Chlordane in Tecolote Canyon

Chlordane is a pesticide that was commonly used to control various insect populations in the United States from 1948 to 1988. However, when it was discovered that this pesticide is highly toxic to humans, all approved uses of chlordane were cancelled. Although it is doubtful that new chlordane-contaminating sources are emerging, it is very likely that chlordane is still present in our environment due to it degrading at a very slow rate, allowing for it to remain in soil for over 20 years. Currently, humans can be exposed to chlordane by living in homes that were treated with chlordane in the past to exterminate termites or by digging in soil where chlordane was applied. The Environmental Protection Agency (EPA) provides much more information regarding the sources and potential means of human of exposure to chlordane, which can be found here. Also, here is a very interesting and amusing video clip from the 1959 film, “Goodbye, Mrs. Ant,” which instructs how chlordane was to be used as a pesticide before being banned. According to the EPA, the acute effects of chlordane consist of gastrointestinal distress and neurological symptoms, such as tremors and convulsions. Also, chronic inhalation of chlordane can results in serious effects on the nervous system. It is clear that chlordane pollution can be a serious issue to human health if not properly controlled.

In 2010, it was found that chlordane levels in the Tecolote Canyon area in San Diego, California have been declining since 2007. This year, Environmental Chemistry students attending the University of San Diego have conducted a study to see if this trend continues by revisiting many of the sites previously tested in the Tecolote Canyon and measuring the chlordane concentration in collected sediment samples. Furthermore, soil was characterized by particle size distribution, pH level, and the percentage of water, calcium carbonate, and organic matter to see if any of these sediment properties correlate with chlordane concentration. The sampling locations included the river near the YMCA, Tecolote Creek, the creek near the transformer station, Mission Bay, and Fiesta Island. From the data that was collected, it was determined that chlordane was present in all sediment samples with concentrations ranging from 46.5 to 450.4 ppb. The order of highest to lowest average chlordane concentration was determined to be as follows: Mission Bay (357 ppb), Fiesta Island (316 ppb), the creek near transformer station (224 ppb), the creek near YMCA (189 ppb), and Tecolote Creek (132 ppb). When compared to concentrations measured in past years, it was difficult to determine whether or not chlordane levels have continued to decrease due to the fact that some sites contained more chlordane currently while others contained less. Based on these results, more investigation is needed in order to more accurately determine how chlordane concentrations have changed over time. 

High chlordane levels did not seem to correlate with any of the sediment properties measured (particle size distribution, pH, % water, % calcium carbonate, or % organic matter); however, a trend was asserted based on the geographical location of the sediment samples and their respective chlordane concentration. Due to the fact that the samples collected from Mission Bay and Fiesta Island had the highest average chlordane concentrations, it was postulated that the ocean, which drains directly into these two locations, might serve as a chlordane source. Also, with Mission Bay and Fiesta Island being much more residential areas than the other sites tested, it is possible that residential runoff is another source of this toxic pesticide. Overall, this study supports that chlordane continues to wash through the Tecolote Canyon area.