 In 2004 , while reading Sanjoy Hazarika 's book Bhopal : Lessons of a Tragedy , Ravi Kumar got the idea of making a film based on the disaster . The Bhopal disaster is considered the world 's deadliest industrial disaster . Seeing that very few people of the newer generation knew about the disaster , Kumar decided to make a film based on it . He chose several well known actors for the film because he felt that this provided more chances of showing the " story to the world . " He wanted to cast Sheen for the role of Anderson , because of his political views and acting skills . Tannishtha Chatterjee and Rajpal Yadav were also cast for the film . Sienna Miller was previously attached to the project , but later dropped out and her role was given to Mischa Barton . In December 2008 , it was confirmed that Barton , Martin Sheen and Kal Penn were filming in India for the project . A copy of the script was sent to Penn , who agreed to join the project . Penn played the role of an Indian journalist and learnt Hindi from an instructor . In January 2009 the film 's shooting was wrapped up . Initially , the film 's story was written like a thriller and then dramatic elements were added to the film . Kumar wanted to depict Anderson as a victim of organisational error of judgement but Sheen insisted that Anderson should be depicted as a guilty and so he rewrote some of the scenes . Made on a total budget of US $ 12 million , the film was shot in Hyderabad 's Charminar area and Golconda Fort , Mumbai and the Union Carbide factory in Bhopal during a course of 18 months . A few scenes were also shot in Los Angeles . Hyderabad was chosen since it bore great resemblance to Bhopal in terms of its Mughal influence and architecture . Only a few important scenes were shot in Bhopal while the majority were shot on different factory locations and sets in order to create the setup for the period . 
