The website, lifehacker.com, provides a recipe for a non-toxic metal polish, which includes vinegar. The recipe is noted below:
In a glass or plastic bowl (never metal) mix 2/3 cup distilled white vinegar with 2/3 cup flour. All I had was whole wheat flour, so my cleanser is for heart-healthy tarnish. Once the mixture is smooth, add 1/2 cup of salt and stir until mixed in. This isn’t the sort of thing that keeps well, so make this polish on an as-needed basis.
To read the article (including directions on using the polish), use this link.