Light pollution is caused by poorly designed lighting that shines light upward and outward instead of focusing it downward. There are two types of light pollution: light glare, which is unused light shining up and out, and light trespass, which lights up windows and property. Streetlights are a major contributor, accounting for 35-50% of light pollution. Light pollution wastes energy, disrupts ecosystems and human health and psychology, and interferes with astronomy. Solutions include using fully shielded fixtures, turning lights off after hours, and reducing light levels on storefronts and parking lots. Light pollution is one of the most easily addressed types of pollution.