The Biden administration is proposing tougher standards for a deadly air pollutant, saying that reducing soot from tailpipes, smokestacks and wildfires could prevent thousands of premature deaths a year. A proposal released Friday by the Environmental Protection Agency would set maximum levels of 9 to 10 micrograms of fine particle pollution per cubic meter of air, down from 12 micrograms set a decade ago under the Obama administration. The standard for particle pollution, more commonly known as soot, was left unchanged by then-President Donald Trump, who overrode a scientific recommendation for a lower standard in his final days in office....