threshold concentration

例句：

1. 1. Thethreshold concentration for the virus is very low.
   病毒的门槛浓度非常低。
2. 2. The researchersfound that the threshold concentration of the pollutant was too high.
   研究人员发现污染物的门槛浓度太高了。
3. 3. Thethreshold concentration of the pollutant is critical to thehealth of the environment.
   污染物的门槛浓度对环境的健康至关重要。