Canada\'s national health agency is recommending reducing the use of cellphones, particularly among children, as a hedge against possible carcinogenic effects. \"There are a small number of epidemiology studies that have shown brain cancer rates might be elevated in long-term/heavy cellphone users,\" Health Canada said in a release, although it acknowledged other studies hadn\'t come to the same conclusion. The agency recommended parents supervise and reduce the amount of time their children spend on cellphones, as they are \"typically more sensitive to a variety of environmental agents,\" Postmedia News reported. The recommendation came a month after some parents demanded a school board north of Toronto turn off its WiFi system in schools because of radiation risks. The board refused, citing scant evidence of risks. Health Canada said by the end of 2010, there were 24 million cellphone users in the country. In May, the World Health Organization\'s International Agency for Research on Cancer issued a report saying electromagnetic fields from cellphones could be \"possibly carcinogenic\" to the human brain.