Mercury and heavy metal disposal

Most of this work starts with one find, then grows when someone looks in the next cupboard. The list usually includes:

• elemental mercury in bottles or sealed glass
• thermometers, barometers, manometers, switches and similar devices, intact or broken
• mercury salts such as mercury(II) chloride, oxide, nitrate and sulfate
• lead, barium, cadmium, chromium, nickel, cobalt and silver compounds
• waste solutions from heavy metal practicals and analyses
• dental amalgam, along with old bulk dental mercury

Thallium salts, arsenic compounds and old stains with mercury content are not common, but they are still found in older stores, and we would want them flagged clearly. Any mercury compound that looks degraded, and any metal salt stored with an incompatible chemical, may need a closer look. Anything unstable, along with radioactive compounds such as uranyl and thorium salts, goes to a manual enquiry.

• the item or chemical name and an approximate quantity or weight
• for mercury devices, the type, number, and whether each is intact or broken
• container material and condition, including whether the closure looks secure
• the shelf height and location, particularly for heavy bottles
• any history of a spill in the store, even if it was years ago
• whether salts are solids or solutions, and the concentration if known
• access arrangements and the person who will sign

A history of spills matters more than people think. Mercury in the floor or under a bench can go on giving off vapour long after a thermometer was swept up. If you suspect that, please say so, because it raises a question that a collection alone will not answer.

Mercury is found almost everywhere that once measured temperature or pressure. A school physics store may have a barometer. A chemistry department may have manometers, a bottle of mercury and a drawer of old thermometers. Clinics may still hold sphygmomanometers that have been out of use for years. The Environment Agency's guidance note on measuring devices explains that mercury-containing devices are classed as hazardous waste. It also sets out the restrictions on placing many of them on the market.

Mercury needs careful storage for a few specific reasons. It gives off vapour at room temperature, and the warmer the store, the more it produces. It is also very dense, so a small bottle weighs much more than it looks, and a shelf or thin plastic container may not be up to it. It reacts with aluminium and many other metals, so keep it away from aluminium items and metal fittings. Glass bottles on a high shelf are a real risk. They should not be moved to a lower shelf if the closure is doubtful or there are signs of a previous spill.

Broken thermometers are the most common incident. UK Health Security Agency guidance addresses small domestic spills, advising disposable gloves, double-bagging of waste, ventilating the room for at least 24 hours and, under no circumstances, using a vacuum cleaner, because it can increase exposure by inhalation. The guidance also says that a vacuum cleaner already used on mercury should itself be double-bagged and disposed of.

Workplaces should go further. The HSE's emergency guidance under COSHH expects you to plan for foreseeable incidents, including having suitable equipment and the right people trained, and arrangements for dealing with the waste. A mercury spill kit is a cheap piece of preparation in any store that holds mercury. Keep the broken glass and the recovered mercury as hazardous waste, and do not put them in a sharps bin. Used absorbents and spill materials are waste too, and HTM 07-01 says those from chemical spills in healthcare fall under chapter 15 of the List of Waste.

Larger spills need different handling. Barometers and other large devices can release much more mercury, and droplets can run into floorboards, gaps and service ducts. Clear the area, close the door and get advice. Do not let the mercury reach a drain. If it does, tell your water company, and report it to the Environment Agency incident hotline on 0800 80 70 60 if you are in England. If anyone has been exposed or feels unwell, get medical advice.

Mercury appears in several parts of the List of Waste, according to what it is and where it came from. Laboratory chemicals generally sit under 16 05 06*. Dental amalgam has its own code, 18 01 10*. Mercury-containing batteries are 16 06 03*. Fluorescent tubes and other mercury-containing waste are 20 01 21*, and wastes containing mercury from inorganic chemical processes are 06 04 04*. Heavy metal salts and solutions from those processes come under 06 03 13* and 06 04 05*.

Your chemist or carrier will help confirm the code. What the paperwork needs from you is an accurate name and an idea of quantity, because the rest depends on them, and responsibility for an accurate description stays with your organisation. A solution of unknown metal content may need more thought than a labelled bottle of the solid.

Teaching stores usually hold a shelf of metal salts bought for colour tests, electrolysis and solubility work. Lead nitrate, lead bromide and barium chloride are the common ones in schools, along with potassium dichromate and silver nitrate. They are often in very good condition and are usually far more than anyone needs. Many have been replaced in the curriculum, or at least the quantities used have fallen, so there is rarely a reason to keep the whole original kilogram jar.

Research labs may add less common items. Cadmium salts are found in older materials work, osmium in microscopy, and thallium in some legacy analytical work. Thallium deserves particular care, since its salts are highly toxic and can look like harmless white powders. Some of these appear on the Home Office list of poisons, and that adds a security dimension. Keep them locked and accounted for until they leave.

Waste solutions need attention too. Lab work with metal salts generates small volumes of dilute solution, and it can be tempting to think of these as harmless. They are not. Collect them in a labelled container, one for each metal where practicable, and do not combine them with other waste streams. Dilution is not a treatment.

Dental practices have their own duties under Article 10 of the retained mercury regulation, including amalgam separators and collection of amalgam waste by an authorised business. HTM 07-01 calls for marked white containers with mercury vapour suppressants. Our dental practices page goes through what that means in a practice.