The number of years drug abusers are staying below the radar has doubled in the last five years, Hong Kong's drugs tsar revealed yesterday as she announced plans to consult the public on introducing "mandatory drug testing".
The average amount of time a person had been using drugs before coming to the attention of the authorities was four years last year - compared with just 1.9 years in 2008.
The figures from the Central Registry of Drug Abuse also showed that for those aged under 21, the figure had risen from 1.2 years to 1.8 years.
Most said they used drugs at home or at their friends' homes, in parks or public toilets.
Commissioner for Narcotics Erika Hui Lam Yin-ming said the situation was worrying and parents should pay more attention to their children.
"[Some] 97 per cent of these young people are taking psychotropic substances, which causes … irreversible harm to their health, and consequently translates into a burden on our medical and welfare system," she said.
The figures also showed, however, that the total number of drug abusers reported to the government dropped 5 per cent last year to 11,554. Heroin was the most popular drug.
Hui said it was the right time for society to discuss the "sensitive" issue of whether mandatory testing was needed. She did not go into detail.
Professor Daniel Shek Tan-lei, chairman of the government's Action Committee Against Narcotics, said police officers could not carry out drug tests on the grounds of reasonable suspicion under the current law.
He said the government had been discussing mandatory testing since 2009 but cautiously because, he said, of the political atmosphere in recent years.
Law Yuk-kai, director of the Human Rights Monitor, said it would be dangerous to give police powers that could allow them to intercept anyone for drug testing.
"Such a scheme would appear to infringe on human rights and individuals' privacy," Law said.
It would be more legitimate if police obtained a court order before testing people suspected of committing a crime, he said.
Meanwhile, some students in 30 out of 31 universities and colleges, 105 out of 106 secondary schools and 86 out of 100 primary schools were said to have tried drugs, according to a survey commissioned by the narcotic division of the Security Bureau.
Hui said it showed that even a reputation for academic performance did not mean a school was untouched by drug abuse.
But the percentage of secondary schools where pupils admitted having taken illegal drugs in the last 30 days dropped to 82 per cent from 90 per cent in the 2008-09 school year, when a similar survey was conducted.
The latest survey polled 155,859 students.
Some 21 per cent of students said they had taken drugs alone, up from 15 per cent from the previous survey.
And 64 per cent said they had taken drugs on the mainland or in Macau; another 40 per cent said they had taken drugs overseas. One in 10 said they were under the age of 10 when they first tried drugs.