EVALUATION OF THE GENOTOXICITY OF MUNICIPAL SEWAGE EFFLUENT USING THEMARINE WORM PLATYNEREIS-DUMERILII (POLYCHAETA, NEREIDAE)

Samples of settled (primary) effluent were collected from a municipal sewage treatment works at Newton Abbot, Devon, UK, a site which discha rges primary effluent via long sea pipeline into the English Channel ( minimum of 200-fold initial dilution), Sewage samples were collected d uring the period February-April 1995 and were analysed for standard ph ysico-chemical parameters (ammonia, chemical oxygen demand, conductivi ty, non-purgeable organic carbon and settled solids). Samples were als o tested for cytotoxicity, genotoxicity, and for developmental effects in the embryo-larval stage of the marine worm, Platynereis dumerilii. Exposure to sewage concentrations of greater than or equal to 10% (v/ v) in seawater at 20 +/- 1 degrees C led to a marked reduction in norm al embryo-larval development (7 h EC50 values from 10% to 18% v/v, n = 5). There was also evidence of a simultaneous delay in the cell cycle progression (as determined by sister chromatid differential staining) following embryo-larval exposures to sewage concentrations of greater than or equal to 10% (v/v). Following the calculation of the Maximum Tolerated Dose (MTD), based on cytotoxic and developmental effects, ce lls from the same embryo-larvae were analysed for chromosomal aberrati ons (CAs). Results were consistent for all samples tested, demonstrati ng the absence of cytogenetic damage following the in vivo exposure of polychaete embryo-larvae to settled sewage.