Tag Archives: EPA

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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Tryone Hayes and the global decline of amphibians

By: Justin Scioli

Dr. Tyrone Hayes is the kind of guy that is impossible to not admire. While growing up, a young Hayes spent his free time chasing frogs, his greatest passion, through the swamps and woodlands of his native South Carolina. He took his passion in Herpetology, the study of amphibians and reptiles, all the way to Harvard University to receive his undergraduate biology degree and to UC Berkeley to receive his doctorate and later to join the faculty. But the most admirable thing about Hayes is that he is a hard-nosed scientist, keeping his data unbiased even when the results are ugly truths that many people don’t want to face. And some of Hayes’ findings are quite ugly, especially to some powerful chemical corporations.

Hayes has been primarily studying the effects of chemicals, specifically pesticides, on development of amphibians. Many of his studies examine the effects of Atrazine, the most commonly used herbicide in the United States and one of the most common in the entire world. Atrazine is used to kill weeds in crops, however like all chemical pesticides it is easily spread through runoff. This runoff carries the potent pesticide into nearby rivers, lakes, and other bodies of water where it affects the flora and fauna there.

In 2002, Hayes published a study that examined the effects of Atrazine on the sexual development of African clawed frogs (Xenopus laevis) which have been introduced in North America. The results showed that even a very small amount of Atrazine was capable of causing a tenfold decrease in testosterone levels in male frogs, making them into hermaphrodites. Hayes believes this is because Atrazine induces Aromatase which promotes the conversion of testosterone into estrogen. This basically means reducing the stuff that makes boys into boys. Of course this has detrimental effects on the sex ratio of frog populations, and Hayes believes the use of pesticides could be a major factor in a worldwide decline in amphibian populations.

Since the 1980’s amphibians, like frogs and salamanders, have been declining severely. The rate of extinction in this group is 211 times the background extinction rate, meaning that they are going extinct 211 times more frequently than rate of natural extinction recorded due to geological and ecological changes in the environment. Many causes are believed to contribute to this massive decline. In addition to pesticides, culprits such as sound pollution that interferes with vocal communication, the spread of a fatal fungus, as well as climate change and habitat destruction that is affecting nearly all life on earth. The loss of an entire class of animals would spell serious damage to food webs from the tropics to temperate regions, and some ecosystems are dependent on amphibians as an entire trophic level of organisms. What Hayes and other biologists are extrapolating from the amphibian decline is even closer to home for us.

Amphibians are a very sensitive group, largely because they absorb water through their skin. This makes them an ideal “canary in the coalmine” for seeing the levels of chemical toxicity due to pollution in a given environment in which they are naturally occurring. When amphibians are dying, that is a good sign that toxicity levels are increasing. More and more studies are showing the detrimental effects of pesticide exposure on human health. In a talk given in 2008, Hayes discussed that levels of toxicity are shown to be lower in breastfeeding women. This is due to the fact that they are excreting toxin through their breast milk and thereby transferring it to their child. Frog or human, developmental stages of life are much more sensitive to toxic pesticides than adults. This spells compromised immune systems for the young and developing, and the fact that Atrazine is the most common contaminant in ground, surface and drinking water is concerning for many.

The European Union banned the use of Atrazine in 2004. The United States on the other hand continues not just to use it in agriculture but to allow a given concentration of it in drinking water. Recent studies show that the allowed amount of Atrazine can lead to low birth rates, birth defects and menstrual problems. Despite this, the EPA continues to suggest that there is no need for concern and is not officially suggesting water filters to pregnant mothers. They will not review those studies until next year at the earliest, and in the meantime pregnant women throughout the U.S. could be sipping up Atrazine any time they drink from a tap.

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