No way in hell Google isn't going to use this for advertisement. It's exactly the kind of huge free money that drives everyone else to collect data totally unrelated to their core business. Even if the intentions are benign now, there's no reason to trust they'll be so later, based on Google's track record and the typical tech mindset.
Just imagine the kind of profiles you could build on people with medical data. Beyond targeted drug advertisement, medical devices, and the like, you know which people are sedentary, which play sports, who probably smokes, and I'd bet good money there are correlations between certain conditions and shopping habits, religious preference, and even political preferences. Just begging to be clustered with the latest hot neural net.