Items that break down over time naturally, like food scraps or paper, are biodegradable. According to the World Wildlife Foundation, most biodegradable items are made from animals or plants, but some artificial materials designed to mimic these organic substances can also degrade over time. When the environment--air, sunlight, water or ground soil substances--cannot break down the waste, it is considered non-biodegradable. These products have a longer-lasting effect on the environment.
Lifespan of Materials
Just because an item is biodegradable does not mean that it will break down quickly. According to a chart from the Coral Reef Alliance, a banana peel degrades in two months, while notebook paper will break down in three months. Harder substances take longer. Soda cans can take up to 350 years, while the plastic rings that hold together a six-pack of those cans can take up to 450 years. Glass bottles and styrofoam products might never biodegrade. The danger is that products that do not biodegrade will continue to pile up over time, requiring more and more land devoted to holding waste.
Contaminated Ground Water
Long-term exposure to air, light and water can cause synthetic materials like plastic to emit toxic pollutants. Plastics, which are petroleum-based, contain toxins that can leach into water supplies. A 2007 study released by the Environmental Working Group showed that low doses of Bisphenol A--a chemical used in water bottles, food containers and hard plastics--leach into foods and water over time and are carcinogenic, cause insulin resistance and interfere with conception.
Plastic pollutes the air in much the same way it taints water supplies. Constant exposure to heat melts plastic, emitting gases into the atmosphere in a process known as outgassing. According to the conservation website Mindfully, incinerating plastic causes toxic fumes to be released into the atmosphere. The same problem happens with plastics exposed to constant sunlight.