Fluorescent bulbs and certain ballasts contain hazardous materials, such as mercury, which can contaminate the environment and is harmful to human health. Each fluorescent lamp contains around four milligrams of mercury, which means one hundred fluorescent lamps contain four grams of mercury. It doesn’t sound like much, but mercury is extremely hazardous even in the smallest of quantities, and it only takes one ounce of mercury to contaminate a lake for centuries. That’s why it is imperative that all fluorescent lamps be properly recycled.