## Drexel, Missouri

– Summary of Notification and Response to Safe Drinking Water Act (SDWA) Atrazine Sample Result from Finished Water Sample Collected May 26, 2010
Sample Collection and Reporting

A routine finished water sample taken for SDWA compliance was collected at the Drexel, MO CWS on May 26, 2010. The result of the analysis (31.2 ppb atrazine) was reported to MO Department of Natural Resources (MO DNR) about 1 PM CST on July 23, 2010. Shortly thereafter, the MO DNR notified the Missouri Departm ent of Health and Senior Services (MO DHSS) of this finding. In response, a MO DNR public notice was issued about 6:30 PM CST reporting this detection . This notice also included the following text: “The Department of Health and Senior Services does not expect to see any significant acute health effects as a result of this monitoring spike. The Missouri Department of Health and Senior Services recommends neither using the water for drinking nor using it to cook, wash dishes or make ice.” Syngenta first became aware of this detection through this public notice the evening of June 23.
Syngenta Follow

- U p with MO DNR and MO DHSS
On Thursday, June 24, Syngenta contacted the MO DNR for additional information regarding the atrazine detection. We were told tha t MO DNR had sent someone to Drexel to collect additional compliance sample s on June 23 and June 24. In addition, the CWS was also provided with sample kits for each day the week beginn ing Jun e 28. T he results from the June 24 test were expected to be

av ailable as soon as Friday (June 25). We also learned the “do not drink” recommendation from MO DHSS was taken from an Agency for Toxic Substances and Disease Registry ( ATSDR ) Environmental Media Evaluation Guide (EMEG) value of 30 ppb atrazine based on a child’s body weight and water consumption. This value is more than three times lower than the 100 ppb EPA Office of Water (EPA

OW) one

- day and ten

- day Health Advisory Level (HAL) for atrazine , which is also based on a child’s body weight and water consumption . The ATSDR EMEG is approximately 10 fold lower than the 298 ppb DWLOC published by EPA Office of Pesticide Programs

. From a review of the ATSDR Minimum Risk Levels (MRL) worksheets, the difference is due to an extra three

- fold uncertainty factor that has been applied in the derivation of the 30 ppb ATSDR intermediate term exposure value from the EPA

- OW HAL of 100 ppb (both use a 1 mg/kg/day reference dose)

. This is the first instance we are aware of in which these ATSDR value has been used by a CWS . In Appendix A of the ATSDR Toxicological Profile for Atrazine, the following disclaimer is given: “It is important to note that MRLs are not intended to define clean

- up or action levels.” Therefore, this value of 30 ppb should not have been used by the Drexel CWS.
On Friday, Jun e 25, Syngenta contacted the MO DHSS to discuss the atrazine detection and health advisory notice for the city of Drexel. Prior to the meeting we had provided to MO DNR and MO DHSS copies of the EPA

- OW documents and Syngenta summaries, of atrazine HALs an d Maximum Contaminant Level (MCL) for atrazine in drinking water. We explained that the monitoring result did not show that any EPA

- OW HALs had been exceeded for children or adults. S ince the EPA short

- term HAL had not been exceeded, a recommendation to not use the water for drinking, cooking, dishwashing orice

- making was not justified. Syngenta requested, and has since received, the atrazine ATSDR documentation from MO DHSS.
MO DNR Confirmatory and Atrazine Monitoring Program (AMP) Results for Drexel CWS
On Friday afternoon (June 25 , 7 PM CST ) the results of the confirmatory sample taken and the Drexel CWS on June 24 were reported as 0.36 ppb atrazine in finished water . Within a couple of hours MO DNR issued a public notice with these results and tha t the water use restrictions had been lifted. This notice also reiterated the following: “The department has been working with the Drexel Public Water Supply on compliance issues for several years. The Drexel water system is currently constructing

a con nection to the Tri

- County Water Authority in Independence. The water system has signed an agreement to begin purchasing water from Tri

- County by the end of the year.” Based on our own conversations with MO DNR, historic compliance issues include high tur bidity and non

- compliance with Total Trihalomethanes (TTHMs), a disinfection byproduct.

The 2010 results from Syngenta’s Atrazine Monitoring Program (AMP) available to date are shown below : Sample Collection Date Raw Water Atrazine (ppb) Finished Water Atrazine (ppb) SDWA Finished Water Atrazine (ppb) 11

- Jan

- 10 0.80 0.70
--- 9

- Feb

- 10 0.56 0.55
--- 22

- Feb

- 10 0.37 0.46
--- 8

- Mar

- 10 0.41 0.42
--- 22

- Mar

- 10 0.49 0.39 --- 7

- Apr

- 10 0.28 0.26
--- 10

- Apr

- 10 0.27 0.28
--- 28

- Apr

- 10 29.72 23.57
--- 3

- May

- 10 28.88 26.81
--- 10

- May

- 10 30.99 29.57
--- 17

- May

- 10 30.67 29.57 --- 24

- May

- 10 23.10 27.44
--- 26

- May

- 10

--- --- 31.2

1

- Jun

- 10 0.13 0.67
--- 24

- Jun

- 10

--- --- 0.36

Historical Monitoring and Current Investigation

The Drexel CWS has been participating in the AMP since April 2006 and also participated in the Syngenta Voluntary Monitoring Program (VMP) from Februar y 1995 to December 1991. From April 2006 through April 10, 2010 , no individua l sample (AMP) had exceeded 3.04 ppb in raw water o r 2.77 ppb in finished water, until April 28 of this year. In the VMP program, the highest single sample values occurred in May 1998, with atrazine concentrations of 14 ppb and 1 2 ppb, in raw and finished water respectively. The next highest VMP atrazine concentrations were 4.32 ppb (raw) and 3.40 ppb(finished). Therefore, the recent measurements are extremely uncharacteristic of this CWS and watershed. Through phone calls and personal visits, Syngenta is currently engaged with the CWS, local officials , a local chemical retailer and growers in the watershed to further investigate this unusual result

. The raw water source for the Drexel CWS is Drexel Lake. This approximately 40

- 45 acre lake has a watershed area of 534 acres. At full pool storage, th is lake holds 345.1 acre

- feet of water. The average water use by the CWS is approximately 10 2 ,000 gallons/day. As stated earlier, the Drexel CWS is slated to be decommissioned and the city will begin purchasing finished water from Tri

- County Water Author ity in Independence by the end of this year or early 2011.