E-cigarettes have been linked to over 100 fires in the UK in two years
Electronic cigarettes are facing bans in several countries as Hong Kong pushes ban.

Researchers have found that electronic cigarettes contained one million times more cancer-causing substances than outdoor air. They also discovered a type of flame retardant in the product, which affected the reproductive system and could lead to cancer.

The study was conducted by the Hong Kong Baptist University and was commissioned by the Hong Kong Council on Smoking and Health. The council has now called for a ban on e-cigarettes as soon as possible before they became more popular.

The council's chairman Antonio Kwong Cho-shing is urging for legislation to enforce a total ban on e-cigarettes as soon as possible. The Food and Health Bureau said it was discussing legislation to ban e-cigarettes with the relevant departments.

The Bureau hopes to submit a proposal to the Legislative Council as soon as possible, he added. So far 16 countries have fully banned the sales, advertising, import, distribution and manufacturing of e-cigarettes.

The researchers analysed 13 types of e-cigarettes in the market. They found that the level of polycyclic aromatic hydrocarbons (PAHs) - a by-product of burning petroleum commonly detected in roadside air - ranged from 2.9 to 504.5 nanograms per millilitre.

That is not all. The substance, which contains highly carcinogenic chemicals such as benzo(a)pryene, also carries various kinds of chemicals that promote growth of cancer cells.

"[Level of PAHs] in e-cigarettes is at least one million times more than roadside air in Hong Kong," said Dr Chung Shan-shan, the assistant professor in the university's biology department. In addition, Polybrominated diphenyl ethers (PBDEs), a flame retardant used extensively in furniture and electronic products, were detected in a range of 1.7 to 1,490ng/ml in the 13 brands of e-cigarettes tested.

The level is higher than in two samples of conventional cigarettes used in the study, which ranged from 5.6 to 6.3ng/ml. The chemical is used to reduce the risk of burning in the plastic combustible component of the e-cigarette.

PBDEs however disrupt the thyroid hormone and cause toxicity of the reproductive development. "Even though we don't know the exact number of e-cigarettes one should take, not to mention that many of the carcinogenic effects are cumulative, I don't think there is a safe margin," said Chung. He said the situation was worrying.

The researchers also discovered that although the packaging of the tested e-cigarettes either claimed they contained no nicotine or did not mention nicotine, they actually contained nicotine levels ranging from 3.5 to 28.5 ng/ml.