Zinc oxide (CAS 1314-13-2): storage and disposal

Dental practices usually hold it as cement powder in a small lidded container beside the mixing area, and the first job is to keep it apart from liquids kept nearby so that a spill cannot turn into a paste on the shelf. School and pharmacy stock does best in a dry cupboard in a screw-top jar with a well-fitting lid, because a fine powder escapes easily and settles on whatever is below it. No cabinet or special store is needed, just a labelled, ordinary shelf away from damp. Because a very small quantity goes a long way, containers are often opened once and kept for years, so write the date opened on the lid and keep a count of how much remains.

The powder can slowly take in moisture and carbon dioxide from the air, and a tin or jar left badly closed will show it as small hard lumps or a crust of coarser material across the surface. A technician will see that the powder no longer pours cleanly and clings to the neck of the container. Check for a fine white film on the outside of the jar, a cracked lid and a label dusted over so that the name cannot be read. There is little else to report: zinc oxide gives few striking signs with age, so caking and a failed seal are the main things to record before collection.

We arrange this by specialist collection. We do not publish a drain or general waste route for any chemical. It is normally packed in a general laboratory pack with compatible chemicals.

Start with what must not happen to it. The powder does not belong in a surgery bin, a classroom waste bin or a sink, because the very toxic aquatic classification follows it wherever it goes. Do not try to wet it down or sweep it into a drain. A laboratory pack usually takes 16 05 06*, discarded stock outside a laboratory pack usually takes 16 05 07*, and a dental or pharmacy setting that counts as human healthcare usually takes 18 01 06*, while a licensed medicine is generally classified under the medicines entries. The producer classifies the waste. Keep the original tin or jar if it is sound, tape the lid, note the dental cement or powder form on the record and request a specialist collection.

Usually held as: powder, dental cement powder.

Tell us the container size and how many you hold. An estimate is enough to start with, and some items cannot be priced until someone has looked at them.