Raynard Kington, acting director of NIH, said last week that the agency had received more than 20,000 comments on its proposed stem cell guidelines and now the number of comments is thought to be even higher, reports Science Insider. One concern expressed in the comments sifted through thus far include that the ethical requirements of the draft guidelines will prohibit the use of many existing human embryonic stem cell lines, including the ones approved by the Bush Administration. The final policy will be issued by July 7th.