Probably, because too much naphthalene isn't very good for humans.

可能是因为吸收太多的萘对人的身体不好。

There's naphthalene, the main ingredient in mothballs.

樟脑丸的主要成分是萘。

The main thing naphthalene does is vaporize, making the air smell very strongly like mothballs and therefore a lot less like urine.

萘非常容易蒸发，这就使中有一烈的樟脑丸的味道，尿液的味道就不太明显了。

That's because, like naphthalene, paradichlorobenzene has a very strong smell and it can interfere with some of the bacteria producing the extra smelly ammonia.

这是因为二氯苯和萘一样也有的味道，它也可以影响产生难闻的氨的细菌。

In the early days of urinal cakes, probably around the turn of the 20th century, the little slabs were mostly made of naphthalene, AKA, olden-day moth balls.

大概在二十世纪初的时候，早期的芳香块主要是萘，也就是以前的樟脑丸。

Many urinal cakes these days are made of a compound called a molecule that looks a little bit like a throwing star and is often used as a naphthalene replacement in moth balls.

现在芳香块的主要成分是二氯苯，一种看起来像是飞镖一样的化学分子，通常在樟脑丸中作为萘的替代品使用。