To shed light on how dangerous it is for humans to live in polluted environments, Chicago Energy Policy Institute has recently developed the Air Quality Life Index (AQLI), a system capable of analyzing air pollution worldwide. According to AQLI findings, Po valley air pollution affects inhabitants so hard that it cuts off about half a year of their life expectancy. The main reasons why there's a big stain of air pollution over the Po valley are strictly connected to livestock and factories. The so-called "NPK fertilizers", made of nitrogen, phosphorus and potassium, along with manure emissions from intensive breeding and high levels of nitrogen dioxide released by diesel and petrol engines are all accountable for this disastrous air condition in Northern Italy. The region of Lombardy produces also vast amounts of animal waste, a big contributor to pollution. It delivers more than 40 percent of Italy's milk production, for example, while over half of the Italian pig production is located in the Po Valley.