There's a lot of nasty chemical things in our world to be afraid of. We're increasingly aware of the risks from endocrine disruptors, and the toxicity of nanomaterials is a growing concern.

But I never thought I'd be afraid of sunscreen.

Why? Because there is new evidence that ingredients in the thousands of metric tons of sunscreen that washes off swimmers around the world each year is re-activating dormant viruses in the symbiotic bacteria that inhabit coral reefs.