Antifreeze as sold now is sweet, and a teaspoon is lethal to humans. Spouses have used it to murder each other.
A simple solution, as proposed by Rep. Gary Ackerman (D-NY), is to add a bittering agent to antifreeze it to make it taste horrible.
The legislation, entitled the Antifreeze Bittering Act, would require denatonium benzoate—the world’s most bitter substance—to be added to antifreeze sold in quantities of 55 gallons or less. The process would cost no more than three cents per gallon.
Children and pets have also been known to inadvertently drink antifreeze and die. I’ve heard stories of backpackers in the High Sierras who parked their car at a remote trailhead miles from anywhere only to return a week later and find dead marmots under their car who had chewed through the radiator hose to get to that sweet-tasting antifreeze.
Some say the bittering agent breaks down under heat,which could render it useless. Others disagree. Maybe another idea is to deliberately make it smell bad, like they do with natural gas.