Response to "Comment on 'Identifying and Prioritizing Chemicals with Uncertain Burden of Exposure: Opportunities for Biomonitoring and Health-Related Research' and 'Beyond the Light under the Lamppost: New Chemical Candidates for Biomonitoring in Young Children'".

We would like to thank Mitchell (2021) for pointing out that the statement “Tens of thousands of chemicals have been approved for use in the United States” found in our paper (Pellizzari et al. 2019) incorrectly suggests that chemicals undergo an approval process in the United States. This is an oversight on our part. The statement should read “Tens of thousands of chemicals are allowed for use in the United States” (Pellizzari et al. 2021). We agree that there are thousands of chemicals currently in use that have not gone through a process that includes evaluating whether they pose a risk to the public, including sensitive life stages such and pregnancy and childhood. This was one of the motivations of our paper.

However, we want to correct several of Mitchell’s statements. First, Mitchell discusses the Toxic Substances Control Act (TSCA) Chemical Substance Inventory and implies that our paper utilized information from this inventory. To the contrary, we did not refer to or rely on information in the TSCA Inventory.

Mitchell also asserts we were “unable to identify the chemicals U.S. children are exposed to.” However, as we stated, our goal was to identify exposure to chemicals that have not yet been included in the National Health and Nutrition Examination Survey. We clearly defined the categories of consumer products included in our review, leaving other categories for future exploration. We agree there is a lack of information on the number of chemicals that Americans are exposed to, so we are pleased that our paper can add data to priorities for studies such as the National Institutes of Health’s Environmental Influences on Child Health Outcomes consortium work.

Finally, Mitchell states that we identified only 155 chemicals. However, we identified 720 candidate chemicals and selected a subset of 155 chemicals for in-depth evaluation and prioritization as candidates for biomonitoring. This left 565 candidate chemicals that were not evaluated in our paper, which we stated also should be evaluated for prioritization.

Again, we want to thank Mitchell for raising the importance of these issues, and for pointing out the fact that there are thousands of chemicals to which the public is likely exposed. We strongly believe we need research investments to understand and address those that can put the public’s health at risk.