Publication Abstract

Toxicity Reduction Evaluation; Toxicity Identification Evaluation and Toxicity Tracking in Direct Toxicity Assessment

Toxicity Reduction Evaluation; Toxicity Identification Evaluation and Toxicity Tracking in Direct Toxicity Assessment

M. Hutchings, I.,Johnson E. Hayes, A. Girling, J. Thain, K. Thomas, R. Benstead, G. Whale, J. Wordon, R. Maddox and P.Chown

This paper describes Toxicity Reduction Evaluations (TRE) undertaken as part of the UK Direct Toxicity Assessment (DTA) demonstration programme. A systematic approach using toxicity testing to identify both the cause and source of toxicity at two locations was undertaken. The TREs were based on the approach described by the US EPA, but adapted to tackle the specific problems of the two sites. The case studies selected for this work were a large discharge in to the lower Tees estuary and a smaller outfall from Langholm sewage treatment works into the river Esk. A combination of toxicity tracking and Toxicity Identification Evaluation (TIE) were used at both locations to enhance the understanding of source and type of toxicants present.

The assessment of toxicity at Langholm focused on a number of pesticides that were found to be present in the sewerage network. The TIE programme indicated that the most likely toxic agents within the effluent were the organophosphate pesticides diazinon and to lesser extent propetamphos. These two compounds, did not however, account for all of the toxicity observed. The exact source of these toxicants was not clear although toxicity tracking identified two potential candidates.

The TRE undertaken on the discharge to the lower Tees utilised high-throughput methods with standard test organisms in order to generate toxicity information throughout a complex sewerage network. The toxicity tracking information was used in conjunction with TIEs to identify a number of key sources of toxicity. Considerable toxicity was associated with a currently untreated industrial effluent. Chemical analysis and TIE highlighted cyanide as the likely toxicant in this effluent and its possible significance in the final discharge. Final effluent toxicity was also contributed to by a number of branches of the sewerage network. However, this toxicity source was more diffuse and a precise toxicant could not be identified.

Reference:

M. Hutchings, I.,Johnson E. Hayes, A. Girling, J. Thain, K. Thomas, R. Benstead, G. Whale, J. Wordon, R. Maddox and P.Chown (2004) Toxicity Reduction Evaluation; Toxicity Identification Evaluation and Toxicity Tracking in Direct Toxicity Assessment.  Ecotoxicology, 13(5): 475-484

M. Hutchings, I.,Johnson E. Hayes, A. Girling, J. Thain*, K. Thomas*, R. Benstead, G. Whale, J. Wordon, R. Maddox and P.Chown

Ecotoxicology, 13(5): 475-484