 Very little is known about the toxicity of rhenium and its compounds because they are used in very small amounts . Soluble salts , such as the rhenium halides or perrhenates , could be hazardous due to elements other than rhenium or due to rhenium itself . Only a few compounds of rhenium have been tested for their acute toxicity ; two examples are potassium perrhenate and rhenium trichloride , which were injected as a solution into rats . The perrhenate had an LD50 value of 2800 mg / kg after seven days ( this is very low toxicity , similar to that of table salt ) and the rhenium trichloride showed LD50 of 280 mg / kg . 
