Automobile exhaust tetraethyl lead is a highly toxic substance.

汽车尾气中的四乙基铅是剧毒物质。

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Singlet oxygen, a byproduct of the photosynthetic process by which certain cells convert sunlight into energy, is a highly toxic and reactive substance that tears cells apart.

单态氧是特定细胞在其光合作用过程中的副产物之一，而细胞通过这一过程将光转化为能量。该物质具有很高的毒性，同时也是一种可使细胞破碎的活性物质。

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Ricin is a highly toxic substance made from castor beans.

NPR: FBI: Arrest Made In Wash. State Ricin Letter Scare

Ricin is a highly toxic substance derived from castor beans.

CNN: Ricin scare rattles Washington