Experimental Studies of Molybdenum Physiology and Toxicity

Bacteria

International Molybdenum Association
Toxicity Testing Programme: Bacteria a

Substance

Toxicity/ mg/l

Acute bacterial growth inhibition

Acute bacterial respiratory inhibition

EC10 b

3 h EC50 c

Molybdenum trioxide (pure)

d

820

Molybdenum trioxide (tech)

d

3000

Ammonium dimolybdate

13

Sodium molybdate

50

Notes

a There are no EC criteria for bacterial toxicity. It is however factored into the German Water Hazard Classification. Under the German classification scheme, which takes into account fish, mammal and bacterial toxicity, the materials tested would give a maximum Water Hazard Classification of 1(weak hazard for waters).

b The EC10 is the concentration that causes a 10% reduction in turbidity. Test culture incubated with various concentrations of test substance for 18 hours. Turbidity measured by light transmission.

c The EC50 is the concentration that causes a 50% reduction in respiration. Test culture and test substance were left in contact for 30 minutes and three hours. At the end of each time period the dissolved oxygen content of the solution was measured.

d Growth inhibition is determined by the decrease in turbidity of test solution. Therefore, this method cannot be used on insolubles.