Linking health to geology-a new assessment and zoning model based on the frame of medical geology

With the growing concerns about the Earth's environment and human health, there has been a surge in research focused on the intersection of health and geology. This study quantitatively assesses the relationship between human health and geological factors using a new framework. The framework considers four key geological environment indicators related to health: soil, water, geological landform, and atmosphere. Results indicate that the atmospheric and water resource indicators in the study area were generally favorable, while the scores of geological landforms varied based on topography. The study also found that the selenium content in the soil greatly exceeded the local background value. Our research underscores the importance of geological factors on human health, establishes a new health-geological assessment model, and provides a scientific foundation for local spatial planning, water resource development, and land resource management. However, due to varying geological conditions worldwide, the framework and indicators for health geology may need to be adjusted accordingly.


Introduction
The relationship between the geological environment and human health has long been recognized.The overall health of life is closely related to geological materials and processes (Shen et al., 2020).The advent of modern medicine in the nineteenth century helped discover the importance of chemical elements to health (Selinus et al., 2018).There are many examples of the impact of the elements on the environment and health, such as the high geological background being the main reason for the soil pollution by heavy metals in the area (Chen et al., 2021).Previous studies also have shown that an alkaline hydrogeological environment, high temperature, low rainfall and evapotranspiration were the main factors for high fluoride content in groundwater in northern India (Raju, 2017;Mukherjee Singh, 2018;Ali et al., 2019).However, high fluoride concentrations in groundwater are a global health concern (Alarcón-Herrera et al., 2020;Podgorski Berg, 2022).Selenium is an essential element in soil (Sun et al., 2016).Selenium-rich rocks mainly include claystone, black mudstone, and shale, and topographic factors such as the altitude, slope, and topographic wetness index also significantly affect the selenium content in soil (Fernández-Martín-ezCharlet, 2009).Geology plays a fundamental role in controlling the selenium levels in soils and crops (Li et al., 2012).Groundwater arsenic levels in different regions are related to geochemical processes such as volcanic eruptions and erosion of arsenicbearing minerals.Long-term exposure to arsenic can lead to diseases such as cancer (Machado et al., 2020;WardropLe Blond, 2015).These results show that geological features are closely related to health problems.Medical geology is a discipline that studies the relationship between specific geological features and the development of a range of health problems (WardropLe Blond, 2015), as well as the prevention and treatment of human and animal diseases by studying the role of geological materials and processes on the distribution of these diseases (Davies, 2019).The current field of medical geology is generally concerned with the effects on human health by contaminants generated by specific geological activities or processes (e.g., arsenic, fluoride, dust storms, volcanic activity, earthquakes) (Gwenzi, 2020).As the study of medical geology intensifies, so does the interest in regional health issues, which indicates the vital link between medicine, environmental science, health science and earth science (Orem et al., 2011).Based on this, we propose the concept of "health geology," which is similar to medical geology and is an emerging interdisciplinary field.
"Medical geography", "health geography", "medical geology" and "medical geochemistry" are close to the field of "health geology".The main difference between health geology and medical geology is that the scope and object of research are different.
Health geology focuses on exploring the beneficial and harmful effects of the geological environment on various aspects of human health.However, medical geology focuses more on the relationship between human diseases and the abundance and deficiency of geological elements, emphasizing the study of endemic diseases (Berger, 2003).Health geology is a systematic discipline related to geological action and human health.Its goal is to discover geological factors that affect human health by studying geological conditions related to human health and identifying geological resources that serve and influence human health.The core of health geology research is to determine the extent to which the content of beneficial and harmful elements, combination characteristics and ecological effects in rocks, soil, organisms, and atmosphere, as well as the restricted topographic and climatic conditions, affect human health and habitability under specific geological structure conditions.Medical geology continues to evolve and become increasingly important in the future (Bundschuh et al., 2017), as will health geology.
This study is based on a healthy geological concept; it aims to realize the beneficial geological zoning, deeply understand the transition and transformation of elements in the supergene environment, and accurately determine the factors of the source, the influence of geological setting and the result.This work further reveals the impact of various geological indexes on health and is the foundation of evaluating elements and their effects on health.The main objectives of this study are (1) Use administrative divisions as evaluation units, considering Anji in Zhejiang Province of East China as an example.The research area is a famous tourist area in the Yangtze River Delta region, with good references for natural and human settlements and a geological environment in which selenium and cadmium coexist.Moreover, evaluate the suitability of water, soil, and air for human health; (2) Utilize geochemical elements as evaluation criteria and employ the Analytic Hierarchy Process and Matrix Method as evaluation techniques, to quantify the geological and geochemical evaluation criteria in environmental media, such as the watersoil-atmosphere-organism system, which have a significant impact on human health.This will ultimately lead to the realization of healthy geological suitability zoning.(3) Analyze the limiting and favorable factors of healthy geological suitability classification within the evaluation unit, minimize adverse health risks and enhance positive health elements.This study presents a new evaluation framework through a series of studies, providing a scientific basis for implementing health geology in various evaluation units and proposing research ideas for the field of health geology.

The evaluation model of healthy geology
A health geology survey is conducted, as shown in Fig. 1.Firstly, data on the topography and landform, climatic factors, geological background, water, soil, atmosphere, and ecology of the survey area were obtained through data collection, field investigation, and remote sensing interpretation for developing the core evaluation index.Health conditions and economic and education levels were used as auxiliary evaluation indicators.Using the analytic hierarchy process (AHP), matrix method, and expert scoring method, each index's weight and grade division standards were obtained according to the degree of impact of each index on human health and the suitability of the living environment.
According to the degree of influence of each indicator on human health and the suitability of the living environment, the hierarchical analysis method and matrix method was applied to obtain the weights of each indicator and the classification criteria.Based on this, we conducted the healthy geological zoning of the evaluation unit and identified the limiting and high-quality factors of health geology.Finally, we proposed planning strategies to reduce harmful health risks and enhance health elements.Based on the above principles, the evaluation unit was divided into health geological zones to identify the limiting and advantageous health geological factors.Furthermore, we proposed planning strategies to avoid and reduce harmful health risks and improve health factors.

Evaluation indicators
The core evaluation indicators include the water resources, soil characteristics, geomorphology, and climatic conditions, which comprise the first level indicator layer.The secondary indicators of water resources are the water quality conditions and the water supply rate.The indicators of soil properties are the risk of potentially toxic heavy metals contamination.The abundance and deficiency of beneficial elements, radioactivity, and sea wave height are indicators of geological features.The comfort and air pollution indexes are indicators of climatic conditions.The evaluation indicators in each secondary indicator layer are presented in Table 1.The health conditions and economic level are auxiliary indicators for health geology grading.

Grading for evaluation
The weight of each indicator layer, the range of evaluation indicator scores, and the grade scores are shown in Table S2.The sum of the weights of each evaluation indicator layer is 1.The first-level indicator layer weight (W 1 ) is expressed in Eq. 1.The weights of secondary indicators are those of geomorphology (W G ), climatic conditions (W C ), soil characteristics (W S ), and water resources (W W ), with values of 0.25, 0.3, 0.15, and 0.3, respectively.
Each secondary weight equation is expressed in Eqs.
The economic level and medical conditions are nongeological health factors but significantly impact the human health and can even be considered as decisive factors.Therefore, the health geological classification of different areas can be corrected by downgrading or upgrading according to the actual economic and medical conditions of the various evaluation units.Owing to China's vast territory, diverse topography and geomorphology, and regional differences in the economic development, medical conditions, and folk customs, healthy geological zoning should consider the corresponding standards of different regions.The study area is located in East China, and the standards for the remaining evaluation units should be based on the actual situation of the survey area when grading healthy geology.The evaluation framework of this study considered the case of Anji in Zhejiang Province, China.
(1) Comprehensive score calculation.First, the scores for each level of the indicator were calculated as follows.
where f i is the score of the i-th level indicator; C i,j is the score of the jth secondary indicator under the i-th primary indicator; W i,j is the weight of the jth secondary indicator under the i-th primary indicator; and m is the number of secondary indicators included in the i-th primary indicator.After obtaining the scores of all level 1 indicators, the composite score is determined.
where f c is the composite score, f i is the score of the ith level indicator, and W i is the weight of the ith level indicator.N is the number of first-level indicators to be evaluated.

Classification method
Secondary indicator tier scores and grades belong to two categories.
When there is only one evaluation index in the same index layer, such as the radiation dose rate, altitude, days with comfortable body temperature, etc., the assigned values and grade classification are based on the score of the evaluation index (Table S2).
When there are multiple evaluation indicators within the same indicator layer, the composite indicator score of the evaluation layer will be assigned or calculated according to the following method.
Using the "inferior" principle to assign a value implies that the score of the evaluation layer is equal to that of the lowest evaluation index, rather than the average value used for evaluating the soil characteristics and drinking water quality.
(a) Limiting factors for soils Based on the risk and limit values (Table S3) of soil under different pH conditions in the national standard (Chinese MWR and Chinese MH, 2004), the evaluation guidelines state that when the actual measured value is less than the screening value, the score is 100; when it is between the screening and control values, the score is 80, when it is more significant than the control value, the score is 60. when the values of Cu, Zn, and Ni are greater and lesser ( 7) than the screening value, the scores are 80 and 100, respectively.

(b) Advantageous factors in soils
The level of each element is determined according to the content interval presented in Table S4, and the element level and corresponding score are then determined.Subsequently, the average score is used to obtain the soil beneficial element index score.

Identification factors of health geology
The evaluation index with the highest scores in the same evaluation index layer is the advantageous geological factor.The evaluation index with the lowest scores in the same evaluation index layer is the limiting geological factor.The advantageous and limiting factors of health geology are identified as follows.
The advantageous and limiting factors of the firstlevel indicators.In particular, for each evaluation cell (vector polygon or raster), we identified the category of primary indicators corresponding to the maximum and minimum values in f i × W i , and those corresponding to the advantageous and limiting of the unit's health geological factor, respectively.
We identified the strengths and weaknesses of secondary indicators.If a first-level indicator was identified as the first-level dominant health geological element, the second-level indicator with the maximum value below it is considered the second-level dominant health geological element.Similarly, if a specific first-level indicator is identified as the firstlevel inferior health geological element, the secondlevel indicator with the minimum value below it is considered the second-level inferior health geological element.

Data sources and processing
We obtained relevant data through sample collection, measurement analysis, and literature reviews, as described in the supplementary information.Surface water and groundwater quality and soil samples were measured by sampling (Fig. S1).Auxiliary indicators, including the economic and health conditions, were obtained according to the Statistical Communique on National Economic and Social Development.The final data results were calculated using ArcGIS 10.8 software (Environmental Systems Research Institute, Inc., USA), and each indicator was spatially integrated and plotted through a spatial grid calculator.

Geological factors linked to health
The results show that the radiation dose rate of the whole area is < 0.20 mSV/a, thus the radioactivity index is Grade 1.The landform of the study area is terraced (Jiang et al., 2002).The study area is generally 800-1500 m above sea level, with higher and lower terrain in the south and north, respectively, and mountains, hills, and plains accounted for 11.5, 63.1 and 25.4% of the country's total area, respectively (Nie et al., 2021).Finally, the three secondary indicators of geological landforms were calculated according to the weights based on the spatial overlay of Arc-GIS.The results are shown in Fig. 2. Notably, in the geological and geomorphological evaluation results of the study area, the first-grade range is mainly distributed in the central and northern parts, the secondgrade accounts for the most part, and the third-grade accounts for only a tiny fraction of the southern part because the terrain exceeds 1000 m.

Fig. 2 Geological factors evaluation results
Vol.: (0123456789) Water resources and climate factors linked to health According to the population survey and the literature, the comfort level of climatic conditions in the study area is in the secondary range (Ren et al., 2022), and the number of days with an air quality index > 100 is 111 days (Li et al., 2017a(Li et al., , 2017b)), which is also in the secondary range.This secondary indicator considers the average value across the region.Therefore, the climatic condition score of the primary indicator in the study area is calculated as: 90(0.6*90+ 0.4*90).
The study area, Anji, is in the Taihu Lake plain (Chen et al., 2020), where water resources are more abundantly distributed.According to the zoning results presented in Table S1, the study area belongs to Zone 5.However, the total amount of water resources is abundant, and the per capita possession is minor in China.Therefore, in addition to evaluating the per capita water resources, the per capita water resources in the study area were evaluated to be 1000-3000 m 3 (Zhou et al., 2018).
The surface water was sampled and analyzed in the area, and the evaluation standard adopted the national standard (Chinese EPA, 2002).Statistics show that (Tables 2 and 3): Cd, Hg, Cu, Se, Zn, and fluoride meet the national "Nature Reserve and Source Water Standards" (Class I).Cr, Pb, ammonia nitrogen, and phosphate in some areas reached the "centralized living drinking water surface water source level 1 standard" (Class II).The surface water quality in the region is excellent; water belonging to classes I and II can be used as a direct source of drinking water and industrial and agricultural production.The shallow groundwater environment in the area was sampled and analyzed, and the national groundwater quality standards (Chinese AQSIQ, 2017) were used for evaluation.Therefore, a comprehensive analysis indicated that the secondary index water quality score is 100.The content of water quality indicators is complex, combined with the remaining secondary indicators.The comprehensive evaluation indicated that the score of the entire region of primary water resource indicators was 99(0.1*100+ 0.1*90 + 0.8*100).

Soil quality linked to health
According to the analysis results of soil geochemical samples (Chinese MEE, 2018), we conducted  the environmental quality evaluation of soil in the Anji area, and detected the total elements in 473 samples.The analysis of elements in the soil is divided into beneficial and harmful elements through geological background investigation and analytical testing of the soil, and the average value lacks accuracy due to the presence of outliers in the data.Therefore, we used the median value for comparison with the background value in Zhejiang Province (Table S5).Except for As, the median values of the remaining elements are less than the background value, and previous work in this study area found that As poses a slight ecological risk in the soil (Li et al., 2022).The frequency distribution shows the frequency of the data, wherein more concentrated distributions were observed for As and Cd (Fig. S2).The spatial distributions of hazardous elements in the study area (Fig. 3) also show that the distribution of As and Cd were concentrated in the southern part of the study area, which belongs to the Lower Cambrian Hetang Formation, and As and Cd are easily enriched in the black shale of its stratum (Yu et al., 2014;Zhang et al., 2021).
Based on the prediction of geostatistical models, this study uses Kriging interpolation with uniform regional sample data coverage, followed by the continuous estimation of its results (Goovaerts, 2014).
Although the median values of Se and I were higher than the background values, and the distribution of I was more uniform across the whole area (Fig. 4), the I values were evaluated at level 3.Alternatively, the values of F and Mo were not higher than the background values, and the distribution of Mo was more concentrated (Fig. S3), which was unsuitable for the distribution of beneficial elements across the whole area.Therefore, only Se was selected as the dominant element.The distribution of Se-rich soil and soil Se content is restricted by the geological background.The spatial distribution map clearly shows that the Se content is higher in the southern region, and previous studies have also proved that the strata in the southern region are rich in Se (Armstrong et al., 2019).The results of the regionwide soil evaluation score are shown in Fig. 5. Notably, the scores of most soil indicators in the region are above 85 points, and that of a small part of the southern region is less than 85 points, this is because the strata here belongs to the Cambrian Lower Unified Hetang Formation, whose black shale is not only rich in Se, but is also accompanied by the presence of Cd, and the Cd in the soil is positively correlated with the bioaccessible concentration of Cd in rice (Yang et al., 2021).Heavy metals in soil can also be a significant source of heavy metals in tea (Tao et al., 2021).Soil contamination by Cr and Pb elements poses a relatively lesser health risk (Yang et al., 2014).

Health geology zoning
In this study, we used the AHP method to combine the evaluation of each level of indicator to derive a comprehensive evaluation result.Previously, researchers used AHP models to delineate the groundwater potential zone in the study area based on seven hydrogeological factors, including the geology, geomorphology, slope, drainage, rainfall, soil and land use, and land cover (Ghosh et al., 2020).In this study, the appropriate weights of factors were determined according to the degree of influence of individual factors on the health geological zoning.
The evaluation results of each level of indicators were superimposed using the spatial calculation of ArcGIS (Fig. 6a).Some studies also analyzed the spatial distribution of toxic metals in different soil layers after superimposing the evaluation results (Zeng et al., 2022).The overall score of the study area is good, and mainly comprises two levels, namely, 89.6-90.0 and 90.0-96.5, wherein levels 2 (89.6-95.0)and 1 (95.0-96.5)accounted for 80.4 and 19.6%, respectively (Fig. 6b).The areas with lower terrain and nonpolluted soil generally scored higher.Additionally, the results of sanitary conditions and GDP (Gross Domestic Product) per capita in the auxiliary indicators show that the GDP and GDP per capita in Zhejiang Province have increased exponentially in the last 20 years (Liao et al., 2022).According to the statistical bulletin on national economic and social development in the study area, the annual GDP was 48.7 billion Chinese Yuan (Equivalence in 7.2 billion US Dollars or 6.6 billion Euro), and the basic health insurance participation rate was 99.82%.The indicators of the study area are better, thus, further corrections to the consolidated results are not required.Fig. S3 shows that the Se content in soil samples is generally between 0.175-0.600mg/kg, accounting for 63.7%;only 1% of samples showed the Se content of 2-3 mg/kg, and 72.2% of primary indicators of soil Se showed a value of 0.4-3.0mg/kg.The spatial distribution of Se content in the study area is shown in Fig. 4, and the distribution of soils with high Se content is consistent with the distribution characteristics of the rock stratum with high Se content.Near the distribution area of coal seams of vanadium-bearing rock, the soil Se content is high can easily result in selenium-rich agricultural products; further away from the coal seams, the soil Se content decreases rapidly (Wang, 2021).These results also illustrate the basic concept of medical geology.The elements in water and soil are derived from the geological environment.These elements are beneficial or harmful to humans or other life (M.LI. L, 2019).

Discussion
To promote the emerging discipline of health geology, we consider the four main aspects of geological landforms, climate, water resources, and soils to build an evaluation framework focusing on health geology.Regarding the geological landscape-level indicators, we considered the effect of natural radiation on the human body from the geological background, and the study shows that the variation of radiation dose rate is influenced by the location and mainly depends on the soil type and geological structure of the location (Alomari et al., 2019).Studies have explored the relationship between geographical location and humans, and some studies have even linked suicide rates to high altitudes (Wang et al., 2022).Additionally, phytochemicals and biological activities, such as the growth of grapes, are also enhanced at low altitude conditions (Gouvinhas et al., 2020).Therefore, a higher score was associated with a lower elevation in the evaluation framework.Landforms are generally associated with tectonic deformation (Ahmad et al., 2018).A clear understanding of local landforms and morphology is essential for land use and water management (Gupta et al., 2022).
Climate and its interaction with potentially toxic elements (PTEs) in the environment and geological heterogeneity can affect plant diversity and ecosystem function (Lu et al., 2021).Elevation, mean annual temperature, and soil microbial diversity were also positively correlated (Zhu et al., 2022).Climatic fluctuations have been regarded as triggers for influenza epidemics in temperate regions (Lam et al., 2020).The AQI (Air Quality Index) and temperature are the main factors controlling the comfort level.However, there is no clear standard to determine the thermal comfort level of each person, and the thermal comfort level will change with climate change (Ren et al., 2022).Water resources play an essential role in maintaining the health of an ecosystem, and the quality and abundance of water are inextricably linked to human health and are essential resources for social, agricultural, and economic development (Chiarelli et al., 2022;Lam et al., 2020;Veldkamp et al., 2017).Although China ranks 4th in the world in terms of total water resources, its per capita water resources are only 1/4 of the world average (Zhao et al., 2018).As such, in terms of water shortage, we comprehensively consider the zoning unit's water resource richness and per capita water resources.Overall, the trend of water resources in the study area (the southern part of the monsoon region of eastern China) is good, as the study area has a relatively large share of water resources.The water quality sampling and analysis results show that most sampling areas' indicators are primary indicators.Although the content of NO 3 − , Fe, Zn, and Cr 6+ in a small part of the sampling area reached the Level 3 standard, through the adsorption of soil clay particles in the flow area, as well as the confluence of tributary water and the dilution of precipitation, the above indicators have dropped to irrigation water standards before entering the farmland.
Vol:. ( 1234567890) As a source of nutrients for crops, the elements contained in the soil are critical for soil evaluation (Wen et al., 2020).Soil contamination with trace elements is a serious problem because of the non-biodegradability and persistence of these contaminants (álvarez-AyusoAbad-Valle, 2021).Similarly, the beneficial elements in the soil are eventually absorbed and used by the human body through the crop ingestion.The elements in the soil are mainly derived from the weathering and leaching of rocks, and different elements are derived from different geological backgrounds.For example, black shale is rich in Se and Cd (Duan et al., 2020).As is usually associated with geochemical environments, such as alluvial lacustrine sedimentary basin fills, volcanic deposits, etc. (Raju, 2022).Surface instability of exposed carbonate bedrock under the multiple influences of climatic, biological, or chemical action and soil pH changes, results in the release of F into the water, soil, and air, which in turn has an impact on human health (Li et al., 2017a(Li et al., , 2017b)).Cd in the soil can also be absorbed by plants and eventually enter the human body, thereby posing a health risk (Chen et al., 2018).Therefore, evaluating the distribution and content of elements in soils is necessary to study the association between the geological background and human health.Evaluating the results of beneficial and limiting elements in the soil can mitigate pollution and determine the local dominant geological elements.These results can be used to develop and utilize the study area and provide guidelines for its land resource management.
The results of each level of the evaluation index are plotted using ArcGIS.The results are integrated by hierarchical analysis and spatial overlay, which can clearly show the health geological classification of the zoning unit.(Xia et al., 2022) evaluated the distribution characteristics of element abundance and deficiency related to the population health in the study area by analyzing the environmental characteristics of element abundance and deficiency in the Xiongan New Area, China.They combined these results with the hydrogeological and hydrogeochemical models and completed the health geological zoning work.The discipline of health geology is still in its infancy, and owing to the differences in geological structure, geochemical environment, and geological background of each zoning unit, many idiosyncratic problems still exist in the evaluation process that needs to be corrected through practice.Some secondary indicators, such as climate comfort, are not determined in the evaluation process; follow-up assessments or surveys can be conducted through polls.It is necessary to investigate the association between geology and human health from four primary indicators: geomorphology, meteorology, water resources, and soil.Health geology is the result of multidisciplinary research across medical geology, geochemistry, geology, and hydrogeology, and it focuses on the link between health and geology.

Conclusion
A clear link between health and geological background has become obvious in the recent past.This study evaluates the geological factors that are closely related to human health in the study area in terms of geomorphology, water resources, meteorology, and soil.Finally, we calculated the health geological score of each evaluation unit to determine its health geological level.The results show that the overall score of the study area is high.The comprehensive score in the evaluation unit belongs to levels 1 and 2, wherein soil Se content can be used as a dominant geological factor in the study area and exploited by local people.This study provides a scientific basis for local spatial planning, water resource development, and land resource management, and provides decision support for developing advantageous resources and improving people's health.Additionally, this study establishes a new evaluation framework to study the connection between the geological background and human health.The results are based on hierarchical analysis using GIS for spatial operations.However, the discipline of health geology is still in development, and the evaluation framework and indicators developed for health geological zoning in this study may need to adjust accordingly.Moreover, some of the secondary indicators are complex, and the definition criteria need to be comprehensively considered and defined.Similar to medical geology, the discipline of health geology requires interdisciplinary research and is still in its development stage.Finally, we believe that health geology is a new bridge to "One Earth, One Health" which is a collaborative, multisectoral, and transdisciplinary approach-working at the local, regional, national, and global levels-with the goal of achieving optimal health outcomes recognizing the Vol.: (0123456789) interconnection between people, animals, plants, and their shared environment.

Fig. 3
Fig. 3 Spatial distribution of harmful elements in soil

Fig. 5
Fig. 5 Soil quality evaluation in the study area

Table 1
Evaluation index framework of healthy geological zoning Vol.: (0123456789)

Table 2
Surface water quality assessment Sampling sites pH Phosphate