You can't see it, smell it, or taste it, but too much of it can be explosive -- literally. We're talking about methane gas.
Landfills and dump sites are a primary source of methane, and they can be danger spots if not properly maintained.
Americans produce a lot of trash. In 2010, the Environmental Protection Agency says Americans threw away about 250 million tons of it. All that decomposing waste produces the toxic gas. In fact, landfills are the third largest source of methane emissions in the country.