问题39:允许无限期延长允许NAOCl向饮用水中贡献50%的EPA 10ppb溴酸盐MCL的例外情况，但有一项谅解，即饮用水添加剂联合委员会将定期对其进行审查。

Issue 39: Allow for an indefinite extension of the exception that allows NAOCl to contribute 50% of the EPA's MCL of 10ppb bromate to potable water, with the understanding that it will be periodically reviewed by the Joint Committee on Drinking Water Additives.