The paper won’t release noxious chemicals, and will not burn.
Phone calls to several manufacturers put any safety worries to rest: Using parchment at higher-than-recommended temperatures does not release noxious chemicals, and the paper will not burn.
But there’s no question that it can darken and turn brittle. For pizza and other flatbreads that bake in 20 minutes or less, the parchment doesn’t turn brittle quickly enough for it to be an issue.
For dishes that are in the oven at high temperatures for more than 30 minutes, such as our Almost No-Knead Bread, parchment can break down enough to fall apart—a particular issue in this recipe, in which we use the parchment as “handles” to remove the bread from the hot pan.
In this case, we’d recommend seeking out paper rated for use at the highest temperature available (our favorite parchment paper from King Arthur Flour is rated for up to 450 degrees, and did not become overly brittle or tear in prolonged high-heat applications) and placing a strip of folded aluminum foil (4 or 5 inches wide) beneath the parchment when baking. The foil had no detrimental effect on the color or texture of the bread we baked, and it made for easy removal of the loaves, even after the parchment itself had become brittle.