It is a recognized carcinogen.
Benzene primarily attacks the blood-forming tissues of the body. Benzene damages the bone marrow where red blood cells, white blood cells and platelets are formed. These three components make up the blood and a shortage of any one of them will result in serious blood disease. Benzene is known to affect all three of these components and thus workers exposed to benzene show a variety of blood diseases.
Among the various blood diseases are anemia (shortage of red blood cells); leukopenia (shortage of white blood cells); and thrombocytopenia (shortage of platelets).
Most serious is benzene's ability to cause leukemia, a fatal cancer of the white cell producing tissue. There are many types of leukemia classified by the duration and character of the disease as well as the type of cell involved. Acute leukemia, as the name implies, progresses rapidly while chronic leukemia develops slowly.
Acute poisoning refers to an exposure to a high level of benzene in a short period of time. This type of exposure usually happens in an enclosed space such as a tank or vessel with benzene residues, or from spills or equipment failure. Acute poisoning affects the central nervous system with symptoms such as dizziness, excitement, staggering gait; also headache, nausea, fatigue, insomnia, flushed face, incoherent speech, tingling in hands and feet. Symptoms can last up to two weeks and the length of recovery will depend on the severity of exposure. However, if the exposure is severe enough, the breathing center of the brain is paralyzed and death occurs.
First aid for acute poisoning: keep the victim calm and quiet and move the victim to fresh air; CPR may be necessary. If benzene has come into contact with skin or eyes, remove contaminated clothing and flush affected area for 15 minutes.
Chronic poisoning refers to exposure to low levels of benzene over a long period of time. This is the more common form of industrial benzene poisoning. In addition, if a person is rescued from an acute exposure, he or she may then develop chronic, long-lasting effects.
Symptoms of chronic benzene poisoning are vague and thus deceptive. Tiredness, dizziness, headache, nausea, loss of appetite, weight loss and general weakness can easily be attributed to other causes. It is only later in the course of the disease that nosebleeds, bleeding gums, pallor and purple disfigurations appear. Benzene may also cause damage to chromosomes, and that chromosomal damage also confirms the cancer-causing potential of benzene.
The action level of 0.5 ppm triggers other provisions of the standard including methods of compliance, personal protective equipment, employee monitoring, medical surveillance, medical removal protection, hazard communication, regulated areas and record-keeping. Loading and unloading operations at bulk wholesale storage facilities which use vapor control systems for all loading and unloading operations are excluded.
The Standard lays out the requirements for initial air monitoring, periodic monitoring, and monitoring frequency. Representative 8- hour time weighted average (TWA) employee exposures shall be determined on the basis of one sample or samples representing the full shift exposure for each job classification in each work area. To determine compliance with 5 ppm, 15 minute STEL, operations should be measured where exposures are believed to be high such as where tanks are opened, filled, unloaded or gauged; where containers or process equipment are opened and where benzene is used for cleaning or as a solvent in an uncontrolled situation.
If the initial monitoring shows employee exposure above the TWA, the employer shall repeat the monitoring at least every six months. If the initial monitoring shows exposures at or below the TWA, the employer shall repeat the monitoring for each such employee every year. The monitoring frequency depends on the exposure levels. The employer is required to monitor whenever there is a change in production, process, control equipment, personnel or work practices which may lead to additional or new benzene exposures. Employees have to be notified, within 15 working days of receipt of results, of the monitoring results and employees or their designated representatives must be allowed to observe the monitoring.
Your employer has to establish a regulated area limiting access to authorized persons, when benzene concentrations exceed or are expected to exceed the permissible exposure limits, either the 8- hour average or the 15-minute limit. Note: OSHA considers "designated representative of employees" for the purpose of exercising the right to observe monitoring and measuring procedures as an authorized person.
Methods of Compliance.
Unless the employer can prove they are unfeasible, engineering controls and work practices must be used to control benzene exposure levels.
When exposures are over the PEL, the employer shall establish and implement a written program for reducing exposures and copies must be made available upon request to employees and designated representatives.
Respiratory protection should never be a substitute for proper engineering controls; i.e., substitution and direct exhaust ventilation. Respiratory protection can be used:
a. if feasible controls cannot be implemented
b. during implementation of engineering controls
c. during emergencies The respiratory protection program must be an OSHA approved program and comply with 29 CFR 1910.134.
Protective Clothing and Equipment
It "shall be worn where appropriate to prevent eye contact and limit dermal exposure to liquid benzene. Protective clothing and equipment must be provided by the employer.
Components of initial, periodic, and emergency medical examinations are specified. The Standard states what must be included in a physician's written opinion to the tested employee. Outlines the medical removal protection plan which provides a 6-month rate retention clause for employees who must be temporarily removed from exposure and a permanent guarantee for permanent job removals. The employer shall maintain the current wage rate, seniority and other benefits as though the employee had not been removed.
The Standard also calls for signs and labels, information and training, and record- keeping. For exposure monitoring, records should be maintained for at least 30 years and for medical records, duration of employment plus 30 years.
* When a safer substitute is available, benzene should
never be used.
* In the production as well as use of benzene as a raw material or intermediate in chemical manufacture, the process should be completely enclosed. A regulated area should be established so that entry and exit into a benzene area is controlled. Direct exhaust ventilation should also be provided to control possible exposure during maintenance and repair work.
* Regular air monitoring for benzene should be conducted to determine if control measures are effective. Employees should be allowed to observe the monitoring and results should be retained for 40 years and available to employees upon request.
* Workers at risk of exposure shall be provided with appropriate protective clothing (coveralls or other full-body clothing) and gloves impervious to benzene which should be changed daily and laundered at the company's expense. Separate lockers should be provided for work clothes and street clothes. Showers should be taken at the end of the shift before the employee goes home, and shower time should be provided.
* The company should provide every worker with a booklet outlining how and where benzene is used in the plant, safe methods of handling, hazards involved, proper maintenance and cleanup methods, proper respirator usage and a description of medical surveillance and air monitoring programs. The booklet should also contain a description of emergency first aid procedures for benzene.
* Where there is the possibility of contact with liquid benzene, splash-proof face shields and goggles must be worn.
* Special procedures should be set up for maintenance work and entry into tanks or other enclosed spaces.
(a) Annual physical examinations, including medical history. The medical history need only be taken initially and should include history of exposure to benzene and other chemicals toxic to the blood; information on bleeding abnormalities, kidney disease and liver disease.
(b) Complete blood count, including hematocrit, hemoglobin, mean corpuscular volume, white blood cell count including differential, and platelet estimation from the differential slide.
(c) Reticulocyte count.
(d) Serum bilirubin.
(e) Urinary phenol.
* Used extensively in the manufacture of a large number of chemical compounds because it reacts easily with various chemicals, making the production of new chemicals much easier and faster. Used in the making of styrene, phenols, detergents, explosives, medicines, dyes.
* Was used widely as a solvent. Its ability to dissolve organic compounds made it popular in the production of rubber, plastics, paints, inks, oil, fats. It vaporizes easily and was used in processes where fast drying was necessary.
Revised January 1993. Information originally published in "Lifelines" January, 1977; OCAW Health and Safety Alert October 1987;and Benzene: Is it Dangerous? by Stellman, Cottingham & Hricko 1972.