Table 1.

Mean lethal concentrations (50%) (LC ₅₀ ) of chromium and zinc in newborn G. tigrina acute tests for sensitivity assessment

	LC 50 (mg/L)
Test	Cr 6+				Zn 2+
	24 h	48 h	72 h	96 h	24 h	48 h	72 h	96 h
I	13	11	8	7	2	2	2	2
II	11	11	11	7	1.6	1.6	1.6	1.6
III	*	27	20	11	1.6	1.6	1.6	1.6
IV	*	29	18	15	1.6	1.6	1.6	1.6
V	18	8	5	3	1.3	1.3	1.3	1.3
VI	15	10	5	4	1.6	1.6	1.6	1.6
VII	14	5	2	5	1.7	1.7	1.7	1.7
Mean	14.2	14.4	9.8	7	1.6	1.6	1.6	1.6
SDa	2.5	9.5	6.8	4.6	0.2	0.2	0.2	0.2
CV (%)b	18	66	69	66	12	12	12	12

Asterisk indicates LC₅₀, not calculable for the statistical method employed. ^aSD standard deviation of the mean. ^bCoefficient of variation. The tests indicated as I, II, III, IV, V, VI, and VII correspond to independent experiments.