Various nations have developed and produced chemical weapons -- substances whose main use is to harm people -- such as nerve gas or mustard gas.

There are places along the Mississippi River (e.g. New Orleans) where many people live in areas that would normally be flooded, were it not for levees or other flood control works.

The WTC victims were killed not just by terrorists, but by the buildings themselves.

Cropduster flights resumed Sept. 25, 2001. The FBI had ordered cropdusters grounded nationwide temporarily in late Sept. 2001.

The President's Commission on Critical Infrastructure Protection was set up in July 1996 under President Clinton's Executive Order 13010.

A likely upcoming shift in California's strategy to reduce smog from cars could affect new vehicles rolling onto roads nationwide over the next few years.

Timber-rich states and regions grapple with public calls for ending clear-cutting.

On Feb. 1, 2001, the Army Corps of Engineers is expected to release its final implementation plan for returning the flow of the Missouri River to more natural levels.

The heads of Obama administration Congressional committees and subcommittees will likely be in the spotlight in the coming months. This overview will help you get a feel for who these people are, or who will soon be chosen.

The Southern Environmental Law Center's top 10 places in America's South that face "immediate, potentially irreparable threats in 2009" represent a cross-section of the major environmental issues facing these states.