Formaldehyde is a significant source of chemical waste in hospitals. It is used to clean and disinfect equipment
(e.g. haemodialysis or surgical equipment); to preserve specimens; to disinfect liquid infectious waste; and in
pathology, autopsy, dialysis, embalming and nursing units.
Photographic fixing and developing solutions are used in X-ray departments where photographic film continues
to be used. The fixer usually contains 5–10% hydroquinone, 15% potassium hydroxide and less than 1% silver. The
developer contains approximately 45% glutaraldehyde. Acetic acid is used in both “stop” baths and fixer solutions.
Wastes containing solvents are generated in various departments of a hospital, including pathology and histology
laboratories and engineering departments. Solvents include halogenated and non-halogenated compounds. Waste
organic chemicals generated in health-care facilities include disinfecting and cleaning solutions, vacuum-pump
and engine oils, insecticides and rodenticides. Waste inorganic chemicals consist mainly of acids and alkalis,
oxidants and reducing agents.
Wastes from materials with high heavy-metal contents represent a subcategory of hazardous chemical waste and
are usually highly toxic. Mercury is an example of a highly toxic yet common substance in health-care facilities.
Mercury wastes are typically generated by spillage from broken clinical equipment, but their volume is decreasing
in many countries with the substitution of mercury-free instruments (e.g. digital thermometers, aneroid blood-
pressure gauges). Whenever possible, spilt drops of mercury should be recovered. Residues from dentistry also
have high mercury contents. Cadmium waste comes mainly from discarded batteries. Reinforced wood panels
containing lead are still used in radiation proofing in X-ray and diagnostic departments.
Many types of gas are used in health care and are often stored in portable pressurized cylinders, cartridges and
aerosol cans. Many of these are reusable, once empty or of no further use (although they may still contain residues).
However, certain types – notably aerosol cans – are single-use containers that require disposal. Whether inert or