Review Reports - Distribution of 40K, 137Cs, and 90Sr from Cow Milk to Cottage and Livno Cheese in Bosnia and Herzegovina: Physicochemical Associations, Regional Variation, and Radiological Safety

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript needs a major revision before it is considered for publication. I am hereby returning the paper to you, pointing out comments to the authors:

Introduction and Literature review

1/ The majority of citations are either previous reviews/handbooks (IAEA 2010, HASL-300 1997) or the authors' own previous work. Only the 2025 citation (ref 30) is found. There is a need for more inclusion of post-Fukushima or post-2022 (Ukraine conflict-related radiological monitoring) food-chain radionuclide literature in the paper to be published in 2026, as this paper frames the issues as "ongoing global instability.

2/ The introduction refers to only the authors' recent 2023 paper on the processing factors of the hard cheeses studied and not to other studies of processing factors for other types of hard cheese (e.g., Mediterranean or Balkan hard cheeses) conducted in the last 5 years. This further reduces the reference point for the reader who does not know the literature on the transfer factor.

3/ Recommend drawing attention to the rationale behind the use of Livno cheese as a hard cheese comparator (mentioned in the discussion but might be more effective in the Introduction if it were introduced at the front of the paper).

Methods

4/ Cottage cheese, milk, and Livno cheese milk are from two different regions and two different herds/seasons, and cheese technology is completely confounded. The authors do mention it in their Conclusion (which is good practice and recommends a "fully crossed design" for future research), but the limitation deserves its own subsection or at least a clear paragraph in their methods/discussion section, not just at the end.

Author Response

Dear Reviewer, we sincerely appreciate the time and effort you devoted to evaluating our manuscript and providing constructive feedback. Here are your comments and our responses:

Response: We thank the reviewer for this constructive suggestion. We agree that the Introduction needed broader, more up-to-date contextualization, particularly because the manuscript frames radionuclide monitoring in dairy systems in relation to contemporary radiological preparedness and ongoing global instability. Accordingly, we revised the Introduction by adding recent post-Fukushima food-chain monitoring literature, as well as more recent references related to radiological monitoring and preparedness in Europe and Ukraine after 2022. These additions better support the relevance of long-term radionuclide surveillance in food-chain matrices, including milk and dairy products, and reduce reliance on handbooks, older methodological references, and our previous work.

Response: We agree with the reviewer that additional reference points for radionuclide processing factors in cheese would improve the Introduction. We have therefore expanded the text by including further literature on radionuclide transfer during milk processing, curd formation, whey separation, and cheese maturation. However, to the best of our knowledge, recent studies specifically addressing radionuclide processing factors in traditional Balkan or Mediterranean hard cheeses remain very limited, and the cited 2023 study appears to be the only directly comparable work currently available for this cheese category and regional context. We have clarified this limitation in the revised Introduction. If the reviewer is aware of additional relevant studies, we would be pleased to cite and discuss them in the manuscript.

Response: In response to the reviewer’s recommendation, we have moved the rationale for selecting Livno cheese earlier in the manuscript and now introduce it in the Introduction. Livno cheese is presented as a traditional hard full-fat cheese from the Livanjsko polje region and was selected as a hard-cheese comparator because its production technology, ripening period, curd structure, and regional environmental setting differ substantially from fresh cottage cheese. This addition clarifies from the outset why Livno cheese was appropriate for evaluating differences in radionuclide partitioning between fresh and hard cheese matrices.

Methods

Response: We thank the reviewer for this important comment. We agree that the comparison between cottage cheese and Livno cheese is affected by confounding because the respective milk samples originated from different regions, herds, and sampling periods, while the cheese-making technologies also differed. To make this limitation more explicit, we have added a dedicated limitation paragraph in the Discussion and clarified in the Methods (Experimental design section) that the study was not based on a fully crossed design. We now state that regional origin, herd-related factors, season, milk composition, and cheese technology cannot be completely separated statistically in the present dataset. Accordingly, the comparison between cottage cheese and Livno cheese is interpreted as an applied comparison of two real production systems rather than as an isolated effect of cheese technology alone. We also retained the recommendation that future studies should use a fully crossed design in which milk from each region is processed using both cheese technologies under standardized conditions.

Revised manuscript is in the attachment.

Reviewer 2 Report

Comments and Suggestions for Authors This study compares the partitioning behavior of three radionuclides — natural and anthropogenic and — across cow milk, curd and whey during the manufacture of two traditional cheeses in Bosnia and Herzegovina: cottage cheese from central Bosnia and Herzegovina and ripened hard Livno cheese from the southwestern region. It further dissects how physicochemical parameters and regional environmental conditions govern radionuclide transfer, assesses the radiological safety of dairy products, and derives critical intervention thresholds for raw milk in the event of radiological or nuclear emergencies. The research topic exhibits interdisciplinary novelty bridging environmental radiology and dairy processing. The experimental methodology is standardized, the dataset is comprehensive, figures and tables are clearly presented, and all conclusions are well-supported by empirical data. However, the manuscript cites relatively few references published within the past five years. The paper is recommended for acceptance pending revisions.

Author Response

This study compares the partitioning behavior of three radionuclides — natural ⁴⁰K and anthropogenic ¹³⁷Cs and ⁹⁰Sr — across cow milk, curd and whey during the manufacture of two traditional cheeses in Bosnia and Herzegovina: cottage cheese from central Bosnia and Herzegovina and ripened hard Livno cheese from the southwestern region. It further dissects how physicochemical parameters and regional environmental conditions govern radionuclide transfer, assesses the radiological safety of dairy products, and derives critical intervention thresholds for raw milk in the event of radiological or nuclear emergencies. The research topic exhibits interdisciplinary novelty bridging environmental radiology and dairy processing. The experimental methodology is standardized, the dataset is comprehensive, figures and tables are clearly presented, and all conclusions are well-supported by empirical data. However, the manuscript cites relatively few references published within the past five years. The paper is recommended for acceptance pending revisions.

Response: Dear Reviewer, we sincerely appreciate the time and effort you devoted to evaluating our manuscript and providing constructive feedback. We acknowledge that the previous version relied insufficiently on recent studies, particularly in relation to contemporary radiological monitoring and food-chain radionuclide literature. In response, we have revised the manuscript by adding new paragraphs supported by more recent references. We believe that these revisions have substantially improved the context, balance, and relevance of the manuscript. We hope that the changes made in this major revision adequately address your concerns.

Revised manuscript is in the attachment.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript addresses an interesting and relevant topic. However, several methodological and interpretative aspects require clarification before the manuscript can be considered for publication.

The detailed comments and suggested revisions are provided in the attached document. I encourage the authors to address each point carefully and revise the manuscript accordingly.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English is generally understandable, but moderate language editing is recommended to improve grammar, wording, consistency, and overall readability.

Author Response

The manuscript addresses an interesting and relevant topic. However, several methodological and interpretative aspects require clarification before the manuscript can be considered for publication.

The detailed comments and suggested revisions are provided in the attached document. I encourage the authors to address each point carefully and revise the manuscript accordingly.

Title – The term “Physicochemical Drivers” appears too strong for the present study design. The analyses identify associations between physicochemical parameters and radionuclide concentrations, but do not establish that these parameters are causal drivers. Please consider replacing “Drivers” with “Associations” or similar wording.

Response: Dear Reviewer, thank you for the observation. Current title does seem too strong. We also changed “Regional differences” to “Regional variation” to be more appropriate. Therefore, the revised title is: “Distribution of ⁴⁰K, ¹³⁷Cs, and ⁹⁰Sr from Cow Milk to Cottage and Livno Cheese in Bosnia and Herzegovina: Physicochemical Associations, Regional Variation, and Radiological Safety”

Abstract – Please revise the statement that significant regional differences were observed for ^90Sr. Only a very small second-stage subset was analyzed for this radionuclide, and the corresponding statistical evidence should be interpreted cautiously. The Abstract should reflect the exploratory nature of these comparisons.

Response: Thank you for the suggestion. The Abstract has been corrected accordingly.

Introduction/Objectives – Please clarify the novelty of the present study in relation to your previous publication on ^40K and ^137Cs transfer during cheese production. It should also be stated whether the samples/data used in the present study are entirely independent from those previously published.

Response: We appreciate the observation. The corrections in the Introduction section were made. We hope that the changes made adequately address your concerns.

Section 2 – Study design – The design does not allow the effects of geographical origin and cheese technology to be separated because milk from Central Bosnia was used for cottage cheese, whereas milk from the Livno region was used for Livno cheese. Please acknowledge this limitation clearly and avoid attributing differences between cheeses exclusively to either region or processing technology.

Response: Thank you for your comment. We completely agree; in fact, one other reviewer commented the similar thing, therefore the changes have been made. Hopefully, the changed section is now adequate.

Section 2.2.2 – ^90Sr determination – Please report more clearly the exact number of samples selected from each region and cheese type and indicate which milk and cheese samples were paired. Table 6 shows only 3 vs. 2 milk samples and 2 vs. 3 cheese samples for the two production systems, respectively.

Response: We thank the reviewer for pointing this out. We agree that the previous description of the ⁹⁰Sr subset was insufficiently detailed. The revised manuscript now reports the exact number of samples selected from each region and cheese type and specifies the paired milk-cheese samples. We have also clarified that ⁹⁰Sr was analyzed only in a randomly selected second-stage subset, because the available analytical capacity allowed the examination of five milk and five cheese samples. Accordingly, a small number of samples was randomly selected from each milk and cheese set. The final subset comprised three milk samples from the cottage-cheese production system and two milk samples from the Livno-cheese production system, while the cheese subset comprised two cottage cheese samples and three Livno cheese samples. We have revised the manuscript to make clear that the ⁹⁰Sr results are exploratory and should be interpreted with caution because of the limited subset size.
At the same time, we respectfully consider these ⁹⁰Sr results to be valuable despite the limited number of samples. The determination of ⁹⁰Sr in dairy matrices is analytically demanding, time-consuming, and considerably more resource-intensive than gamma-spectrometric determination of ⁴⁰K and ¹³⁷Cs. Consequently, studies reporting ⁹⁰Sr in milk and cheese often include relatively small analytical subsets. Nevertheless, ⁹⁰Sr remains a key radionuclide for radiological assessment of milk and dairy products because of its calcium-like behaviour and potential retention in calcium-rich matrices. Therefore, we believe that reporting these data, while clearly acknowledging their exploratory character and avoiding overinterpretation, provides useful additional information for the food-chain radioactivity literature.

Section 2.3 – Processing factors – Please check the calculation and dimensional interpretation of Pf, Pe and Fr. Milk activity is reported in Bq/L, whereas cheese activity is reported in Bq/kg, although the resulting factors are described as dimensionless. Please explain the conversion used or revise the calculations accordingly.

Response: We thank the reviewer for identifying this point. Even though the differences are probably negligible, we did the recalculations and reviewed the Results section. Also, we agree that the previous wording could imply a dimensional inconsistency, because milk activity was reported in Bq/L and cheese activity in Bq/kg. We have revised the Methods section to clarify that milk activities were converted to a mass basis using milk density before calculating Pf and Fr. Therefore, the reported factors are dimensionless only after unit harmonization, and the revised manuscript now explicitly states this conversion and interpretation.
Section 2.4 – Statistical analysis – The inferential analysis of ^90Sr requires revision because of the very small sample size. Please report the result of the exact permutation test mentioned in the Methods and distinguish it from the t-test result. The ^90Sr comparisons should be presented as exploratory unless supported by the exact test. Pearson correlations based on n = 5 should also be described as exploratory.

Response: We thank the reviewer for this important statistical comment. We agree that the inferential analysis of ⁹⁰Sr required a more cautious presentation. In th revised manuscript, we have clarified that the pooled-variance two-sample t-test and Cohen’s d effect size were reported only as exploratory descriptive comparisons, and that the exact permutation test was used as an additional small-sample check. We have now reported the exact permutation test result separately from the t-test result in the Results section and revised the interpretation accordingly. The ⁹⁰Sr comparisons are no longer presented as confirmatory unless supported by the exact test, and the wording in the Results, Discussion, Abstract, and Conclusion has been adjusted to reflect their exploratory nature. We have also clarified that Pearson correlations involving ⁹⁰Sr were calculated from only five milk samples and five cheese samples, without subdivision by production type, and should therefore be interpreted as descriptive exploratory associations rather than robust inferential evidence.

Section 3.2 – ^90Sr results – Please reconsider the statements that ^90Sr differed significantly between the two milk and cheese groups. The reported p-values should be checked against the exact permutation analysis and revised if necessary.

Response: Thank you for the observation. Changes have been made accordingly in the manuscript.

Section 3.3 – ^90Sr retention – The reported retention values of 94.8% and 97.6% should be presented as estimates. They were calculated from a small and not fully paired subset together with general milk-to-cheese yield values rather than batch-specific yields. This limitation should be stated when interpreting these results.

Response: Thank you. Clarification in accordance with your comment has been made in the Discussion section.
Table 10 – Please recheck all calculations. For Livno cheese and ^90Sr, the reported value of 9.06 Bq/kg does not appear consistent with the stated Pe and Fr values; using the values provided in the manuscript gives approximately 9.86. The unit used for milk should also be checked because milk activity is otherwise reported in Bq/L.

- Thank you for this very important observation. Since we recalculated Pf and Fr values after converting Bq/L to Bq/kg, these values in Table 10 were incorrect. We calculated those values again and revised them in Table 10.

Discussion – Please distinguish more clearly between effects associated with geographical origin and those associated with cheese technology. Because the two factors are confounded in the present design, statements attributing radionuclide distribution simultaneously to processing technology and regional exposure should be moderated.

Response: Thank you for your comment. Here we will address this comment, as well as comment number 13. We agree that the comparison between cottage cheese and Livno cheese is affected by confounding because the respective milk samples originated from different regions, herds, and sampling periods, while the cheese-making technologies also differed. To make this limitation more explicit, we have added a dedicated limitation paragraph in the Discussion and clarified in the Methods (Experimental design section) that the study was not based on a fully crossed design. We now state that regional origin, herd-related factors, season, milk composition, and cheese technology cannot be completely separated statistically in the present dataset. Accordingly, the comparison between cottage cheese and Livno cheese is interpreted as an applied comparison of two real production systems rather than as an isolated effect of cheese technology alone. We also retained the recommendation that future studies should use a fully crossed design in which milk from each region is processed using both cheese technologies under standardized conditions.

Discussion – radiological safety – Please clarify that the maximum levels from Council Regulation (Euratom) 2016/52 refer to nuclear or radiological emergency conditions. Therefore, the comparison demonstrates that the measured activities were far below these emergency regulatory levels, but does not by itself constitute a complete radiological risk assessment.

Response: We revised the Discussion to make clear that our comparison demonstrates that the measured activity concentrations of ¹³⁷Cs and ⁹⁰Sr in milk and cheese were far below the relevant emergency regulatory levels. However, we have also clarified that this comparison alone does not represent a complete radiological risk assessment. The revised text now avoids overstatement and presents the regulatory comparison only as a contextual food-safety benchmark, while acknowledging that a full risk assessment would require additional exposure modelling, including consumption rates, dose conversion coefficients, age-specific intake scenarios, and cumulative dietary exposure.

Conclusions – Please revise the conclusions in line with the study design and the limited ^90Sr dataset. The regional and technological effects should not be presented as independently demonstrated, and the ^90Sr findings should be described as preliminary or exploratory. The recommendation for a future fully crossed design is appropriate and should be retained.

Response: This comment is addressed together with the number 11. The conclusion section has been revised as per your advice.

Revised manuscript is attached, and all the changes have been highlighted.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revised manuscript has significantly improved, and the authors have addressed all comments and concerns raised by the reviewer.

Reviewer 3 Report

Comments and Suggestions for Authors

The revised manuscript has been substantially improved, and the authors have adequately addressed the main methodological and interpretative concerns raised during the previous review. In particular, the limitations associated with the small ^90Sr subset, the exploratory nature of these analyses, the confounding between geographical origin and cheese-making technology, and the interpretation of radiological safety have now been clearly acknowledged and appropriately discussed.

Comments on the Quality of English Language

The English language has improved and the manuscript is generally clear and understandable. Only minor grammatical and stylistic proofreading is recommended before publication.