Updated December 2012
States continue to consider adding a bittering agent (most commonly, denatonium benzoate) to antifreeze in order to protect pets and small children from ingesting the substance. California has required the addition of a bittering agent to antifreeze since 2002 and Oregon since 1991. Since 2005, Arizona, Georgia, Illinois, Maine, Maryland, Massachusetts, New Jersey, New Mexico, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, and Wisconsin have passed legislation requiring the addition of a bittering agent to antifreeze.
In 2006 and 2007, Illinois and Pennsylvania adopted resolutions in support of the passage of the federal antifreeze bittering additive legislation.
The Alabama, Missouri, Nevada, New York, Ohio, Pennsylvania, and South Carolina legislatures have considered but not passed bills requiring a bittering additive in recent years.
At the federal level, the Antifreeze Bittering Act was introduced in the 108th Congress (2005-06) but did not advance after its placement on the Senate Legislative calendar. In the U.S. House, H.R. 2567 passed the House Energy and Commerce Committee, but did not progress any further. The AVMA supported the passage of both bills and encourages the use of clear warning labels emphasizing the potential danger of Ethylene Glycol to animals.
In December 2012, the Humane Society Legislative Fund and the Consumer Specialty Products Association announced an agreement to voluntarily add a bitter flavoring agent to antifreeze and engine coolant manufactured for sale for the consumer market in all 50 states and the District of Columbia. This comes as a result of years of battling over legislation addressing the issue. The Humane Society Legislative Fund estimates that 10,000 to 90,000 animals are poisoned each year after ingesting ethylene glycol, the highly toxic substance used in antifreeze and coolant.