Which technique does the author use to help readers understand the meaning of contaminants in paragraph 4?

contaminants definition below

Explanation:

a polluting or poisonous substance that makes something impure.

ian mortimer in his book "the time traveller's guide to elizabethan england" uses a narrative in his style, which successfully conveys a clear description of the life in england in the 16th century. he writes in second person, which makes it comfortable to reader and easy to understand, he captures the readers attention with views of the landscape, the streets, the people including rich and poor. he also depicts some cultural traits from how people behave, eat or what they wear. his descriptions range from the social, economical, the political power to the examples of the life of common people. it could be tell that this book is about social history rather than a   novel.