Hog farming in Portugal is mostly located in the basin of the river Lis, Leiria District, which is known for its high level of pollution. The Lis basin occupies 850 km2 and is constituted by the river Lis (length 40 km) and its tributaries. It receives annually the equivalent of 2 million human fecal discharges in organic matter, nitrogen and phosphorus contained in the swine waste that are released almost entirely in water supplies.
Portugal has 2 million pigs, of which 45% are in Ribatejo and Leiria concentrating 1/3 of the total in this region (equivalent to 15% of the national total) with highly specialized exploitations with an average of 200 animals each, the second production region is the Alentejo with 25% and the third the Beira Litoral, with 21% of pigs.
In 1971 discussions about the existence of pollution in Lis began and in this year the first survey of the causes of its pollution were held. Several causes of pollution were listed, including sewage discharges, slaughterhouse discharges and swine. In the late 1970s, the pollution in the river Lis had worsened and became publicly known.
The pollution episodes - with the occurrence of discharges of effluents and deaths of fishes occured repeatedly. Sewage activity was considered responsible for the most relevant impacts.
In June 1987 a group of inhabitants of Carvide parish organized a petition with 365 signatures against pollution of the river Lis. In 1988, the press referred to the Lis situation as the "Disaster of Suinobyl" in reference to the Chernobyl nuclear power station. In the 90s, due to the increase of pollution and popular discontent was the Association for Environment Defense and Heritage of Leiria (OIKOS) was founded .
In 2002 and 2003, the most significant episodes of pollution in Lis occurred: for several days the water supply was cut due to contamination in the city of Leiria and a ban on bathing on beach Vieira, on the coast of Leiria, was put into force due to sewage pollutant discharges. These events led to the creation of a committee of local residents, the Commission of Environment and Defense of the Ribeira dos Milagres (CADRM), and to the establishment of Recilis, a company mostly composed by pig farmers in the region established to deal with and to treat the activity of effluents. In the following years, discharges continued and were denounced by the population, CADRM and Quercus, a national environmental association. The government announced a project to build a treatment plant for effluents from pig farming, which should have been operating by 2008, however, the project wasn’t implemented. Allegations of discharges of effluents continued and in 2008, OIKOS announced the results of a monitoring study about the Lis basin water which had been initiated in 1990: the level of fecal pollution was disturbing and the most problematic points were the Ribeiras do Sirol, dos Milagres and the Arrabalde Bridge (Leiria).
Since 2003, the EU has provided specialized legislation for the protection of pigs, especially related to the living conditions and feeding, legislation that should be implemented by all european countries by January 1st, 2013. Representing an investment of 200 EUR/animal, by mid-2013 only 75% of farms had complied with the new legislation. According to the President of the Portuguese Federation of Pig farmers (FPAS in Portuguese) the reason for the failure in implementing the legislation, is related to the high costs to be paid by swine farmers, estimated at 50 million Euros. However, it was expected that by September 2013, 100% of farms would have complied with the new regulations. In the meantime Portugal is required to pay fines to the EU for breaking the law.
In April 2010, Quercus held a protest near Ribeira dos Milagres, claiming for supervision and solutions to the swine culture pollution problem. New discharges were reported. In 2013, the government signed a protocol for the construction of a treatment plant in the region expected to be completed in two years.
In other locations in Portugal, populations suffering from the effects of swine culture pollution have also mobilized in opposition. In Póvoas and Rio Maior (Santarém) pollution caused by swine culture generated popular protests and was discussed in Parliament and in Castro Verde (Beja), where in the first 10 years of the 21st century attempts to expand hog farming met strong resistance from the local population, and they organized a petition to prevent the licensing of a company.