微克每毫升

For nicotine, that level was a mere 1.8 nanograms per milliliter — too low to be picked up in tests.

对于尼古丁，仅仅是1。8毫微克每毫升，太低而不易提取。

The mean blood lead levels in the 12-to-19-year-olds were 1.5 micrograms per deciliter in 1991 to 1994 and 1.1 micrograms per deciliter from 1999 to 2000, researchers say.

研究人员说，从1991年到1994年，12至19周岁美国人的平均血铅水平在0。015微克每毫升；1999年到2000年这一数字变为0。011微克。

In general, people are considered to be deficient if they have blood levels below 15 or 20 nanograms per milliliter.

一般来说，如果血液水平低于15或20毫微克每毫升即可被认为是不足。