Safety is operated by statistics, not boolean logic.

Things are not either safe or unsafe. It all depends on trade-offs, and what risks we can accept in exchange of other values, such as comfort.

The article mentionds, though, two worrying things such as the bias in investigations and ongoing GPS technology usage increase.

I would also stress that it _might be not_ linear. Combined risk of few hundrends of turned on cell phones is not a mere multiplication of risk for a single device.