total chemicals

Dave Cesark, an executive at Mesa Energy Partners LLC, tried to reassure, saying that fracking chemicals constitute "just a drop in the bucket": only 0.5% of the total fluids, including water, that the company uses to drill natural gas.

Mesa能源合伙公司经理戴夫？？赛萨科希望人们打消顾虑，他说，他们在破裂法中使用的化学品只是一篮水中的一滴，仅占包括水在内的液体总量的0.5%。

Polycyclic aromatic hydrocarbons ( PAHs), a kind of POPs are ubiquitous in air, contributing more than 1/ 3 of the total carcinogenic chemicals, with the source of oil-leak, traffic emissions, environmental tobacco smoke, fuel-burning, cooking oil-fumes, and, so on.

多环芳烃（PAHs）是大气中广泛存在的一类持久性有机污染物，占自然界中致癌物质总量1/3以上，主要来源有石油泄漏、汽车尾气、环境烟草烟雾、燃料燃烧及烹调油烟等。