Learn Russian: Что касается чистоты, то комната очень чистая. - As for cleanliness, the room is very clean.

The verb касаться (to touch / to concern) always requires its object to be in the Genitive case. Because the fixed phrase что касается literally means "what touches", the topic introduced must always take the Genitive.

Why do we need the word то after the comma? Can I just leave it out?

No, you cannot leave it out. The construction Что касается ..., то ... is a mandatory paired structure in Russian. When you introduce a new topic in the first clause, то (which normally means "then") acts as a required bridge to connect it to the main statement.

Are чистоты and чистая related words?

Yes! чистота is the abstract noun for "cleanliness", while чистая is the feminine adjective for "clean". The suffix -ота is a very common way to turn adjectives into nouns in Russian, similar to how красота (beauty) comes from красивый (beautiful).

Could I use the short-form adjective чиста instead of the long-form чистая at the end of the sentence?

Grammatically, yes, you could say комната очень чиста. However, short-form adjectives often sound quite formal, literary, or dramatic. For an everyday statement about a room being clean, the long-form чистая is much more natural and common.