Sure, only because the chemicals weren't regulated yet by the government (and they fought as hard as they could to keep that from happening). Funny enough, DuPont actually had its own regulations for dumping such chemicals and knowingly violated them (which became the cornerstone for the class action lawsuits against them).

That said, there's plenty of cases of illegal dumping out there with chemicals that are regulated.

For example: https://apnews.com/9717f8be97db4944a825088dc5eee379/US-prose...