Both the immigrant population and the social use of opium fell into decline.
British Dictionary definitions for immigrant
immigrant
/ˈɪmɪɡrənt/
noun
1.
a person who comes to a country in order to settle there Compare emigrant
(as modifier): an immigrant community
2.
an animal or plant that lives or grows in a region to which it has recently migrated
Word Origin and History for immigrant
n.
"one who immigrates," 1792, in an American context, from French immigrant, from Latin immigrantem (nominative immigrans), present participle of immigrare (see immigrate). Emigrant is older. As an adjective from 1805.