Yesterday they visited an art museum.

is that base, past, past particle, or present particle?

Past

Explanation:

In the given sentence Past tense is used.

Here the  subject visited an art museum yesterday. Hence it was an completed action and it falls under past tense category.

Here the subject completed the action in a definite time in the past.

Here the verb is in the past form of "visit". Hence from the above statements it is clear that Sentence type belongs to PAST.

being ignored by someone and then accepting the fact was really tough

i guess the cause and effect would show how being around the smoke(the cause) can have negative effects on the body.

explanation: