Another advantage of the biological system is that it requires no heating or cooling, and no toxic chemicals.

生物学处理过程的另一个好处是它无需加热或冷却，而且无有毒化学品。

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Workers who remove the metals often have no protective equipment and breathe in high levels of toxic chemicals, which are then released into the atmosphere.

工人经常是在没有保护设施的情况下做清除金属的工作，吸进高度有毒的化学物质，这些化学物质又被排放到空气中。

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Workers who remove the metals often have no protective equipment and breathe in high levels of toxic chemicals, which are then released into the atmosphere.

工人经常是在没有保护设施的情况下做清除金属的工作，吸进高度有毒的化学物质，这些化学物质又被排放到空气中。

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