June 16, 2012. The U.S. Environmental Protection Agency (EPA) proposed tougher pollution standards for soot, a step that supporters said will protect public health and industry groups and Republicans warned would crimp economic growth. The annual standards for particulate matter, or microscopic particles released from automobile exhausts, power plants or factories, would be set from 12 to 13 micrograms per cubic meter under a proposed rule the EPA released. The current standard is 15 micrograms per cubic meter. The agency said it would issue the final rule by Dec. 14.