An activity involving physical exertion and skill that is governed by a set of rules or customs and often undertaken competitively. b. often sports (used with a sing. verb) Such activities considered as a group: Sports is a good way for children to get exercise.
Rust is Iron Oxide. Hence, any warnings concerning the ingestion of iron may apply. Ingesting too much iron, whether it be via rust, suppliments, or otherwise, can lead to unpleasant symptoms including nausea and vomiting. Long-term side affects such as liver damage can be associated with excessive iron intake.
Rust isn't bad for you, with the possible exception of men who have hemochromatosis. Even then, I don't think that the uptake from iron oxide is very high. The reason rust forms is due to the high heat the grate is exposed to.