Several agencies came together to discuss the problem at an emergency meeting at Belfast City Hall on Friday.Representatives were discussing the prevalence of substance users in the Smithfield area of the city centre."There are big issues around an increase in anti-social behaviour were some of the traders are actually being threatened by people who are high on these substances," Sinn Féin Councillor Deirdre Hargey explained."There is also a big safety concern for young people who are in and around the area using these substances, (some) are actually passing out to the extent where some of them are choking on their own vomit and emergency services have to be called."Despite being called legal highs - most are illegal to sell, supply or advertise for human consumption.But there are still retailers in Belfast offering the substances and now local representatives, traders and voluntary and statutory bodies are working with the police to clamp down on these shopkeepers.Groups working with vulnerable young people say the use of legal substances is a growing problem.Marie Wright from Opportunity Youth said that around 60% of those abusing substances have been dabbling or have been affected by legal highs."Cannabis and alcohol would still be the most dominant substances among young people but when you through a legal high into the mix that cocktail of drugs can have quite serious effects," she explained.A PSNI statement said its officers were involved in a significant operation last November in three affected areas - Writer's Square, Gresham Street and Castle Street.During that time 13 arrests were, 56 searches carried out and 14 referrals given to the Youth Justice Agency.A police spokesman said some court proceedings are ongoing.Following the meeting, Cllr Hargey added: "We hope from today that there will be a co-ordinated plan of action around trying to deal with this issue on the one hand that there can be enforcement for those shops that choose to sell these substances, also that there can be potential legislative change."But the big one is raising the awareness of the dangers of what's going on in that particular area and to try and combat that."