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The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
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The https:// ensures that you are connecting to the
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Freedman DA, Navidi WC.Freedman DA, et al.Environ Health Perspect. 1989 May;81:169-88. doi: 10.1289/ehp.8981169.Environ Health Perspect. 1989.PMID: 2667978Free PMC article.Review.