A little math will show that histological specimen waste contains far 
more than 100 ppm formaldehyde.

A specimen that has been reasonably well fixed will have had its free 
water completely replaced by the fixative.  Assume for the moment 
that the specimen was 100% water.  It now is 10% formalin, which 
contains 3.7 % formaldehyde, which is 37,000 ppm formaldehyde.

Obviously, the specimen is not 100% water.  Most living tissue is at 
leat 50% water, so such a specimen would contain 18,500 ppm 
formaldehyde.

If the specimen contained only 1% water, the formaldehyde content 
would be 3,700 ppm, still way over the 100 ppm limit.

You could wash the formalin out of the specimen with water, but now 
you have a huge volume of hazardous waste liquid, so nothing has been 
gained.

When faced with this dilemma, it is time to consider a formalin 
substitute that is more environmentally acceptable.  These are 
available from a number of vendors.

Dick