Products like baby mattresses and car seats that use flame retardants have come under heavy scrutiny in recent years because they contain powerful toxins that are known to cause impaired neurological development and a variety of other health problems. In an ironic twist, new research suggests that flame retardants, even though they may slow the spread of flames, can produce deadlier fires. A not-yet-published study in Great Britain finds that flame retardants increase the amounts of carbon monoxide and hydrogen cyanide — two of the biggest killers in fires — when they are burned. Few details about the new research have been released so far, but this sounds like another strong case against the continued use of flame retardants.