# I. RECOMMENDATIONS FOR
If "exposure" to other chemicals also occurs, for example to toluene, provisions of any applicable standards for the other chemicals shall also be followed.

# Section 2 -Medical
Medical monitoring (biologic monitoring and medical examinations) shall be made available to workers as outlined below.

# (a) Biologic Monitoring
Biologic monitoring shall be provided to all workers subject to "exposure to benzene." It consists of sampling and analysis of urine for total phenol content. Such monitoring shall be performed to ensure that no worker absorbs an unacceptable amount of benzene. Unacceptable absorption of benzene posing a risk of benzene poisoning is demonstrated at levels of 75 mg phenol/liter of urine (with urine specific gravity corrected to 1.024) or greater as sampled and determined by the method specified in Appendix III, or alternative methods shown to be equivalent in accuracy and precision. "Spot" urine specimens of about 100 ml shall be collected as close to the end of the working day as feasible. Any urine specimens with a specific gravity less than 1.010 shall be discarded and another sample obtained.
To satisfy the biologic monitoring requirement, every worker subject to "exposure to benzene" shall have urine sampling and analysis made  available to him at quarterly intervals.
The schedule of biologic monitoring may be altered if indicated by the results of a professional industrial hygiene survey.
If environmental sampling and analysis demonstrate that environmental levels are at, or greater than, the environmental limit, the interval of biologic monitoring shall be increased so that a phenol analysis shall be conducted every 2 weeks on every worker.
This increased frequency shall be continued for at least 2 months after the high environmental level has been demonstrated.
If a worker's urine phenol level is found to be 75 mg/liter or greater, calculated to a specific gravity of 1.024, two followup urine samples shall be obtained within 1 week after receipt of the results, one as close Co the beginning and one as close to the end of the same working day as possible.
If the original elevated finding is confirmed, steps to reduce the worker's absorption of benzene shall be taken promptly.
Steps to be considered should include improvement of environmental controls, of personal protection or personal hygiene, and the use of administrative controls. For those workers with confirmed high biologic levels of phenol as determined from the biologic sampling, a medical examination for possible benzene poisoning shall be considered and the OSHA area industrial hygienist shall be informed.
Biologic monitoring shall also be provided where the OSHA area industrial hygienist has reason to believe operations produce unusual exposure excursions or that environmental samples do not adequately describe worker exposure.

# (b) Medical Examinations
Medical examinations shall be provided for all workers subject to "exposure to benzene" or when unacceptable absorption of benzene is demonstrated as judged by biologic monitoring. An evaluation of the advisability of a worker's using negative-or positive-pressure respirators shall also be made.
( Respirators shall also be provided and used for nonroutine operations (occasional brief exposures above the ceiling of 25 ppm and for emergencies); however, for these instances, a variance is not required, but the requirements set forth below continue to apply. Appropriate respirators as described in Table 1-1 shall only be used pursuant to the following requirements :
(1) For the purpose of determining the type of tespirator to be used, the employer shall measure the atmospheric concentration of benzene 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 increase the benzene concentration. The employer shall ensure through proper respirator selection, fit, use, and maintenance that no worker is being exposed to benzene in excess of the standard.
(2) The respirator and cartridge or canister used shall be of the appropriate class- as determined on the basis of exposure to benzene.
The employer shall provide respirators in accordance with Table 1-1 and shall ensure that the employee uses the respirator provided.
(5) Respiratory protective devices described in

# Less than or equal to lOOx

# Greater than lOOx
(2) Type C supplied air respirator, demand type (negative pressure), with quarter or half mask.
(1) Gas mask with chin style canister for organic vapors.
(2) Gas mask with front or back mounted chest type canister for organic vapors.
(3) Type C supplied air respirator, demand (negative pressure), with full facepiece.
(4) Self-contained breathing apparatus in demand mode (negative pressure) with full facepiece.
(5) Combination supplied air respirator, pressure-demand type, with auxiliary self-contained air supply and full facepiece.
(1) Self-contained breathing apparatus in pressure-demand mode (positive pressure). with full facepiece.
(2) Type C supplied air respirator, pressure-demand or continuous flow type with full facepiece or hood.
(3) Combination supplied air respirator, pressure-demand type, with auxiliary self-contained air supply with full facepiece. Respirator Type for Benzene
(1) Self-contained breathing apparatus in pressure-demand mode (positive pressure) with full facepiece.
(2) Combination supplied air respirator, pressure-demand type, with auxiliary self-contained air supply and full facepiece.

# Evacuation or escape (No concentration limit)
(1) Self-contained breathing apparatus in demand or pressure-demand mode (negative or positive pressure).
(2) Gas mask with organic vapor canister and mouthpiece respirator.

# (b) Skin Protection
(1) Benzene-wetted clothing shall be removed promptly and benzene-exposed parts of the body shall be washed thoroughly. (2) Benzene or benzene-containing materials shall not be discharged where there is a potential for vapor ignition.

# (f) Food
Food preparation and eating should be prohibited in benzene work areas.
(g)

# Restricted Access to Benzene Areas
Entry to any area where there is the possibility of exposure to benzene shall be permitted only on the basis of need; all persons entering shall be protected as required for workers regularly assigned to that area.    Originally, the most important early sign of benzene poisoning was thought to be the change in the white blood cell (WBC) count. Greenburg considered cases as positive which showed less than 5,500 WBC/cu mm (7,500-9,000 was considered the normal count). A reduction of the WBC count to less than 4,000 and the red blood cell (RBC) count to less than 4 million /cu mm was found in 10 of 26 workers. Three of 8 workers studied in detail showed less than 50% polymorphonuclear leukocytes, 2 showed a lymphocyte population greater than 45%, and 2 showed eosinophils of more than 5%. In all groups listed in Table XII-3 workers examined, 130 were found to be suffering with varying degrees of benzene poisoning, 22 of these to a severe extent whereas 43 were early cases. The RBC count was less than 4.5 million in 48% of these subjects, the platelets were less than 100,000 in 33%, and the WBC count was less than 5,000 in 15% of the total workers, in 30% of the early cases, and in 86% of the 22 severe cases of poisoning. The hemoglobin (Hgb) was less than 13 g/lOOml of blood in 15% of 235 workers examined.
From the detailed blood studies which were performed on 102 of the workers, the incidence of significant abnormalities has been summarized and is presented in

# Correlation of Exposure and Effect
Liquid benzene on the skin may cause erythema and blistering, and a dry, scaly dermatitis may develop on prolonged or repeated exposure.
     The information in Table IV-   The accuracy of the tests with in-line calibration was approximately 5% better than that in (1) above which lacked the in-line calibration. The data, however, were insufficient to show whether the difference was statistically significant.

# V. DEVELOPMENT OF STANDARD

# Basis for Previous Standards
The In the study by Smith,  the ages were quite evenly distributed between 17 and 52 years. Susceptibility to benzene poisoning was about equally marked between young and old, so youth was not considered to be a predisposing factor in benzene poisoning.
In view of the borderline hematological changes which occur in both man and animals from exposures to benzene and of the consequences which result from overexposure, it is considered that a conservative limit must be recommended. Therefore, in order to provide protection of workers to the effects of benzene poisoning over a working lifetime, it is recommended that an environmental limit for benzene of 10 ppm as a time-weighted average for up to a 10-hour workday, 40-hour workweek be adopted. In addition, in order to preclude acute effects from benzene, it is considered that exposures of workers should be kept at or below 25 ppm; therefore, a ceiling is recommended for which benzene concentrations shall not be permitted to exceed 25 ppm.
It is recognized that many workers handle small amounts of benzene or are working in situations where, regardless of the amount used, there is only negligible contact with the substance. Under these conditions, it should not be necessary to comply with many of the provisions of this recommended standard, which has been prepared primarily to protect worker health under more hazardous circumstances. Concern for worker health requires that protective measures be instituted below the enforceable limit to insure that exposures stay below that limit. For these reasons, "exposure to benzene" has been defined as exposure above half the   Hemolysis is discovered early by laboratory estimation of the breakdown products of hemoglobin, of which bilirubin is the easiest to measure.
Again, the frequency of the determination is predicated upon the level of individual exposure.

# Normal Hematologic Values
The generally accepted ranges of normal for the hematologic tests discussed in the body of this document are presented in

# Smith AR:
Chronic benzol poisoning among women industrial workers-A study of the women exposed to benzol fumes in six factories. Studies on the inhalation of 1:3-butadiene with a comparison of its narcotic effect with benzol, toluol, and styrene, and a note on the elimination of styrene by the human. J Ind Hyg  (5) A mechanical or electronic integrator or a recorder and some method for determining peak area.
(6) Small glass-stoppered test tubes or equivalent tubes.
(7) Syringes: 10 juliter syringe, and other convenient sizes for preparation of standards.

# (g) Reagents
(1) Spectroquality carbon disulfide
(2) Benzene, preferably chromatoquality grade.
(3) Bureau of Mines Grade A helium.
(4) Prepurified hydrogen.
(5) Filtered compressed air.

# (h) Procedure

# Cleaning of Equipment
All equipment used for the laboratory analysis should be washed in detergent followed by tap and distilled water rinses.
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# As Sulfates and Glucuronides Eliminated in Urine