BBC News 31 July 2007
A single cannabis joint could damage the lungs as much as smoking up to five tobacco cigarettes one after another, scientists in New Zealand have said.
The research, published in the journal Thorax, found cannabis damaged the large airways in the lungs causing symptoms such as coughing and wheezing. It also damaged the ability of the lungs to get oxygen to, and remove waste products from tissues. Experts say the study confirms that the drug represents a serious health risk.
This research confirms that cannabis poses a serious health risk to the lungs, and smoking a joint can be more harmful to the lungs than smoking a cigarette.
In the study researchers from the Medical Research Institute of New Zealand, Wakefield Hospital and the Wellington School of Medicine and Health Sciences, studied 339 volunteers. They took CT scans of their lungs and tested their lung function through breathing tests to assess their lung damage.