Well, one of the interesting intents of the EPA

环境保护署的一个有趣的意图
was to reduce the particle size, to reduce the larger particles.

是减小颗粒的尺寸缩小较大的颗粒
And what happened when the engines became more efficient

接下来发生了什么当引擎变得更有效
to accomplish that was they produced more,

实现了产生更多
but smaller particles.

但更小的颗粒
So the finer particles, less than one micron in size,

这些微小的颗粒在尺寸上小于1微米
not thinking that these finer particles can be more deeply inhaled

并没有想到这些更微小的颗粒
into the lung, they reside there,

会被吸入更深进入肺部它们就留在那
they get stuck to the sides of the airways,

它们附在呼吸道的边上
particularly in those that have background illnesses

特别对那些已经有背景疾病的人来说
such as asthma, emphysema, lung cancer.

诸如哮喘肺气肿肺癌
So that these particles don't get expired,

因而这些颗粒无法被排出