Evaluation of the aquatic toxicity of two veterinary sulfonamides using five test organisms.

The aquatic toxicity of sulfaquinoxaline (SQO) and sulfaguanidine (SGD) was evaluated on the following test organisms: Daphnia magna (reproduction test), Pseudokirchneriella subcapitata, Scenedesmus dimorphus, Synecococcus leopoliensis (algal growth inhibition test) and Lemna gibba (duckweed growth inhibition test). Furthermore, the additivity of the two compounds was measured on D. magna (acute immobilisation test) and P. subcapitata (algal growth inhibition test) using the isobologram method. Results show that SQO and SGD are more toxic to green algae and daphnids, respectively, than other veterinary sulfonamides (SAs) and that their mixtures have a less then additive interaction. Taking into account the highest concentrations detected so far in surface waters for SQO (0.112 µg L(-1)) and for SGD (0.145 µg L(-1)) and the lowest NOECs obtained with the five test organisms, divided by an assessment factor of 10, the following PNECs and risk quotients (RQs) were calculated. SQO: PNEC 2 µg L(-1); RQ 0.056. SGD: PNEC 39.5 µg L(-1); RQ 0.004. Consequently, at the concentrations actually detected in the aquatic environment, the two SAs alone should not harm the freshwater organisms. However, it seems advisable, for veterinary mass treatments, the use of other SAs that have a lesser impact on the aquatic environment. Furthermore, considering the high probability of having complex mixtures of different SAs residues in water, each individual contamination should be evaluated by applying to the SAs mixtures the conservative criteria of additivity.

Induction of meiotic chromosomal aberrations by sulphaguanidine.

Cytological investigations on the effects of sulphaguanidine on meiotic cells have been carried out. Concentrations of 4.165, 6.25 and 8.33 mg of the drug were orally administered to Swiss albino male mice as single and cumulative doses. In the latter the drug was fed consecutively for 5 days at 24 h intervals. Meiotic chromosomal preparations were made after 24 h and at weekly intervals up to the fifth week following drug administration. Structural aberrations like gaps, breaks, fragments and multivalent associations (translocations) were scored for assessing clastogenic activity. Mitoclasic effects were analysed by scoring the polyploids. A high rate of both autosomal and sex chromosomal univalents were recorded in the series treated. A non-clastogenic and a very weak mitoclasic property of the drug is suggestive and is comparable to observations on the effects of sulphadiazine previously reported.