Response to Comment on 'Mutagenic Azo Dyes, Rather than Flame Retardants, are the Predominant Brominated Compounds in House Dust'

摘要

We appreciate the opportunity to respond to the comments by P. Lee Ferguson and Heather M. Stapleton regarding our article, and we also hope to further clarify the findings of our work. The major concern of Ferguson and Stapleton1 about our article~2 was that [M-H]~- was presumed as the only ion. As stated in our original method study,3 highlighted in Figure 5 of that article,~3 we have clearly shown that multiple possible neutral molecular formulas might exist for a detected ion. In the present study,2 we also stated that other ions might be formed. For example, [M-Br+O]~- ions of PBDEs were detected and shown in the main body of the manuscript and also in the supporting data. In fact, in addition to the [M•]~- ions mentioned by Ferguson and Stapleton, other ions such as [M +formic acid-H]~- can also exist. As stated in our previous studies,3'4 we could use several strategies such as positive mode ionization, derivatization, or ESI to distinguish among these ions, though for most chemicals, these strategies might not be feasible due to insufficient sensitivity. Thus, these different ions are technically difficult to distinguish, and validation by use of authentic standards as was done by Ferguson and Stapleton is likely the only/best way to confirm ions. Considering this, we did not distinguish specific types of ions in our manuscript nor did we provide neutral formulas in either Table 1 or the supporting data. Instead, formulas of detected ions were provided, which is beneficial to other groups that might use different types of ions to match in their personal database, as was done by Ferguson and Stapleton.