There are people who are actively involved in volunteer activities.
On the other hand though, there are those who have no interest in them.
ご質問ありがとうございます。
"There are people who are actively involved in volunteer activities."＝「ボランティア活動に積極的に関わっている人々がいます。」
"On the other hand though,"＝「もう一方では」
"there are those who have no interest in them."＝「それらに興味がゼロの人々もいます。」
ご参考に。
アメリカ合衆国 
