The Department of Health has released this update to a previous alert issued in 2007 on the potential health harms associated with the use of cannabis contaminated with glass particles. The following advice is based on emerging information from the Forensic Science Service, which includes analysis of seizures of cannabis:
- Contaminated cannabis has been in circulation since at least July 2006 and in significant numbers since at least November 2006.
- Contaminated cannabis has been found in approximately 5-10% of herbal cannabis seizure cases examined; the proportions in seized cannabis in February (4.6%) and March (5.9%) are lower than that in January (9.6%), which may indicate that the market is changing in response to the media and concerns of users.
- Glass-contaminated cannabis has now been found in most parts of the UK, but not in Wales, and with no recent seizures in Northern Ireland; there is evidence to support the view that contaminated cannabis is being imported, probably from the Netherlands.
- The reason for adding the glass particles remains uncertain, but it still seems likely that they are added to improve the apparent quality and weight.
- Internet cannabis forums are now reporting the appearance of cannabis contaminated with much finer particles that are not easily detected as a gritty feeling; and if growers are using much smaller particles of glass beads, this could, theoretically increase the health risk of smoking contaminated cannabis.