Which statement is FALSE?

The best way to appraise the risk to the health of a person who has amalgam restorations is to measure the mercury vapors in his mouth.

The early mercury toxic threshold may be expressed in relation to the quantity of mercury excreted in urine.

The early signs of mercury intoxication suggest that the most sensitive organs are the central nervous system and the kidney.

The early sign of mercury intoxication may appear as urinary mercury concentration reaches 50 microgrammes/gramme of creatinin.

The total contirbution of the environment and amalgam restorations to the urinary excretion of mercury remains below 4 microgrammes/gramme of creatinin.