lakes - substantial inland bodies of standing water.

law - an act or bill which has become part of the legal code through passage by Congress and approval by the President (or via Congressional override).

lead - a naturally-occurring heavy, soft metallic element; human exposure can cause brain and nervous system damage, especially in children.

lead poisoning - damaging the body (specifically the brain) by absorbing lead through the skin or by swallowing.

least-cost planning - a process for satisfying consumers' demands for energy services at the lowest societal cost.

leukemia - a form of bone marrow cancer marked by an increase in white blood cells.

life cycle assessment - methodology developed to assess a product's full environmental costs, from raw material to final disposal.

light pollution - environmental pollution consisting of harmful or annoying light.

litter - waste material which is discarded on the ground or otherwise disposed of improperly or thoughtlessly.

logging - cutting down trees for commodity use.

longlines - fishing lines stretching for dozens of miles and baited with hundreds of hooks. Longlines are indiscriminate and unintentionally catch and kill immature fish along with a wide variety of other animals in the Atlantic including tunas, sharks, marlins, sailfish, sea turtles and occasionally pilot whales and dolphins.

low-emission vehicles - vehicles which emit little air pollution compared to conventional internal combustion engines.

low-impact camping - camping that does not damage or change the land, where campers leave no sign that they were on the land.

lumber - wood or wood products used for construction.

lung diseases - any disease or damaging conditions in the lung or bronchia such as cancer or emphysema.

lymphoma - a tumor marked by swelling in the lymph nodes.