The Problem

For over a century , dioxins – and specifically chlorinated dioxins – have been notorious as some of the most toxic and persistent environmental pollutants. This means that these man-made chemicals don’t easily break-down, remaining stable in our ecosystems for many decades. Among a large family of dioxin compounds, a chemical known as TCDD is by far the most toxic.

The toxicity of TCDD is such that varying doses of the toxin had caused cancer in all animals tested and had affected nearly all of their organs. Severe developmental and birth defects are observed in exposed animals and humans as well. TCDD is more toxic than cyanide, ricin and even plutonium. A dose as small as a peanut can kill several adult elephants.

Now, TCDD’s extreme toxicity is only one of the reasons we decided to address this issue. Another reason involves its chemical features. TCDD is both a dioxin and a poly-chlorinated compound, which are two distinct types of ubiquitous pollutants. By creating a degradation pathway for TCDD, we, in turn, create a solution for both types of pollutants.

If, despite TCDD's extreme toxicity and its pervasiveness, there existed solutions practical enough to truly address TCDD pollution on the global scale that it is found, we would not have devoted ourselves to this issue. However, to date, the existing solutions are astoundingly impractical and inefficient.

For example, during the Vietnam war in the 60’s, tens of thousands of kilometers of land were heavily sprayed with an herbicide called Agent Orange, which was used to clear heavily forested areas for combat purposes. But TCDD was an unintended byproduct of Agent Orange production; thus, the military had unknowingly contaminated all of that land with this toxin. Even today, over 50 years after the events took place, the United States is spending hundreds of millions of dollars to reclaim that land.

The method currently being used to decontaminating soils in Vietnam involves the transport of only the most heavily contaminated soils to a castle-sized, makeshift “oven” that burns the soil at temperatures of about 350°C. Although this method successfully rids soils of their dioxin contaminants, they can only gather so much soil for purification. It doesn’t even begin to address the thousands of kilometers of forests, rivers and lakes that stretch beyond the reach of this clean-up project… And yet, it is the only method of TCDD purification being used today.

It is important to note that dioxin pollution is found in small amounts nearly everywhere in the world – soil-burning is far too inefficient and expensive to deal with these types of contaminations. Furthermore, this solution is detrimental to the ecosystem, killing essential microbial communities [in the soil] and destroying the soil’s structure.

Our motivation for addressing the issue of global TCDD pollution is that this problem can and should be solved through synthetic biology in an efficient and ecologically safe manner. We wanted to find a solution that treats ubiquitous contamination on a global, not local, scale. As many of us are students of Agroecology and Plant Sciences, it quickly became clear that our teams’ passion for the environment would guide our decision, eventually leading us to a this project in bioremediation.