Any plastic that's smaller than a few micrometers is called a nanoparticle, and research has found that these microscopic particles can even pass through biological barriers, such as cell membranes.

小于几微米的塑料可被称为纳米微粒，研究发现这些微小颗粒可穿过类似细胞膜的生物屏障。

This helps maintain a biological barrier that prevents the creature from moving northward, and thus safeguards a programme spanning decades and countries that has got rid of the fly from North America.

这有助于维持一种生物屏障，阻止这种生物向北移动，从而维持了一个为期数十年、横跨多国的项目，这一项目使这种苍蝇在北美消失。