TLV value

Exposure limits (threshold limit value or TLV) are those set by the Occupational Safety and Health Administration and represent conditions to which most workers can be exposed without adverse effects. The TLV value is expressed as a time weighted average airborne concentration over a normal 8-hour workday and 40-hour workweek. 

Although molybdenum is an essential element, excess levels can have deleterious effects. The LD q and TLV values of the most common Mo compounds are Hsted in Table 3 (63,64). In general the toxicity of Mo compounds is considered to be low. For example, M0S2 has been found to be virtually nontoxic even at high levels. Certain Mo compounds such as MoCl and Mo(CO), have higher toxicity because of the chemical nature and reactivity of these compounds rather than the Mo content. Supplementary dietary Cu ", thiosulfate, methionine, and cysteine have been shown to be effective in alleviating Mo toxicity in animals. 

Threshold limit values (TLV) adopted by the ACGIH are guidelines for the control of health hazards. Table 3 shows the eight-hour TWA and the STEL TLV values for those lower alkylamiaes Hsted ia the ACGIH guideliae (18). 

A listing of known TLV values and odor thresholds for a variety of thiols is given ia Table 5. ... 

Eor deicing fluid appHcations, exposure to vapors and mists is the more likely means of exposure. Ethylene glycol has a threshold limit value (TLV) of 50 ppm for vapors. When proper deicing procedures are foUowed and proper protective equipment worn, the exposure of deicing personnel to vapor and mist is expected to fall weU below this TLV value. This mode of exposure is unlikely for engine cooling appHcations. 

Hygienists (ACGIH). TLV values for specific chemicals can be found in this handbook. 

Health hazards caused by chemicals are represented by the Toxic Exposure Subindex (ITox). hi the ISI the evaluation of toxic exposure is based on the Threshold Limit Values (TLV) because TLV data is readily available for most substances in process industry. TLV values express the harmful exposure limits of substances in the threshold time of 8 hours. The index value is higher, when the TLV is lower i.e. the substance is more toxic. It is important to use TLVs with same threshold time so that the results are comparable. Score limits in Table 13 are based on Mond Index (ICI, 1985). 

Threshold limit values (TLV) which also apply to a 40 hour workweek are published by the American Conference of Governmental Industrial Hygienists. The PEL values of OSHA are frequently based on the TLV values issuing from the American Conference of Governmental Industrial Hygienists (7). 

TLVs are revised by the ACGIH annually as new information becomes available. Each year, additional substances of interest are added to the TLV list. Certain compounds that are proven or suspected carcinogens in humans such as benzidine, 4-aminodiphenyl, and 4-nitrodiphenyl have no TLV value, and human exposure to these agents should be avoided. Note For a detailed discussion of carcinogenic risks to humans, the publications of the lARC should be consulted. 

Ethylene dichloride is a colorless liquid with a bp of 84°C. As with many chlorinated hydrocarbons, it is quite toxic and has a TLV value of 10 ppm (TWA). It is on the list of Reasonably Anticipated to Be Human Carcinogens. ... 

A low value of TLV indicates a more toxic chemical than a high value, so that some authors prefer to work with the reciprocal 1/TLV as a measure of the toxicity. Some of the TLV values for elements, from the most toxic to the relatively benign are listed in table 6.6. 

The paraffins and 1-alcohols are relatively low-risk compounds. When we make a comparison of their TLV values versus the number of carbon atoms Ac, we find that paraffins from methane to propane are not considered toxic, but the paraffins from butane to nonane are increasingly more toxic with Ac, which is shown in figure 10.4. The 1-alcohols make a curious volcanic curve, starting from the toxic methanol to the relatively harmless ethanol, and the trend is downwards from propanol to butanol. The aromatics are much more toxic, but the lower molecular weight benzene is more toxic than toluene, which is more toxic than the higher molecular weight ethyl benzene. 

Threshold Limit Value (TLV) — the exposure level under which most people can work for eight hours a day, day after day, with no harmful effects. A table of these values and accompanying precautions for most common industrial materials is published annually by the American Conference of Governmental Industrial Hygienists (ACGIH). TLV values for specific chemicals can be found in this handbook. 

The reader is reminded that MAK and TLV values are revised periodically, hence current values should be used. 

The control limits should not be exceeded and wherever possible reduced, and in any case these substances are subject to specific Regulations or Codes of Practice. The RL values are annually reviewed, but the CL values may be altered at shorter time intervals. The TLV value is used in the UK if a RL or CL value is not available. With some substances, long-term or short-term exposure limit values (LTEL or STEL) are published. Finally it should be noted that the Council of Europe is proposing to introduce a harmonised list of exposure standards for adoption by the EEC countries. 

It should be emphasized that this kind of comparison is quite theoretical, and it does not provide absolute unsafe exposures, nor does it specify safe levels. However, with the present understanding of the animal experiments it would appear prudent to lower the TLV values for the compounds for which the human exposure may be up to 1/100 of the effective human dose. Even though the extrapolation from animal tests is compounded by uncertainties, the revision of the hygienic standards concerning the pregnant worker appears justifiable in such cases. With ever-increasing female participation in the work force, more emphasis should be placed on reproductive hazards and their prediction, in the absence of adequate epidemiologic data, from experimental results. 

The threshold limit value (TLV) is the maximum allowable solvent vapor concentration which should not be exceeded. The values reported in this table are in accordance with the American Conference of Governmental Hygienists (ACGIH). The value is typically given as a time-weighted average (TWA) or a ceiling limit value (CL) which workers can be exposed to for a normal 8-h day, 40-h work week without ill effects. The notation skin indicates that the solvent penetrates the skin and that skin contact should be avoided even if the TLV value is not exceeded. The short-term exposure limit (STEL) is provided, as available, to indicate the vapor concentration value which should not be... 

Chemical analysis of the air by GC/MS showed several VOCs, all present at concentrations far below ACGIH workplace TLVs. Table 12.7 shows the chemicals found, their concentrations, TLV values, and the Kqw values (octanol water partition coefficients) for these. The data are those reported. The Kqw values were added here. 

Occupational exposure to mercury (0.08) and chemical solvents, including styrene (2.95), tetrachloroethylene (3.40), /j-hexane (3.90), toluene (2.73), and carbon disulfide (1.94), has been shown to impair color vision in exposed workers J48l Color vision impairment was also observed for those exposed to solvent mixtures at levels below TLV values. I49l No explanation was offered by the authors for the observed mixture effect. 

Threshold Limit Value. (TLV). A set of standards established by the American Conference of Governmental Industrial Hygienists for concentrations of airborne substances in workroom air. They are time-weighted averages based on conditions that it is believed that workers may be repeatedly exposed to day after day without adverse effects. The TLV values are revised annually and provide the basis for the safety regulations of OSHA. They are intended to serve as guides in control of health hazards rather than definitive marks between safe and dangerous concentration. In this book, these are indicated by TLV. 

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