Does environmental liability under Ontario law automatically pass to a new owner when contaminated land is sold?

Yes, in general. Ontario's environmental protection framework focuses primarily on who currently owns or controls a contaminated property, not on who historically caused the contamination, which means a new owner can become responsible for investigating and remediating a problem they didn't create, simply by taking title. The ministry's ability to issue an order requiring action is generally tied to the person in a position to control or address the land today.

This is exactly why environmental due diligence before closing matters so much on any property with a real risk of contamination: once you own the land, the liability is generally yours to manage regardless of how it got there, and pursuing the previous owner for costs afterward is a separate, often difficult, legal process rather than something that happens automatically. Contractual protections like an environmental indemnity, a price adjustment, or a holdback of sale proceeds can help address this risk in the purchase agreement itself, but they don't change the ministry's ability to look to the current owner first. Buyers should treat "the previous owner caused it" as a possible later claim, not a shield against present responsibility.