Chlordane is among us!

Image obtained from:;pid=452106;d=this

Chlordane’s rocky history

In Rachel Carson’s book Silent Spring (published in 1962), Carson warns the readers against the evil chlordane, a chemical that is capable of mass destruction on both the environment and the health of humans and other organisms. It was introduced to the US in 1947 as an insecticide to control pests. Despite Carson’s warnings, chlordane was not restricted by the EPA until 1983. Even in 1983, it could still be used for termite control. Now, thankfully, it is only permitted for fire ant control in power transformers. Why exactly did the EPA finally decide to ban chlordane? Because chlordane was proven to negatively impact the nervous system, digestive system, thyroid, and liver. It also was shown to be a potential cancer risk, and was able to build up in body fat of humans and animals AND soils. Are those enough reasons for you? Sure is for me!

So if it is banned, what is the problem?

Even though the chemical has been heavily restricted for many years now, we still see it in our environment! Why? Because it is very persistent and does not biodegrade at all. Once applied, a good portion of it remains unaltered in the environment. Eventually, the chlordane might slowly evaporate into the atmosphere or leach out into water, but typically you can easily find chlordane in soils and sediment in pretty high concentrations.

But how am I exposed to it, exactly?

Well, if you have lived in a home that was treated with chlordane for termites, you have probably had the highest level of exposure to it. You can also ingest chlordane-contaminated food! How? Because when food is grown, the soils likely still have chlordane in them from when it was commonly used way back in the 70’s (or earlier)! Chlordane also can be found in fish and shellfish caught in chlordane-contaminated bodies of water. Also, when other animals eat these fish, then they store the chlordane in their body fat. When we eat the animal fat, we store the chlordane in OUR fat!

Taking matters into our own hands!

Our environmental chemistry class measured this dangerous pesticide in samples of sediment, and found some chlordane presence in every single sample we analyzed. In fact, a few locations in Tecolote Canyon even had as much as ~530 ppb! According to the EPA, drinking water should contain no more than 0.5 ppb for children or 2 ppb for adults if they drink the water for a long period of time. Additionally, crops should have no more than 300 ppb and animal fat and fish should have no more than 100 ppb. 530 ppb seems like a lot now, right? Even though the content in the soil may be higher than in the water, crops, and animals, it is still something to think about as it can accumulate in organisms (including humans) very quickly.

The “good” news

This is not the first year that USD’s environmental chemistry class measured chlordane concentration in sediments in Tecolote Canyon. Previous classes in 2005, 2007, 2010, 2012, and 2014 also measured chlordane concentrations. From compiling all of the concentrations, the general concentration of chlordane in the Tecolote Canyon is decreasing. So, it seems reassuring that chlordane concentrations are not increasing… the banning finally seems to work!

Take home message

Although chlordane concentrations may be decreasing in the environment with time, we should be aware that we are always coming into contact with the dangerous chemical. It is pretty scary that we can still take relatively random samples and find chlordane concentration in every single one. It is especially concerning since this pesky compound likes to build up in our fat! We should not only be cautious about chlordane, but also about other pesticides that are still currently being used. Be careful when using them on your own gardens… some man-made pesticides can have long lasting effects on our beautiful Planet Earth!

Image obtained from:



  1. Anderson Marcia. EPA Ban on Chlordane (accessed Apr 18, 2018).
  2. De Haan, David et al. USD environmental chemistry lab notebook
  3. Toxic Substances Portal – Chlordane (accessed Apr 18, 2018).

One thought on “Chlordane is among us!

Leave a Reply

Your email address will not be published. Required fields are marked *