Practitioners of traditional Chinese medicine have agreed to cooperate with the Department of Health to improve the safety of traditional medicines after concerns that they may contain potentially toxic or carcinogenic ingredients.

Last week the Committee on Safety of Medicines said that random tests were still finding banned substances such as mercury and arsenic in traditional Chinese medicines sold in the United Kingdom, despite previous warnings. Some medicines also contained steroids, even though the label did not declare it.

Banned products containing the herb aristolochia, which has been associated with two cases of kidney disease in the United Kingdom in 1999, are also still …