Negotiators have agreed to a global phase-out of chemicals that run some air conditioners and refrigerators, but are also big contributors to global warming. That has countries and researchers scrambling to come up with clean and affordable alternatives.
Bed nets were hailed as the solution to the malaria epidemic killing thousands of children in tropical parts of the world. But now, years after they were distributed en masse, the mosquitos have developed resistance and the bed nets have holes. In other words, they're not working so well any more.