Threshold Limit Values, various

To protect humans and other mammals, proposed air-quality criteria range from 0.01 to less than 1.0 mg/m3 for metallic nickel and slightly soluble nickel compounds, 0.015-0.5 mg/m3 for water soluble nickel compounds, and 0.005 to 0.7 mg/m3 for nickel carbonyl (Table 6.10). Inhalation of nickel subsulfide concentrations (0.11 to 1.8 mg Ni/m3) near the current threshold limit value of 1 mg Ni/m3 can produce detrimental changes in the respiratory tract of rats after only a few days of exposure (Benson et al. 1995). Additional animal studies are recommended to identify minimally effective inhalation exposure levels for the various nickel compounds (USPHS 1993). Continued monitoring of nickel refining, nickel-cadmium battery manufacture, and nickel powder metallurgy installations is recommended because ambient air levels of bioavailable nickel at these... 

It has been shown that all doses of arsenic trioxide are characterized by different toxicokinetics parameters. Arsenic compounds have long half-times and the tendency to accumulate in the body. The excretion rate decreased with decreasing blood concentration. The present study confirms the ability of toxicokinetic models to improve the study of various toxic substances and to estimate the Biological Threshold Limit Values. 

An example of a nonoccupational exposure is methanol, which is formed endogenously, probably as the result of the activities of intestinal flora or enzymatic processes. It is present in a number of consumer products. Methanol may be present in low concentrations in some foods, juices, and alcoholic beverages. Methanol can also be derived from the intestinal enzymatic hydrolysis of the artificial sweetener aspartame, which results in methanol absorption from the intestine (Butchko et al. 2002). It is estimated that a 355-mL serving of aspartame-sweetened beverages and of various fruit and tomato juices may contribute about 20-100 mg of dietary methanol (Butchko et al. 2002). For comparison purposes, exposure at the current Threshold Limit Value time-weighted average of methanol (262 mg/m3) would result in a daily dose of about 1,500 mg, assuming an 8-hour inhaled volume of 10 m3 of air and absorption of 57%. 

The threshold limit values for exposure to various types of radiation given must not be exceeded. For electromagnetic fields at 60 Hz, the threshold limit is 10 Gauss and the limit is 1 Gauss for people with pacemakers. 

Hazard This category includes flammability, toxicity characterization, explosion risks, and so on, based on authoritative data. Also given are the Threshold Limit Values (TLV) for workroom exposures established by the American Conference of Government Industrial Hygienists (ACGIH) and various rulings of the Food and Drug Administration. 

Metallic or elemental mercury volatilizes to mercury vapor at ambient air temperatures, and most human exposure is by way of inhalation. The saturated vapor pressure at 20.0°C is 13.2mg/m. This value far exceeds the threshold limited value (TLV) of 0.05 mg/m accordingly, mercury intoxication due to inhalation of the vapor readily occurs in various occupational and environmental situations. Mercury vapor readily diffuses across the alveolar membrane and is hpid soluble so that it has an affinity for the central nervous system and red blood cells. Metallic mercury, unlike mercury vapor, is only slowly absorbed by the G1 tract (0.01%) at a rate related to the vaporization of the elemental mercury and is of negligible toxicological significance. 

Surface treatment has been proven to be the method of choice because it is simple and has no environmental impact. Mehra and Soni [3] investigated the deterioration of cast iron with time in various aqueous salt solutions. In order to minimize the corrosion problem in a water supply system, it is important to identify the mechanism of corrosion rate (CR) of ions with cast iron and the extent to which they contribute to corrosion in potable water, as well as their threshold limiting values to which the CR should be minimized in order to provide excellent corrosion resistance. It... 

The TLV is one of various indices of permissible exposure levels to chemicals another is the Short Term Exposure Limit (STEL), which represents a 15-minute concentration which should not be exceeded in an 8-hour workday. Its aim is particularly to prevent the acute effects of short-term exposure. STEL values can be found, along with a more precise definition, in Threshold Limit Values, published by the ACGIH (Cincinnati, USA). 

Regulations and assessment of VOCs are under discussion in Germany, e.g., discussion of various threshold limit values of TVOC (total volatile organic compounds) < 200 4,g/m according studies of Molhave and 300 llg/m according to BGA. ... 

Most of the selected female reproductive toxicology studies examined explicitly stated chemical exposure levels either as parts per million, stratifying as to number of days of exposure, or as estimates of the percentage of the threshold limit values. Medline, Toxline, and Dissertation Abstracts databases were utilized to search for all research papers published in any language from 1966 to 1996. In total, 559 studies were obtained from the literature search. Of these, only 21 studies explicitly stated some sort of exposure level for the various chemicals. These chemical exposure levels in the literature and subsequent pregnancy outcomes were compared to lOL chemical exposure indices. The following is an example of one of the many chemical exposures encountered, namely exposure to toluene. For other compounds, Table 20.3.5 contrasts values in the literature with lOL indices of chemical exposure. 

Are employees aware of the hazards involved with the various chemicals they may be exposed to in their work environment, such as ammonia, chlorine, epoxies, caustics, etc. Are you familiar with the Threshold Limit Values or Permissible Exposure Limits of airborne contaminants and physical agents used in your workplace ... 

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