David A. Sheahan

Oestrogens and oestrogenic activity in raw and treated water in Severn Trent Water.

Sewage effluent discharged to surface water has been shown to contain human hormones, particularly oestrogens, and synthetic chemicals which may be able to disrupt the endocrine system. Since many surface waters which receive sewage effluent are subsequently used as drinking water sources, it is important to demonstrate that treated drinking water is not contaminated. Oestrogenic activity in rivers and drinking water in the region of Severn Trent Water was studied using a combination of bioassay, to integrate exposure over time, and advanced chemical analysis. There was little or no evidence of substances that were oestrogenic, even in waters receiving significant amounts of sewage effluent. Oestrogenic activity, as measured in the rainbow trout vitellogenin assay, was seen at the Tame/Trent confluence but this activity was relatively weak. There was no activity detected at raw water intakes and no hormones or substances that are oestrogenic were detected in the final drinking water.

Toxicity characterisation of organic contaminants in stormwaters from an agricultural headwater stream in South East England

The transient movement of pesticides at biologically active concentrations during storm events is considered to be a cause of biological impoverishment in some headwater streams. The programme of work described sought to identify compounds that are the cause of toxic effects during such events. Along with targeted pesticide analysis, toxicity identification evaluation (TIE) procedures were used to identify compounds with a demonstrated toxic effect. These procedures were specifically directed towards isolating and attributing toxicity to classes of organic contaminants in samples collected from an English headwater stream during a storm event. The organic load was isolated by means of solid-phase extraction (SPE). Bioassay of the SPE extract at x 100 whole water concentrations confirmed that the samples contained substances toxic to Daphnia magna, although the raw samples were not toxic. Targeted pesticide analysis identified simazine and diuron as the major pesticides present and, using a toxicity unit (TU) approach. were shown to be responsible for a significant amount of the observed concentrate toxicity during a runoff event. However, they were not present in sufficient quantities to be totally responsible for a more toxic later event. By simplification of the SPE isolate using reverse-phase HPLC, fractions from which were tested for toxicity, the cause of concentrate toxicity in the later event was isolated to two discrete fractions. GC-MS analysis of these fractions identified nonylphenol. endosulfan sulphate and pendimethalin as present, with the majority of toxicity attributed to nonylphenol (NP). The main advantage of the TIE approach is that it allows biological active compounds with a demonstrated effect to be identified that may not be selected by more traditional techniques.

The potential for oestrogenic effects of pesticides in headwater streams in the UK

Twenty-six pesticidal compounds and samples of stormwater from two different agricultural catchments were screened for oestrogenic activity using an in vitro recombinant yeast-based assay. Only six fungicides showed an oestrogenic response with low comparative biological activity of 5000 to 2.5 million times less potent than 17beta-estradiol (E2), a natural steroidal oestrogen. Concentrations of biological activity expressed as E(2) equivalents for the headwater stream stormwater samples ranged from <0.01 to 0.11 ng E2/l. These values are at least one order of magnitude below levels that have been documented to produce oestrogenic effects in fish and are therefore considered to represent a low risk to associated headwater stream communities. The potential sources of the oestrogenic activity measured in the headwater streams are discussed.

The joint toxicity of pesticide tank-mixes to rainbow trout

Abstract The joint toxicity to rainbow trout fingerlings ( Salmo gairdneri Richardson) of eleven tank-mixes composed of pairs of six fungicides and herbicides (prochloraz, fenpropimorph, diclofop-methyl, tridemorph, benzoylprop-ethyl and propiconazole) was measured using 96 h LC 50 tests. The toxicity of the mixtures ranged from being half of that expected on the basis of additive toxicity of the components, to less than 1.4 times the expected value. In view of the degree of experimental error inherent in the LC 50 determinations, these data provide no evidence for the existence of synergistic (i.e. more-than-additive) toxicity of the respective tank-mixes.