Pathology Handbook

Formalin acts a preservative (fixative) preventing the autolytic decomposition of surgically removed human tissue. It is the standard tissue preservative used for histological specimens world wide. Formalin is an aqueous solution routinely used at a concentration described as 10%. The solution is buffered to pH 7.4 with phosphate salts. In reality, the solution consists of a 3.7% weight per volume solution since the formalin concentrate from which it is prepared has a concentration of only 37% formalin.   

 

Although formalin is a commercially produced and highly reactive chemical it is a natural endogenous product present in all living cells. It is broken down metabolically to CO₂ and water.

 

The majority of the specimens sent to the Histopathology department are received in 10% Formalin fixative. Handling formalin containers can present an occupational hazard due to the irritant nature of formalin fumes, eye damage on contact and the potential for inhalation or contact sensitization. Specimen containers with formalin should be handled as if they were ‘High Risk’ samples and suitable precautions taken. These include the use of basic protective equipment such as gloves, gowns and eyewear.

 

Pre-filled specimen containers are dispatched by Anatomical Pathology to various clinics within The Alfred, Sandringham and Caulfield hospitals. All formalin supplied by Anatomical Pathology has a purple/blue indicator dye added to distinguish it from water and saline.

 

 

Based on the NOHSC’s Approved Criteria for Classifying Hazardous Substances (NOHSC, 2004), the appropriate risk (R) phrases for a mixture containing formaldehyde at ≥ 3% to < 10% are:

Staff should always wear a protective gown, gloves and eyewear when handling formalin filled specimen containers, or decanting formalin into larger containers.

 

In the case of spills or leakages, the appropriate protective equipment (PPE) should consist of;

PPE for Minor formalin spill (100 ml or less)

       requires no additional PPE other than gloves and protective eyewear.

PPE for Moderate formalin spill (1000 ml or less) requires gloves (nitrile preferred), long sleeved gown, goggles, waterproof footwear or shoe covers, a carbon filter mask or half face organic chemical respirator (eg Moldex 8000 series).         

PPE for Major formalin spill (greater than 1000 ml) requires gloves (nitrile preferred), disposable long sleeved gown or overalls, waterproof safety footwear or shoe covers, a full face organic chemical respirator or self contained breathing apparatus.  

 A major spill is a mandatory Code Yellow situation and staff should respond accordingly. Staff should not put themselves at risk to clean up a major spill. This is best left to Emergency Response personnel.