Chlordane in Sligo Creek

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Health of Sligo Determined Using Asiatic Clams

• Pp 6-7. Chapter One:



• The Problem and Its Setting: Introduction to the Problem.


Sligo Creek, an Anacostia watershed stream, is a beautiful stream in a residential area that serves as a site for contact with nature for the proximal residents. The citizens of the Anacostia watershed area are considering naming Sligo Creek a model stream in the area. This would mean that Montgomery County's cleanup crew would make a conscious effort to provide a cleaner and more stable environment for the surrounding ecosystem, using Sligo as an example. This effort is intended to both measure the success rate of the cleanup effort and to encourage other Anacostia watershed area stream residents to pay attention to the struggling ecosystems around them, and while this is a valiant cause, the driving force behind it has not yet run a full toxic panel on the stream. Essentially, the caretakers of Sligo know very little about the toxic levels in the stream. This study will give those who are invested in Sligo Creek's health more information about the toxins present as well as adding to the information available about the stream.


• Hypothesis


Based on observations of Sligo Creek as a physically healthy stream with defined banks, as well present vertebrate populations, if any toxins are present at all, they will be in trace amounts.
• Pp 30-32. Chapter Five: Conclusions (Summary)

Sligo Creek presented as a biochemically healthy stream and was elected to serve as the model stream for an Anacostia Watershed cleanup effort. However, the stream never had a toxic panel run on it and very little information was known about the chemical and toxic makeup of the water. The purpose of this study was to clarify the chemical status of the stream and make more information available for interested parties including residents, scientists and regulatory groups.

The Asiatic Clam was used in this study as a bioaccumulator to measure trace amounts of toxins and pollutants in the water. The clams were used to find PAHs (Polycyclic Aromatic Hydrocarbons), PCBs (Polychlorinated Biphenyls and Heavy Metals (editors note: they were 67 EPA Priority Pollutants including 21 Pesticides plus six metals). These are all violently toxic and the presence in the water indicates poor stream health and a need for a significant cleanup effort.

The clams were collected from Fort Foote and placed in mesh baskets and placed at two sites in Sligo Creek. Each site contained 40 clams and the combined tissue was sent to a Test America lab in Burlington VT. The results were presented as three data systems: Sligo Creek Upper (SCU), Sligo Creek Lower (SCL) and Fort Foote (FF) which was used as the reference site. Fort Foote is a healthy functioning ecosystem, and was used as a control when performing statistics. The data was analyzed using Excel's Data Analysis T Test: Two-Sample assuming Unequal Variances. The data is presented in parts per billion.For all but two data points, there was not a significant enough difference to say that levels in Sligo indicate that it is a polluted stream. For two levels, however, the P-value in the T-Test was below 0.5, indicating that the two sets of data were significantly different. Specifically, Chlordane and the Semivolatile Componds in Sligo Creek Lower as both 2-3 ring structures and 4 ring structures (editors note: PAHs) should be examined. There is cause for concern as the presence of these compounds indicates just the beginnings of a dangerous problem for the residents and the ecosystem that are dependent on Sligo Creek.

Even though the hypothesis {'if any toxins are present at all, they will be in trace amounts'} for the most part, was disproved, there is significance in the measurements that were taken and there is a hope that a continuation of this research could make it clear to the community that Sligo has significant levels (of) toxic chemicals."


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Update: March 29, 2010

Two more sets of clams were placed in upstream sections of Sligo Creek, one set in the Wheaton Branch and one set in the main stem, for chlordane concentration analysis. Higher chlordane levels were found in the upstream main stem. Friends of Sligo Creek arranged for a meeting between Dr. Phelps and the Department of Environmental Protection to discuss the findings, scheduled for April 2010.



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Update: May 21, 2010

The Gazette had an article on April 28th reporting on Dr. Phelp's finding high levels chlordane in Sligo Creek. This article also reported: "In 2007, MDE conducted its own clam studies in the Anacostia Watershed, including Sligo Creek, and did not find excessive levels." Because the Department of Environmental Protection decided they wanted an MDE representative to attend the meeting with Dr. Phelps that had been scheduled to take place in April, the meeting was postponed and is now likely to take place in late June. Friends of Sligo Creek contacted the Maryland Department of the Environment for their findings, and they sent a small printout showing the results for chlordane from their 2007 study.

Because Dr. Phelp's studies found Sligo chlordane levels ranging between about 200-500 parts per billion, while the Maryland Department of the Environment's study found them between 1-2 parts per billon (i.e., nanograms/gram), the labs used by Dr. Phelps and the MDE are now talking with each other to try to figure out the reason for the discrepancy. The MDE's findings are shown here:

2007 MDE Clam Tissue Station Results for Total Chlordane in Sligo Creek (data under review)

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	ANAR-05A (Sligo Creek at Riggs Road)			ANAR-05A (Sligo Creek at Riggs Road)			ANAR-08B (Sligo Creek at Colesville Road)			ANAR-08B (Sligo Creek at Colesville Road)
	2 week reported values (ng/g wet wt)	method detection level (ng/g wet wt)	adjusted values	4 week reported values (ng/g wet wt)	method detection level (ng/g wet wt)	adjusted values	2 week reported values (ng/g wet wt)	method detection level (ng/g wet wt)	adjusted values	4 week reported values (ng/g wet wt)	method detection level (ng/g wet wt)	adjusted values
Oxychlordane	0.00	0.10	U	0.03	0.10	U	0.01	0.10	U	0.04	0.10	U
trans Chlordane	0.15	0.10	0.15	0.40	0.10	0.40	0.43	0.10	0.43	0.54	0.10	0.54
trans Nonachlor	0.17	0.10	0.17	0.61	0.10	0.61	0.43	0.10	0.43	0.54	0.10	0.54
cis Chlordane	0.15	0.10	0.15	0.54	0.10	0.54	0.48	0.10	0.48	0.62	0.10	0.62
cis Nonachlor	0.08	0.10	U	0.23	0.10	0.23	0.18	0.10	0.18	0.20	0.10	0.20
Methoxychlor	0.00	0.10	U	0.00	0.10	U	0.00	0.10	U	0.00	0.10	U
Total Chlordane			0.47			1.78			1.51			1.91


Notes:
<0.1 ng/g are reported for information purposes only, i.e. compound was quantified below method detection levels
U - compound was analyzed, but detected below method detection level
Total Chlordane is defined as the sum of cis chlordane, trans chlordane, cis nonachlor, trans nonachlor, and oxychlordane reported above method detection levels.



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Update: July 13, 2010

A meeting was held at the Department of Environmental Protection headquarters in Rockville on June 25th. Attending were Keith VanNess, Meo Curtis, and Steve Shofar from the Department of Environmental Protection, Dr. Harriette Phelps, Bruce Sidwell from Friends of Sligo Creek, and representatives of the Maryland Department of the Environment, Charlie Poukish and Chris Luckett.

Dr. Phelps and the MDE have used clams for water quality studies in the Anacostia, most recently in Sligo Creek. Field methods are very similar, but lab methods may vary and the variability must be understood so that results can be comparable. By the end of the meeting, DEP, the MD scientists and Dr. Phelps agreed that the lab chemical assay methodology should be re-visited using standardized clam samples. It may be that samples that show high levels of Chlordane are due to a lab method that did not completely separate out non-chlordane compounds at the chlordane peak site. At the meeting, MDE agreed that three labs would assay the standards: the one used by Dr. Phelps, the one routinely used by MDE, and a third lab - likely a USGS lab. Hopefully, this work can be done in the next several months. Meanwhile, it seems unlikely that a new clam bioassay will be run by either Dr. Phelps or MDE until the comparability issue is resolved. However, MDE will be conducting water analysis for chlordane in lower Sligo this year.