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The 10 worst pollution problems in the world

Oct. 16, 2009, 11:21 p.m.
Spraying pesticides over crops.

Photo: Mike Dabell/iStockphoto

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Groundwater contamination

Groundwater accounts for 97 percent of the world's accessible freshwater reserves. It seeps into the ground from rain, snowmelt, lakes and rivers. So too does water tainted by fertilizers, pesticides, motor oil and industrial waste, which in turn flows into drinking wells, streams or lakes.