The amount by which something, especially a pollutant, exceeds a standard or permissible measurement.

某种物体的数量，尤其是指污染物，超过测量标准或是可容许的程度。

youdao

Sulfur dioxide, a major contributor to acid rain, is an especially serious pollutant because it diminishes the respiratory system's ability to deal with all other pollutants.

二氧化硫是酸雨的主要成因之一，它是一种特别严重的污染物，因为它会降低呼吸系统处理其他污染物的能力。

youdao

The experimental results of a full-size combustor show that the influence of humid air on pollutant emission is different for hydro-carbon fuels and synthesis gas, especially on co emission.

全尺寸燃烧室的实验结果表明，空气加湿对于碳氢燃料与合成气火焰污染物排放的影响不同，尤其是对CO排放的影响。

youdao

This is especially true the cleaner a country gets: eliminating the last 5% of a given pollutant usually costs more at the margin than cutting the first 50%.

ECONOMIST: Energy and the environment