Genetic Polymorphisms as Modifiers of Health Risks from Exposure to Toxic Elements: A Traditional Literature Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Genetic Susceptibility as Potential Modifier of Health Risks from Exposure to Toxic Elements

• Title: The title indicates as if the study is on all toxic elements, while the main body focuses on metals.  There are many toxic non-metals too such as Se and P
• Section 2 is not at the centre of this study and therefore should either be very brief or removed altogether.
• Traditionally, ALAD (delta-aminolevulinic acid dehydratase), VDR (Vitamin D Receptor), and HFE (Hemochromatosis) have been reported to modify lead toxicity.  Why have these genes not mentioned at all  
• Section 3 on biomonitoring discusses the usual biomonitoring approaches. This section can better follow the G x E interactions section to discuss the potential biomarkers of susceptibility that can be implemented in light of the issues discussed in this paper.
• One would wonder whether genes do not modify excretion and therefore should be portrayed in Fig 1. Does detoxification included in the figure include excretion?

Author Response

Title: The title indicates as if the study is on all toxic elements, while the main body focuses on metals.  There are many toxic non-metals too such as Se and P.

We thank the reviewer for this valuable comment. We would like to clarify that the use of the term “toxic elements” in our manuscript was intentional and aimed at overcoming the limitations and ambiguity associated with terms such as “heavy metals.” As specified in the Introduction, TEs include not only metals but also metalloids (e.g., arsenic), and the terminology is adopted to reflect a broader and more accurate chemical classification.

We acknowledge that several toxic non-metals (e.g., Se and P) exist. However, this review specifically focuses on a subset of TEs—primarily arsenic, cadmium, chromium, lead, and mercury—which are consistently prioritized by international health and environmental agencies due to their high toxicity, persistence, bioaccumulation, and widespread environmental and occupational exposure. For this reason, the main body of the manuscript emphasizes these elements.

Section 2 is not at the centre of this study and therefore should either be very brief or removed altogether.

According to the reviewer’s suggestion, we have synthesized Section 2 as follows:

“Toxic elements (TEs) are naturally present in the Earth’s crust and are released into the atmosphere, hydrosphere, and lithosphere through processes such as rock weathering, volcanic activity, and geochemical cycling, establishing background levels that vary with local geology. However, over the past century, human activities—including industry, agriculture, and waste management—have significantly increased their mobilization and environmental distribution [11,12].

As is naturally released through weathering of As-bearing minerals and geothermal or volcanic activity and can persist in soils and sediments due to its past use in pesticides, feed additives, and wood preservatives. Major anthropogenic sources include mining and smelting, coal combustion, and industrial processes such as electronics and glass production, resulting in emissions to air, water, and waste streams [13]. Cd, naturally present in zinc, lead, and copper ores, is released through weathering and volcanic activity. Anthropogenic inputs derive mainly from mining, smelting, battery production, wastewater discharge, and the use of Cd-contaminated fertilizers and pesticides, as well as the disposal or incineration of Cd-containing products such as batteries, plastics, pigments, and paints [14].

Cr(VI9  forms naturally through oxidation of Cr(III)-bearing minerals, particularly in manganese oxide-rich or ultramafic soils, but is predominantly associated with anthropogenic activities such as mining, electroplating, leather tanning, and pigment and dye production, as well as improper waste management, leading to contamination of soils, water, and air [15,16]. Pb occurs naturally in rocks and is released via weathering, forest fires, and particulates, but its environmental levels have increased more than 1000-fold in the past three centuries due to mining, smelting, battery production, use of lead-based paints, fossil fuel combustion (including leaded gasoline), and lead-arsenate pesticides [17]. Hg is naturally emitted through volcanic activity, weathering, and ocean and soil emissions, but about two-thirds of atmospheric Hg is anthropogenic, mainly from coal combustion, mining, cement production, and metal manufacturing, which has significantly altered its natural cycle [18].

Human exposure to TEs occurs mainly through ingestion and inhalation, while dermal absorption is generally less relevant. Dietary intake is a major pathway: As is associated with rice and crops grown in contaminated soils [19]; Cd is found in vegetables, cereals, potatoes, and some fish [20]; Cr(VI) exposure occurs primarily via contaminated drinking water [21]; Pb is present in vegetables and drinking water, particularly from lead service lines [22,23]; and Hg exposure is mainly linked to fish and sea mammals [24].

Inhalation represents another major exposure route, especially in occupational settings. Elevated levels of As, Cd, and Pb have been observed in foundry workers [25], while Hg vapor exposure occurs in dental and industrial environments [24], and Cr(VI) exposure is common in chrome plating, welding, and surface treatment industries [26]. Nevertheless, inhalation exposure is also relevant in indoor environments, including homes, schools, offices, and public transport, where airborne TEs may pose non-carcinogenic and carcinogenic risks, often exceeding outdoor levels and international thresholds [27].

Smoking further increases exposure to TEs, as tobacco plants accumulate As, Cd, Cr, Hg, and Pb [28]. These elements are concentrated in different plant tissues, with Cd and Hg particularly present in leaves, and Cr, As, and Pb accumulating mainly in roots [29,30]. Tobacco smoke therefore exposes both active and passive smokers, with children being especially vulnerable due to higher exposure to contaminated household dust [31].

Dermal exposure is less significant but still possible: arsenite can penetrate the skin [32,33], Cd shows dermal bioaccessibility [34], Cr(VI) can be absorbed from contaminated soils and leather products [35], Pb may contribute to systemic burden in occupational settings [36], and Hg can be absorbed through the skin depending on chemical form and exposure conditions, including cosmetic use [37]”

Traditionally, ALAD (delta-aminolevulinic acid dehydratase), VDR (Vitamin D Receptor), and HFE (Hemochromatosis) have been reported to modify lead toxicity.  Why have these genes not mentioned at all.

As reported in Paragraph 3 and in Figure 1, we have focused on key biological pathways, metal transport, detoxification, and DNA repair, that are also common to different toxic elements.

Section 3 on biomonitoring discusses the usual biomonitoring approaches. This section can better follow the G x E interactions section to discuss the potential biomarkers of susceptibility that can be implemented in light of the issues discussed in this paper. One would wonder whether genes do not modify excretion and therefore should be portrayed in Fig 1. Does detoxification included in the figure include excretion?

The term “detoxification” already includes excretion. Moreover, as you can also see in Table 1, urinary levels can be influenced by multiple pathways among those considered.

Reviewer 2 Report

Comments and Suggestions for Authors

In this study, the authors summarized the principal toxic metals, synthesize epidemiological evidence linking exposure to adverse health outcomes, and explore the contribution of genetic variability in modulating individual risk of metal-induced disease. The manuscript was written well with novel view, good organization, and elegant texts and figures. It can be considered to accept in current form. It will be better if a graphical abstract is provided.

Author Response

In this study, the authors summarized the principal toxic metals, synthesize epidemiological evidence linking exposure to adverse health outcomes, and explore the contribution of genetic variability in modulating individual risk of metal-induced disease. The manuscript was written well with novel view, good organization, and elegant texts and figures. It can be considered to accept in current form. It will be better if a graphical abstract is provided.

Thank you very much for your kind and positive comments about our manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

I hope that my comments will help to improve the manuscript.

Please find my suggestions in the attached document.

 

Comments for author File: Comments.pdf

Author Response

Title

• The title does not clearly specify the type of article (for example, whether it is an original study, a narrative review, or a meta-analysis). Moreover, given that the manuscript focuses on reviewing studies related to SNP polymorphisms and susceptibility to heavy metals, it is suggested that the title be more specific and more accurately reflect the focus of the work.

Thank you for your suggestion. Accordingly, we have reformulated the title of our review as follows:“Genetic polymorphisms as Modifiers of Health Risks from Exposure to Toxic Elements: A Traditional Literature Review “

Abstract

• It is suggested to reorganize the content of the abstract following a clearer structure, including introduction, objective, methodology, and main results, as in its current form it may be confusing for the reader. It would also be important to briefly describe the methodology used, including keywords, databases consulted, search strategies, and inclusion and exclusion criteria.

We have chosen to include the criteria used (as done in several reviews in the literature) at the end of the Introduction (see below) to better clarify the message for the reader, whilemaintaining the abstract structure typical of a traditional review and in accordance with MDPI style.

“Therefore, this review focuses on genetic susceptibility and gene–environment interactions in the context of TE exposure. In particular, it examines the main toxic elements, summarizes epidemiological evidence of associated health risks, and highlights how genetic variability may modulate individual susceptibility to, or provide partial protection against, TE-related toxicity, based on the current state of the evidence. A bibliographic search was conducted in March 2026. The search was performed using PubMed, with keywords related to the topics mentioned above. To ensure comprehensive coverage, no restrictions were applied regarding publication type or study design. Only articles published in English were included, encompassing original research papers, reviews, and meta-analyses. The reference lists of the selected articles were also screened to identify additional relevant studies.”

Nevertheless, the abstract has been completely revised also in light of the comments below:

“A growing body of epidemiological and toxicological evidence indicates that exposure to toxic elements (TEs), including As, Cd, Cr(VI), Pb, and Hg, is associated with a wide range of adverse health outcomes, including cancer, neurological and cardiovascular disease. Given their widespread presence and toxicity, understanding the factors underlying inter-individual differences in susceptibility is essential, as not all exposed individuals develop the same health effects. Genetic variability, particularly single-nucleotide polymorphisms (SNPs), is increasingly recognized as a key determinant of individual response to TE exposure. Variants in genes involved in metal transport, detoxification, and DNA repair, including DMT1, GSTP1, MT2A, hOGG1, and XRCC1, may influence internal dose and biological effects and have been proposed as potential susceptibility markers. However, current evidence remains inconsistent due to small sample sizes, heterogeneous exposure assessment, and limited consideration of ethnic diversity and gene–environment interactions. Future research should prioritize large and well-characterized populations integrating detailed exposure and lifestyle data. This review focuses on genetic susceptibility and gene–environment interactions in TE exposure, with particular emphasis on SNPs as key modulators of individual risk. It summarizes major toxic metals, reviews epidemiological evidence of associated health risks, and highlights the role of genetic background in modulating TE-induced toxicity.”

• Clear examples of relevant SNPs or key findings are not mentioned.

• Suggestion: explicitly include As, Cd, Pb, Hg, and Cr(VI) in the abstract for greater precision.

• Additionally, it is recommended to more explicitly incorporate the main health effects associated with exposure in order to strengthen the relevance of the work.

Accordingly, we have reformulated the abstract of our review. Please see our response above regarding the revised version of the abstract.

Introduction

• The introduction provides a comprehensive overview of toxic elements, their sources, and associated health effects; however, it could be made more concise. On the other hand, and most importantly from my perspective, although the title focuses on genetic susceptibility, these concepts are introduced late in the introduction and only briefly. In this regard, the section would benefit from further development and a better integration of the genetic aspects to properly align with the focus of the manuscript.

We thank the reviewer for these useful suggestions. We have modified the entire Introduction as follows, making the first part more concise and including the criteria used in our manuscript to better clarify the message for the reader.

“Potentially toxic elements (PTEs), or toxic elements (TEs), are environmental pollutants of growing scientific concern due to their impact on human health. They are often referred to as “heavy metals,” although this term is imprecise, as it may include metalloids (e.g., arsenic) and elements essential at trace levels [1]. Among TEs, arsenic (As), cadmium (Cd), hexavalent chromium (Cr(VI)), lead (Pb), and mercury (Hg) are the most relevant due to their high toxicity at low concentrations, environmental persistence, and bioaccumulation potential. These elements arise from both natural and anthropogenic sources and are widely distributed in air, water, soil, and food [2]. Human exposure occurs mainly through ingestion and inhalation, particularly in industrial and occupational settings [3]. Because they are non-biodegradable, toxic elements accumulate in environmental and biological systems, leading to long-term exposure and health risks. Epidemiological and toxicological evidence links As, Cd, Cr(VI), Pb, and Hg exposure to multiple adverse health outcomes affecting the nervous, renal, cardiovascular, immune, endocrine, and reproductive systems [4]. Given their pervasive nature and serious health risks, it is crucial to understand the factors that contribute to differences in susceptibility among individuals [5]. In fact, not all individuals exposed to similar levels of TEs develop the same health effects, reflecting substantial inter-individual variability. A central mechanism underlying this phenomenon is gene-environment (G×E) interaction, whereby the effects of environmental exposures on disease risk are influenced by an individual’s genetic profile [6]. Among genetic determinants, single-nucleotide polymorphisms (SNPs) are the most common type of variation, present in a population with a frequency ≥ 1% [7]. They can be considered as internal contributing factors in susceptibility of individuals to TEs effects. In this regard, SNPs are considered relevant as they belong to essential pathways, such as TEs transport and detoxification, oxidative stress and DNA repair [8,9,10]. However, deeper investigations about mechanisms underlying genetic influence on response to toxic elements are needed and robust evidence about their potential role as disease predictors are required. Understanding the interplay between genetic factors and environmental exposures can be crucial for identifying individuals at higher risk of adverse health outcomes, improving risk assessment, and informing preventive or therapeutic strategies. Therefore, this review focuses on genetic susceptibility and gene–environment interactions in the context of TE exposure. In particular, it examines the main toxic elements, summarizes epidemiological evidence of associated health risks, and highlights how genetic variability may modulate individual susceptibility to, or provide partial protection against, TE-related toxicity, based on the current state of the evidence. A bibliographic search was conducted in March 2026. The search was performed using PubMed, with keywords related to the topics mentioned above. To ensure comprehensive coverage, no restrictions were applied regarding publication type or study design. Only articles published in English were included, encompassing original research papers, reviews, and meta-analyses. The reference lists of the selected articles were also screened to identify additional relevant studies.”

Objective

• There is a certain inconsistency when comparing the title with the objective stated at the end of the introduction. While the title focuses on genetic susceptibility to health risks associated with exposure to toxic elements, the objective appears broader and more descriptive, incorporating general aspects that dilute the main focus of the manuscript. Therefore, it is suggested to reformulate the objective to better align with the title, explicitly emphasizing genetic susceptibility and gene–environment interactions as the core focus of the work.

This is a correct comment; we have reformulated the aim of our review as follows:

“Therefore, this review focuses on genetic susceptibility and gene-environment interactions in the context of TE exposure. In particular, it examines the main toxic elements, summarizes epidemiological evidence of associated health risks, and highlights how genetic variability may modulate individual susceptibility to, or provide partial protection against, TE-related toxicity, based on the current state of the evidence.”

Methodology

The manuscript lacks a clearly defined methodology section. It is not specified whether the study is a narrative review, systematic review, or meta-analysis. Additionally, key methodological aspects such as databases consulted, search strategy, keywords, inclusion and exclusion criteria, and time frame are not described.

This limits the transparency and reproducibility of the work. The authors are encouraged to include a dedicated methodology section to clarify the study design and strengthen the scientific rigor of the review.

As reported in the responses to the reviewer’s comments above, we have revised the title and the final part of the Introduction section to better define the scope of our manuscript, in line with the reviewer’s suggestion. However, we believe that the inclusion of a dedicated Methods section would not be appropriate, as it would not be consistent with the primary aim of our work, which is to provide a traditional literature review—i.e., a comprehensive analysis of the existing literature on a specific topic, intended to summarize, evaluate, and synthesize existing knowledge.

Main text

Sources of toxic elements and routes of exposure

• This section provides a detailed overview of the sources of toxic elements; however, it is largely descriptive and could be made more concise, particularly in the case of arsenic, where excessive detail may impair readability. Furthermore, the section reads more like a book chapter than a scientific article, so a more concise approach that is better aligned with the manuscript’s objectives is recommended.

Accordingly, we have revised the paragraph and made it more concise as follows, also in light of the comments from another reviewer.

2. Sources of toxic elements and routes of exposure

Toxic elements (TEs) are naturally present in the Earth’s crust and are released into the atmosphere, hydrosphere, and lithosphere through processes such as rock weathering, volcanic activity, and geochemical cycling, establishing background levels that vary with local geology. However, over the past century, human activities—including industry, agriculture, and waste management—have significantly increased their mobilization and environmental distribution [11,12].

Arsenic (As) is naturally released through weathering of As-bearing minerals and geothermal or volcanic activity and can persist in soils and sediments due to its past use in pesticides, feed additives, and wood preservatives. Major anthropogenic sources include mining and smelting, coal combustion, and industrial processes such as electronics and glass production, resulting in emissions to air, water, and waste streams [13]. Cadmium (Cd), naturally present in zinc, lead, and copper ores, is released through weathering and volcanic activity. Anthropogenic inputs derive mainly from mining, smelting, battery production, wastewater discharge, and the use of Cd-contaminated fertilizers and pesticides, as well as the disposal or incineration of Cd-containing products such as batteries, plastics, pigments, and paints [14].

Hexavalent chromium (Cr(VI)) forms naturally through oxidation of Cr(III)-bearing minerals, particularly in manganese oxide-rich or ultramafic soils, but is predominantly associated with anthropogenic activities such as mining, electroplating, leather tanning, and pigment and dye production, as well as improper waste management, leading to contamination of soils, water, and air [15,16]. Lead (Pb) occurs naturally in rocks and is released via weathering, forest fires, and particulates, but its environmental levels have increased more than 1000-fold in the past three centuries due to mining, smelting, battery production, use of lead-based paints, fossil fuel combustion (including leaded gasoline), and lead-arsenate pesticides [17]. Mercury (Hg) is naturally emitted through volcanic activity, weathering, and ocean and soil emissions, but about two-thirds of atmospheric Hg is anthropogenic, mainly from coal combustion, mining, cement production, and metal manufacturing, which has significantly altered its natural cycle [18].

Human exposure to TEs occurs mainly through ingestion and inhalation, while dermal absorption is generally less relevant. Dietary intake is a major pathway: As is associated with rice and crops grown in contaminated soils [19]; Cd is found in vegetables, cereals, potatoes, and some fish [20]; Cr(VI) exposure occurs primarily via contaminated drinking water [21]; Pb is present in vegetables and drinking water, particularly from lead service lines [22,23]; and Hg exposure is mainly linked to fish and sea mammals [24].

Inhalation represents another major exposure route, especially in occupational settings. Elevated levels of As, Cd, and Pb have been observed in foundry workers [25], while Hg vapor exposure occurs in dental and industrial environments [24], and Cr(VI) exposure is common in chrome plating, welding, and surface treatment industries [26]. Nevertheless, inhalation exposure is also relevant in indoor environments, including homes, schools, offices, and public transport, where airborne TEs may pose non-carcinogenic and carcinogenic risks, often exceeding outdoor levels and international thresholds [27].

Smoking further increases exposure to TEs, as tobacco plants accumulate As, Cd, Cr, Hg, and Pb [28]. These elements are concentrated in different plant tissues, with Cd and Hg particularly present in leaves, and Cr, As, and Pb accumulating mainly in roots [29,30]. Tobacco smoke therefore exposes both active and passive smokers, with children being especially vulnerable due to higher exposure to contaminated household dust [31].

Dermal exposure is less significant but still possible: arsenite can penetrate the skin [32,33], Cd shows dermal bioaccessibility [34], Cr(VI) can be absorbed from contaminated soils and leather products [35], Pb may contribute to systemic burden in occupational settings [36], and Hg can be absorbed through the skin depending on chemical form and exposure conditions, including cosmetic use [37].

Biomonitoring and Health Effects of Toxic Elements

- I suggest condensing it; it's quite long. There are sentences that could be shortened to streamline the content. On the other hand, it is purely descriptive; there is no discussion in which the findings are compared.

Thank you for the suggestion; however, in all honesty, we believe that this section is already sufficiently concise, as it describes the main evidence related to the health effects (neurological and cardiovascular disorders, and cancer), which represent distinct and not easily integrable aspects. We also consider this approach to be consistent with the need to allocate more space to the genetic susceptibility section, as requested by different reviewers.

Gene-environment interaction: the role of single-nucleotide polymorphisms in susceptibility to toxic element-induced effects

• This section is the core of the manuscript and is well aligned with the title.

Thank you very much for your positive comment about this section.

• However, it is purely descriptive; the opening paragraphs present general concepts that could be made more concise. The SNPs are introduced appropriately, but the discussion lacks depth regarding their functional relevance and mechanistic implications.

As requested by the Reviewer, we have reduced the opening paragraph 4 as follows:

“Multifactorial diseases arise from the interplay of genetic and environmental factors. These determinants act both independently and through gene–environment (G×E) interactions, whereby environmental exposures influence gene expression and genetic variation modulates individual susceptibility. In this context, genomic variability, particularly SNPs, contributes to inter-individual differences in response to environmental exposures [65]. SNPs affecting susceptibility to toxic elements can be functionally grouped into key pathways involved in metal transport, detoxification, and DNA repair, reflecting the complex nature of their metabolism and toxicity [8] (Figure 1). “

• I suggest justifying the classification into transport, detoxification, and DNA repair pathways.

We have justified the choice of the classification into transport, detoxification, and DNA repair pathways in the opening paragraph 4 as follows: “SNPs affecting susceptibility to toxic elements can be functionally grouped into key pathways involved in metal transport, detoxification, and DNA repair, reflecting the complex nature of their metabolism and toxicity “

• Include a discussion that is critical and integrative, comparing findings across studies and emphasizing the biological and clinical relevance of specific SNPs.

We have addressed and discussed this point more thoroughly in the final paragraph of our review. Please see the comment below and the additional text that has been added.

Discussion

A discussion section is not included, either as an independent section or integrated within each subsection; therefore, it is necessary to develop one to strengthen the interpretation and critical analysis of the findings. In the discussion, it is suggested to incorporate a more critical analysis of the limitations of the field, including the challenges associated with integrating results from heterogeneous studies, as well as the main difficulties in interpreting the findings. It would also be relevant to indicate the geographic distribution of the studies (e.g., the countries where most of the evidence has been generated) in order to better contextualize the results and their potential biases.

In this regard, it is important to discuss the biological and epidemiological implications of certain alleles being more prevalent in specific populations, as this may influence differential susceptibility among groups and limit the generalizability of the findings to other regions. Likewise, factors such as sample size, type and level of exposure (environmental or occupational), and differences in study design may significantly affect the consistency of the results.

Finally, it is recommended to expand the discussion on the applicability of these associations, particularly in terms of their potential use as susceptibility biomarkers, their contribution to risk assessment, and their possible integration into prevention strategies or personalized medicine.

Thank you for this insightful suggestions. Accordingly, we have incorporated these key concepts into the last paragraph, which summarizes the main points of the review. We have also modified the paragraph title.

“5. Conclusions and Future Perspectives: Key Points and Emerging Directions

TEs are bioaccumulative and exert a wide range of adverse effects on the human body, including cancer, neurological, and cardiovascular disorders. Their accumulation is influenced not only by environmental exposure levels but also by biological processes governing absorption, distribution, metabolism, and elimination. These processes vary substantially between individuals and strongly affect internal metal burden and toxicity outcomes. Investigating genetic variants and their interactions with environmental factors therefore provides crucial insight into individual susceptibility to TE-induced health risks.

It is now well established that genetic background represents a central component of the complex network of determinants defining sensitivity to metals. At the same time, additional internal and external factors, such as lifestyle, nutritional status, and co-exposures, further modulate biological responses. The interplay between genetic variability and environmental influences contributes to distinct phenotypes and heterogeneous responses to toxic exposures.

Identifying variations in genes involved in TE metabolism remains essential for understanding susceptibility, identifying high-risk populations, and supporting the development of targeted preventive and therapeutic strategies. Among the most extensively studied candidate genes are those involved in transport, detoxification, and DNA repair, including DMT1, GSTP1, MT2A, hOGG1, and XRCC1. Various studies have explored the impact of SNPs within these genes, and some variants have been proposed as potential susceptibility markers for toxic element toxicity. Importantly, the overall risk should also be considered in terms of cumulative exposure across multiple pathways, which collectively influence the internal dose and biological effects of toxic elements.

However, findings remain inconsistent due to the heterogeneity of available studies. Differences in study design, sample size, exposure assessment methods, and population characteristics often hinder the integration of results and contribute to inconsistent findings. In particular, small cohorts and limited statistical power reduce the robustness of associations, while variability in exposure type (environmental vs. occupational) and intensity further complicates comparisons across studies. Moreover, the geographic distribution of research is imbalanced, with most evidence generated in specific regions, potentially introducing biases and limiting the generalizability of conclusions to underrepresented populations.

In this context, the population-specific distribution of genetic variants warrants careful consideration. Certain alleles may be more prevalent in specific ethnic or geographic groups, and this can influence biological susceptibility to toxic elements and may partly explain inconsistencies across studies. At the same time, this raises important questions regarding the transferability of findings between populations, emphasizing the need for broader representation in genetic and epidemiological research.

Despite these limitations, the investigation of gene–environment interactions holds significant promise for practical applications. Genetic variants associated with altered susceptibility could serve as biomarkers for identifying vulnerable individuals or subgroups, thereby improving risk stratification. Their integration into risk assessment frameworks may enhance the accuracy of exposure–response models and support the development of more effective prevention strategies. In the longer term, these insights could contribute to personalized and precision medicine approaches, where interventions are tailored according to individual genetic and environmental risk profiles.

To address current gaps, future research should prioritize multicentric study designs involving larger and more diverse populations exposed to varying levels of toxic elements. Harmonization of methodologies, including exposure assessment and biomarker measurement, is essential to improve comparability and reproducibility. The integration of epidemiological data with computational exposure models, alongside the application of artificial intelligence and machine learning, offers new opportunities to manage complex datasets and uncover subtle interaction patterns. Furthermore, the adoption of multi-omics approaches—encompassing genomics, epigenomics, transcriptomics, and exposomics—will enable a more comprehensive characterization of the exposome, capturing both internal biological responses and external environmental influences. This systems-level perspective is critical for elucidating the mechanisms underlying differential susceptibility.

Recent advances in induced pluripotent stem cell (iPSC) technology provide an additional complementary strategy. By reprogramming accessible somatic cells into iPSCs and differentiating them into tissue-specific models, researchers can investigate gene–environment interactions in a controlled and human-relevant context. These models allow the identification of susceptibility-associated variants, early molecular alterations, and potential therapeutic targets prior to disease onset, thereby supporting earlier and more effective prevention strategies [95,96].

Incorporating these integrative approaches, including multicentric studies, advanced in vitro models, AI-driven data analysis, and multi-omics integration, will help overcome current limitations and reduce uncertainties in the field. Ultimately, such efforts will improve risk assessment, enhance prevention strategies, and facilitate the translation of mechanistic insights into public health policies and precision medicine applications.

Overall, this review highlights the importance of gene–environment interactions and SNP-based susceptibility in shaping individual responses to toxic element exposure. Advancing this field requires not only methodological standardization and broader population representation but also a stronger focus on translating scientific evidence into actionable tools for risk assessment, prevention, and personalized health management.”

Conclusion

It is suggested to structure the conclusion in accordance with the objective of the manuscript. While general concepts are summarized, the section tends to be more descriptive than analytical and, in some parts, repeats ideas already presented in the introduction. It is recommended to more clearly emphasize the most relevant findings, as well as the main limitations identified across studies, in order to provide a more critical and coherent synthesis.

We have retitled and revised this paragraph as mentioned above.

Other comments

Lines 246-249:

Gene-environment interaction in exposure to toxic elements: single-nucleotide polymorphisms can affect susceptibility to disease risk. Image partially generated with AI Microsoft Copilot. Abbreviations: As: arsenic; Cd: cadmium; Cr(VI): hexavalent chromium; Hg: mercury; Pb: lead; SNPs: single-nucleotide polymorphisms; DNA: deoxyribonucleic acid; CVD: cardiovascular disease.

Suggestion: Gene-environment interaction in exposure to toxic elements: single-nucleotide polymorphisms can affect susceptibility to disease risk. As: arsenic; Cd: cadmium; Cr(VI): hexavalent chromium; Hg: mercury; Pb: lead; SNPs: single-nucleotide polymorphisms; DNA: deoxyribonucleic acid; CVD: cardiovascular disease. Image generated with AI Microsoft Copilot.

Linea: 256

Says: Cd, Pb, cobalt, manganese, nickel, zinc, and copper

Change: Cd, Pb, Co, Mn, Ni, Zn y Cu

Linea 257-258

Please clarify what is meant by “also referred to as DCT1, NRAMP2, SLC11A2,” as it is not entirely clear whether these are synonyms of the same gene/protein. If so, it is suggested to include these synonyms in the table to facilitate understanding.

Regarding the previous comments, we have modified the manuscript as suggested by the reviewer.

Lines 259–263:

It is mentioned that this study suggests a possible risk of hypertension; it is recommended to describe the differential findings among wild-type homozygous, mutant homozygous, and heterozygous individuals. This observation applies to all polymorphisms.

This is a useful comment. We have checked all polymorphisms cited in the text. Moreover, regarding the DMT1 IVS4+44 C/A polymorphism, we have modified the text as follows:

“The findings suggested that individuals with the A/A genotype had an increased risk of lead-associated hypertension.”

Table 1

• Move the reference column to the end

• In the Effect column, always start with a capital letter.

• Replace arsenic with As

• Effect column: remove commas.

• It says. Ejm. ↑ urinary As levels and ↑ carotid intimamedia thickness

• Change.

• ↑ Urinary levels

• ↑ Carotid intimamedia thickness

• What do the colored circles column represent? Please move this explanation as a table footnote.

Suggestion: The colored circles in the Effect column indicate the nature of the association: green circles represent a protective effect, whereas red circles indicate increased toxic effects.

We have modified the table accordingly, in line with the reviewer’s suggestion and the MDPI style guidelines where possible.

Linea 439-441:

• Abbreviations: ↓: decrease of; ↑: increase of; As: arsenic; Cd: cadmium; Cr(VI): hexavalent chromium; Hg: mercury; Pb: lead; SNPs: single-nucleotide polymorphisms; DNA: deoxyribonucleic acid;

• Change: ↓: decrease of; ↑: increase of; As: arsenic; Cd: cadmium; Cr(VI): hexavalent chromium; Hg: mercury; Pb: lead; SNPs: single-nucleotide polymorphisms; DNA: deoxyribonucleic acid.

• Comment: It is recommended to better align the text with the data presented in the table, as not all polymorphisms are sufficiently described or contextualized.

We have modified this part accordingly, thank you.

Reviewer 4 Report

Comments and Suggestions for Authors

Manuscript ID: toxics-4241418

Title: Genetic Susceptibility as Potential Modifier of Health Risks from Exposure to Toxic Elements

Authors: Mariangela Palazzo, Andrea Borghini, Elisa Bustaffa, Silvia Baldacci, Francesca Gorini, Fabrizio Minichilli

 

The manuscript addresses a relevant topic in environmental health - how genetic variability (SNPs) modulates the risk associated with toxic element (TE) exposure. The review synthesizes epidemiological evidence linking toxic element exposure to chronic diseases focusing on current research limitations such as small sample sizes and heterogeneous exposure assessments.

Reviewer`s comments and suggestions:

1. Please, include the studied elements - As, Cd, Pb, Hg, and Cr(VI) in the Abstract section.
2. The manuscript lists studies for specific pathways, such as Transport and Detoxification pathways, but it would benefit from a paragraph discussing the cumulative risk from multiple pathways. Consider adding a Discussion section addressing possible cumulative risk.
3. Line 17: In the sentence “… for toxic element (TE) toxicity.” “toxicity" is used twice. Please, revise the sentence.
4. Line 180: Provide explanation for “breast mill”.
5. In the text you mention Figure 1 but you do not explain the concepts depicted in the illustration. Please, add an explanatory paragraph. Additionally, ensure that all symbols appearing in the figure are in the caption. For example, add explanations for “ABC” and “MT” to the caption list, as they appear in the boxes.
6. In the caption of Table 1 you include the same abbreviations as in Fig. 1: “As: arsenic; Cd: cadmium; Cr(VI): hexavalent chromium; Hg: mercury; Pb: lead; SNPs: single-nucleotide polymorphisms; DNA: deoxyribonucleic acid”. Please, avoid this repetition.

      7. It would be better for the manuscript if in the Conclusion section you add 1-2      sentences that state what this review contributes and why it is important for the subject area.

Author Response

The manuscript addresses a relevant topic in environmental health - how genetic variability (SNPs) modulates the risk associated with toxic element (TE) exposure. The review synthesizes epidemiological evidence linking toxic element exposure to chronic diseases focusing on current research limitations such as small sample sizes and heterogeneous exposure assessments.

Reviewer`s comments and suggestions:

Please, include the studied elements - As, Cd, Pb, Hg, and Cr(VI) in the Abstract section.

We have included them in the abstract section.

The manuscript lists studies for specific pathways, such as Transport and Detoxification pathways, but it would benefit from a paragraph discussing the cumulative risk from multiple pathways. Consider adding a Discussion section addressing possible cumulative risk.

Thank you for this useful suggestion. Accordingly, we have added a section in the Conclusions as follows:

 “Various studies have explored the impact of SNPs within these genes, and some variants have been proposed as potential susceptibility markers for toxic element toxicity. Importantly, the overall risk should also be considered in terms of cumulative exposure across multiple pathways, which collectively influence the internal dose and biological effects of toxic elements”

Line 17: In the sentence “… for toxic element (TE) toxicity.” “toxicity" is used twice. Please, revise the sentence.

Line 180: Provide explanation for “breast mill”. In the text you mention Figure 1 but you do not explain the concepts depicted in the illustration. Please, add an explanatory paragraph. Additionally, ensure that all symbols appearing in the figure are in the caption. For example, add explanations for “ABC” and “MT” to the caption list, as they appear in the boxes.

Accordingly, we have made the requested modifications in the text.

In the caption of Table 1 you include the same abbreviations as in Fig. 1: “As: arsenic; Cd: cadmium; Cr(VI): hexavalent chromium; Hg: mercury; Pb: lead; SNPs: single-nucleotide polymorphisms; DNA: deoxyribonucleic acid”. Please, avoid this repetition.

We have left the abbreviations according to the MDPI style.

It would be better for the manuscript if in the Conclusion section you add 1-2   sentences that state what this review contributes and why it is important for the subject area.

We have added a part at the end of the Conlusions section as follows:

“Overall, this review integrates current evidence on gene–environment interactions and SNP-based susceptibility to toxic elements, emphasizing how these factors shape individual risk and underscoring the need for integrated approaches to more effectively translate mechanistic insights into public health strategies and precision medicine applications.”

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have responded to my queries

Author Response

Reviewer's comment: The authors have responded to my queries.

Thank you very much for your positive comment.

Reviewer 3 Report

Comments and Suggestions for Authors

Please, In Table 1:

• Toxic element colum, move at the fisrt
• Pathway colum move at de 2do
• Move  the reference column to the end.
• The text --- Circles in the “Effect column” are green when SNPs are correlated with a protective action, red with increased toxic effects--- Move it to the footer of the table.

Author Response

• Toxic element colum, move at the fisr, Pathway colum move at de 2d, Move  the reference column to the end. The text --- Circles in the “Effect column” are green when SNPs are correlated with a protective action, red with increased toxic effects--- Move it to the footer of the table.Thank you for your minor comment. Accordingly, we have moved the sentence to the end of the Table. The order of the columns will be adjusted to comply with MDPI style.