Areas of Miami, Florida, are now being sprayed with the insecticide naled in an attempt to eradicate the Aedes aegypti mosquito — carrier of the zika virus. Naled, a potent neurotoxin that kills mosquitoes on contact, is perfectly safe, or so the Environmental Protection Agency insists, despite Puerto Rico’s rejection of its use to combat the spread of zika there — due to concerns about its safety.To keep naled airborne where it would be most effective, the agent is sprayed in very fine aerosol droplets — about two tablespoons can be dispersed to cover an area the equivalent of...