In Calcutta, India, the 457-meter-long Howrah Bridge is being Threatened by pedestrian's spit. Why? Gutkha - the popular mixture of betel leaf, areca nut, and slaked lime, which many citizens chew and spit - is highly corrosive. According to the Calcutta newspaper The Telegraph. ''the commuters' collective spit power [has] reduced the thickness of the steel hoods protecting the [bridge's] pillars from six to three millimetre [s] since 2007.''
Some 500,000 pedestrians and 100,000 vehicles use this river crossing every day.