Question: When did air pollution start in the city where Spectre was filmed after filming where Giovanni Gronchi died?

full_context: Document 1: Mexico City: By the 1990s Mexico City had become infamous as one of the world's most polluted cities; however the city has become a model for dramatically lowering pollution levels. By 2014 carbon monoxide pollution had dropped dramatically, while levels of sulfur dioxide and nitrogen dioxide were nearly three times lower than in 1992. The levels of signature pollutants in Mexico City are similar to those of Los Angeles.[citation needed] Despite the cleanup, the metropolitan area is still the most ozone-polluted part of the country, with ozone levels 2.5 times beyond WHO-defined safe limits.
Document 2: Giovanni Malagodi: Giovanni Francesco Malagodi (12 October 1904 in London – 17 April 1991 in Rome) was an Italian liberal politician, secretary of the Italian Liberal Party and president of the Italian Senate.
Document 3: Spectre (2015 film): Whilst filming in Mexico City, speculation in the media claimed that the script had been altered to accommodate the demands of Mexican authorities—reportedly influencing details of the scene and characters, casting choices, and modifying the script in order to portray the country in a "positive light"—in order to secure tax concessions and financial support worth up to $20 million for the film. This was denied by producer Michael G. Wilson, who stated that the scene had always been intended to be shot in Mexico as production had been attracted to the imagery of the Day of the Dead, and that the script had been developed from there. Production of Skyfall had previously faced similar problems while attempting to secure permits to shoot the film's pre-title sequence in India before moving to Istanbul.
Document 4: Air pollution in the United States: Los Angeles has the most contaminated air in the country. With a population of roughly over 10 million, the Los Angeles area is a large basin with the Pacific Ocean to the west, and several mountain ranges with 11,000 - foot peaks to the east and south. Diesel engines, ports, motor vehicles, and industries are main sources of air pollution in Los Angeles. Frequent sunny days and low rainfall contribute to ozone formation, as well as high levels of fine particles and dust. The strong relationship between AQI and ozone levels may be found on air pollution maps.
Document 5: Spectre (2015 film): A brief shoot at London's City Hall was filmed on 18 April 2015, while Mendes was on location. On 17 May 2015 filming took place on the Thames in London. Stunt scenes involving Craig and Seydoux on a speedboat as well as a low flying helicopter near Westminster Bridge were shot at night, with filming temporarily closing both Westminster and Lambeth Bridges. Scenes were also shot on the river near MI6's headquarters at Vauxhall Cross. The crew returned to the river less than a week later to film scenes solely set on Westminster Bridge. The London Fire Brigade was on set to simulate rain as well as monitor smoke used for filming. Craig, Seydoux, and Waltz, as well as Harris and Fiennes, were seen being filmed. Prior to this, scenes involving Fiennes were shot at a restaurant in Covent Garden. Filming then took place in Trafalgar Square. In early June, the crew, as well as Craig, Seydoux, and Waltz, returned to the Thames for a final time to continue filming scenes previously shot on the river.
Document 6: Spectre (2015 film): With filming completed in Rome, production moved to Mexico City in late March to shoot the film's opening sequence, with scenes to include the Day of the Dead festival filmed in and around the Zócalo and the Centro Histórico district. The planned scenes required the city square to be closed for filming a sequence involving a fight aboard a Messerschmitt-Bölkow-Blohm Bo 105 helicopter flown by stunt pilot Chuck Aaron, which called for modifications to be made to several buildings to prevent damage. This particular scene in Mexico required 1,500 extras, 10 giant skeletons and 250,000 paper flowers. Reports in the Mexican media added that the film's second unit would move to Palenque in the state of Chiapas, to film aerial manoeuvres considered too dangerous to shoot in an urban area.
Document 7: Mexico City: To clean up pollution, the federal and local governments implemented numerous plans including the constant monitoring and reporting of environmental conditions, such as ozone and nitrogen oxides. When the levels of these two pollutants reached critical levels, contingency actions were implemented which included closing factories, changing school hours, and extending the A day without a car program to two days of the week. The government also instituted industrial technology improvements, a strict biannual vehicle emission inspection and the reformulation of gasoline and diesel fuels. The introduction of Metrobús bus rapid transit and the Ecobici bike-sharing were among efforts to encourage alternate, greener forms of transportation.
Document 8: Ticino League: In 1991, after some public campaigning in the Sunday journal "Mattino della Domenica" against political power and use of public money, the editor Giuliano Bignasca and the director Flavio Maspoli founded the Ticino League to continue the fight at the political level. Bignasca (1945–2013) was the League's "president for life".
Document 9: Spectre (2015 film): After wrapping up in England, production travelled to Morocco in June, with filming taking place in Oujda, Tangier and Erfoud, after preliminary work was completed by the production's second unit. An explosion filmed in Morocco holds a Guinness World Record for the "Largest film stunt explosion" in cinematic history, with the record credited to production designer Chris Corbould. Principal photography concluded on 5 July 2015. A wrap-up party for Spectre was held in commemoration before entering post-production. Filming took 128 days.
Document 10: Giovanni Gronchi: The unhappy Tambroni experiment tarnished Gronchi’s reputation for good, and until the end of his period of office he remained a lame-duck President. In 1962 he attempted to get a second mandate, with the powerful help of Enrico Mattei, but the attempt failed and Antonio Segni was elected instead. As he ceased to be Head of State, he became a life senator by right, according to the Italian Constitution. He died in Rome on 17 October 1978 at the age of 91.
Document 11: Air pollution in Mexico City: It has been said that ``Mexico City's air has gone from among the world's cleanest to among the dirtiest in the span of a generation. ''Historic air pollution episodes of the 1950s led to acute increases in infant mortality.
Document 12: Mexico City: The World Bank has sponsored a project to curb air pollution through public transport improvements and the Mexican government has started shutting down polluting factories. They have phased out diesel buses and mandated new emission controls on new cars; since 1993 all new cars must be fitted with a catalytic converter, which reduces the emissions released. Trucks must use only liquefied petroleum gas (LPG). Also construction of an underground rail system was begun in 1968 in order to help curb air pollution problems and alleviate traffic congestion. Today it has over 201 km (125 mi) of track and carries over 5 million people every day. Fees are kept low to encourage use of the system and during rush hours the crush is so great, that authorities have reserved a special carriage specifically for women. Due to these initiatives and others, the air quality in Mexico City has begun to improve, with the air becoming cleaner since 1991, when the air quality was declared to be a public health risk for 355 days of the year.[citation needed]
Document 13: Roman Republic: Tiberius' brother Gaius was elected tribune in 123 BC. Gaius Gracchus' ultimate goal was to weaken the senate and to strengthen the democratic forces. In the past, for example, the senate would eliminate political rivals either by establishing special judicial commissions or by passing a senatus consultum ultimum ("ultimate decree of the senate"). Both devices would allow the Senate to bypass the ordinary due process rights that all citizens had. Gaius outlawed the judicial commissions, and declared the senatus consultum ultimum to be unconstitutional. Gaius then proposed a law which would grant citizenship rights to Rome's Italian allies. This last proposal was not popular with the plebeians and he lost much of his support. He stood for election to a third term in 121 BC, but was defeated and then murdered by representatives of the senate with 3,000 of his supporters on Capitoline Hill in Rome. Though the senate retained control, the Gracchi had strengthened the political influence of the plebeians.
Document 14: Spectre (2015 film): Mendes revealed that production would begin on 8 December 2014 at Pinewood Studios, with filming taking seven months. Mendes also confirmed several filming locations, including London, Mexico City and Rome. Van Hoytema shot the film on Kodak 35 mm film stock. Early filming took place at Pinewood Studios, and around London, with scenes variously featuring Craig and Harris at Bond's flat, and Craig and Kinnear travelling down the River Thames.
Document 15: Trilussa: A very popular person in his city and Italy, Trilussa was named Life Senator on December 1, 1950, by the Italian President Luigi Einaudi. He died twenty days later.
ground_truth: 1950s
sub_queries: Where did he die? Answer: Rome
Where did Spectre filming take place after Rome ? Answer: Mexico City
when did air pollution start in Mexico City Answer: 1950s