Air pollution is deadly: A new study links exposure to it to more than 107,000 premature deaths in the United States in 2011. It isn’t just killing us; it cost the country $866 billion, more than double the value of all the economic activity in a country like Ireland, according to the study, published Monday in the Proceedings of the National Academy of Sciences. Particulate matter, or particle pollution, is the mix of solid and liquid droplets floating in the air, according to the Environmental Protection Agency. It can come in the form of dirt, dust, soot or smoke. Particulate pollution comes from coal- and natural gas-fired plants. Cars, agriculture, unpaved roads, construction sites, and wildfires can also create it.