A few years back my son embarked on the bright and shiny adventure known as Middle School. Suddenly, his academic world quadrupled in size to a 2,000-kid student body. So my husband and I did what any responsible parents would do: We got him a phone. According to the non-profit Teens Turning Green, of the more than four billion people who have cell phones, half are under the age of 20. Yet because of their thinner skulls, children receive double the cell phone radiation exposure as adults, according to the Environmental Health Trust. Long-term cell phone use significantly increases brain tumor risk. And those who began using cell phones as…