The recommended standard is measurable by techniques that are valid, reproducible, and available to industry and governmental agencies. Sufficient technology exists to permit compliance with the recommended standard. Pertinent new information will be reviewed periodically and the recommendations will be revised as necessary.
Section 1 -Environmental (Workplace air) (a) Concentration
(1) Occupational exposure to trichloroethylene shall be controlled so that workers will not be exposed to trichloroethylene at a concentration in excess of 100 ppm determined as a time-weighted average (TWA) exposure for an 8-hour workday, as measured by a minimum sampling time of 10 minutes.
(2) No worker shall be exposed to a peak concentration of trichloroethylene in excess of 150 ppm, as measured by a maximum sampling time of 10 minutes.
(b) Sampling, Calibration, and Analysis
Procedures for collection of environmental samples shall be as provided in Appendix I, or by an equivalent method. Analysis of samples shall be as provided in Appendix II, or by any method shown to be equivalent in precision, sensitivity, and accuracy to the method specified in Appendix II.
Section 2 -Medical (a) Medical surveillance as specified in this section shall be made available to workers who are exposed to trichloroethylene.
(1) A preplacement examination shall be made available to all workers who will be exposed to trichloroethylene and within 6 months to all workers who are exposed to trichloroethylene on the effective date of this standard, and it shall consist of:
(A) A comprehensive medical history of each work applicant shall be taken. The history should be directed towards but not limited to the incidence of headaches, nausea, and dizziness; particular attention should be focused on complaints and evidence of eye, mucous membrane and skin irritation. Workers who complain of chronic eye irritation should have an ophthalmic (eye) examination.
(B) A comprehensive physical examination shall be made available, with emphasis on cardiac, pulmonary, liver, and kidney examinations.
(2) Periodic medical examinations shall be made available to workers exposed to trichloroethylene annually. (1) Only appropriate respirators, as defined below, shall be provided and used when a variance which allows the use of respirators as a means of controlling exposure for routine operations has been granted or while action on application for a variance is pending.
(2) The requirements set forth in this section shall apply for nonroutine operations such as a brief exposure to concentrations in excess of the environmental standard as a result of maintenance or repair activities or in emergency situations.
(3) A respiratory protection program meeting the general requirements outlined in section 3.5 of American National Standard Practices for Respiratory Protection Z88.2-1969 shall be established and enforced by the employer. This program shall include instructions on the selection, fitting, use, testing for leakage, cleaning, and maintenance of the respiratory protective devices.
(4) For the purpose of determining the class of respirator to be used, the employer shall measure the atmospheric concentration of trichloroethylene in the workplace when the initial application for variance is made and thereafter whenever process, worksite, climate or control changes occur which are likely to affect the concentrations of airborne trichloroethylene. Only appropriate respirators as described in (5) Employees who experience breathing difficulty while wearing a respirator shall be medically examined to determine their ability to wear the respirator. Greater than 10000 ppm Chemical cartridge respirator with organic vapor cartridge(s).
Type C demand type supplied air res pirator with half mask facepiece.
Gas mask, chin type, with organic vapor canister.
Type C demand type supplied air res pirator with full facepiece.
Type C continuous flow supplied air respirator.
Self-contained breathing apparatus in pressure-demand mode (positive pressure)
The self-contained breathing apparatus shall be made available and used for emergencies. (a) Each employee exposed to trichloroethylene and its decomposition products shall be apprised of all hazards, the consequences of overexposure, appropriate emergency procedures, proper conditions for safe use, and precautions to minimize exposure. This apprisal shall include, as a minimum, all information set forth in Appendix III which is applicable to that specific product or material containing trichloroethylene.
(b) Each employee shall be apprised of the location of the information prescribed in paragraph (c) of this section. This information shall be kept on file and shall be readily accessible to all employees at each establishment where exposure to trichloro ethylene occurs. (1) Disposal of small quantities of trichloroethylene call be accomplished by pouring the liquid onto a mixture of 10% soda aSh and sand and placing the mixed material in a paper container and incinerating.
(2) Waste from cleaning contaminated with trichloroethylene should be stored in a ventilated area until ready for disposal and may be burned in an incinerator. (2) Smoking should not be permitted in areas where vapor of trichloroethylene is present.
(3) Powdered metals or turnings shall not be used or stored in any area where trichloroethylene liquid is in use or stored.
Section 7 -Sanitation Practices Showers, hand-washing facilities, soap, and water shall be available.

# Section 8 -Monitoring and Recordkeeping Requirements
Workroom areas where it has been determined, on the basis of an industrial hygiene survey or the judgment of a compliance officer, that environmental levels of trichloroethylene are less than half of the TWA limit shall not be considered to have trichloroethylene exposure.
Records of these surveys, including the basis for concluding that air levels of trichloroethylene are below half of the Later in the 1930's it was used as a surgical anesthetic  and proposed for use as the basis for treatment of various nervous disorders.
 The first reported evidence of acute overexposure to trichloroethylene in industrial applications  resulted from its use as a grease solvent.
This first report of chronic poisoning from trichloroethylene in industrial situations  suggested that the observed effects were more likely due to impurities in the material rather than to trichloroethylene itself. From 1963 to 1967 the common manufacturing process for trichloroethylene  produced as an intermediate chemical They noted that the daily excretion of trichloroacetic acid reached a maximum at 1:00 pm daily, irrespective of the quantity of urine excreted. Excretion of trichloroethanol began soon after the initial inhalation and rose rapidly to its maximum a few hours after the end of exposure; the total excreted was equivalent to 32 to 59% (average, 50) of the retained trichloroethylene. Excretion of trichloroethanol also appeared to fall as the sum of two exponential rates, the first phase lasting 3 or 4 days, the second lasting 7 to 9 days. Trichloroethanol excretion did not exhibit fluctuations related to time of day. In these studies, the total amount of metabolites excreted amounted to 43% to 100% (average, 73) of the trichloroethylene absorbed and the three metabolites, monochloroacetic acid, trichloroacetic acid, and trichloroethanol were found in the ratios of 1:5:12, respectively.
Bartonicek,  using eight resting volunteers exposed to a concentration of 1 milligram per liter (186 ppm) of trichloroethylene in five-hour periods, found that they excreted an average of 45.4% of the retained trichloroethylene as trichloroethanol and 31.9% as trichloroacetic acid, thus accounting for 77.3% of the retained trichloroethylene. Expired air analyses were performed to estimate retained trichloroethylene. Three days after exposure, the average concentration of trichloroacetic acid was 2.4 milligrams per 100 milliliters of blood plasma and 0.5 milligram per 100 milliliters red blood cells. These studies indicated that a small amount of trichloroacetic acid was excreted in sweat and in feces and, on the third day after exposure, 0.23 milligram per 100 milliliters of saliva was measured. They showed that 58% (a range of 51 to 64) of trichloroethylene inhaled at a concentration of 186 ppm was retained.
Trichloroethanol excretion was maximal at the first post-exposure test (within the first 24 hours after exposure) and decreased exponentially while the rate of trichloroacetic acid excretion reached its peak 3 days after exposure and decreased more gradually for 18 days.  This test was shown to be a less sensitive indicator of effects of trichloroethylene than of effects of alcohol.
Todd  reported the case of a man who had ingested unknown amounts of trichloroethylene.
After prolonged unconsciousness and some cyanosis, the result was a temporary paranoid psychosis and a distortion of both vertical and horizontal vision so that persons appeared 12-18 inches high, an effect described as "Lilliputian hallucinations". (e) Other Effects
Friborska  showed that leukocyte alkaline phosphatase levels increase in persons repeatedly exposed to trichloroethylene. The acid phosphatase in blood also increased. These increases persisted after two weeks without exposure. The investigator considered that these findings might signify a defense mechanism or an increased capacity to metabolize alcohols, might be a response to changing pH of the blood, or be related to glycogen metabolism in the liver. For the workers studied, the following percentages of complaints were indicated: dizziness, 88%; headache, 74%; nausea, 43%; euphoria, 31%; palpitation, 29%; disturbances of vision, 21%; and sleepiness at the end of the shift, 29%. The study further showed an insidious onset after some months, up to one or two years, of the following complaints: fatigue, 68%; irritability, 56%; disturbed sleep, 46%; anxiety, 27%; loss of appetite, 50%; alcohol intolerance, 21%.
Accompanying findings included excessive sweating in 39%, palpitation in 29%, nausea in 19%, and some parasthesias. While the percentage of workers that indicated complaints are in excess of the percentage of samples at or below 50 mg/cu m (about 10 ppm), a direct relationship can not be established since the sampling protocol is unknown. and the description of the bone marrow led the authors to the conclusion that chronic intoxication to trichloroethylene has a direct action on the bone marrow and thus causes myelotoxic anemia.
Another factor studied was dehydration before trichloroethylene exposures. Baetjer,  in careful hypothalamic self-stimulation performance tests, showed that a three-day dehydration caused rats to make fewer responses than nondehydrated rats. After exposure to trichloroethylene, neither group performed as well as before exposure.
The dehydrated rats performed better than the nondehydrated rats, although some tolerance for trichloroethylene developed in both groups. Recovery of nondehydrated rats was prompt after moderate exposures but was not completed in 24 hours, suggesting that either the trichloroethylene concentration in the brain was greater or the dehydrated brains were more resistant to trichloroethylene or both.
Ten-day dehydration tests and trichloroethylene exposure resulted in further decrements in performance after the fifth day of exposure, suggesting that high concentration of trichloroethylene combined with dehydration may have produced some residual brain damage. to produce lighter anesthesia but it lasted two to three hours.
Bartonicek and Brun  made extensive studies of brain tissue, EEG, acid phosphatase levels, and erythrocyte sedimentation rates in two groups of rabbits. In one group, rabbits were injected with 3 ml trichloroethylene into the muscle three times per week for 29 days (a total of 53 g per rabbit).
The second group was given 2 ml trichloroethylene twice a week for periods lasting from 41 to 247 days, or a total of 18-133 g per rabbit. Controls were also studied. acid was also excreted but in much smaller quantity. Friberg et al  showed that rats exposed for four hours to 640, 1150 or 2500 ppm excreted trichloroacetic acid increasingly up to 24 hours after exposure then decreasingly for up to six days irrespective of dosage.
Studies by Forssman and Holmquist  showed that rats exposed for studied rabbits' metabolism for a year and concluded that their metabolism was qualitatively like humans and only the relative quantities differed. Rabbits excreted 10 times more trichloroethanol than trichloroacetic acid and about 50 times less trichloroacetic acid than man, but equally slowly.
Fabre and Truhaut  studied tissue homogenate. They found trichloroethylene in all tissues obtained during exposure, greatest in fat, then in lungs, spleen, liver, and least in brain and kidney.
Trichloroacetic acid was present in greatest concentration in fresh spleen, suprarenal glands, reproductive organs, and urine. In vitro studies of tissue homogenates exposed to trichloroethylene showed the most active conversion of the substance to its metabolites in the spleen, and decreasing activity in the lung, brain, liver, and kidney tissues.
In 1967 Leibman and McAllister  reported studies with liver microsomal tissue extracts. They were able to show that there was an increase in the ability to metabolize trichloroethylene to chloral and to trichloroethanol when the animals from which the tissue extracts were obtained had been previously treated with phenobarbital. Rats pretreated with phenobarbital and then exposed to trichloroethylene also excreted more metabolites in the first few hours than the similarly exposed but not pretreated controls.
The authors pointed out that drug intake might vitiate conclusions drawn from levels of trichloroacetic acid urinary excretion based on single samples.

# Correlation of Exposure and Effects
The most meaningful studies for purposes of establishing a welldefined cause-and-effect relationship are those in which an attempt has been made to relate the environmental exposures with subsequent effects in the exposed population.
Longley and Jones  reported that unconsciousness suddenly occurred in a worker who entered a tank in which a paint containing in excess of 75% trichloroethylene had been recently used. An attempt was made to simulate conditions which produced the unconsciousness and air sampling was conducted within the tank after application of some of the paint. Concentrations of trichloroethylene within the tank varied by location between 1700 and 3300 ppm. The authors estimated that a concentration of 3000 ppm would cause unconsciousness in human subjects after a 10-minute exposure. Their studies indicated no significant effect on psychomotor performance at the 100 ppm level.
There was a slight decline in performance at the 200 ppm level which became progressively more pronounced at the 300 and 500 ppm concentrations. A relatively high frequency of subjective complaints, alterations of the involuntary nervous system and of neurological and psychiatric symptoms were reported. The frequency showed a good relationship with total duration of exposure (months on the job). A total of 96 air samples were collected during the study, the results of which ranged between 1 and 335 ppm, many of them lying between 20 and 40 ppm. The authors stated that a series of consecu tive samples collected during a period of 3 to 4 hours in one workplace showed a great variation in concentrations due to the actual degree of ventilation and utilization of the degreasing apparatus.
The authors admitted that air measurements provided Insufficient indication of the total exposure. Laboratory tests of hepatic function showed no significant changes. On that basis they stated that they could not conclude that there was any causal relationship between liver troubles and exposure to trichloroethylene.  In the case in question, the workman emptied the tank, rinsed it with water from a powerful hose pipe, then got inside the tank and spent half an hour cleaning with a scrubbing brush. Analyses of the air showed a concentration of 1,120 ppm outside the tank while the hose pipe was in action, with 815 and 395 ppm inside the apparatus during and after the scrubbing respectively."
Skinner  reported the use of baffles on windows near degreasers in the plant to control high velocity drafts.
Trichloroethylene concentrations of 170 to 230 ppm were reduced to 30 to 40 ppm with this approach to control.
Hargarten et al  reported results of tests carried out from 1952 to 1957 around 43 degreaser operations. Ninety-three percent of the operators' breathing zone samples taken during the cleaning cycle of the degreasers were 100 ppm or less. Methods of sampling and analysis were not stated.
In a 1963 report Ahlmark et al  found that during the preceding decade, when 570 degreasing plants were inspected in Sweden,

# Process ventilation
Ventilation is by far the most common engineering method for controlling solvent vapors. Vapor recovery sytems are sometimes used when a high airflow exhaust system is required for good ventilation. In 1967 this standard was revised by the Z-37 Committee.
 The revision established 100 ppm as an acceptable time-weighted average concentration for an 8-hour workday. In addition, an accept able ceiling concentration of 200 ppm, provided that the time-weighted average is kept at or below 100 ppm, was recommended. Furthermore, a concentration of 300 ppm for a duration of not more than 5 minutes was judged acceptable if encountered not more than once in 2 hours during In summary, deaths of several workers from exposure to trichloroothylene have been reported ; in the. best documented case, exposure was at levels estimated to be between 1700 and 3300 ppm for ten minutes. Exposures at 1000 ppm for even short periods of time have resulted in effects on the central nervous system. Subjective complaints by one of 8 male volunteers was reported  at exposure levels of 300 ppm for two hours. No adverse effects were noted by psychophysiological testing of the same subjects at 100 ppm. In another paper,  results of psychophysiological testing of one subject for 2-1/2 hours indicated no significant effect on psychomotor performance from exposure at 100 ppm, but a slight effect was noted at 200 ppm. Adverse effects were reported by 3 of 7 subjects exposed at 160 ppm for less than 83 minutes. These effects, subjective in nature, included headache, drowsiness and mild eye irritation. trichloroethylene except when it is contaminated by other compounds, especially tetrachloroethane, is the correct explanation.
As discussed above, the study by Salvini et al  indicates that exposures of approximately 100 ppm may interfere with the psychophysiological efficiency of the worker. Therefore, a TWA limit of 100 ppm will protect most of the workers but with probably very little margin of safety at this level of exposure. The effects of short exposures to trichloro ethylene on swimming performances and motor activity of rats. Am Ind Hyg Assoc J 24:376-79, 1963  (1) Air sampling instruments shall be calibrated after making any repairs or modifications to the sampling system and at least once a year with a reference such as a wet test meter over a normal range of flowrates and pressure drops.
(2) The wet test meter shall be in good working condition and shall have been calibrated against a spirometer (or other primary standard) upon procurement, after each repair, and at least annually. (2) The charcoal in the tube is transferred to a small test tube and desorbed with carbon disulfide.
(3) An aliquot of the desorbed sample is injected into a gas chromatograph. If a particular atmosphere is suspected of containing a large amount of trichloroethylene, it is recommended that a smaller sampling volume be taken.

# (c) Interferences
(1) When the amount of water in the air is so great that condensation actually occurs in the tube, organic vapors will not be trapped.
Water vapor does not seem to be a problem, only water present as a mist.
(2) Any compound which has the same retention time as trichloroethylene at the operating conditions described in this method could be considered an interference. This type of interference can be overcome by changing the operating conditions of the instrument.

# (d) Precision and Accuracy
(1) Precision of the analytical method: plus or minus 4.8%.
(2) Precision of the analytical method plus field sampling with the personal sampling pump has not been established.
(3) The accuracy of the sampling and analytical method, as established during breakthrough testing of the front section of activated charcoal: 91%.

# (e) Advantages and Disadvantages of the Method
This method is advantageous in that it provides one basic method for determining many different organic solvents. The sampling device is small, portable, and involves no liquids. Interferences are minimal, and most of those which do occur can be eliminated by altering chromatographic conditions. The analysis of the tubes is accomplished using a quick instrumental method.
One disadvantage of the method is that the amount of sample which can be taken is limited by the weight of sample which the tube will hold before overloading. Also the precision of the method is limited by the reproducibility of the pressure drop across the tubes.
Variability in this pressure drop w^Lll affect the flowrate, causing the volume to be imprecise since the pump is usually calibrated for one tube only.
(f) Apparatus consists of:
(1) An approved coal mine dust personal sampling pump for personal samples or any vacuum pump whose flow can accurately be determined at 1 liter per minute or less. (3) Gas chromatograph equipped with a flame ionization detector.
(4) Column (20 ft x 1/8 in) with 10% FFAP stationary phase on 80/100 mesh acid washed DMCS Chromosorb W solid support.
One liter per minute is the recommended sampling rate. A 10-liter sample is normally adequate. The tube must be supported in a vertical position for sampling. Due to the high resistance of the charcoal tube, this sampling method places a heavy load on the personal sampling pump. Therefore, it should not be assumed that this pump will run a full 8 hours without recharging the battery. After the sample is collected, the tube must be capped; caps are provided with commercial tubes.
One charcoal tube should be treated in the same manner as the sample tubes (break, seal, ship) with the exception that no air be drawn through it. This tube will serve as a blank.
If bulk samples are submitted in addition to charcoal tubes, the tubes should be shipped in a separate container from the bulk sample. It is convenient to prepare standards in terms of mg/0.5 ml of carbon disulfide because samples are desorbed in this amount of carbon disulfide.
To minimize error due to the volatility of carbon disulfide, twenty times the weight can be injected into 10 ml of carbon disulfide. For example, to prepare a 0.3 mg/0.5 ml standard- 6.0 mg is injected into exactly 10 ml of carbon disulfide in a glassstoppered flask. The density for trichloroethylene is used to convert 6.0 mg into microliters for easy measurements with a microliter The first method is used because of its simplicity.
Because desorption efficiencies may vary from one laboratory to another and with different batches of charcoal, each laboratory should determine its own. However, for comparison, NIOSH determined a value of 97% for trichloroethylene, with one lot of activated charcoal.

# (j) Calculations
(1) The first step in calculating the results is to read the weight in milligrams corresponding to each peak area from the standard curve. The standard curve is based on mg/0.5 ml of carbon disulfide, and therefore, no correction need be made for the volume of the sample injected, since this is identical to the volume of the standards injected.
(2) The weight of trichloroethylene in the front section of the blank tube is subtracted from the weight determined for the front section of each sample; a similar procedure is followed for the backup sections.
(3) Amounts present on the front and backup sections of the same tube are then added to calculate the total amount in the sample.
(4) This total weight of trichloroethylene in the tube is corrected by dividing by the desorption factor to determine the total number of milligrams in the sample. (1) Toxic level for total compound or mixture, relevant symptoms of exposure, skin and eye irritation properties, principal routes of absorption, effects of chronic (long-term) exposure, and emergency arid first aid procedures.
(g) Section VI. Reactivity Data.
(1) Chemical stability, incompatibility, hazardous decomposition products, and hazardous polymerization.
(h) Section VII. Spill or Leak Procedures.
(1) Detailed procedures to be followed with emphasis on precautions to be taken in cleaning up and safe disposal of materials leaked or spilled. This includes proper labeling and disposal of containers containing residues, contaminated absorbents, etc.
(i) Section VIII. Special Protection Information.
(1) Requirements for personal protective equipment, such as respirators, eye protection, protective clothing, and ventilation, such as local exhaust (at site of product use or application), general, or other special types.
(j) Section IX. Special Precautions.
(1) Any other general precautionary information such as personal protective equipment for exposure to the thermal decomposition products listed in Section VI, and to particulates formed by abrading a dry coating, such as by a power sanding disc.
(k) The signature of the responsible person filling out the data sheet, his address, and the data on which it is filled out.  1 ppm = 5.38 mg/m3 @25 C 1 mg/liter = 186.1 ppm   Mean time spent by each operator at the various locations. It is understood that an operator may perform at a given location with greater frequency than another operator.
(1) Breathing zone samples shall be collected as near as practicable to the worker's face without interfering with his freedom of movement and shall characterize the exposure from each job or specific operation in each production area.
(2) A portable battery-operated personal sampling pump plus an activated charcoal tube shall be used to collect the sample.
(3) The activated charcoal tube shall be attached to the worker's clothing; the shirt collar is convenient for this purpose.
(5) A mechanical or electronic integrator or a recorder and some method for determining peak area.
(6) Small glass-stoppered test tubes or equivalent.
(7) Micro syringes: 10 pi, and convenient sizes for making standards.
(g) Reagents
(1) Spectroquality carbon disulfide.
(2) Trichloroethylene, preferably chromatoquality grade.
(3) Bureau of Mines Grade A helium.
(4) Prepurified hydrogen.
(5) Filtered compressed air.
(h) Procedure
(1) Cleaning of Equipment All equipment used for the laboratory analysis should be washed in detergent followed by tap and distilled water rinses.
(2) Collection and Shipping of Samples Both ends of the charcoal tube should be broken to provide openings of at least 2 mm which is one-half the I.D. of the tube. A smaller opening causes a limiting orifice effect which reduces the flow through the tube.
The smaller section of charcoal in the tube is used as a backup section and should therefore be placed nearest the sampling pump. Tubing may be used to connect the back of the tube to the pump, but no tubing must ever be put in front of the charcoal tube.  Values in parentheses are approximate conversions where the standard was published in only one of the two units listed above.
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