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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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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