This is the 393rd most frequent Chinese word.
有关
Related; concerning; about.
This sentence uses "有关" to mean "about" or "related to" and describes the subject matter of something (the book discussing history).
这本书有关历史的知识。
This book is about historical knowledge.
Here, "有关" is employed to express "being related to," in this case, describing people connected to a situation.
与此事件有关的人已经被通知了。
The people related to this incident have already been notified.
In this sentence, "有关" indicates a relationship or relevance to a topic, which is environmental issues here.