Threshold Limit Value-Time Weighted Average


Threshold limit value, time-weighted average.  [c.298]

Threshold limit value—time weighted average. Defined as the maximum time weighted average concentration to which a worker may be exposed repeatedly and without adverse effects for a normal 8 h/d, 40 h/wk period.  [c.318]

Consequences of Exposure. Bromine has a sharp, penetrating odor. The OSHA/ACGIH threshold limit value—time-weighted average for an 8-h workday and 40-h workweek is 0.1 ppm in air (61). Monitors are available for determining bromine concentrations in air. Concentrations of about 1 ppm are unpleasant and cause eyes to water 10 ppm are intolerable. Inhalation of 10 ppm and higher concentrations of bromine causes severe bums to the respiratory tract and is highly toxic. Symptoms of overexposure include coughing, nose bleed, feeling of oppression, dizziness, headache, and possibly delayed abdominal pain and diarrhea. Pneumonia may be a late complication of severe exposure.  [c.288]

Calcium carbonate is Hsted as a food additive (7) and not considered a toxic material. The exposure to dust is regulated and a Threshold Limit Value—Time-Weighted Average (TLV—TWA) of 10 mg/m is set (10). Both natural ground and precipitated calcium carbonates can contain low levels of impurities that are regulated. The impurities depend on the source of material, processing, and the final grade impurities are typically trace metals and naturally occurring minerals.  [c.411]

Threshold limit value—time-weighted average. Intraperitoneal.  [c.392]

Toxicity is referenced to the Threshold Limit Value — Time Weighted Average established for each refrigerant. This is defined in ASHRAE Standard 15-1994 as (refer to the manufacturer s product data for more complete detail)  [c.312]

Class A signifies refrigerants for which toxicity has not been identified at concentrations less than or equal to 400 ppm, based on data used to determine Threshold Limit Value-Time Weighted Average (TLV-TWA) or consistent indices from Section 6.1.2.  [c.312]

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.  [c.1198]

Styrene toxicity is regarded to be relatively low. It is an irritant to the eyes and respiratory tract, and while prolonged exposure to the skin may cause irritation, styrene is unlikely to be absorbed through the skin in harm fill amounts. The American Conference of Government Industrial Hygienists (ACGIH) threshold limit value (TLV) for styrene is 50 ppm time-weighted average (TWA) (155). More information on human exposure to styrene in the workplace is available (156,157) (see Styrene).  [c.197]

American Conference of Government Industrial Hygienists (ACGIH) threshold limit value = 5 ppm on an 8-h time-weighted average.  [c.472]

The threshold limit value for the time-weighted average (8-h) exposure to pentanes is 600 ppm or 1800 mg/m (51 mg/SCF) the short-term exposure limit (15 min) is 750 ppm or 2250 mg/m (64 mg/SCF) (39). Pentanes are classified as simple asphyxiants and anesthetics (qv).  [c.404]

Nickel Carbonyl. Nickel carbonyl is an extremely toxic gas. The permissible exposure limit (PEL) in the United States is 1 part per biUion (ppb) in air (127). The American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) for an 8-h, time-weighted average concentration is 50 ppb (128). Nickel carbonyl may form wherever carbon monoxide and finely divided nickel are brought together. Its occurrence has been suspected but never demonstrated in some industrial operations, eg, welding of nickel alloys.  [c.13]

The 1994—1995 threshold limit values as recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) are given in Table 8. These time-weighted average values are those levels to which nearly all workers may be exposed for an 8-h workday and a 40-h work week without adverse effect (99).  [c.103]

Threshold Limit Va.lue. The American National Standards Institute (ANSI) has pubHshed standards regarding the maximum acceptable concentration for certain gases and vapors in the air at work locations. A Hst of threshold limit values (TLVs), pubHshed annually by the American Conference of Governmental Industrial Hygienists (ACGIH), provides the concentrations of dust, mist, or vapor beHeved to be harmless to most workers when exposed for 5 8-h days per week (13). The 1970 TLVs were adopted by OSHA as a consensus standard for time-weighted averages (TWAs) or ceiling limits. The National Institute for Occupational Safety and Health (NIOSH) has documented concurrence with some of these values or has recommended different and usually lower values in a few cases (57). The American Industrial Hygiene Association (AIHA) has carefully evaluated the effect of several toxic vapors (47 as of 1995 (58)) and has developed Emergency response planning guides (ERPGs).  [c.96]

According to the U.S. Department of Labor (OSHA), exposure to dimethyl sulfate shall not exceed an eight-hour time-weighted average of 1 ppm in air (119). Because both liquid and vapor can penetrate the skin and mucous membranes, control of vapor inhalation alone may not be sufficient to prevent absorption of an excessive dose. Dimethyl sulfate is fisted as an industrial substance with suspected carcinogenic potential in humans (119). Thus, the ACGIH recommends a time-weighted average threshold limit value of 0.1 ppm, based on tests with laboratory animals.  [c.202]

Exposure to tantalum metal dust may cause eye injury and mucous-membrane irritation. The threshold limit value (TLV) in air is 5 mg/m, LD q is <400 mg/kg and the Occupational Safety and Health Administration (OSHA) time weighted average (TWA) exposure limit is 5 mg/m (47). The immediate dangerous to life or health (IDLH) concentration is 2500 mg/m (48). Whereas some skin injuries from tantalum have been reported, systemic industrial poisoning is apparently unknown (47).  [c.331]

Inhalation Exposure. Workers exposed to barium carbonate dust for 7—27 years did not reveal any specific chronic poisoning (21). The American Conference of Governmental Industrial Hygienists (ACGIH) and the Occupational Safety and Health Administration (OSHA) have recommended a threshold limit value (TLV) of 0.5 mg/m as Ba, as a time weighted average, for soluble compounds of barium. This time weighted average is an average airborne exposure in any 8-h work shift of a 40-h work week which should not be exceeded.  [c.483]

Because pulp bleaching agents are, for the most part, reactive oxidising agents, appropriate precautions must be taken in their handling and use. For example, it is important to ensure that the threshold limit values (TLV) (20) in Table 2 are not exceeded in the workplace air. These are airborne concentrations in either parts per million by volume under standard ambient conditions or mg per cubic meter of air. They "represent conditions under which it is beUeved that nearly all workers may be repeatedly exposed, day after day, without adverse effect" (20). TWA refers to a time-weighted average for an 8-h workday STEL is a short-term exposure limit or maximum allowable concentration to which workers can be continuously exposed for 15 minutes.  [c.158]

The hquid and vapors of hydrobromic acid are highly corrosive to tissue. The threshold limit value for HBr gas in an 8-h day is 3 ppm time-weighted average. Inhalation of vapor is so irritating to the nose and throat that a person does not voluntarily remain in an area when vapors are present in hazardous concentrations. Symptoms of overexposure to HBr include coughing, choking, burning in the throat, wheezing, or asphyxia.  [c.291]

The 1991 Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL), 8-h time-weighted average standard (TWA) is 100 P-g/m of air for cadmium fume, having a ceiling concentration of 300 pg/m, and 200 pg/m of air for cadmium dust, 600 pg/m ceiling concentration. In 1990, the American Conference of Governmental Industrial Hygienists (ACGIH) specified a threshold limit value (TLV) and ceiling concentration of 50 pg/m for both cadmium fume and dust. However, in 1991 the ACGIH proposed a TLV of 10 pg/m total cadmium and 2 pg/m respirable fraction, along with an A2 suspected human carcinogen designation. Meanwhile, the National Institute of Occupational Safety and Health (NIOSH) recommended a PEL of 40 pg/m for both cadmium fume and dust at a 200 pg/m ceiling concentration for both. EinaHy, in 1991 OSHA proposed to lower the PEL to a level of 1 pg/m or 5 pg/m for cadmium and all cadmium compounds.  [c.388]

Methylene chloride is one of the least toxic chlorinated methanes. The LD q in rats is in the range of 1.6—3.0 g/kg body weight. The fatal dose for a 68-kg person ranges from 80 mL (1.5—2.5 02) to 470 mL (1 pint). Methylene chloride is painful and irritating if splashed directly into the eye. The ACGIH threshold limit value (TLV) for methylene chloride is 50 ppm by volume for an eight-hour exposure. The OSHA permissible exposure level is 500 ppm time-weighted average, 1000 ppm ceiling with 2000 ppm peak concentration. This is currently under revision.  [c.521]

Exposure Limits. The American Conference of Governmental Industrial Hygienists (ACGIH) has recommended a threshold limit value (TLV) of 1 ppm aHyl chloride in air based on a time-weighted average (TWA) of an eight-hour work day, with a short-term exposure limit (STEL) of 2 ppm. OSHA has estabHshed its permissible exposure limit (PEL) at this same level (24,50). The National Institute for Occupational Safety and Health (NIOSH) recommends that exposure to aHyl chloride be controHed to a concentration no greater than 1 ppm of air by volume, which is the TWA for up to a 10-h workday in a 40-h work week, or a ceiling concentration of no more than 3 ppm for any 15-min period (51).  [c.35]

Cumene is a primary skin and eye irritant. Exposure may result ia significant narcosis, headache, and nausea. Because the depressant action has a slow induction period and a long elimination period, possible cumulative effects need to be considered. The recommended threshold limit value (TLV) is 50 ppm (243 mg/m ), which is an 8-h time-weighted average for exposure to cumene (12). In the absence of human data, this value is recommended to prevent the induction of narcosis. The TLV contains a notation that cumene can be absorbed through the skin, and therefore this route should be considered when evaluating total exposure to cumene. The permissible exposure limit for cumene, given by the Occupational Safety and Health Administration, is also 50 ppm (245 mg/m ), again with a skin notation.  [c.364]

The ACGIH threshold limit value (TLV), time-weighted average for an 8 hour workday, 40 hour workweek, was set at 50 ppm (- 200 mg/m ) with a notation for skin absorption (29).  [c.427]

The time-weighted average OSHA permissible exposure limit (PEL), as weU as the ACGIH threshold limit value (TLV), for cyclohexanone is 25  [c.427]

Permissible Exposure Limit (PEL) A Permissible Exposure Limit (PEL) is the maximum amount or concentration of a chemical that a worker may be exposed to under OSH A regulations. PEL can be defined in two different ways as discussed in the OSHA regulation on air contaminants 1910.1000 Ceiling values at no time should this exposure limit be exceeded. 8-hour Time Weighted Averages (TWA) This is an average value of exposure over the course of an 8 hour work shift. TWA levels are usually lower than ceiling values. Thus, a worker may be exposed to a level higher than the TWA for part of the day (but still lower than the ceiling value) as long as he is exposed to levels below the TWA for the rest of the day. See 1910.1000 for the formulas used in the calculations. PELs are defined by OSHA in 3 Tables Table Z-1 Limits for Air Contaminants, Table Z-2 Acceptable maximum peak above the acceptable ceiling level for an 8 hour shift. Table Z-3 Mineral dusts. In general, PELs refer to substances that may be inhaled, although some can be absorbed through the skin or eyes. When working with materials that have a PEL or TWA listed use proper precautions to minimize the generation of a vapor or dust in the first place. Always use appropriate personal protective equipment (PPE) such as gloves, dust masks, and respirators to limit your exposure to chemicals. Remember, exposure limits are not some magic threshold that define the border between safe and dangerous. A PEL that was acceptable in 1950 may be recognized as dangerously high today. Therefore, always do everything reasonable to limit the airborne release of chemicals or dusts in the first place. Chemical Sampling Information at OSHA lists the PELs and/or TWAs for many substances, health effects, and equipment/manufacturers that can monitor concentration for PEL/TWA compliance.  [c.541]

With regard to limiting the concentration of particular contaminants, these are generally referred to in terms of threshold limit values (TLV), expressed either in terms of a time-weighted average (TLV - TWA) which represents the average concentration for a normal working day over a 40-hour week to which nearly all workers may be exposed on a repeated basis or as a short-term exposure limit (TLV - STEL), which represents the maximum  [c.55]

TLV-TWA, THRESHOLD LIMIT VALUE - TIME WEIGHTED AVERAGE (USa) A limit fOf the atmOSpliei ic concentration of a chemical, averaged over an 8-hr day, to which it is believed that most people can be exposed without harm.  [c.19]

Threshold Limit Value-Time Weighted Average (TLV-TWA) The time-weighted arerage concentration for a coinentioiial 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect,  [c.321]

Health and Safety Factors. Trimellitic anhydride may cause respiratory irritation and, in some cases, individuals exposed over long periods may become sensitized and experience mild to severe reactions upon subsequent exposure. It should be handled with caution and treated as a toxic agent in the workplace because exposure may result in irritation of the pulmonary tract, eyes, nose, and skin (117), immunological sensitization and, in rare cases, hemolytic anemia and noncardiac pulmonary edema. Allowable and recommended exposure limits have been estabUshed by the Occupational Safety and Health Administration for a permissible exposure limit (PEL), the American Conference of Governmental Industrial Hygienists for a threshold limit value (TLV), and Amoco for a ceiling limit are aU 0.4 mg/m. The PEL and TLV are an 8-h time-weighted average. The mean lethal acute oral dosage in rats is 5.6 g/kg. Handling precautions include effective ventilation and use of respirators, protective clothing, and goggles when exposure to dust is expected.  [c.497]

The recommended threshold limit value (TLV) of MDA is 100 ppb for an 8-h time-weighted average (TWA) skin. MDA is a suspected human carcinogen (56,58,59). The oral LD q = 830 mg/kg. In May of 1989 OSHA proposed a new standard for regulating MDA. The proposal cites a permissible exposure limit (PEL) for occupational exposure of MDA to an 8-h TWA of 10 ppb and a STEL (short-term exposure limit) of 100 ppb for a 15-min TWA (50). The standard does not apply if initial monitoring shows less than the action level of 5 ppb for an 8-h TWA (airborne) and if no dermal exposure is likely. The employer is required to implement engineering and work practices (eg, respirators) to maintain employee exposure levels at less than or equal to the permissible exposure limit. The proposal also includes having a changing room and showers for changing all contaminated clothing after a work shift employer laundering of clothing removal of clothing prior to eating, drinking, smoking, etc and washing hands and face prior to eating. If food and beverages are consumed in the work area, the employer is expected to provide a positive pressure eating area. AH surfaces must be maintained as free as possible from visible accumulations of MDA. The employer is responsible for conducting medical surveiHance and record keeping, as weH as for conducting periodic monitoring of the area according to existing exposure level guidelines.  [c.251]

Occupational Protection and Radiation Considerations. The main adverse factor during the mining and processing of uranium and uranium-containing minerals is airborne dust. Personal protection should include respinators, protective clothing, surgical gloves, suitable footwear, use of wet processes wherever possible, and in operations involving dust formation, face masks, constant ventilation, and glove boxes. Local exhaust ventilation is necessary since one of the daughter products of U is radioactive radon. Environmental protection measures against radioactive contamination in the mining and processing of uranium ores has been described in detail (245). In the United States, the hygienic standards for both soluble and insoluble compounds of natural uranium are, expressed as threshold limit values, 0.2 mg/m for an 8-h time weighted average and 0.6 mg/m for a short-term exposure (8). Finely divided uranium metal, some alloys, and uranium hydride are pyrophoric, therefore such materials should be handled in an inert atmosphere glovebox.  [c.336]

The American Conference of Governmental Industrial Hygenists (ACGIH) has set threshold limit values (TLVs) for airborne concentrations in the workplace (ppm, time-weighted average, 8-h day) as follows AGE, 5 ECH, 2 EO, 1 and PO, 20 (44). However, the ACGIH has reexamined data on ECH, and has proposed lowering the TLV to 0.1 ppm it has categorized this monomer as Group A2, a suspected human carcinogen (45).  [c.557]

Toxicity data are presented in the literature by such terms as "LDjo" and "LC50, that lethal dose per kilogram of body weight or lethal concentration that can kill 50 percent of an animal population. Such data are found, for example, in the Registry of Toxic Effects of Chemical Substances (RTECS). With data such as these obtained from animals closely resembling the human in biochemistry, relative toxicities can be established to characterize chemicals. These data in conjunction with air contaminant threshold limit values (TLV) or permissible exposure limits (PEL), set by law for short periods of exposure or eight-hour, time-weighted average exposure, have produced safe working exposure limits for the worker. Many of these values are contained in the OSH A Standards and the American Conference of Governmental Industrial Hygienist s (ACGIH) in their publications on Threshold Limit Values and Biological Exposure Indices.  [c.181]

This knowledge is also important in order to determine if air tests conducted by OSHA compliance officers are valid. For example, if threshold limit value in the health standard is an 8-hour time-weighted average, the air sample should be obtained by sampling over the entire shift in the employee s breathing zone. It cannot be measured by a few short term samples, even if spaced over the full shift unless the worker is in a relatively fixed location with no variation in his work procedure or in the process. Such an event is generally the exception rather than the rule.  [c.261]

The problem of determining the exposure of a worker to air contaminants is further complicated by the mobility of most workers who move about, in and out of, many areas of a workroom. This mobility is characteristic of many assigned jobs. Therefore, the concentration of contaminants in each work area, and the time spent in each must be considered in determining the full shift time-weighted average concentration to which each worker is exposed. Exposure is concentration averaged over a time period, which in the general case is a full 8-hour shift. However, threshold limit values in the list published in the OSHA safety and health standards are peak concentrations or "ceiling values." Such standards indicate the maximum concentration which is allowed for any time period. Although a single specific sampling strategy cannot be applicable for all air monitoring, general principles or considerations, which should be incorporated in such a strategy, can be developed.  [c.262]

Number of Samples. A reliable estimate of an employee s exposure requires replicate samples irrespective of their duration. This is basic whether or not one is concerned with 8-hour time-weighted concentrations, operational exposures or areal contamination. Differences involving a factor of five or more are not rare. Therefore, a minimum of three samples should be obtained, until experience dictates an upward or downward revision, based upon the variability so determined. One cannot emphasize too greatly that the objective of a sampling program is worker protection and not the collection of numbers. An occasional exposure to a concentration which exceeds the threshold limit values would result in a violation if the compliance officer is sampling on the day that such an exposure exists, even though the average of several daily samples obtained during the same week is within the standard. This demonstrates the difference between good evaluation techniques and the mere application of numbers.  [c.264]

Duration of Samples For a practical viewpoint the duration of samples will be dictated by the requirements in the OSHA standards. These are continuous 8-hour samples or short-term samples when the standard has a "ceiling value" or peak concentration limit. Scientifically speaking, the minimum volume of air to be sampled, or the duration of sampling, is based on the following considerations (1) the threshold limit value (TLV) or regulatory standard (2) the sensitivity of the analytical procedure or (3) the estimated air concentration. Thus, the volume of sample needed may vary from a few liters, where the estimated concentration is high to several cubic meters where low coneentrations are expected. Then, knowing the sensitivity of the analytical procedure, the TLV and the sampling rate of the particular instrument in use, one can determine the minimum time necessary for an adequate sample. However, the collected sample should represent some identifiable period of time — usually a complete cycle of an operation or so many minutes out of each hour. This will enable the worker s exposure on a time-weighted average basis to be ealculated.  [c.265]


See pages that mention the term Threshold Limit Value-Time Weighted Average : [c.326]    [c.397]    [c.239]    [c.171]    [c.432]   
Health, safety and accident management in the chemical process industries (2002) -- [ c.321 ]