Benzene is an organic compound that is a colorless or light-yellow liquid that has a relatively high melting point. It is highly flammable, has a sweet odor and quickly evaporates into air. Its vapor is heavier than air, which makes it sink into low-lying areas. Benzene dissolves only slightly in water and floats on top of it. Its molecular formula is C6H6 (sometimes abbreviated Ph–H).
Benzene is formed from both natural and man-made processes. Natural sources include volcanoes and forest fires. Benzene is also a natural constituent of crude oil and gasoline. Its most widely-produced derivatives include styrene, which is used to make polymers and plastics, phenol for resins and adhesives and cyclohexane, which is used to manufacture Nylon. Smaller amounts of benzene are used to make certain types of rubbers, lubricants, dyes, detergents, drugs, explosives, napalm and pesticides.
Exposure to benzene is a global health problem and has serious health hazards. People working in industries that make or use benzene may be exposed to the highest levels. Other means of exposure include:  
  • Outdoor air, which contains benzene from tobacco smoke, gas stations, motor vehicle exhaust and industrial emissions.
  • Indoor air, which generally contains higher levels of benzene than outdoor air. This comes from products such as glues, paints, furniture wax and detergents.
  • The air around hazardous waste sites or leaks from underground storage tanks that also contaminates well water.
Immediate signs and symptoms of exposure to benzene — effects that can appear within minutes or several hours — include drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion and unconsciousness. Eating or drinking foods containing high levels of benzene can cause vomiting, irritation in the stomach, dizziness, sleepiness, convulsions and death (at very high levels).
The major effects of benzene are manifested via long-term exposure (exposure of one year or more) through the blood. Benzene damages the bone marrow and can cause a decrease in red blood cells, leading to anemia. It can also cause excessive bleeding and depress the immune system, increasing the chances of infection. Benzene causes leukemia, particularly Acute Myeloid Leukemia or Acute Non-Lymphocytic Leukaemia (AML & ANLL) and is associated with other blood cancers.
The U.S. Environmental Protection Agency has set the maximum permissible level of benzene in drinking water at 0.005 milligrams per liter (0.005 mg/L). The EPA requires that spills or accidental releases into the environment of 10 pounds (4.5 kg) of benzene or more should be reported to the EPA.
The U.S. Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 1 part of benzene per million parts of air (1 ppm) in the workplace during an 8-hour workday, 40-hour workweek. The short term exposure limit for airborne benzene is 5 ppm for 15 minutes.
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(Text by Purvi Gajjar)

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