GUANGZHOU, Dec. 24 (Xinhua) -- Liu Cheng decided to gradually quit vaping as he found purchasing electronic cigarettes (e-cigarettes) online is not as easy as before.

"Many vapers have made the same decision," said Liu, a college graduate in south China's Guangzhou.

E-cigarettes were the "first whiff of smoke" for many teenagers. About 10 million Chinese aged 15 or above are using e-cigarettes, data from the Tobacco Control Office at the Chinese Center for Disease Control and Prevention showed.

The vaping rate among young people was higher than other age groups, with those aged 15 to 24 the highest, and around 45.4 percent of e-cigarettes were bought online.

E-cigarettes that contain nicotine are referred to as an "electronic nicotine delivery system" (ENDS) by the World Health Organization. An ENDS is considered responsible for lung cancer, cardio-cerebrovascular diseases, and other smoking-related illnesses if inhaled for a long period of time, according to the organization.

Chinese authorities have taken multiple measures since November to intensify the oversight on online selling of e-cigarettes, including banning online sales and advertisements of e-cigarettes.

Several well-known domestic e-commerce platforms including Taobao, JD.com and Suning.com have henceforth removed e-cigarette products from their shelves.

"We could sell thousands of e-cigarettes a day online. But we still shut down the online store in response to the new regulation," said the owner of a Taobao store.

"Exposure to nicotine in adolescents may have long-term adverse consequences for brain development and may increase the risk of cardiovascular and smoking-related diseases," said Zhuang Runsen, executive vice president of the Shenzhen Tobacco Control Association.

Zhang believed that restricting sales of e-cigarettes will reduce the chance for minors to have access to cigarettes.

E-cigarette companies are also taking action. Recently, an e-cigarette store in Beijing has used advanced technology such as artificial intelligence and facial recognition to prevent minors from purchasing their products.

Wang Ying with RELX Technology, which holds a 60-percent share in China's domestic e-cigarette market, said that customers need to register their names and ID numbers on the tablet computer in their store and complete a face-scanning recognition before placing an order.

"There were some complaints, but they understand the laws and regulations and are all very cooperative," said Wang.

Wang said the registration system will be expanded to all its stores nationwide in the next seven months and they will avoid areas such as schools and youth cultural activity centers to open new stores.