Artificial light: It stresses our eyeballs, fiddles with our biological clocks, and may even contribute to obesity. These are just a few of the health concerns associated with indoor lighting in the developed world.
But in warm, developing countries, light bulbs can be literal beacons for human disease when buildings aren't uniformly equipped with screens or glass windows. In Brazil, for example, a fluorescent light can invite deadly pathogens on the backs of mosquitos, sandflies and more. Chagas disease, leishmanias, and malaria are all diseases transmitted by insects, whose attraction to light—especially to the blue and ultra-violent end of the spectrum—is well documented. According to the World Health Organization, some 584,000 people die of malaria alone each year.