It's safe to use aluminium foil at the bottom of a grill pan, to save washing up, as long as the food does not touch it. We have long been recommended to avoid using aluminium cooking pans, as aluminium toxicity is thought to be one of the many, many contributory causes of dementia. And recently I read in the press that that now includes aluminium foil - all those take-away and frozen foods that are contained in aluminium containers.
I also use the non-stick oven liner at the bottom of my oven, but oven manufacturers recommend that if your oven is heated from below, the oven can be damaged - they never say how, and presume that would go for aluminium also. It is fine in most ovens.
"Green" considerations are another factor as aluminium may be recyled, if clean. Furthermore its use should be avoided as much as possible as aluminium mining is an environmentally damaging process.
Cooking food directly on non-stick oven liner concerns me, as I assume it is a plastic, and perhaps there is a possibility of plastics migrating into the food with heat. I guess the jury is still out on this.