximum acceptable daily intake is 5 pg/kg. The toxicity of some of the organic solvents, such as kerosene, used in the application of dicophane has probably contributed to dicophane fatalities. 

Figure 17.2.4. The predicted steady-state concentrations (Css) of each solvent in groundwater at the compliance point as a function of its Maximum Permissible (MPC) Concentration (Roy et al. ).

To prevent an excessive temperature increase across the bed due to the heat of adsorption, inlet solvent concentrations are usually limited to about 50 g/m. In most systems the solvent-laden air stream is directed upwards through a fixed carbon bed. As soon as the maximum permissible breakthrough concentration is attained in the discharge clean air stream, the loaded adsorber is switched to regeneration. To reverse the adsorption of the solvent, the equilibrium must be reversed by increasing the temperature and decreasing the solvent concentration by purging. 

For worker exposure to trichloroethylene vapor, OSHA set a maximum eight-hour time-weighted average (TWA) concentration of 100 ppm. This severely restricted certain appHcations, and many organizations converted to other chlorinated solvents. As a result, U.S. production of trichloroethylene declined about 70% from a peak in 1970 (Table 2). In 1989, OSHA lowered the permissible exposure limit (PEL) from 100 ppm eight-hour TWA to 50 ppm eight-hour TWA (33). This added further pressure for some users to consider changing to alternative solvents. 

The maximum allowable working concentration of the solvent in air to which employees may be exposed is regulated by law. Solvents with small toxic potential and health risk have high exposure values. The toxicity and other stability and reactivity aspects are important in terms of environmental relevance, e.g. the amount of solvent that is permitted to be vented into the atmosphere. As such the working concentration of the solvent has an impact on the investment in and operational costs of the solvent recovery system. It determines whether the process needs official permission and to what extent regular inspections are necessary. If the amount of solvent to be vented is not restricted this simplifies very much the design of the whole process, as the different steps do not need to be sealed completely. 

The Navy s Occupational Safety and Health Standards Board has considered the potential for storage and operation of the fueled vehicles in the ship s cargo holds to be hazardous to naval service personnel exposed to fuel vapors during the servicing of these vehicles or while working in their vicinity. To protect personnel from exposures to toxic concentrations of fuel vapors, the board recommended an interim 8-hr time-weighted average (TWA) permissible exposure limit (PEL) of 350 mg/m3 and a 15-min short-term exposure limit (STEL) of 1,800 mg/m3 for vapors from all three fuels. Those interim exposure limits were based on the board s review of the manufacturers technical documentation and the National Institute of Occupational Safety and Health s recommendations for maximum exposure to refined petroleum solvents. 

TLV Values, In the United States, the equivalent of the MAK value is the threshold limit value (TLV). The TLV value is that concentration of a substance in the air to which virtually all workers can be exposed daily without any harmful effects. This value is subdivided into TLV-TWA (time-weighted average eoncentra-tion), TLV-STEL (short-term exposure limit), and TLV-C (ceiling limit). TLV-TWA applies to a normal 8-h working day or a 40-h week, TLV-STEL is the maximum concentration for an exposure time of 15 min, and TLV-C is the concentration that should at no time be exceeded. The TLV values published by the ACGIH are recommendations, whereas the PEL values (permissible exposure limit) specified by OSHA (Occupational Safety and Health Administration) are enforced by law. The safety limits are recommended to OSHA by NIOSH (National Institute of Occupational Safety and Health). Solvent TLV values for the USA and several European countries are listed in Table 13. 

Figure 12.3. Absorption maximum v (cm ) of benzophenone plotted against the solvent polarity parameter Et(30) for w-tt transitions. Surfactant concentration is 0.10 mol dm. (Reproduced with permission of the American Chemical Society.)...

Mechanistically, this photorelease reaction occurs via photosolvolysis of the aryl ether carbon-oxygen bond. The resulting resonance stabihzed S-pixyl carbocation reacts with water to form 69. Control experiments showed that the photoprotected alcohols are stable under thermal conditions that is, refluxing in aqueous acetonitrile resulted in no detectable decomposition. Each of the caged products was obtained as a sohd, a convenience for laboratory purification and manipulation. The best deprotection yields were obtained with solvent mixtures containing the maximum concentration of water permissible, limited only by the solubility of the protected alcohol. Concentrations of water ranged from 40 to 60%, depending on the type of alcohol used. In most cases, excellent deprotection yields were obtained. 

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