Updated at 5.56pm: The Department of Health on Monday warned about the dangers of passive smoking - saying medical studies now confirmed it could lead to serious health problems. A spokesman for the department said it would be supporting 'World No Tobacco Day' on Tuesday - an international anti-smoking day used to emphasise the dangers of the habit. The department plans to organise an activity entitled 'I Love Smoke-free Wong Tai Sin' from Monday to Wednesday in order to raise public awareness about the hazards of smoking. The spokesman said people were invited to participate in the activity - which is to be held in collaboration with the Healthy City in Wong Tai Sin Steering Committee and United Christian Nethersole Community Health Service. He stressed that it was now an established fact that second-hand smoking was hazardous to people's health. 'Second-hand smoke has been classified as Grade 1 Carcinogenic Substance. Evidence showed that long-term inhalation of second-hand smoke will dramatically increase our chances of suffering from deadly illnesses,' the spokesman said. He said medical studies showed that people frequently exposed to second-hand smoke could have three times as much cancer-causing agents in their urine as unexposed people. 'Second-hand smoke is the most important indoor air pollutant. If somebody smokes in some public indoor premises, everyone in the premises will inevitably be subjected to second-hand smoke,'' the spokesman said. He added that the problem of indoor second-hand smoke should not be neglected. 'The department will up a series of anti-smoking exhibitions in Lung Cheung Mall from Monday to Wednesday,'' he said. An anti-smoking ceremony would be held at 5pm on Tuesday on 1st Floor, Lung Cheung Mall, Wong Tai Sin. 'Let's strive for a smoke-free Hong Kong,' the spokesman said, appealing to people to take part in the activity. Studies on smoking have shown that it can lead to heart disease, lung cancer as well as bronchitis and emphysema. Smoking is a serious health concern in Hong Kong. According to recent reports, the government spends $900 million a year treating smoking-related diseases. Statistics show that about 5,500 people die in the territory of smoking-related diseases each year. Smokers account for about 15 per cent of Hong Kong's total population.