Effluent standards for developing countries: combining the technology- and water quality-based approach.

It is a challenge for developing countries to realize socio-economical development without impairing water resources in an unacceptable way. A possible means for controlling water pollution is through defining, applying and enforcing effluent standards for wastewater discharges. However, in many developing countries the definition of effluent standards is still poor. They are either too stringent because they are based on standards from developed countries, or too relaxed and therefore they do not guarantee the safe intended uses of water. In order to define an approach for setting effluent standards that suits the needs and means of developing counties, water quality management practices in the USA, the EU, the New Independent States (NIS) and the Philippines were analyzed and compared. Four criteria (protection of the environment, technical viability, economic feasibility and institutional capacity requirements) were used to assess the suitability of these practices for developing countries. It is concluded that a combined approach that is based on best available technology not entailing excessive costs and environmental quality standards is the best way to define effluent standards that restrict water pollution against affordable costs.

Fish embryos as teratogenicity screens: a comparison of embryotoxicity between fish and birds.

Early life stage (ELS) toxicity experiments were carried out with zebra fish (Brachydanio rerio) and rainbow trout (Salmo gairdneri) and 10 chemicals used in the rubber industry. Several of these chemicals appeared to be teratogenic. A good correlation (r = 0.95) was found between the 7-day EC50 for zebra fish and the 60-day EC50 for rainbow trout for total embryotoxicity (embryolethality and malformations). The S. gairdneri test appeared to be slightly more sensitive than the test with B. rerio. It is therefore concluded that this short-term test is a good alternative for the long-term test with S. gairdneri. A remarkably good correlation (r = 0.90) was found between the ED50 for chicken embryotoxicity reported in the literature and the EC50 for embryotoxicity for both zebra fish and rainbow trout. This may, among other things, be explained by similarities in embryonic development and the absence of maternal and placental metabolism of the toxicants in tests with eggs of both fish and birds. It may therefore be concluded that both the short-term ELS test with B. rerio and the chicken egg test have the same predictive power for mammalian teratogenicity; i.e., both are suitable screening tests for direct-acting teratogens.

Effects of chemical stress on the population dynamics of Daphnia magna: a comparison of two test procedures.

Ten substances were tested to compare two methods that can be used in chronic toxicity studies with the Cladoceran Daphnia magna. In semistatic experiments with cohorts (life-table studies) survival appeared to be a dominant factor in exponential population growth. Specific inhibition of reproduction as a result of toxic stress was observed only in tests with bromide and 2,4-dichloroaniline. For some substances (cadmium, bichromate, metavanadate, and bromide) individual growth (carapace length) was found to be a sensitive parameter. In intermittent-flow experiments with small expanding populations the yield (carrying capacity) proved to be a highly sensitive parameter, probably owing to the fact that in these tests populations grow logistically, i.e., become additionally stressed by food limitation. Chemically induced reductions in food ingestion and conversion efficiency may thus become very predominant. In view of the place of these crustaceans in the food web such reductions in the carrying capacity would seem to be of great ecotoxicological importance.