Water with twice the recommended limit of fluoride has been linked to lower IQs in children, according to a Department of Health and Human Services report.

The Wednesday report, from HHS’s National Toxicology Program, acknowledges the potential neurological risk of high levels of fluoride exposure “with moderate confidence,” the second-highest level of confidence used by the NTP. While the report, which is an analysis of previous research, did not quantify the number of IQ points lost due to exposure, some of the research cited say children with higher exposure can lose between 2 and 5 IQ points.