Dataset-Based Assessment of Heavy Metals Pollution in Taihu Lake Fish and Their Health Risk

Xiaobo Liu Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Science Congtian Lin Key Lab of Animal Ecology and Conservational Biology, Institute of zoology, Chinese Academy of Sciences Yangyu Wu Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Science Haining Huang Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences Liting Zhu Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese of Academy of Sciences Ru Jiang Department of Obstetrics and Gyencology, The Frist A liated Hospital of Nanchang Unversity Qiansheng Huang (  qshuang@iue.ac.cn ) Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences https://orcid.org/0000-0002-3788-3164


Introduction 41
Located in the lower reaches of the Yangtze River, Taihu Lake is the third largest lake in 42 China. The lake, also known as the land of fish and rice, provides the eastern region with drinking 43 water, fisheries and tourism resources (Wu et al., 2019). After decades of development, Taihu has 44 become an important industrial and agricultural base in China, which has also resulted in a huge 45 inflow of industrial and urban sewage. Various types of pollutants are widely distributed through 46 the sediment, water, and organisms in Taihu. 47 Of varied types of pollutants, heavy metals receive great concern as their high contents and 48 adverse ecological impacts. Niu et al have performed systematic statistical and associated risk 49 assessment of heavy metals in the surface sediments of Taihu using meta-analysis and showed that 50 cadmium (Cd) is the main contaminant of heavy metals in the sediments of Taihu and is the main 51 factor contributing to the potential hazards of heavy metals. Besides, arsenic (As), chromium (Cr), 52 copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn) in Taihu are also serious and 53 should be given greater attention (Niu et al., 2020). Jiang et al found that the heavy metals content 54 in the surface water of Taihu Lake is high, and some heavy metals content may cause chronic 55 toxicity to the organisms in Taihu Lake (Jiang et al., 2012). Heavy metals also have been widely 56 detected in aquatic organisms of Taihu. The enrichment of heavy metals in fish from Taihu has 57 been shown in many studies (Fu et al., 2013;Rajeshkumar et al., 2018). However, those studies 58 only revealed the short-term effect of heavy metal in some specific species. Compiling these data 59 together and further analysing would provide a comprehensive understanding of the accumulation 60 levels of heavy metals in the organism. 61 Heavy metals can be bio-accumulated through the food chain (Zuo et al., 2018). Some studies 62 7 The data from the Taihu Lake area was retrieved from the dataset, followed by filtering the 129 fish data from these data, and finally, the data of Zn, Cr, As, Pb, Hg, and Cd in Taihu Lake fish 130 were extracted separately. Ultimately, a total of 1174 data from species contaminant concentration 131 records in 46 fish species were used for our statistical analysis. We further classified the fish into 132 herbivorous, omnivorous and carnivorous according to their feeding habits, and all data units were 133 transformed before being entered into the dataset. For the purpose of comparison, we converted the wet weight concentration is the dry weight 137 concentration, the formula is as follows: 138 where C d and C w are the concentrations expressed relatively to dry and wet mass respectively, 139 and with the percentage of humidity in wet tissues (%H) classically ranging around 80% for a vast 140 range of species (Bonito et al., 2016;Cresson et al., 2017). 141

142
It is generally believed that the larger the number of samples, the more reliable the results 143 obtained. In this study, the collected fish were divided into three kinds according to the food chain, 144 herbivorous fish, omnivorous fish, and carnivorous fish. In order to make the data of each 145 category more representative, we used a weighted average of the number of samples for each 146 species as follows: 147 Ni represents the number of samples of Species i, C i is the concentration of heavy metals in 148 species i, and both of N i and C i are obtained from the original references (Niu et al., 2020). 149

150
In order to evaluate the pollution of various metals in fish, the single pollution index model 151 (Pi) was used to evaluate the pollution degree of heavy metals in aquatic products (Liang et al., 152 2016;Liu et al., 2021). The formula is as follows, 153 In the formula, Pi is the single pollution index, C i is the measured concentration of pollutants, 155 and S i is the standard value or reference value of pollutants (Liu Yang, 2013;NMPA, 2017 Where THQ is the target hazard quotient; EF is exposure frequency (365 days/year); ED is 170 exposure duration (70 years); FIR is the food ingestion rate (g/person/d, fish: 36 g/person/day) 171 (Storelli, 2008). C i is the concentration of metal i in fish (mg·kg -1 dw); BW is the average body 172 weight (children:30kg, adults: 70kg); AT is exposure time for non-carcinogens (365 days per 173 year× ED). RfD is the oral reference dose (mg/kg/day), Oral RfD for As (inorganic), Cd, Hg 174 (Methyl Mercury), Cr, Zn and Pb is 0.0003, 0.001, 0.0001, 1.5, 0.3 and 0.004 mg/kg/day 175 respectively); If the ratio is less than 1, the exposed population is unlikely to experience obvious 176 adverse effects (Zhuang et al., 2009). It is well known that inorganic arsenic is the main 177 component of the toxic effects of arsenic, and according to EFSA, in this study we assumed that 178 the inorganic arsenic content was 20% of the total arsenic content (EFSA, 2014). 179 The total target hazard quotient (TTHQ) was calculated with the aid of the following equation where TTHQ is total target hazard quotient, and THQi is a non-carcinogenic risk of each 182 metal. 183

carcinogenic risk assessment 184
The estimated daily intake is an important indicator of health risk assessment in humans. It is 185 used to estimate the daily intake of heavy metals. This paper uses this formula to estimate the 186 intake of heavy metals through the consumption of fish. 187

= ×
Where EDI is estimated daily intake(mg/kg/day), FIR is the food ingestion rate (g/person/d, 188 fish: 36 g/person/day), C i is the concentration of metal i in fish (mg·kg -1 dw). 189 The incremental lifetime cancer risk (ILCR) indicates that a person's lifetime probability of 190 developing cancer is increased by exposure to potential carcinogens. It was used to calculate the 191 risk of heavy metals carcinogenesis through the ingestion of fish from Taihu Lake. 192

Heavy metals in Taihu Lake fish 199
The concentrations of heavy metals in various kinds of fish from Taihu Lake since 2000 were 200 collected and all the wet weight data were transformed by the dry and wet weight conversion 201 formula for a unified generalization of the data. Finally, a total of 1174 records were obtained, 202 including 46 species of fish and 6 species of heavy metals. Table 1 shows the levels of the six 203 heavy metals in three different types of fish. It can be seen that there is a significant difference in 204 the concentrations in fish between different heavy metals. and the overall level of each metal in 205 descending order is Zn> Pb> Cr> As> Cd> Hg. The levels of heavy metals in different food chains 206 are also different, the distribution of heavy metals in herbivorous fish is Zn> Cr> As> Pb> Hg> 207 Cd, the distribution of heavy metals in omnivorous fish is Zn> Pb> Cr> As> Cd> Hg, the 208 distribution of heavy metals in carnivorous fish is Zn> Cu> As> Pb> Cr> Cd> Hg. 209 At the level of the food chain, only Hg and Cd increased with the level of the food chain, and 210 the other four heavy metals, zinc, copper, arsenic, and mercury, were omnivorous fish, carnivorous 211 fish, and herbivorous fishes. Overall, the levels of the heavy metals in different feeding fishes in 212 Taihu Lake are omnivorous fish > carnivorous fish > herbivorous fish. In addition, there is 213 significant variation in the content of the same metal in the same predatory fish, with the highest 214 As content in carnivorous fish being 99.75 times higher than the lowest As content. Table 1  Hg also showed significant fluctuations, with a difference of 39.19 times, 10.05 times, 4.27 times, 235 and 2.13 times between the highest and lowest years, respectively. 236

Single-factor evaluation of heavy metals in Taihu fish 237
In order to accurately calculate the PI and MPI values, the present study extracted whole-body 238 concentration data from a dataset of 23 species of fish tested, and based on the information in the 239 literature and the fish database (www.fishbase.org), the fish were classified into herbivorous fish, 240 omnivorous fish, carnivorous fish according to their feeding habits, and classified fish into upper 241 fish, middle-upper fish, middle-lower fish, bottom fish according to the layer in which they live. A 242 comprehensive and detailed list of fish taxonomies is given in Table S1. All the results of the 243 calculations are presented in Table 2, the PI values of Hg, Pb, Cd, Zn, As and Cr in Taihu Lake 244 fish were 0.074~1.042, 0.064~19.36, 0.03~10.6, 0.09~1.70, 0.08~7.56, 0.11~1.81 respectively. 245 According to the average PI values for all species, the heavy metals are contaminated with As > 246 Pb > Cd > Zn > Cr > Hg in that order. And the three metals Pb, Cd, and As, which had pi values 247 higher than 1, indicating heavy pollution. 248 In Fig. 2, the pollution level of fish in different living habits and feeding habits was calculated. 249 The results showed that in fish with different living habits, the heavy pollution degree was the 250 most in the upper layer fish and the lower layer fish, the least pollution level in the middle-lower 251 layers. And a high proportion of uncontaminated and light pollution fish in middle-lower and 252 middle-upper fishes. The overall level of contamination is in the order of bottom fish > upper fish > 253 middle-upper fish > middle-lower fish. Among the different feeding fishes, omnivorous fishes had 254 the highest proportion of heavy pollution degree, followed by carnivorous fishes and herbivorous 255 fishes had the lowest proportion of heavy pollution degree. Overall, the contamination levels of 256 these three types of fish were in the following order omnivorous fish > carnivorous fish > 257 herbivorous fish. 258

Comprehensive evaluation of heavy metals contamination in Taihu fish 259
The results of the MPI values for all fish are presented in Table 2. It can be seen that the 260 bottom fish has the highest MPI value, followed by the upper fish, and the middle fish has a 261 smaller MPI value, compared to the middle-low fish, the MPI value of the middle-upper fish is 262 slightly higher than the lower middle fish (Fig. 3A). Concerning the feeding habit, it is obvious 263 from Fig. 3B that the MPI values of different feeding fishes are ranked as omnivorous fish > 264 carnivorous fish > herbivorous fish. 265

Non-carcinogens risk 267
In order to analyze more accurately the impact of eating Taihu fish on human health, our 268 further collated the heavy metals content of Taihu fish, the concentrations in each organ known in 269 the literature were averaged as a whole, and the results were presented in Table S2. Because of the 270 differences in body weight and food consumption between adults and children, the THQ model Hg > As > Cr > Zn > Pb > Cd for children; Hg > Pb > As > Cr > Zn > Cd for omnivorous fish; Hg > 276 Cd > As > Zn > Pb > Cr for carnivorous fish. Compared with children, the THQ values of heavy 277 metals exposed to adults by eating fish are lower than those of children, but the ordering 278 distribution in each fish is consistent. And detailed information on THQ is provided in Fig. S3. 279 Noteworthy, the THQ values of Hg, Pb in omnivorous fish and Hg in carnivorous fish are higher 280 than 1. This suggests that they have potential non-carcinogenic effects on children's health. And 281 the THQ of Hg in omnivorous fish is close to 2, indicating that the Hg content in omnivorous fish 282 may cause non-carcinogenic health effects in adults. 283 From Fig. 4, the TTHQ for all fish is greater than 1 for both children and adults, suggesting 284 that consumption of fish from the Taihu Lake region may have adverse non-carcinogenic health 285 effects for consumers. It should be noted that children consuming omnivorous fish from Taihu 286 Lake with TTHQ above 5, which means a possible negative non-carcinogenic effect on human 287 health and should be of great concern. The highest contribution of Hg to TTHQ can be clearly 288 seen in Fig. 4, with herbivorous, omnivorous, and carnivorous fish accounting for 66.21%, 289 29.87%, and 44.03%, respectively. The contribution rate of Pb in three types of fish accounted for 290 2.09%, 22.98%, and 6.77% of children's TTHQ respectively. TTHQ values also differed among 291 different types of fish, but the trend was consistent in adults and children, with the largest TTHQ 292 values in omnivorous fish, followed by carnivorous fish and finally herbivorous fish (Fig. 4). In 293 general, the consumption of Taihu fish by adults and children may have adverse non-carcinogenic 294 health effects, especially for children. The risk of human health from different types of fish 295 consumption is different, and the risk of non-cancer health is highest in omnivorous fish, then in 296 carnivorous fish, and the potential risk of herbivorous fish is lowest. 297

Carcinogens risk 298
The results in Table 3 show that the carcinogenic risk of herbivorous fish from the Taihu Lake 299 area for adults and children is below the EPA threshold risk limit of ILCR>10 -4 . This indicates that 300 the carcinogenic risk from consumption of herbivorous fish from Taihu Lake is acceptable. 301 However, in omnivorous fish, the ILCR values of As for adults and children were 1.74E-04 and 302 4.06E-0 respectively, and the ILCR value of Cd for children was 1.52E-04, both of which were 303 greater than 1×10 -4 and exceeded the EPA threshold risk limit. Unlike omnivorous fish, the ILCR 304 values for Cd in carnivorous fish exceeded 1×10 -4 for adults and children, and the ILCR values for 305 As in children exceeded the EPA threshold risk limit. After rigorous examination, it was 306 discovered that the ILCR values of As in omnivorous fish and Cd in carnivorous fish in Taihu 307 exceeded the EPA threshold risk limit for both adults and children, and the ILCR values of Cd in 308 omnivorous fish and As in carnivorous fish for children also exceeded the threshold risk limit.  Pb (1.68, 1.12-2.6 mg·kg -1 dw) in Nansi Lake fish was smaller than that in Taihu fish, the average 348 concentration was higher than that in Taihu fish, while the As (0.3, 0.2-0.4 mg·kg -1 dw) content 349 was significantly smaller than that in Taihu fish (Zhu et al., 2015). In the comparison with Taihu 350 fish, only the mean concentration of Zn, Cd, Pb in the Nansi Lake was higher than that of Taihu 351 fish, while the range and mean concentration of heavy metals in the remaining fish were lower 352 than that in Taihu Lake. Combining the results in Fig. 2 and Fig. 3, it can be seen that the benthic fishes have the highest 357 level of contamination, which may be due to longer exposure of their skin to sediment and greater  quantitative estimate of the probability of adverse health effects in exposed populations, but rather 380 provides an indication of the risk level of exposure (Storelli, 2008). In this study, the TTHQ for all 381 types of fish is greater than 1 for children and The TTHQ of omnivorous and carnivorous fish to 382 adults was also higher than 1 suggesting that consumption of fish from the Taihu Lake region may 383 have adverse non-carcinogenic health effects for consumers. In contrast to the results of this study, 384 several existing studies have shown that human consumption of Taihu fish had a TTHQ of less 385 than 1, and there were no significant health risks to humans (Liu et al., 2009;Tao et al., 2012;Xia 386 et al., 2019). The results of ILCR showed that the exposure hazard of As and Cd in omnivorous 387 fish and carnivorous fish in Taihu to children exceeded the threshold risk limit specified by EPA, 388 and the ILCR values of As in omnivorous fish and Cd in carnivorous fish to adults also exceeded 389 the threshold risk limit, although these values only just exceeded the threshold risk limit, they 390 should cause people to pay attention. There is a lack of studies on ILCR assessment of fish from 391 Taihu. In this study, we calculated the inorganic arsenic content as 20% of the total arsenic, which 392 may overestimate the inorganic arsenic content in fish (Julshamn et al., 2012). And in the 393 calculation process, we used different standards such as FIR, BW, etc. than other literature, and on 394 the other hand, the fish heavy metals data used in this study is the average of long-term data, while 395 other data in the literature only calculate the fish heavy metals of a period of time. This may be the 396 reason for the difference between the results of this study and those of other studies. 397 It is worth noting that the levels of Zn, Pb, and Cr are relatively high in these three elements, 398 but the THQ results show that the intake of these three heavy metals does not pose a health risk to 399 humans. As and Hg, on the other hand, have lower concentrations, but higher health risks than the 400 first three metals. Therefore, in the process of pollution prevention and control, the hazard quotient 401 of the pollutant should be used as a guide rather than simply the concentration of the pollutant 402 mass. It is recommended that the scope of biological testing be extended to include regular 403 monitoring of organisms within a certain range. Long-term continuous testing in heavily 404 contaminated areas is necessary. Meanwhile, a unified detection method should be established to 405 standardize the monitoring data, and these standardized monitoring data should be integrated 406 regularly. 407

Conclusion 408
In this paper, we extracted the data related to the heavy metals content in fish of Taihu Lake 409 using a dataset that has already been built, and we systematically counted and described the data. 410 A total of 1174 records were obtained, including 46 species of fish and 6 kinds of heavy metals. 411 The concentration of heavy metals in Taihu Lake fish were Zn (64.92, 14-157.675 mg·kg -1 dw),        Total target hazard factor in adults and children due to ingestion of metals in Taihu Lake sh. H, herbivorous; O, omnivorous; C: carnivorous, Different colors indicate different heavy metals and the area of different colors in the column indicates the THQ value of that heavy metal.

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