A British scientist warned that youngsters who use mobile phones risk suffering memory loss sleeping disorders and. Other health. Problems children are particulars vulnerable to radiation penetration. Because their skulls are smaller and thinner , making it easier for the waves to get through . Their immune systems are less robust and are still developing . There are about 35 million mobile phone users in britain . A further 40,000 phones are sold each year . Children aged 9 and 10 are beieved to be one of the most rapidly growing markets . Brightly colored phones , and the capacity to send text massage are popular with schoolchildren .