While the radioactivity is low, the element's chemical properties pose a health risk.
New studies reveal that humans are rapidly draining a third of the world's aquifers, and nobody knows how much water is left in them.
The Colorado River Basin's underground water supplies are shrinking faster than they're being replenished.
Nearly 70 percent of the groundwater stored in parts of the United States' High Plains Aquifer, could be used up within 50 years.
Groundwater could be contaminated by the natural gas extraction process known as hydraulic fracturing, or fracking, after a decade or less.
Plants in Florida have fewer stomata now than they did a century ago - reducing the amount of moisture they release into the air.