What is benzene?
C6H6 is a clear, colorless, volatile, non-corrosive, highly flammable, fat-soluble liquid at room temperature with a strong aromatic odor. The major use of
C6H6 is as a chemical intermediate in the manufacture of consumer goods. In addition, C6H6 and its derivatives are used in dyes, lubricants, solvents,
cleaning products, drugs, pesticides and other agricultural chemicals. Most of the C6H6 produced is a component of petroleum fuels such as gasoline.
Sources of benzene
There are three main sources of human exposure to C6H6 : environmental, occupational and through consumer products. C6H6 can be released into the
environment from a variety of sources:
1) Gasoline filling stations
2) Underground leaking petroleum storage tank
3) Vehicle exhaust fumes
4) Cigarette smoke
5) Waste water from industries that use benzene
6) Poorly maintained toxic waste sites
7) Chemical spills
8) Contaminated surface or groundwater
9) Some food products that contain C6H6 as a natural constituent
Occupational exposure can occur in a variety of settings. Some of the more significant exposures are associated with the rubber industry, shoe manufacturing,
chemical plants, oil refineries, gasoline storage and shipment and retail stations. Consumer products that contain benzene include household cleaning products,
glues, adhesives, art supplies, cigarettes, paint, varnish, stain removers and gasoline. Very small amounts of benzene are found in some foods.
Routes of exposure and health effects
C6H6 can enter the body when a person breathes air or eats or drinks food or water that is contaminated. C6H6 is readily absorbed into the body. Entry
into the body following direct contact with the skin does not occur as readily. Once C6H6 enters the body, it is widely distributed to tissues. Accumulation in
body fat is slow; however, the total potential uptake is high in these tissues because of the high lipid solubility of C6H6 . The primary route of environmental
exposure of the general public to C6H6 is through inhalation. C6H6 is commonly found in the environment and inhalation of C6H6 from cigarette smoke
is also a concern.
Occupational exposure to C6H6 is mainly through inhalation of the vapor; however, skin contamination with the liquid also occurs. Occupational exposures
provide a much greater risk of causing adverse health effects.
Groundwater can be contaminated with C6H6 as a result of illegal dumping, leaking from storage tanks and through leaching from waste disposal
sites. Human exposure via contaminated water can occur from consumption (drinking water), direct contact (showers, baths) and inhalation (showers, baths).
C6H6 is considered to be a human carcinogen by the World Health Organization, the International Agency for Research on Cancer, the U.S. Environmental
Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA). Exposure to C6H6 through inhalation or ingestion may produce
adverse effects in the blood, on the central nervous system, and the immune system. Human health studies have demonstrated significant excesses of leukemia,
multiple myeloma, and lymphatic cancers as well as chromosomal aberrations.
Human health studies also have shown that breathing air containing C6H6 affects the central nervous system causing effects such as dizziness, headache,
nausea and vomiting, fatigue, blurred vision, irregular heart rate and drowsiness, as well as eye, nose and throat irritation. Exposure to C6H6 has the potential
to decrease the body's ability to overcome infection. Repeated or prolonged contact with liquid may cause dermatitis.
Regulatory and advisory standards
The EPA has established a Maximum Contaminant Level of five micrograms per liter (�g/L) for C6H6 in water. The OSHA regulates C6H6 in the workplace.
The Permissible Exposure Limit for an eight-hour workday is one part per million (ppm) as a time weighted-average (TWA).