All the "bad stuff" is also in the skin if it's not organic.

And if it's organic. Organic does not mean they don't use fertilizers or have cleaner apples in general.

If you're worried about bad chemicals that can't be washed off then the core would likely be poisoned as well because it's going through the skin.

In europe, with organic foods you have a very clear list of which fertilizers are authorized. And those authorized are not poison, they are not harmful for the organism.

For dirt, you can just wash it. Dirt is not harmful and doesn't penetrate the fruit.

About chemicals, a large part stays in the skin of fruits / vegetables, so it's always better to remove it when you're eating non organic food.