The severity of irritation increases as concentrations increase, and acute exposure to concentrations above 25 ppm can cause serious injury, including fatal pulmonary edema. An oral dose of one ounce can be fatal. Regulations Formaldehyde solutions are regulated in Washington State as category B toxic compounds due to inhalation toxicity. Based on equivalent concentration criteria, formaldehyde solutions designate as hazardous wastes at concentrations of 0.1 percent in water. Since formaldehyde solutions are hazardous above this concentration, the discharge limit to the King County sewer system is 0.1 percent formaldehyde in water.
Formaldehyde solutions can never go into septic systems or storm drains.
Solutions that are more than 0.1 percent formaldehyde must either be disposed as hazardous waste or chemically treated to reduce the formaldehyde concentration to acceptable levels. Chemical Treatment Solutions that are more than five percent formaldehyde should be diluted with water to under five percent formaldehyde prior to chemical treatment. Formalin is readily treatable. According to product data, these compounds will reduce the concentration of a treated sample of formalin to under 0.1 percent formaldehyde. Filtering of solid residues and pH adjustment may be required following treatment.