When informed by the occupational physician that a biological limit value for a chemical agent hazardous to health has been exceeded, under the conditions laid down in Article R. 4412-51-1, the employer :
1° Carry out a risk assessment in accordance with subsection 2 ;
2° Implements the preventive measures and means provided for in articles R. 4412-11, R. 4412-15 and R. 4412-16.