I know a couple of big-scale farmers in the US. They are Christian, and believe in Creation. That doesn't stop them from using the necessary pesticides, or choosing the adequate strain of corn seeds, etc.
Believing in Creation doesn't turn you into an illiterate moron. Believing God created everything according to a design and purpose is not incompatible with acknowledging the presence of similarities and design patterns throughout all of Creation, and believing that doesn't suddenly poof take away your rational capabilities to think and understand things.
Either way, I was asking for is a real situation in which someone will be negatively impacted because they hold a Creationist belief.
Will a Creationist live a sad life without fully embracing the misteries of goose-bumps? Will a farmer not use pesticides, or choose the wrong one because Creationism? Will Advil won't work on a Christian because they don't understand that rats and rabbits are our cousins? Will their knees hurt more (or maybe less?) because they think humans were standing up from the beginning?