Used or leftover antifreeze is poisonous to flora and fauna alike. After being used, antifreeze can contain heavy metals which can contaminate watersheds and soils. As antifreeze is petroleum based, it’s also a non-renewable resource, and takes energy to produce, which increases its impact on our planet. Proper disposal of antifreeze, as a household hazardous waste, is imperative to protect children and pets from poisoning and our rivers and oceans from pollution.