He explains that lead can enter the ground from leaded paint and leaded fuel and from industry.

VOA: special.2009.06.09

So, you've got polonium or thorium sitting inside this leaded box with one opening.

把钋或者钍放在,开一个小口的含铅的盒子里面。

麻省理工公开课 - 固态化学导论课程节选