Upton sincliar is known as being a muckraking journalist for his exposing of abuses in which industry?

He discovered mistreatment of people in the meat packing industry. Look up the Jungle.

Upton Sinclair was a muckraking journalist who authored the Jungle.

The Jungle focused on the disgusting abuses in the meat industry and forced many Americans to reevaluate what they were eating and for President Theodore Roosevelt to set up new regulations.