The veto by Mayor Daniella Levine Cava, a Democrat, pushed back on a growing campaign against the mineral, which has been used for decades to prevent cavities.
Other big technology companies have been boisterous in their courtship of the new administration. But Nvidia and Microsoft have avoided the Washington spotlight.
The fast-growing popularity of the Chinese artificial intelligence software hit shares in tech giants like Nvidia, as Silicon Valley worried about what comes next.
The research could further complicate the polarized politics of abortion because the drug in the study is the key ingredient in a pill used for emergency contraception.