There’s no way to check the whole thing, but you can totally pick a component and reverse engineer it, which is something people do quite a bit. When spying is found, it’s usually a private company doing it.
The NSA doesn’t care about your search history, but advertisers do. (and the government ever did, they’ll just call up google)
A lot of these use strong bases, like sodium hydroxide, that will dissolve fats and proteins but leave most metals and plastics unharmed. (except aluminum)