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Dangerous Dioxins

By: Lizzie Caldwell

According to Chemical And Engineering News, the US Environmental Protection Agency(aka EPA, largest government agency in the US to protect human health and the environment) has recently proposed to tighten its guidelines for remediation dioxins and related chemicals in soils.

Dioxins are chemicals that are extremely dangerous for humans. The full name is “polychlorinated dibenzodioxins”. This name sounds long and complicated, but let’s break it down.

“Poly” means multiple. “Chlorinated” means it has chlorine, so we know that a typical dioxin molecule has multiple chlorines as a part of it. We’re halfway there!
“Di” means two. “Benzo” is the prefix for “benzene”, which is a 6 carbon ring:

Benzene molecule.

The C is carbon, the H is hydrogen, and the lines represent that the two atoms are connected. Two lines means the connection is “stronger” than one line, etc. Beside it is its shorthand version, which is what is commonly used.

Benzene is the simplest carbon ring ever, and it is everywhere. It is used to make plastics, rubber, drugs, and dyes. It used to be in our gasoline, until we realized that benzene causes cancer. Thus, from this name, we already know that the molecule is bad. For the last part, “di” means “two”, and “oxin” is the prefix for oxygen; thus, polychlorinated dibenzodioxin has two benzene rings, two oxygens, and a variable amount of chlorine atoms(which can be anywhere from 1 to 8). These molecules are generally referred to as “dioxin” for short.

PCDD, or polychlorinated dibenzodioxin. (The “n” and the “m” just symbolize that there are chlorines present, it just depends on the dioxin as to how many chlorine atoms on each benzene ring.)

How is dioxin worse than benzene? This rule can be applied to any molecule: organic molecules that occur in nature, like benzene, break down rather quickly. Organic molecules with chlorines attached to them, like most dioxins, make the molecule very stable. Thus, while benzene causes cancer, it only lasts from 3 – 10 days before it breaks down and is no longer dangerous. Dioxin, on the other hand, lasts from 7 – 10 years(Dioxinfacts.org). Imagine how many cancer-causing molecules one individual can accumulate if they lived near a place that produced dioxin molecules!

One type of dioxin, called “tetrachlorinated dibenzodioxin”(that means it has 4 chlorines. tetra = 4) is a powerful herbicide.

Picture of TCDD(tetrachlorinated dibenzodioxin).

It kills vegetation by making it grow uncontrollably until it dies. It is a byproduct of the molecules used to make Agent Orange. It was used during the Vietnam war, and the dioxins are still found in their soil today. The National Toxicology Program defined it as a cancer-causing molecule, and has been linked with non-Hodgkin’s lymphoma, Hodgkin’s disease, and chronic lymphocytic leukemia. It has affected the lives of hundreds of thousands of people; Europeans, veterans who were also exposed, and now, residents of the state of Michigan.

How did dioxins get to Lake Huron? Normally, dioxins are created in manufacturing plants. Manufacturing plants use a lot of fire and heat to make whatever they need; and when heat and chlorine are present around organic molecules(like benzene, a 6-carbon ring), a reaction happens that creates dioxins. Manufacturing plants don’t mean to make dioxins, it’s just a by-product of their process to make the chemicals and products they want to sell to you.

One of the unfortunate characteristics of dioxin is that it is aromatic – which means that it evaporates into thin air, there it can be easily distributed. This is how dioxin ends up in close lakes, and in the soil. Dioxin is a very expensive and inconvenient responsibility that EPA cleaned up for years. In 1998, the EPA made it the company’s responsibility to clean up the mess, and they set up guidelines. Now, with new reports claiming that dioxins are also present in soil, EPA wants to strengthen its guidelines to include soil. Dow Chemical’s spokeswoman criticizes the new guidelines, saying that “Soils aren’t really a primary route of exposure”(Chemical and Engineering News, Jan 2010). Luckily for Dow, the EPA cannot implement these new guidelines until it finishes reassessing health and environmental risks associated with dioxins; but we can all agree we don’t want dioxins around, isn’t that right, Ukrainian politician Viktor Yushchenko?

Before dioxin poisoning                  After dioxin poisoning


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