Reregisteration of Diazinon and Chlorpyrifos

G. Fred Lee & Associates
27298 E. El Macero Drive
El Macero, California 95618
ph: (530) 753-9630 fx: (530) 753-9956

December 27, 1997

Ben Chambliss
Mail Code 7508W
401 M Street, S.W.
Washington, D.C. 20460

Dear Mr. Chambliss:

Previously, I have contacted you concerning the work we have been doing on diazinon and chlorpyrifos toxicity. I wish at this time to provide you with a copy of a report covering the first year of this work. This work further supports that diazinon and chlorpyrifos are a widespread cause of toxicity in urban area streams and rivers. The problems are due to the use of these chemicals by homeowners for structural and lawn and garden pest control. The work that we have been doing in Orange County is supported by independent work that is being done in the San Francisco Bay region, Sacramento, and Davis, California. All of these areas' urban waterbodies are experiencing high levels of aquatic life toxicity due to diazinon, and in some cases, chlorpyrifos in stormwater runoff. As discussed in the enclosed report, as well as in the enclosed summary slides used in my presentation to the State of California Stormwater Quality Task Force, the issue that has to be addressed is the significance of this toxicity to the beneficial uses of the waters, where it occurs. This is one of the primary issues that we will be addressing as part of our ongoing work in Orange County/Upper Newport Bay, California.

The attached report covers our studies for the fall of 1996. There was no rain in Orange County during the spring of 1997; however, we have monitored a number of storms during the fall of 1997, and have found the same pattern as reported in the enclosed report, i.e., substantial amounts of Ceriodaphnia toxicity with each stormwater runoff event. Several of these events have had on the order of 10 toxic units to Ceriodaphnia, where about half of the toxicity is due to diazinon and chlorpyrifos. We are working on identifying the cause of the other half. Also, this fall we have found that the stormwater runoff is highly toxic to a marine zooplankton Mysidopsis bahia. This is an important marine organism that should be protected.

I also wish to bring to your attention a copy of comments that I have prepared in connection with the Novartis white paper on diazinon toxicity issues in the Sacramento/San Joaquin River Delta. I have critically reviewed this white paper, as well as listening to Novartis staff and their consultants discuss these issues. As discussed in the enclosed letter to D. Kelly, the Novartis white paper does not adequately address the issues of concern, namely, the cumulative impacts of organophosphate toxicity in areas that receive multiple pulses of this toxicity from urban and/or agricultural use. In addition to organophosphate pesticide toxicity, there can also be toxicity due to other pesticides which, while not organophosphates, do potentially adversely impact the waterbodies which receive urban and agricultural drainage.

I have recently acquired substantial additional funding to expand the toxicity work that we are doing in the Orange County area to the San Diego region. Further, in cooperation with the University of California, Davis Aquatic Toxicology Laboratory, I am conducting a study of pesticide runoff from individual urban properties in the Davis region. It is now clear from this work, as well as work done by Alameda County, that the use of these pesticides in accord with the label/registration results in urban stormwater toxicity.

Please contact me if you have questions on this report. Also, please let me know if I can be of assistance in the review of the re-registration of both diazinon and chlorpyrifos.

Sincerely yours,

G. Fred Lee, PhD, PE, DEE


References as: "Lee, G.F., 'Reregistration of Diazinon and Chlorpyrifos,' Letter to B. Chambliss, US EPA, Washington, D.C., December (1997)."

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