Jonathan M. Samet, a pulmonary disease specialist who is dean of the Colorado School of Public Health, said the most recent studies showed negative health effects well below the 12-microgram standard.

乔纳森·萨梅特是科罗拉多公共卫生学院院长兼肺病专家，他说，最近的多项研究表明，微粒水平远低于12微克这一标准的空气依然会给人体健康带来负面影响。