Food Safety and Environmental Stewardship

4,4'-DDT, Degradation Products and Dieldrin in the Malheur River

This work is an example of a project that satisfies several of the FSES missions. This project was brought to the attention of the FSES staff by an OSU AES County Extension Agent. The Oregon DEQ in 1998 notified the OSU Extension Agent that the Malheur river (near Ontario, OR) had tested positive for DDT (dichloro diphenyl trichloroethane=4,4'-DDT; 1,1(dichloroethenlyidene)bis(4-chlorobenzene)=4,4'DDE; 1,1dichloro-2,2-bis(p-chlorophenyl)ethance,=4,4'-DDD and Dieldrin), by the USGS in 1990. DEQ indicated a management plan would need to be developed as a consequence. Since the data from USGS was nearly a decade old, it seemed prudent to verify the DDT, DDT degradation products and Dieldrin values. FSES staff set-up sampling at four sites with semi-permeable membrane devices (SPMD). The SPMD were used in the USGS study , and for consistency were used in the current study. Four sites and two QC samples were collected, two sites near Vale and two sites near Ontario. SPMD were selected for sampling since they sample only chemicals in solution (dissolved) while excluding those sorbed on organic matter or particulates. In addition, the aquatic toxicity data, water quality criteria, and threshold limit values are based on dissolved concentrations and not total residue levels. Furthermore, SPMD sampling gives an integrated exposure over the entire sample period (21 days) that may better approximate actual exposure. The samples were analyzed utilizing gas chromatography techniques performed by FSES personnel.

Project Findings:
A report was generated by the FSES program providing the data, discussion of the results, as well as, investigative information. The study indicated a significant drop in levels of Dieldrin as compared to those reported by the USGS in the 1990 study. Due to ambiguity in the USGS DDT values (DDT versus SDDT) as reported to FSES a direct comparison was not possible at this time. However, several important pieces of information were brought to light by this study. The first is that Dieldrin levels have decreased since the 1990 study. Another, is that one site (Ontario-II) had residues levels 4 times higher than the three other sites. Further investigations may lead to a possible point-source near the Ontario II site (note: this site is directly below the airport & landfill). Investigations by FSES staff disclosed applications of DDT in the late 1960's in the Malheur National Forest which is within this watershed.

The age of the DDT was qualitatively evaluated, since DDE is a metabolite of DDT this leads to a hypothesis that these residues are from old applications (reasonable since DDT has been canceled since 1973). None-the-less, it may be important to be able to prove that these are from old applications; since in rare cases, it has been reported that chemicals which have been banned are still being applied by users who "stock-piled" them. On average, the DDE was a factor of 3-4 times higher than DDT concentrations. Generally, DDE/DDT ratios >2 strongly suggests old sources of DDT . Overall, these values will need to be confirmed and additional sampling sites will need to be included, but this study may dramatically affect an effective, comprehensive management plan for this watershed. This limited research project illustrates how the FSES program of "Science Supporting Society" can function. Here the laboratory was able to provide important information that will assist in the effective management plan that will be developed for this region. As well, as providing current information so that the health and toxicity of this watershed can be more accurately assessed.