When the chemicals react with nitrogen oxide--found in pollution from cars--they form ozone, a much bigger health threat to humans and animals.

然后，当这些化学物质与氮氧化合物(存在于汽车排放的废气中)发生化学反应时，就会形成臭氧，这会对人类和动物的健康构成更大的威胁。

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The chemicals form when amino acids react with creatine, a chemical found in muscles.

VOA: special.2010.06.01

The chemicals react, and their products duly register in a nearby computer.

FORBES: A hail of silver bullets

These free radicals are oxygen-rich molecules in which one of the oxygen atoms is particularly likely to react with other chemicals.

ECONOMIST: Trojan DNA

These are tiny glass chips dotted with thousands of microscopic wells where DNA fragments react with other chemicals in order to measure the activity of genes or identify genetic variations.

ECONOMIST: Acoustic microfluidics