Our contribution to Zr environmental hazard, arrived at by means of bioassays on bacteria, microscopic algae and fish, confirms the hypothesis that Zr has low toxicity. Toxic effects revealed with the Microtox test may be attributed to pH rather than specifically to Zr (5 min. EC₅₀ > 4.3 mg L^–1). Fish assays also confirmed the low toxicity of Zr (96-hr LC₅₀ > 20 mg L^–1; 96 hr minimal stress concentration > 20 mg L^–1; Mutagenicity (Fluctuation test) and genotoxicity (S.O.S. Chromotest) assays failed to show any DNA-related effects linked to this metal. Only the algal assays (ATP energy stress) demonstrated genuine toxicity at Zr concentrations between 1.3 and 2.5 mg L^–1.