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Short-chain chlorinated paraffins (SCCPs) are persistent organic pollutants listed in the Stockholm Convention. Medium-chain chlorinated paraffins (MCCPs) structurally similar to SCCPs have similar toxicity. China is the largest producer and consumer of chlorinated paraffins (CPs) in the world. Dietary intake is considered the main route of human exposure to CPs (1).
The China National Center for Food Safety Risk Assessment launched the Sixth China Total Diet Study (TDS). The dietary survey methods, sample collection, and processing methods are referenced in the Foreword in this special issue (2). The concentrations of SCCP and MCCP in each food sample in the Sixth China TDS were 5–265 ng/g wet weight and 4–306 ng/g wet weight, respectively (Table 1). Among the 8 food categories, the highest average concentrations of SCCP and MCCP were found in meats at 63 ng/g wet weight and 70 ng/g wet weight, respectively. The average SCCP and MCCP concentrations in animal-origin foods were generally higher than those in plant-origin foods. A possible reason could be that SCCPs and MCCPs are compounds with high octanol-water partition coefficients and tend to accumulate in the fatty tissues of animals. The highest total concentrations of SCCP in eight food categories were detected in the provincial-level administrative divisions (PLADs) of Hebei, Henan, and Shanxi, while those of MCCP were found in Henan, Hebei, and Ningxia. Overall, the total concentrations of SCCP and MCCP from the eight food samples in the northern PLADs were higher than those in the southern PLADs in this study. The total estimated dietary intakes (EDI) for SCCP and MCCP in eight food categories were listed in Table 2, which ranged from 270 to 2,844 ng/kg body weight per day (average: 1,041 ng/kg body weight per day) and 192 to 2,927 ng/kg body weight per day (average: 918 ng/kg body weight per day), respectively.
Chlorinated paraffins PLADs Cereals Vegetables Potatoes Legumes Eggs Dairy products Meats Aquatic foods Total SCCPs Heilongjiang 265 50 12 44 22 28 31 44 496 Hebei 39 73 15 162 36 83 39 55 502 Shanxi 122 43 25 19 69 89 98 34 499 Ningxia 30 70 28 89 55 85 35 23 415 Guangdong 41 32 38 79 27 117 78 60 472 Qinghai 38 69 40 35 73 71 78 72 476 Shandong 63 40 36 18 27 72 71 142 469 Shaanxi 36 18 14 28 101 82 58 62 399 Sichuan 47 20 40 51 102 53 89 12 414 Liaoning 71 46 44 52 11 50 81 12 367 Beijing 29 18 30 50 28 35 25 22 237 Jilin 22 27 36 50 53 18 84 86 376 Inner Mongolia 43 20 28 51 54 14 49 77 336 Gansu 24 66 40 43 81 9 27 34 324 Henan 162 64 31 86 14 69 48 26 500 Shanghai 21 13 17 16 28 13 39 40 187 Fujian 26 21 35 75 69 34 81 75 416 Jiangxi 5 12 14 12 53 46 32 42 216 Jiangsu 9 113 17 44 65 22 116 56 442 Zhejiang 23 55 27 76 70 43 98 71 463 Hubei 11 42 17 83 61 64 80 87 445 Guangxi 9 24 19 69 74 30 45 47 317 Hunan 38 19 23 12 81 39 80 36 328 Guizhou 13 34 28 93 80 47 50 45 390 Mean 49 41 27 56 56 51 63 53 395 MCCPs Heilongjiang 306 29 12 32 36 19 35 46 515 Hebei 31 70 8 202 40 114 51 72 588 Shanxi 66 30 14 14 51 70 147 40 432 Ningxia 28 72 22 104 59 209 48 37 579 Guangdong 40 21 15 111 31 104 81 82 485 Qinghai 39 70 40 28 177 54 100 58 566 Shandong 99 25 31 16 34 43 74 161 483 Shaanxi 29 14 7 53 79 86 114 61 443 Sichuan 47 18 20 78 47 39 76 12 337 Liaoning 72 27 42 38 29 71 97 17 393 Beijing 23 15 12 40 29 42 30 33 224 Jilin 11 18 70 44 65 33 108 71 420 Inner Mongolia 38 13 17 58 84 19 62 86 377 Gansu 25 80 23 46 92 15 32 33 346 Henan 141 69 24 110 97 111 58 16 626 Shanghai 6 12 10 5 23 5 13 12 86 Fujian 20 18 6 33 48 13 53 47 238 Jiangxi 12 10 4 12 53 15 37 36 179 Jiangsu 21 66 11 12 87 6 103 17 323 Zhejiang 13 16 8 16 23 17 57 30 180 Hubei 10 27 10 36 51 23 95 72 324 Guangxi 11 19 6 34 40 7 71 31 219 Hunan 21 20 6 12 30 13 67 26 195 Guizhou 13 20 8 35 62 11 71 53 273 Mean 47 32 18 49 57 47 70 48 368 Abbreviations: PLADs=provincial-level administrative divisions; SCCPs=short-chain chlorinated paraffins; MCCPs=medium-chain chlorinated paraffins. Table 1. Concentrations of short-chain chlorinated paraffin (SCCP) and medium-chain chlorinated paraffin (MCCP) in ng/g wet weight in the Sixth Total Diet Study — China, 2016–2019.
Chlorinated paraffins PLADs Cereals Vegetables Potatoes Legumes Eggs Dairy products Meats Aquatic foods Total SCCPs Heilongjiang 2,305 254 15 32 14 6 29 19 2,675 Hebei 468 340 15 147 18 32 29 8 1,057 Shanxi 2,009 211 47 21 23 59 213 3 2,587 Ningxia 315 174 44 50 11 21 26 1 642 Guangdong 297 120 15 35 10 68 129 49 723 Qinghai 462 340 64 4 15 60 88 4 1,038 Shandong 633 282 21 40 10 38 133 113 1,271 Shaanxi 436 82 25 37 35 25 33 4 678 Sichuan 724 96 40 55 24 11 182 2 1,132 Liaoning 694 238 50 101 7 35 86 3 1,215 Beijing 366 112 28 81 17 48 27 6 684 Jilin 204 166 69 60 34 9 89 15 646 Inner Mongolia 493 82 54 32 25 8 57 13 765 Gansu 261 260 91 28 29 2 13 2 686 Henan 2,377 282 40 74 7 21 42 2 2,844 Shanghai 150 83 10 30 17 15 69 44 417 Fujian 261 132 23 94 21 19 111 76 738 Jiangxi 52 86 7 14 18 16 48 29 270 Jiangsu 115 762 9 58 29 10 169 35 1,187 Zhejiang 231 388 16 170 27 23 184 56 1,094 Hubei 92 276 24 88 24 7 69 57 637 Guangxi 136 134 4 46 16 9 108 72 526 Hunan 348 161 20 14 30 11 190 38 812 Guizhou 139 220 15 151 20 21 84 3 653 Mean 565 220 31 61 20 24 92 27 1,041 MCCPs Heilongjiang 2,662 148 15 23 23 4 33 20 2,927 Hebei 372 326 8 183 20 44 38 11 1,002 Shanxi 1,087 147 26 15 17 46 320 4 1,663 Ningxia 294 179 35 58 12 51 36 1 666 Guangdong 290 79 6 49 12 60 134 67 696 Qinghai 474 345 64 3 37 46 113 3 1,085 Shandong 994 176 18 36 13 23 139 129 1,527 Shaanxi 351 64 13 70 28 26 65 4 620 Sichuan 724 86 20 84 11 8 155 2 1,089 Liaoning 703 140 48 74 19 50 103 4 1,141 Beijing 290 93 11 65 18 57 32 9 575 Jilin 102 111 133 53 41 17 114 13 584 Inner Mongolia 436 53 33 37 40 10 72 14 695 Gansu 272 315 53 30 32 3 16 1 723 Henan 2,068 304 31 94 46 35 51 1 2,630 Shanghai 45 76 6 9 14 6 23 13 192 Fujian 201 113 4 41 14 7 72 48 502 Jiangxi 120 72 2 14 18 5 55 25 311 Jiangsu 259 445 6 16 39 2 150 11 928 Zhejiang 131 113 4 36 9 9 107 24 432 Hubei 84 177 14 38 20 2 81 47 465 Guangxi 164 106 1 23 9 2 170 48 524 Hunan 192 170 5 14 11 4 160 27 583 Guizhou 139 130 4 57 16 5 119 3 473 Mean 519 165 23 47 22 22 98 22 918 Abbreviations: PLADs=provincial-level administrative divisions; SCCPs=short-chain chlorinated paraffins; MCCPs=medium-chain chlorinated paraffins. Table 2. Estimated dietary intake in ng/kg body weight per day of short-chain chlorinated paraffin (SCCP) and medium-chain chlorinated paraffin (MCCP) in food samples in the Sixth Total Diet Study — China, 2016–2019.
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In this study, the average concentrations of SCCP in the eight food categories ranged from 27 ng/g in potatoes to 63 ng/g in meats. The average MCCP concentrations in the present study ranged from 18 ng/g in potatoes to 70 ng/g in meats. The average levels of SCCP from dairy products, meats, eggs, and cereals in this study were much lower than those found in the Republic of Korea, whereas the average levels of SCCP from vegetables in this study were higher than those found from vegetables in the Republic of Korea (15.1 ng/g wet weight) (3). However, the average CP levels in the eight food categories in China were considerably higher than those in southern Germany (4), Sweden (5), and Japan (6), which may be attributed to the higher production and use of CP in China. In general, dietary exposure to CPs in China was equal or higher than that of other studies in the world. A decrease in the production and use of CPs may be helpful to reduce human dietary exposure to CPs.
In the Sixth TDS, the average concentrations of SCCP and MCCP were significantly lower than those in the Fifth Total Diet Study except the increased concentrations of MCCP in meats (7-9). The highest average concentrations of SCCP and MCCP were found in meats in the present study, while in the Fifth China TDS, the average concentrations of SCCP and MCCP in aquatic foods were the highest. The ratio of MCCP to SCCP in each food category exhibited an increase from the Fifth to the Sixth TDS. This indicated that MCCPs may have become alternative products of SCCPs since SCCPs were listed as initial persistent organic pollutants of the Stockholm Convention.
The highest EDI values of SCCP and MCCP in the present study were much lower than the tolerable daily intake proposed by the International Programme on Chemical Safety (100 µg/kg body weight per day) (10). The European Food Safety Authority margins of exposure for total SCCP and total MCCP in eight food categories were 2×103 and 4×104 (11), respectively, which were much higher than 1,000, indicating that SCCPs and MCCPs ingested from food may not pose a significant risk to human health in China. The EDI of SCCP and MCCP in cereals was the highest among eight food categories, but cereals did not have the highest concentration of SCCP and MCCP. This could be due to the dietary habits in China, where there was higher daily consumption of cereals than meats.
Some limitations of this study include how apparatus for the food sample collection and storage could have been contaminated by chlorinated paraffins and how the complexity of CP mixtures posed a challenge for analysts. Complete separation or purification of individual isomers or congeners was also difficult. Also, there was a lack of standard methods for analysis of chlorinated paraffins.
The dietary exposure and health risk assessment of CP in 8 food categories of 24 PLADs were investigated in this study. Levels of SCCP and MCCP in legumes, cereals, meats, and aquatic foods exhibited a decrease from the Fifth to the Sixth China TDS, except the increased concentrations of MCCP in meats. The ratio of MCCP to SCCP in the foods investigated in this study tended to increase. The estimated dietary exposure to CPs was lower than the threshold set in the current guidelines. Further studies need to be performed to evaluate the health risks through dietary exposure to CPs and the results would be helpful for the development of chlorinated paraffin regulations.
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