Pesticide Residues in Organic and Conventional Apples and Potatoes Served in Tartu (Estonia) School Meals

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In the manuscript (sustainability-3940732), the authors have addressed the issue that public concern over pesticide residues in food has driven the growth in demand for organic agricultural products, yet the actual differences in residue levels between organic and traditional foods remain controversial. Therefore, they researched pesticide residues in organic and conventional apples and potatoes served in school meals in Tartu, Estonia. Generally, the contents meet the requirements of Sustainability. Therefore, I think this manuscript is suitable for publication in Sustainability after a minor revision.

(1) Keywords: Should be “Pesticide residues” rather “pesticides”.

(2) 1. Introduction: It is suggested that the author introduce the standards of organic food in this section, which will be more conducive to readers' understanding of the content of this research. In addition, it is suggested that the author explain the current demand situation for organic food.

(3) 2.1. Samples collection: Why did the author choose all the municipal schools in Tartu? What was the basis for this choice? Is this area representative?

(4) 3. Results and discussion: It is suggested that the author divide "3. Results and discussion" into two parts: "3. Results" and "4. Discussion". In this way, "3. Results" can clearly explain the results of this study. The "4. Discussion" section conducts a detailed analysis of the results and makes comparisons with existing studies.

(5) The results of this study are still relatively limited to surface data at present. It is suggested that the authors conduct more in-depth analyses based on the current results, such as the sources of these pesticide residues, control measures, etc. This provides reasonable suggestions for subsequent production or research.

Author Response

Comment 1: Keywords: Should be “Pesticide residues” rather “pesticides”.

Reply 1: We thank the reviewer for this helpful suggestion. The keyword has been corrected from “pesticides” to “pesticide residues” in the revised manuscript.

Comment 2: Introduction: It is suggested that the author introduce the standards of organic food in this section, which will be more conducive to readers' understanding of the content of this research. In addition, it is suggested that the author explain the current demand situation for organic food.

Reply 2: We thank the reviewer for this useful comment. The manuscript already included a description of what constitutes organic food at the beginning of the introduction part; however, in accordance with the reviewer’s suggestion, we have now added information on the current demand situation for organic food, highlighting recent trends and consumer behaviour (on the page 2 in the manuscript). “The demand for organic food has seen remarkable growth over recent years [7]. Recent estimates indicate that the global organic food market exceeded USD 230 billion in 2023–2024 and is projected to reach between USD 500–660 billion by the early [8]. This surge in demand for organic food reflects a shift in consumer preferences toward healthier and more sustainable choices, as consumers increasingly perceive organic products as safer than conventional foods and are motivated by health concerns as well as ethical considerations related to environmental protection and animal welfare [9, 10, 11].”

Comment 3: 2.1. Samples collection: Why did the author choose all the municipal schools in Tartu? What was the basis for this choice? Is this area representative?

Reply 3: We thank the reviewer for this question. As stated in the Materials and Methods section (2.1, Sample Collection), the study included all municipal schools in Tartu (n = 19), which are required by local procurement regulations to use at least 51% organic ingredients in their school meals. Therefore, this sample represents the full population of municipal schools in the city and accurately reflects the real situation of school catering practices under these procurement requirements, making it representative of the municipal school system in Tartu. To clarify this context, we have also expanded the Introduction (lines 82–87) with additional background information on the local procurement policy and its implications for school catering. “According to this document [30], the Tartu city government has been among the most active in Estonia in promoting the use of organic food in school catering – through its public procurement requirements, all municipal schools in Tartu are obliged to ensure that at least 51% of the ingredients used in school meals are organic. As organic products are generally more expensive [8] and the municipal budget does not fully compensate for the higher costs, parents contribute to covering the price difference.”

Comment 4:  3. Results and discussion: It is suggested that the author divide "3. Results and discussion" into two parts: "3. Results" and "4. Discussion". In this way, "3. Results" can clearly explain the results of this study. The "4. Discussion" section conducts a detailed analysis of the results and makes comparisons with existing studies.

Reply 4: We appreciate the reviewer’s suggestion regarding the separation of the Results and Discussion sections. However, since not many pesticide residues were detected and the dataset is therefore limited, we believe that presenting the results and their interpretation together in one integrated section allows for a clearer and more coherent presentation of the findings. This structure also facilitates immediate comparison with existing studies and avoids unnecessary repetition.

Comment 5: The results of this study are still relatively limited to surface data at present. It is suggested that the authors conduct more in-depth analyses based on the current results, such as the sources of these pesticide residues, control measures, etc. This provides reasonable suggestions for subsequent production or research.

Reply 5: We thank the reviewer for this valuable suggestion. While the current dataset does not allow for detailed tracing of the sources of individual residues, we have strengthened the analytical depth of the discussion (on the page 7 in the manuscript) by incorporating an economic sustainability perspective. Specifically, we now address the affordability of organic food and the economic implications of school meal pricing, emphasizing that sustainable food systems should balance safety, environmental goals, and economic accessibility. “From an economic sustainability perspective, the affordability of school meals has become an important issue. Tartu is currently one of the few municipalities in Estonia where parents contribute to school meals cost, most likely due to the high share of organic ingredients used in school catering. Organic food is considerably more expensive than conventional food, and its inclusion in school menus substantially increases overall meal costs. For example, according to the Estonian Institute of Economic Research, organic milk is on average about 25–30% more expensive than conventional milk, while organic potatoes can cost up to 400% more expensive than conventional ones, depending on the season and packaging type. In the context of rising food prices and growing economic hardship in Estonia, where absolute poverty increased in 2024, such cost pressures may reduce the inclusiveness and long-term sustainability of the system. The present findings of our study—showing that conventional products also met all food safety standards—suggest that a balanced approach combining safety, affordability, and environmental responsibility may offer a more sustainable model for public catering.”

 

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This is an interesting study, a paper easy-to-read and comprehend, that I would recommend to others. Residues of pesticides, veterinary drugs, and heavy metals in food remain a major concern for global regulators. Therefore, continuous monitoring is vital to ensure compliance with MRLs in foods and feeds. Despite the EU bans, traces of substances like Captan, Carbendazim, Spirodiclofen, Glyphosate, and Glufosinate may still occur, as these substances are seen as efficient to control diseases or pests in agriculture. The authors highlighted the limited comparative data between organic and conventional foods, and therefore, this paper would be relevant to help bridge this knowledge gap - especially important for it is targeting children as the study population.

The authors also indicate that the findings are consistent with research over the last two decades showing that reducing dietary pesticide exposure is one of the main reasons consumers choose organic foods. The authors also considered other aspects and some drawbacks of their study, such as the fact that organic food is more expensive than the conventional one, so even though safer that the latter, the majority of people cannot afford it. On the other hand, the legislative bans and restrictions of pesticide use cover all foods not only organic foods so all should comply with the current legislation regarding MRLs of pesticides and contaminants.

There are a few minor editing suggestions that I indicated in comment boxes in the manuscript, but also one separate request referring to one statement that the authors made in the Discussion section, lines 250-251, that would require citing at least two references in support of the authors’ statement.

Comments for author File: Comments.pdf

Author Response

Comment 1: There are a few minor editing suggestions that I indicated in comment boxes in the manuscript, but also one separate request referring to one statement that the authors made in the Discussion section, lines 250-251, that would require citing at least two references in support of the authors’ statement.

Reply 1: We thank the reviewer for this helpful remark. Minor language and punctuation corrections (missing commas and periods) have been made throughout the manuscript according to the comment boxes. In addition, we have added two relevant references—Kazimierczak et al. (2022) and Łozowicka et al. (2025) — to support the statement in the Discussion section (on the page 7 in the manuscript, marked references nr 33 and 58). These studies were conducted in Poland, which is also the origin of the apples analysed in our study, and therefore provide a suitable comparative context. We appreciate the reviewer’s suggestion, as these citations strengthen the argument and improve the completeness of our discussion.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors Rv1_sustainability-3940732 I have read the manuscript "Assessment of pesticide residues in organic and conventional apples and potatoes served in Estonian school meals", which aims to compare the levels of pesticide residues in organic and conventional products used in school canteens in Tartu, Estonia, using accredited chromatographic methods. The article is relevant to the line of research in Sustainable Food Systems, as it addresses a topic of public interest on food safety and the sustainability of European agri-food production. Overall, the manuscript is clear and methodical, but it requires a more in-depth conceptual and analytical review to consolidate its scientific contribution. General comments 1.                   Conceptual positioning.
The article presents a comprehensive regulatory and analytical overview of European legislation on pesticide residues; however, the conceptualization of food sustainability is limited to regulatory compliance. It is recommended to incorporate theoretical frameworks on food system sustainability (e.g., FAO 2018; Lang & Barling 2022) that integrate social, public health, and environmental dimensions. 2.                   Focus and scope.
The study defines itself as comparative, but methodologically it is descriptive. No hypotheses are established, nor is statistical evidence of significance reported for differences between groups; therefore, the results are interpretive, not inferential. 3.                   Sample design and representativeness.
The sample (36 units) comes exclusively from Tartu canteens. It is a limited universe that does not allow generalizing conclusions to the national context. The size and statistical representativeness of the sample must be justified. 4.                   Interpretation of results.
The article interprets compliance with maximum residue limits (MRLs) as evidence of sustainability, a notion that is debatable. Food sustainability transcends regulatory safety; it requires discussing the import impacts, traceability, ecological footprint, and social cost of school meals. 5.                   Critical discussion.
It is recommended to incorporate a comparative discussion with European research that has addressed the detection of prohibited substances, interpreting the results from food governance and cross-border control mechanisms. 6.                   Limitations and future scope.
The limitations are correctly acknowledged, although without detailing the implications in the interpretation of food risk. It is suggested that future lines focus on longitudinal analysis and monitoring of local supply chains. Specific comments 1.                   Introduction: well structured, although excessively normative. It is recommended to reduce legislative references and expand the contextualization of risk and public perception. 2.                   Methodology: the technical level is high, but should include information on analytical validation (accuracy, repeatability, uncertainty) and quality control criteria. 3.                   Results: clear and well tabulated; however, there is a lack of measures of dispersion or statistical contrasts to support comparative claims. 4.                   Discussion: presents a linear reading of the results. I suggest integrating approaches to public health, food economics, and social perception of risk. 5.                   Conclusions: adequate in terms of empirical content, but they should moderate the statement of "sustainability", since the study evaluates safety, not integral sustainability.    

Author Response

Comment 1:  Conceptual positioning.
The article presents a comprehensive regulatory and analytical overview of European legislation on pesticide residues; however, the conceptualization of food sustainability is limited to regulatory compliance. It is recommended to incorporate theoretical frameworks on food system sustainability (e.g., FAO 2018; Lang & Barling 2022) that integrate social, public health, and environmental dimensions.

Reply 1: We thank the reviewer for this valuable suggestion. We have added references to strengthen the sustainability context of the manuscript. As the Lang & Barling (2022) source suggested by the reviewer was unavailable to us, we used a meta analysis on organic farming and sustanability by Lee et al 2015. In addition, the FAO (2018) framework was incorporated to support the conceptual link between organic food and sustainability (on the pages 1 and 2 in the manuscript).

Comment 2: Focus and scope.
The study defines itself as comparative, but methodologically it is descriptive. No hypotheses are established, nor is statistical evidence of significance reported for differences between groups; therefore, the results are interpretive, not inferential.

Reply 2: We thank reviewer for this observation. The study was indeed designed as a descriptive comparison rather than a hypothesis-driven analysis, as the main objective was to monitor and compare pesticide residues in organic and conventional foods rather than to test statistical differences between groups. To better reflect the scope and sustainability perspective of the study, we have revised the manuscript title, which is now “Pesticide residues in organic and conventional apples and potatoes served in Tartu (Estonia) school meals”.

Comment 3: Sample design and representativeness.
The sample (36 units) comes exclusively from Tartu canteens. It is a limited universe that does not allow generalizing conclusions to the national context. The size and statistical representativeness of the sample must be justified.

Reply 3: We thank for this comment. The sample was intentionally limited to Tartu, as it is currently the only local government in Estonia that requires the use of organic food in educational institutions—at least 20% in kindergartens and a minimum of 51% in municipal schools. Therefore, the study includes all municipal schools in Tartu (n = 19), reflecting the total number of schools subject to this requirement. While the results are not intended to be generalized to the national level, the sample is fully representative of the municipal school catering system within Tartu. We have also expanded the Introduction (lines 82–87) with additional background information on the local procurement policy and its implications for school catering. “According to this document [30], the Tartu city government has been among the most active in Estonia in promoting the use of organic food in school catering – through its public procurement requirements, all municipal schools in Tartu are obliged to ensure that at least 51% of the ingredients used in school meals are organic. As organic products are generally more expensive [8] and the municipal budget does not fully compensate for the higher costs, parents contribute to covering the price difference.”

Comment 4: Interpretation of results.
The article interprets compliance with maximum residue limits (MRLs) as evidence of sustainability, a notion that is debatable. Food sustainability transcends regulatory safety; it requires discussing the import impacts, traceability, ecological footprint, and social cost of school meals.

Reply 4: We thank the reviewer for this insightful suggestion. In the revised version, we have expanded the discussion (page 7) to include an economic sustainability perspective. The updated section now addresses the affordability of school meals and highlights that organic ingredients substantially increase meal costs, which may explain why parents in Tartu are required to contribute financially.

Comment 5: Critical discussion.
It is recommended to incorporate a comparative discussion with European research that has addressed the detection of prohibited substances, interpreting the results from food governance and cross-border control mechanisms.

Reply 5: We thank the reviewer for this suggestion. The manuscript already discusses the issue of cross-border residue patterns and the importance of EU-wide monitoring and harmonised regulatory control. This aspect is reflected in the Discussion section, where we emphasize that residue patterns may vary across the EU despite unified legislation, underlining the need for continuous monitoring and effective food governance (pages 5 and 7).

Comment 6: Limitations and future scope.
The limitations are correctly acknowledged, although without detailing the implications in the interpretation of food risk. It is suggested that future lines focus on longitudinal analysis and monitoring of local supply chains.

 

Reply 6: We thank for this constructive suggestion. The limitations have been expanded in the revised Discussion section (page 8) to better explain their implications for food risk interpretation. Specifically, we now highlight that, while no health risks were identified based on the detected residue levels, the findings should be interpreted with some caution due to the sample size. In addition, we have added a note suggesting that future research should include longitudinal monitoring and assessment of local supply chains to better capture temporal trends and potential sources of pesticide residues. “While the results of this study did not indicate any health risks associated with the detected pesticide residue levels, they should be interpreted with caution given the number of samples and the geographically specific focus on Tartu. Consequently, the findings may not be directly generalizable to the national level. Future investigations should therefore adopt a longitudinal design and incorporate detailed monitoring of local and regional supply chains to better identify temporal dynamics and potential sources of pesticide residues within school catering systems.”

Specific comments

Comment 7:  Introduction: well structured, although excessively normative. It is recommended to reduce legislative references and expand the contextualization of risk and public perception.

 

Reply 7: We thank the reviewer for this helpful comment. In accordance with the suggestion, we have adjusted the Introduction section and slightly expanding the contextual background (including demand for organic food and sustainable food systems). “Organic agriculture is perceived as more sustainable due to its focus on environmental health [5]. Nevertheless, sustainability in food systems extends beyond production methods to encompass economic accessibility, social equity, and public health, aiming to balance health, ecological integrity, and social justice [6]. The demand for organic food has seen remarkable growth over recent years [7]. Recent estimates indicate that the global organic food market exceeded USD 230 billion in 2023–2024 and is projected to reach between USD 500–660 billion by the early [8]. This surge in demand for organic food reflects a shift in consumer preferences toward healthier and more sustainable choices, as consumers increasingly perceive organic products as safer than conventional foods and are motivated by health concerns as well as ethical considerations related to environmental protection and animal welfare [9, 10, 11].”

Comment 8: Methodology: the technical level is high, but should include information on analytical validation (accuracy, repeatability, uncertainty) and quality control criteria.

Reply 8: We thank for this observation. The analyses were conducted in an accredited laboratory operating under ISO/IEC 17025 standards, where all procedures follow validated methods with established criteria for accuracy, repeatability, and measurement uncertainty. While the specific validation data are not available to us, we can rely on the laboratory’s certified quality assurance system, ensuring that the results are reliable and reproducible.

Comment 9:  Results: clear and well tabulated; however, there is a lack of measures of dispersion or statistical contrasts to support comparative claims.

Reply 9: We thank the reviewer for this comment. As the number of detected pesticide residues was very limited, statistical contrasts between groups were not feasible. Therefore, the results are presented descriptively rather than inferentially. This approach aligns with the study’s exploratory nature, which aimed primarily to provide an overview of residue presence and compliance rather than to perform statistical comparisons.

Comment 10: Discussion: presents a linear reading of the results. I suggest integrating approaches to public health, food economics, and social perception of risk.

Reply 10: We thank the reviewer for this helpful suggestion. In response, we have expanded the Discussion section by including an economic perspective, addressing the higher cost of organic foods and the implications for affordability and sustainability, particularly in the context of Tartu, where parents contribute financially to school meals. “From an economic sustainability perspective, the affordability of school meals has become an important issue. Tartu is currently one of the few municipalities in Estonia where parents contribute to school meals cost, most likely due to the high share of organic ingredients used in school catering. Organic food is considerably more expensive than conventional food, and its inclusion in school menus substantially increases overall meal costs. For example, according to the Estonian Institute of Economic Research, organic milk is on average about 25–30% more expensive than conventional milk, while organic potatoes can cost up to 400% more expensive than conventional ones, depending on the season and packaging type. In the context of rising food prices and growing economic hardship in Estonia, where absolute poverty increased in 2024, such cost pressures may reduce the inclusiveness and long-term sustainability of the system. The present findings of our study—showing that conventional products also met all food safety standards—suggest that a balanced approach combining safety, affordability, and environmental responsibility may offer a more sustainable model for public catering.”

Comment 11: Conclusions: adequate in terms of empirical content, but they should moderate the statement of "sustainability", since the study evaluates safety, not integral sustainability.    

Reply 11: We thank the reviewer for this valuable comment. We agree that the study primarily focuses on food safety rather than a comprehensive sustainability assessment. Accordingly, the Conclusions section (page 8) has been revised to moderate the sustainability-related statements. The revised version now clarifies that the findings contribute to the broader discussion on sustainable and responsible food procurement in public institutions, rather than evaluating sustainability in full. “While the study primarily addresses food safety, its findings also provide evidence relevant to the broader discussion on sustainable and responsible food procurement in public institutions.”

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Rv2_sustainability-3940732

I have reviewed the revised manuscript and the authors' detailed response. It confirmed that the observations made in the first round were adequately and substantively addressed, which improved the conceptual clarity and interpretative scope of the study.

1. Conceptual positioning.
   The authors incorporated references and theoretical frameworks that contextualize food sustainability beyond regulatory compliance, integrating the FAO (2018) perspective and additional evidence on organic farming. Incorporation strengthens the conceptual support.
2. Focus and scope of the study.
   It was clarified that the study is descriptive rather than inferential, and the title was adjusted to reflect the objective of the comparative analysis accurately. The scope is now clearly defined and consistent with the results.
3. Representativeness of the sample.
   The justification for the sample has been strengthened by explaining that it covers all the municipal schools subject to the policy of acquiring organic food in Tartu. With this, representativeness is adequately specified in terms of the local context.
4. Interpretation of the results.
   The discussion was broadened to include an economic perspective related to the affordability and costs associated with organic school feeding, which broadened the interpretation beyond compliance with maximum residue limits.
5. Critical discussion.
   Reflection on European food governance and surveillance was integrated, strengthening the case for residue variability and the need for continuous monitoring.
6. Limitations and future lines.
   The limitations were expanded, and future research routes were proposed, utilizing a longitudinal approach and traceability in local supply chains, which enhances the projection of the study.
7. Specific settings.
   The introduction was balanced to reduce the normative emphasis and broaden the context of public perception; the discussion was enriched with perspectives from public health and food economics; the conclusion was moderated to distinguish between food security and integral sustainability clearly.

Taken together, the changes made strengthen the conceptual coherence, interpretative clarity, and scholarly relevance of the manuscript.

Fraternally,
Reviser