Ir is found in high concentrations in some meteorites, in which the solar system's original chemical composition is preserved.

人们发现，在一些保存着太阳系原始化学成分的陨石中，铱元素的含量很高。

youdao

In high concentrations, QACs kill bacteria.

在较高浓度下，季铵盐化合物能杀灭细菌。

youdao

In high concentrations, carbon monoxide can harm human health by reducing oxygen to the heart and brain.

高浓度下，通过减少心脏和大脑中的氧气，一氧化碳会危害人体健康。

youdao

So if we consider lithium, potassium, and sodium, they're all together in the same group on the periodic table, knowing what we do about biology we can immediately think of sodium and potassium, or even just knowing what you know about table salt, for example, that these are two elements that we find, and particularly in the ion form in very high concentrations in our body.

我们来考虑一下锂，钾和钠，它们都在周期表中的同一族里，想要知道我们将元素周期律,用到生物学会怎么样，我们首先想到的就是钠和钾，甚至只需要知道食盐，我们发现它们是以很高浓度的离子形式,存在于我们体内的两种元素。

麻省理工公开课 - 化学原理课程节选

It can blister a person's lungs if it is inhaled and can cause death in high concentrations.

CNN: Four compounds from shuttle can harm on contact

For example, nicotine in high concentrations is a potent poison.

ECONOMIST: Suicide technologies

If they occur in sufficiently high concentrations, they can kill a cell.

ECONOMIST: Trojan DNA