of all the tributaries generated along its banks and in the basins of the many rivers and streams that flow into it. The levels of particulate matter in the air are twice as high as that recommended by the World Health Organization, in part because of the large numbers of vehicles in circulation. The waters of Sepetiba Bay are slowly following the path traced by Guanabara Bay, with sewage generated by a population of the order of 1.29 million inhabitants being released without treatment in streams or rivers. With regard to industrial pollution, highly toxic wastes, with high concentrations of heavy metals – mainly zinc and cadmium – have been dumped over the years by factories in the industrial districts of Santa Cruz, Itaguaí and Nova Iguaçu, constructed under the supervision of State policies. The Marapendi lagoon and the Rodrigo de Freitas Lagoon have suffered with the leniency of the authorities and the growth in the number of apartment buildings close by. The illegal discharge of sewage and the consequent deaths of alge diminished the oxygenation of the waters, causing fish mortality. There are, on the other hand, signs of decontamination in the lagoon made through a public-private partnership established in 2008 to ensure that the lagoon waters will eventually be suitable for bathing. The decontamination actions involve the transfer of sludge to large craters present in the lagoon itself, and the creation of a new direct and underground connection with the sea, which will contribute to increase the daily water exchange between the two environments. However, during the Olympics the lagoon hosted the rowing competitions and there were numerous concerns about potential infection resulting from human sewage. Climate Rio has a tropical savanna climate (Aw) that closely borders a tropical monsoon climate (Am) according to the Köppen climate classification, and is often characterized by long periods of heavy rain between December and March. The city experiences hot, humid summers, and warm, sunny winters. In inland areas of the city, temperatures above are common during the summer, though rarely for long periods, while maximum temperatures above can occur on a monthly basis. Along the coast, the breeze, blowing onshore and offshore, moderates the temperature. Because of its geographic situation, the city is often reached by cold fronts advancing from Antarctica, especially during autumn and winter, causing frequent weather changes. In summer there can be strong rains, which have, on some