The developing world faces a silent killer. Could a $1 solar light help?

A Filipino social enterprise is bringing cheap solar lighting to more than 20 countries helping improve safety, reduce air pollution and cut energy costs

Every day at around 6pm, 40 families living in a remote corner of Andhra Pradesh in southeast India - a 6km walk from the nearest road - would be swallowed by darkness. With no access to electricity, sunset was a non-negotiable curfew - going outside was dangerous, people couldn't cook and children were unable to do their homework.

This changed in April 2015 when Liter of Light, a project that transforms plastic bottles into simple solar lights, introduced solar-powered street lamps to the villages. "Some of the children had never seen [artificial] light in their lives," says Pankaj Dixit, co-founder of Liter of Light's Bangalore branch in India. "They said we had added four hours to their lives every day."