In the Indian city of Kolkata lies a bridge that is in danger, although not from vandals, weather or natural erosion, or even age.

No, the culprit is spit.

The Howrah Bridge is a cantilever suspension bridge that crosses the Hooghly River. Over the years, residents have been purchasing and chewing a mix of betel leaf, areca nut, and slaked lime, then spitting the mixture at the base of the bridge.

The mixture, known as paan, is a mild stimulant and, if you take a look at the weakened steel hangars of the bridge, also quite corrosive.

The hangars, which were once 6 millimeters thick, are now a mere 3 mm, prompting authorities to come up with news ways to prevent any future damage.

One such way is to cover the bridge’s steel with a fiberglass casing.

http://www.abc.net.au/news/2011-11-24/human-spit-build-up-could-cause-bridge-collapse/3691468