题目选项分析

Consumer advocates argue that the coating found on non-stick cookware contains harmful chemicals that are released into the air when the cookware is heated above a certain temperature. The manufacturer of the cookware acknowledges this hazard but assures consumers that the temperature threshold is much higher than would ever be needed for food preparation and therefore no special precautions need be taken in using the cookware. Which of the following, if true, would cast the most serious doubt on the claims of the manufacturer?

【选项】There are effective non-stick coatings that do not release toxins when heated