30 mins a day for 4 years, that's way too low. I would have thought everyone on earth would be using phone for more than 30 mins a day, and yeah they would have been using it eversince they are born.
So my only question is "Even if we do conclude this is harmful, there is no way we will stop using phone!!!"
Do you think people stop taking sugar because they fear diabetes or oil cause they fear cardiac arrest. Indian researchers got to use better subjects, here in US, there a lot of better topics that are researched on (I know a few are useless too!!!) than 30 min daily usage