Understanding Benzene—the chemical with a license to kill

This "Chemical of the Quarter" excerpt is from the U.S. Coast Guard “Proceedings of the Marine Safety & Security Council” magazine and was written by Dr. Alan Schneider, formerly of the U.S. Coast Guard Office of Operating and Environmental Standards.


Benzene

What is it?
Benzene is a flammable liquid used to make many chemicals that, in turn, go into common consumer products like plastics, rubber, nylon, dyes, detergents, drugs, synthetic fibers, and pesticides. It’s used as a solvent in paints, varnishes, and lacquer thinners. Because it is so versatile, benzene is shipped in very large quantities as a pure chemical, as well as in mixtures.

How is it shipped?
Benzene boils at 176°F, so it is typically carried unpressurized at room temperature in tank ships and tank barges.

Why should I care?
Benzene is a very common cargo. It is also very dangerous. For example:

• Benzene is flammable and explosive.
• Benzene is a known carcinogen.
• Benzene attacks the lungs, blood, bone marrow, central nervous system, liver, kidneys, and women’s reproductive organs.
• It irritates skin and eyes.
• Ingesting benzene may lower blood pressure and cause vomiting, nausea, dizziness, and loss of consciousness.

Shipping concerns. Benzene vapor may be released during normal cargo venting and transfer operations and during tank cleaning. Because it is heavier than air, the vapor can accumulate on the deck, possibly in concentrations high enough to be damaging or fatal.

Health concerns. How much benzene is “bad”? The official exposure level to avoid is more than 0.5 ppm (parts per million). That's the amount that can be in the air you breathe every day at work (for up to a 30-year career) and not get sick.

Benzene is a dangerous chemical, but years ago people didn’t know this. At one time it was a standard practice for workers to wash grease and oil off their hands with benzene.

What’s the Coast Guard doing about it?
The Coast Guard has detailed rules regarding benzene. You'll find these in the Code of Federal Regulations (46 CFR Subchapter D, 46 CFR Subchapter O, 46 CFR 197 Subpart C).

Benzene safety depends on you. The rules can be inconvenient. For example, it can be uncomfortable wearing a respirator continuously during warm weather, but you have to follow the rules if you want to live to retirement age. Too many marine workers have died from leukemia and other diseases linked to benzene exposure.

For more information:
Full article is available at http://www.uscg.mil/proceedings/fall2009.

Subscribe online at http://www.uscg.mil/proceedings/subscribe.asp.