Introduction

Trace elements have been assigned definite biological functions in maintaining human health (Konikowska & Mandecka, 2018; Shayganfard, 2022; WHO, 1996). Some of these elements, such as arsenic (As), mercury (Hg), lead (Pb), nickel (Ni), and cadmium (Cd), are considered toxic elements (TEs), which can cause abnormal physiological functions and even several serious diseases at any concentration (Halder et al., 2020; Tian et al., 2022). On the other hand, others, such as manganese (Mn), copper (Cu), iron (Fe), selenium (Se), and zinc (Zn), are considered essential trace elements (ETEs), but their long-term dietary intake may pose health risks and potential toxicity when consumed excessively or insufficiently (Cannas et al., 2020; Tong et al., 2021; Xiao et al., 2019). The health effects of these trace elements are summarized in Table 1. Assessing the apportionment of dietary sources and the associated health risks of trace element consumption is crucial in determining contamination levels in an area (Antoniadis et al., 2019).

Table 1 Health effects of TEs and ETEs
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Direct dietary intake, such as food consumption and drinking water, is the primary way in which the general population ingests trace elements (Filippini et al., 2020; Pipoyan et al., 2019). However, soil and dust ingestion also pose a significant pathway for residents in agricultural and pastoral areas (USEPA, 2016). Due to the increasing industrialization and urbanization, it is necessary to comprehensively evaluate the dietary intake of trace elements, especially TEs and ETEs, to assess long-term public health risks in most countries, including China (Gao et al., 2019; Li et al., 2018; Tang et al., 2014; Tian et al., 2020a; Wu et al., 2016; Zheng et al., 2007). Many environmental health organizations worldwide have developed recommendation or limit standards for trace elements and use health risk assessment as an effective approach to alleviate hidden hunger and some endemic diseases (EC, 2000; FAO & WHO, 2009; MEE, 2017a, 2017b; NHC, 2021; NHC & SA, 2006; NHC & SFDA, 2017; USEPA, 1996; USEPA, 2011; WHO, 2005; WHO, 2011).

The food consumption structure of rural residents in the Qinghai–Tibet Plateau (QTP) is relatively simple due to the region’s natural geographical environment. Locally produced grain and meat products are the primary sources of protein, carbohydrate and fat intake (Dermience et al., 2017; Gao et al., 2017; Wang et al., 2021). Studies have confirmed that this simple food consumption structure is the main reasons behind endemic diseases such as endemic arsenic poisoning and Kashin-Beck disease in QTP (Dinh et al., 2018; Li et al., 2012). Therefore, studying dietary trace element intake in QTP have important reference value for assessing the health risk of residents. In recent decades, multiple methods have been used to analyze trace elements contents in the food–water system in parts of QTP (Tian et al., 2018; Wang et al., 2020; Zhang et al., 2021; Zhang et al., 2002). However, existing research on the health risk assessment of QTP has mainly focused on ETEs, especially Se (Dermience et al., 2017; Guo & Wang, 2012; Tian et al., 2016, ; Wang et al., 2020a, ; Zhang et al., 2011; Zhao et al., 2013).

Li et al. (2022) studied the water quality and health risks of trace elements in surface water in the northeast of the QTP, and the results showed that 96% of the water quality belonged to excellent status, the non-carcinogenic health risk of children was high, and Cr was the primary contributor element to the carcinogenic risk in water. Du et al. (2023) studied seven heavy metal concentrations in 126 topsoil samples on the QTP, and the results showed that the risk of Cd and As pollution in soil was high. Wu et al. (2018) collected 70 soil samples from the northeastern QTP to assess health risk. The results showed that the carcinogenic risk of adults and children was determined to be high and very high, while the non-cancer risk of children was higher, while the non-cancer risk of adults was lower. Li et al. (2023) collected and analyzed 130 pairs of representative soil-highland barley samples from the QTP, and the results showed that the Cd concentration in highland barley ranged from 0.57 to 13.62 μg/kg, with an average of 4.57 ± 0.17 μg/kg. According to the literature review, there are only a few systematic reports on the dietary intake of trace elements and their health risk assessment in QTP.

Against this backdrop, this study systematically collected food (including highland barley, wheat, vegetable and meat), drinking water, cultivated soil and sedimentary rock samples in a typical area of Tethys–Himalaya (TH) tectonic domain, and comprehensively analyze the concentration of five TEs (As, Hg, Pb, Ni and Cd) and five ETEs (Mn, Cu, Fe, Se and Zn). The primary objectives of this study are to (a) describe and analyze the concentration characteristics of TEs and ETEs in food, drinking water and soil in the study area; (b) calculate the oral intake dose and assess the dietary health risk of TEs and ETEs to local residents; and (c) estimate the proportion of different source of intake of TEs and ETEs and discuss their underlying impact mechanisms. The results of this cross-sectional study would provide a comprehensive understanding of basic data for effective management of residents’ dietary intake, and have guiding significance and reference value for protecting residents’ health and the sustainability of agricultural production in this region.

Materials and methods

Study area description

The study area, Longzi County, is located in the TH tectonic domain and can be located geographically using the coordinates 91°53′–93°06′ E and 28°07′–28°52′ N (see Fig. 1b). Longzi County is a significant area for agricultural and animal husbandry production in Tibet, with a total population of 33,570 comprising of Tibetan, Luoba, and Han nationalities. Longzi County straddles the Yarlung Zangbo River Suture Zone and Southern Tibetan Detachment System (Dhital, 2015; Zheng et al., 2000).

Fig. 1
figure 1

Sampling locations in study area: a the location of Tibet in China; b the location of the study area in Tibet; c sampling points

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Samples preparation and analysis

In August 2019 and August 2020, a total of 78 food samples (including 60 highland barley, 6 wheat, 8 vegetables and 4 meat), 104 drinking water samples, 73 cultivated topsoil samples and 47 sedimentary rock samples, were collected in study area (Fig. 1c). The sample point coordinates were recorded by the handheld Global Position System manufactured by GARMIN. Each food sample weighing approximately 0.2 kg was collected and stored in a colorless polyethylene (PE) bag; Each drinking water sample was stored in a colorless PE bottle. The bottle were washed beforehand with deionized water and kept at 4 ℃; The cultivated topsoil samples were collected using the quartile method, with approximately 0.2 kg packed into each colorless PE bag; Each sedimentary rock sample weighing approximately 0.1 kg was collected from five blocks of the same outcrop and stored in a colorless PE bag.

The concentrations of Pb, Ni, Cd, Mn, Cu, Fe, and Zn in water samples were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP–MS). The concentrations of As and Se were determined using Hydride Generation Atomic Fluorescence Spectrometry (HG–AFS). The concentration of Hg was analyzed using Cold Vapor Atomic Absorption Spectrometry (CV–AAS). To determine the concentration of Cd, Cu, Fe, Mn, Ni, Pb, and Zn in topsoil, and sedimentary rock samples, the crushed and weighed sample was added to PTFE beaker mixed with acid of 3:3:1 HNO3, HF and HClO4, and heating the mixture at 180 ± 10℃ until the solution became transparent; the crushed food sample was added to glass beaker mixed with acid of 5:1 HNO3 and HClO4 and digested by heating (MEE, 2017a). The concentrations were then measured using ICP–MS. For the determination of As and Se, the crushed and weighed sample was added to aqua regia mixed with acid of a (1 + 1) aqua regia, and water bath digestion for three hours. Aqua regia is a mixture of concentrated nitric acid and concentrated hydrochloric acid at a ratio of 1:3 (volume ratio). After measuring Se, 3 mL of HCl, 5 mL of 5% thiourea solutions and 5 mL of 5% ascorbic acid solutions was added, shake well and take the supernatant to determine the As. The concentrations of As and Se were measured using HG–AFS. The concentration of Hg was determined using crushed and weighed sample via CV–AAS. More information regarding pretreatment and chemical analysis can be found in Appendix Material SA1 and SA2.

Estimated daily intake

Due to the particularity of the climate, the highland barley is the dominant crop in study area. Most of the farmlands are distributed in the Longzi river’ middle reaches (Fig. 1c), and the rest are scattered in small plots around the villages.

Direct oral intake (food consumption, drinking water and soil/dust) by the general population is usually considered the main route of exposure (Marin et al., 2017; USEPA, 2016). In order to calculate the average daily dose of oral intake (ADDoral), the Eq. (1) to Eq. (4) modified according to the equations of USEPA (2016) and NHC (2021) are used as follow:

$${ADD}_{d}=\frac{{(C}_{g}\times {IR}_{g}+{C}_{f}\times {IR}_{f}+{C}_{r}\times {IR}_{r}+{C}_{v}\times {IR}_{v}+{C}_{m}\times {IR}_{m})\times EF\times ED}{BW\times AT}$$
(1)
$${ADD}_{w}=\frac{{C}_{w}\times {IR}_{w}\times EF\times ED}{BW\times AT}$$
(2)
$${ADD}_{s}=\frac{{C}_{s}\times {IR}_{s}\times EF\times ED}{BW\times AT}$$
(3)
$${ADD}_{oral}={ADD}_{d}+{ADD}_{w}+{ADD}_{s}$$
(4)

where ADDd, ADDw and ADDs are the ADD of food consumption, drinking water and soil/dust, respectively; Cg, Cf, Cr, Cv, Cm, Cs and Cw are the average concentrations of trace elements in grain (unit: mg/kg), flour (unit: mg/kg), rice (unit: mg/kg), vegetables (unit: mg/kg), meat (unit: mg/kg), soil (unit: mg/kg) and water (unit: μg /L), respectively; IRg, IRf, IRr, IRv, IRm, IRw and IRs are the ingestion rates of grain, flour, rice, vegetables, meat, water and soil, respectively (Table 2); EF denotes frequency of exposure (unit: days/year), 365 days/year; ED represents duration of exposure (unit: years), according to MEP (2013) and adapted from the life expectancy of Tibet, 45 years for Tibet adults; BW refers to body weight (unit: kg), 55.3 kg for Tibet adults according to MEP (2013); AT is average time (unit: days), 16,425 days.

Table 2 RfD and IR for adults
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Human health risk assessment

The hazard quotient (HQ) of trace elements is calculated by Eq. (5) and Eq. (6) according to USEPA (2016) and NHC (2021):

$${HQ}_{e}=\frac{{ADD}_{oral}}{{RfD}_{e}}$$
(5)
$${HQ}_{i}=\frac{{RfD}_{i}}{{ADD}_{oral}}$$
(6)

where HQe refers to the excessive TEs and ETEs intake of HQ; HQi refers to the insufficient ETEs intake of HQ; RfDe represents excessive reference dose of TEs and ETEs; RfDi represents insufficient reference dose of ETEs. HQ > 1 indicates non-carcinogenic health risk, while HQ < 1 suggests no non-carcinogenic health risk. The RfD of each TE and ETE are listed in Table 2.

Carcinogenic risk (CR) of trace elements is calculated by Eq. (7) according to NHC (2021):

$$CR={ADD}_{oral}\times SF$$
(7)

where SF refers to the slop factor of carcinogenic risk (unit: mg/kg∙day), 1.5 mg/kg∙day, 0.0085 mg/kg∙day, 0.061 mg/kg∙day and 0.0028 mg/kg∙day for As, Pb, Cd and Ni, respectively. Because USEPA (2016) and NHC (2021) do not mention the SF of Hg, CR only calculates the four elements As, Pb, Cd and Ni. CR ≤ 10–6 suggests the CR is negligible, 10–6 < CR ≤ 10–4 indicates the CR is within the acceptable range, while CR ≥ 10–4 indicates a risk of cancer (CALEPA, 2019; NHC, 2021; USEPA, 2016).

Results

Levels of TEs and ETEs in food, drinking water and soil samples

The average concentrations of TEs and ETEs in food, drinking water and soil samples in study area are listed in Table 3. Based on the Food Safety Limits of Contaminants (NHC, 2022), grain, flour and meat samples were within the standard limits, but the concentration of Pb in vegetables was 1.34 times higher than the standard value limits of 0.1 mg/kg (Table 3). In addition, the average concentration of Cu in grain and flour were 1.71 and 2.21 times of the maximum recommended value of 10 mg/kg in the Limits of Eight Elements in Cereals, Legume, Tubes and its Products (MOA, 2004). In highland barley, the average concentrations of Pb, Ni, Mn, Fe, Zn and Cu were 1.12, 3.62, 3.58, 2.12, 1.28 and 4.47 times higher than those reported in some area of QTP, respectively (Che et al., 2019; Chi et al., 2011; Zhang et al., 2017). In meat, the average concentrations of Hg and Cd were 1.30 and 2.00 times higher than those found in Qinghai Province, while the concentrations of Mn, Zn and Fe were much higher than those in Shannan City (Wu, 2020; Xiang et al., 2021; Zhu et al., 2021). Therefore, it can be seen that most TEs and ETEs in food from the study area were slightly high, with the exception of Se, which was slightly low (Table 3).

Table 3 Mean concentrations of TEs and ETEs in food, drinking water and soil
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The average concentrations of TEs and ETEs in drinking water were significantly lower than the limit prescribed by the Standards for Drinking Water Quality (SAMR and SA) (Table 3). Several studies have compared the average concentrations of TEs and ETEs in some QTP drinking water: The average concentration of Hg in study area was much higher (8.26 times) than that in the Rongna River in northern Tibet (Luo et al., 2022); The average concentrations of As and Ni in study area were slightly higher (1.72 and 1.64 times, respectively) than that in Tibet (Yi et al., 2021); The average concentrations of As, Zn and Fe in study area were higher (2.97, 1.44 and 1.53 times, respectively) than those in glacial meltwater runoff in the northeastern of QTP (Li et al., 2020; Qu et al., 2019); The average concentrations of Zn in drinking water of the study area was higher (2.16 times) than that in Luolong County (Zha et al., 2022). These results indicate that the concentrations of TEs and ETEs in drinking water of the study area are suitable, and the concentrations of As, Hg, Mn, Ni, Zn and Fe are higher than those in some parts of the QTP.

The average concentration of As, Pb, Hg, Cd, Ni, Mn, Cu and Zn in soil samples were 199%, 134%, 153%, 152%, 149%, 148%, 126% and 134% of the soil background values in Tibet, respectively (MEE, 1990). By comparing the Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land, it can be found that the average concentration of Pb, Hg, Cd, Ni, Cu and Zn in the soil samples of the study area did not exceed the screening value. However, the concentration of As was 131% of the screening value (SAMR and SA, 2018). The average concentration of Pb and Zn in soil samples was similar to that in Huzhu County of the QTP, while the average concentration of As in soil samples was 322% of that in Huzhu County (Zhang et al., 2022). These results indicating that the concentration of As in soil samples is markedly high.

Estimated daily oral intake of TEs and ETEs

In order to further consider the impact of TEs and ETEs in the daily diet of the study area on the health of local residents, the ADDoral of TEs and ETEs at the township level in study area are calculated using formulas (1) to (4). The ADDoral distribution of As, Pb, Hg and Cd in TEs showed similarities, with high value area of ADDoral was primarily distributed in the eastern part of the study area. On the other hand, the high ADDoral values of Fe, Cu, Zn and Se were mostly found in the northeast of the study area (Fig. S1). Furthermore, by calculating the proportion of ADDoral from different sources of intake (Fig. 2, Table S1, Table S2, Table S3), it was discovered that ADDd (including ADDg, ADDf, ADDv and ADDm) of TEs and ETEs accounted for more than 90% of ADDoral. This suggests that food, particularly grain (highland barley) and meat, are the primary dietary sources of local residents.

Fig. 2
figure 2

The sources of ADDoral intake of TEs and ETEs in Longzi County. a As, b Pb, c Hg, d Cd, e Ni, f Mn, g Fe, h Cu, i Zn, j Se

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The relationship between ADDoral and RfD in the whole study area was shown in Fig. 3. The ADDoral values of As varied from 0.003 mg/(kg·day) in Douyu Township to 0.005 mg/(kg·day) in Rerong Township, both of which exceeded the RfDe. These results suggest that residents in all townships in the study area are exposed to excessive oral intake of As (Fig. 3a). For Hg and Cd, the ADDoral value ranged from 5.10E-05 mg/(kg·day) in Xuesha Township to 9.17E-05 mg/(kg·day) in Douyu Township for Hg, and 4.45E-04 mg/(kg·day) in Rerong Township) to 5.47E-04 mg/(kg·day) in Douyu Township for Cd, respectively. In both cases, the ADDoral values were lower than the RfDe, indicating that the oral intake of Hg and Cd were suitable for the local residents (Fig. 3c, Fig. 3d). For Pb and Ni, The ADDoral values ranged from 0.003 mg/(kg·day) in Jiayu Township to 0.011 mg/(kg·day) in Xuesha Township for Pb, and 0.017 mg/(kg·day) in Zhari Township) to 0.044 mg/(kg·day) in Longzi Township for Ni, respectively. Among the four townships, the ADDoral values of Pb and Ni were higher than the RfDe, suggesting that the oral intake of Pb and Ni were basically appropriate (Fig. 3b, Fig. 3e). The ADDoral values of Mn and Zn ranged from 0.556 mg/(kg·day) in Douyu Township to 1.078 mg/(kg·day) in San’an Qulin Township for Mn, and 1.907 mg/(kg·day) in Longzi Township to 3.260 mg/(kg·day) in San’an Qulin Township for Zn, respectively. In both cases, the ADDoral values exceeded the RfDe, indicating excessive oral intake of Mn and Zn among the residents in the study area (Fig. 3f, Fig. 3i). The ADDoral values of Fe ranged from 3.526 mg/(kg·day) in Douyu Township to 10.857 mg/(kg·day) in San’an Qulin Township, which were 5.090 to 15.660 times higher than the RfDe. This indicated that the residents in all townships were exposed to extremely high levels of Fe through oral intake (Fig. 3g). The ADDoral values of Cu anged from 0.115 mg/(kg·day) in Douyu Township and 0.175 mg/(kg·day) in San’an Qulin Township, which were higher than the RfDe in nine townships. These results indicated that residents in most areas of Longzi County are exposed to excessive levels of Cu through oral intake (Fig. 3h). Finally, the ADDoral values of Se ranged from 0.003 mg/(kg·day) in Jiayu Township to 0.005 mg/(kg·day) in San’an Qulin Township, which were higher than the RfDi and lower than the RfDe. These results suggest that the oral intake of Se was appropriate for residents in the study area (Fig. 3j).

Fig. 3
figure 3

The relationship between ADDoral and RfD of TEs and ETEs in Longzi County. a As, b Pb, c Hg, d Cd, e Ni, f Mn, g Fe, h Cu, i Zn, j Se

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Health risk assessment

The HQ of TEs and ETEs for each township was computed using Eqs. (5) and (6) (Table S5). In addition, The CR of As, Pb, Cd and Ni was calculated using formula (7) to assess the carcinogenic risk of these elements in each township in the study area (Table S6).

The HQe of As was significantly higher than 1 in all township, and the CR of As was higher than 1 × 10–4 (Fig. 4a, Table S5, Table S6). For Pb, the HQe was 2.84 in Xuesha Township, while the HQe in remaining ten townships was slightly higher or lower than 1, and the CR were all between 1 × 10–6 and 1 × 10–4 (Fig. 4b, Table S5, Table S6). The HQe of Cd was lower than 1 in all townships, and the CR of Cd was lower than 1 × 10–4 (Fig. 3c, Table S5, Table S6). For Ni, the HQe was 2.22 in Longzi Township, and other ten townships was slightly higher or lower than 1, while the CR of Ni was between 1 × 10–6 and 1 × 10–4 (Fig. 4d, Table S5, Table S6). The HQe of Hg was lower than 1 in all townships (Fig. 4e, Table S5). The HQe of Mn, Fe and Zn were higher than 1 in all townships (Fig. 4f, Fig. 4g, Fig. 4i, Table S5). The HQe of Cu was higher than 1 in nine townships (Fig. 4h, Table S5). The HQi and HQe of Se were less than 1 in all townships (Fig. 4j, Table S5). These data indicated that there was a non-carcinogenic risk of excessive intake of As, Mn, Fe and Zn in all townships. The townships with non-carcinogenic risks of excessive intake of Pb and Ni accounted for 36.36%, while 81.82% of the townships had non-carcinogenic risks of excessive intake of Cu. There were no non-carcinogenic risks of Hg, Cd and Se in any townships in Longzi County. However, As posed a carcinogenic risk to the residents throughout the study area, while the carcinogenic risks of Pb, Hg and Ni were within the acceptable range. Consequently, high-concentrations food containing As, Mn, Fe, Cu and Zn should be reduced in the daily diet, and dietary distribution should be reasonably regulated to reduce and control the diseases caused by excessive intake of TEs and ETEs.

Fig. 4
figure 4

The Health Risk of TEs and ETEs in Longzi County, a As, b Pb, c Cd, d Ni, e Hg, f Mn, g Fe, h Cu, i Zn and j Se

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Discussions

Dietary intake is an important pathway for humans to consume TEs and ETEs (Rosinger, 2023; Shostak, 2023). Epidemiological studies have demonstrated a link between diet-related diseases and the biogeochemistry of trace elements, as discussed in the Introduction. By estimating the ADDoral of TEs and ETEs, this study found that local residents have excessive intake of As, Mn, Fe, Cu and Zn. Grain and meat are the primary dietary sources for local residents’ TEs and ETEs (Fig. 3, Table S4). In order to determine the sources of these elements in food, we conducted correlation analysis on these elements in matching samples between soil and grain. The results showed that there was a significant correlation between As, Pb, Hg, Mn, Fe, Cu and Se concentrations in grain and soil (r = 0.840***, 0.911***, 0.577*, 0.820***, 0.640**, 0.614** and 0.573*, respectively), as shown in Fig. S2 and Table S7. Previous studies have confirmed that trace elements in grain are primarily absorbed by crop roots from cultivated soil (Abatemi-Usman et al., 2023; Chen et al., 2023). Thus, the enrichment of TEs or ETEs in local food is mainly on account of these high concentrations of TEs or ETEs in the soil.

Soil is mainly formed by weathering of stratum and soil forming parent material (loose debris formed by weathering of surface rocks), so stratum is the main source of trace elements in soil (Miguez-Macho & Fan, 2021). The eastern part of the study area is situated in the Collision zone between the Eurasian plate and the Indian Ocean plate, where with strong tectonic movement and extensive exposure of magmatic rocks (Liu et al., 2020; Tian et al., 2022). This also caused some “heavy” elements from earlier stratum and deep mantle to enter the surface (Wang et al., 2023). The geologic map and numerical age (Fig. S2) indicate that the stratum in the study area mainly comprises the Proterozoic (552–525 Ma), Triassic (201–252 Ma), Jurassic (145–210 Ma) and Cretaceous (66–145 Ma). When comparing the concentrations of TEs and ETEs in the stratum of the study area with the Southern Tibetan crust, it was found that the concentration of TEs in various stratum were higher than those in the Southern Tibetan crust. Notably, the concentrations of As in Proterozoic, Triassic, Jurassic and Cretaceous was 43.09, 12.41, 15.86 and 6.22 times that of the Southern Tibetan crust, respectively (Table S8). Our previous studies have confirmed that the spatial differentiation of heavy metals in the study area is mainly controlled by geological source factors (Tian et al., 2022). Therefore, the ADDoral among local residents is mainly influenced by the concentrations of TEs and ETEs under different geological backgrounds. The high concentration of TEs or ETEs in the geological background leads to the high concentration of these elements in the soil, which in turn causes excessive intake of these elements by local residents through the food chain and biogeochemical cycle. This also explains the spatial differentiation of these elements in the soil.

By reason of the limitations imposed by the natural geographical environment, the food consumption structure of local residents in the TH tectonic domain is relatively homogeneous (Jing et al., 2023). Through analysis of the intake sources of TEs and ETEs, it was found that Mn and Cu were mainly come from local highland barley, while Fe primarily comes from local grains (highland barley and flour accounting for over 75%), and Zn mainly comes from local yak meat (Fig. 2f, g, h and i). Ma et al. (2022) reported that local agricultural activities, such as pesticide spraying and excessive application of chemical fertilizer, could significantly increase the concentration of Cu in the soil. Duncan et al. (2023) have concluded that the concentration of Fe and Zn in livestock feed is generally high, and the excessive use of feed may also be the responsible for the high concentrations of Fe and Zn in local meat products. Therefore, reasonable fertilization and planning the use of livestock feed are effective measures to reduce and prevent health problems caused by excessive consumption by local residents. Besides, balancing the intake of TEs and ETEs by consuming diverse exotic foods and improving the dietary structure (such as increasing intake of vegetables and fruits) can help local residents avoid the health risks associated with excessive intake of TEs and ETEs.

In summary, this study comprehensively analyzed the concentrations characteristics of five TEs and five ETEs in food, drinking water and soil samples, calculating the proportion of ADDoral from different intake source in typical area of TH tectonic domain. The non-carcinogenic and carcinogenic risks of these elements were also assessed. In addition, based on the calculation results, we briefly explained the spatial distribution trend of ADDoral, and discussed the relationship between the concentrations of five TEs and five ETEs in sedimentary rocks of the study area and Southern Tibetan crust. Finally, we clarified and identified the health risks caused by dietary intake of local residents, and proposed dietary recommendations to reduce such risks. However, accurate IR data was not obtained from the questionnaire survey when calculating the ADDoral of five TEs and five ETEs in the study area. Thus, the average intake of various foods for the residents of Shannan City, obtained from the relevant literature, was used, which may cause some deviation between the calculation results of ADDoral and the actual situation in the study area. The follow-up studies could further carry out a systematic participatory rural assessment of local residents’ dietary intake to obtain more accurate IR values. By reason of the foregoing, this study can provide comprehensive basic data for the effective management of healthy dietary intake among residents in TH tectonic domain, with reference value for the health risk assessment and endemic disease prevention and control decision-making among local and even Tibetan residents.

Conclusions

The dietary assessment of typical areas of in the TH tectonic domain is crucial for promoting the health, safety and sustainable development of local residents. The concentrations of several TEs and ETEs in food, drinking water and soil in the study area were higher than those in the QTP and its surrounding areas. Moreover, highland barley and meat were the primary sources of oral intake of TEs and ETEs for local residents. In addition, the non-carcinogenic health risks of Hg, Cd and Se were negligible, whereas the remaining seven elements posed certain non-carcinogenic health risks. Among these elements, As posed both significant non-carcinogenic and carcinogenic health risks throughout the study area. The high concentration of TEs and ETEs in the geological background of the study area pose health risks to local residents through the food chain and biogeochemical cycle. Therefore, it is necessary to increase the intake of vegetables and fruits and consume some exotic food to improve the dietary structure among the local residents in order to avoid the occurrence dietary intake-related diseases.