Zhuzhassarova, Azarbayjani & Zamaratskaia 2024 — Toxic metals in aquatic environments and fish across Central Asia

Zhuzhassarova, Azarbayjani & Zamaratskaia (2024) review arsenic, mercury, cadmium, and lead concentrations in surface waters, fish tissues, and human biomonitoring samples (hair, urine, blood) across the five Central Asian republics: Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The review compiles per-study fish-tissue values from 13 regional studies (Table 2), per-country fish-consumption estimates from FAOSTAT and food-frequency surveys (Table 3), and the Eurasian Customs Union maximum permissible concentrations for fish (Table 1). Despite generally low regional fish consumption (0.63 to 3.86 kg/year/capita in FAOSTAT data, well below recommended intake), specific hotspots — notably Lake Balkyldak in Pavlodar (Hg from the former Pavlodar chlor-alkali plant) and the lower Amu Darya / Syr Darya basins (As, Pb, Cd in water) — drive localized elevated exposure, particularly for Hg in populations relying on contaminated fisheries.

Key numbers

Eurasian Customs Union maximum permissible concentrations in fish (Table 1, mg/kg)

• Arsenic: freshwater fish 1; saltwater fish 5
• Mercury: freshwater non-predatory fish 0.3; freshwater predatory fish 0.6; tuna, swordfish, and beluga (all product types, including dried) 1
• Cadmium: all types of fish products and meat of marine mammals, including dried 0.2
• Lead: all types of fish products (except tuna, swordfish, and beluga) and meat of marine mammals, including dried 1; tuna, swordfish, and beluga (all types, including dried) 2

Water — toxic metals in Central Asian rivers and lakes

• Amu Darya Basin sediment GBVs (Zhan et al.): Cd 0.27, Zn 58.9, Pb 14.6, Cu 20.3, Ni 25.8, Cr 53.4, Co 9.80 mg/kg. Contamination source apportionment: natural 33.5%, industrial discharges 11.4%, agricultural 34.2%, traffic/mining mixed 20.9%.
• Syr Darya River (Rzymski et al.): As 35.8 ± 21.2 µg/L (mean ± SD) — 2–7 times the WHO drinking-water guideline of 10 µg/L. Hg below detection (WHO guideline 6.0 µg/L). Cd and Pb at some locations exceeded WHO guidelines of 3.0 and 10 µg/L respectively.
• Ili River, Kazakhstan: Cd 1.7 to 28.7 µg/L; Pb 0.2 to 87.0 µg/L — exceeding WHO guidelines more than five times at some locations.
• Issyk-Kul Lake, Kyrgyzstan: As ≈16 µg/L (exceeds drinking-water level); Pb ≈0.09 µg/L.
• River Nura (Heaven et al.): Hg 0.46 to 5.36 µg/L range. Shinetova et al.: Hg 4.5 ± 9.8 µg/L in highly contaminated parts; 0.03 ± 0.08 µg/L in low-contaminated parts. Karbide chemical plant (Temirtau City) is the historical source.
• Aktobe region springs (Idrissova et al.): Pb not detected; Cd exceeded WHO guideline in three springs — Islambulak (3×), Bulak ayly (3×), Akshat (5×). Atyrau region: neither Cd nor Pb exceeded guideline levels.
• Shardara Reservoir, Kyzylkum desert along Syr Darya (Allen et al., reference [45]): Pb in roach muscle tissue 0.1 to 3.8 µg/g wet weight.

Fish and seafood — Table 2 occurrence of toxic metals (mg/kg, mean ± SD unless otherwise stated)

Kazakhstan:

• Dam in Bukharzhyrau District (crucian carp, tench, perch, roach, carp; ref [58]): As below LOD; Hg 0.0003 ± 0.001; Cd 0.0023 ± 0.002; Pb 0.0017 ± 0.000.
• Lake Toksumak, Osakarovsky district (crucian carp, tench, perch, roach, carp; [58]): As 0.0022 ± 0.002; Hg 0.0005 ± 0.000; Cd 0.0018 ± 0.001; Pb 0.0019 ± 0.001.
• Dam DSU-58, Nurinsky district (crucian carp, tench, perch, roach, carp; [58]): As 0.0022 ± 0.000; Hg 0.0005 ± 0.001; Cd 0.0026 ± 0.002; Pb 0.0031 ± 0.000.
• Fish nursery of Livkino, Uralsk region (species not specified; [59]): Cd 0.245 (mean value); Pb 0.25 (mean value).
• Lake Lastochka, North Kazakhstan (species not specified; [60]): As 0.0132 ± 0.002; Hg 0.0026 ± 0.0001; Cd 0.0027 ± 0.0002; Pb 0.0027 ± 0.0001.
• Lake Kak, North Kazakhstan (species not specified; [60]): As 0.0027 ± 0.0001; Hg 0.00206 ± 0.0001; Cd 0.0012 ± 0.0001; Pb 0.0046 ± 0.0002.
• Lake Tastemirovka, North Kazakhstan (species not specified; [60]): As 0.0130 ± 0.0001; Hg below LOD; Cd 0.0076 ± 0.00001; Pb 0.0042 ± 0.0002.

Uzbekistan:

• Eastern Arnasay Lake System (common carp Cyprinus carpio; [61]): Hg 0.029 (mean value).
• Lake Tuzkan (pike perch Sander lucioperca, aral shemaya Alburnus aralensis, roach Rutilus rutilus, vostrobryushka Hemiculter lucidus; [61]): Hg 0.065 to 0.138 (range).
• Fish farm Khorezm (silver carp Hypophthalmichthys molitrix; [61]): Hg 0.07 (mean value).

Tajikistan:

• Pit Lake Taboshar (goldfish Carassius auratus; [54]): Hg 0.01 ± 0.01.
• Kairakkum reservoir (pike perch Sander lucioperca; [54]): Hg 0.13 (one sample).
• Kairakkum reservoir (Eurasian carp, not specified; [54]): Hg 0.01 ± 0.007.

Kyrgyzstan:

• Issyk-Kul Lake (Issyk-Kul Chebachok Leuciscus bergi; [48]): As 0.26 ± 0.1; Hg 0.062 ± 0.02; Cd 0.00091 ± 0.0002; Pb 0.022 ± 0.02.
• Issyk-Kul Lake (pike perch Perca schrenkii; [48]): As 0.71 ± 0.4; Hg 0.066 ± 0.02.
• Issyk-Kul Lake (rainbow trout Oncorhynchus mykiss; [48]): As 0.92 ± 0.3; Hg 0.026 ± 0.003.
• Chui region (silver carp and common carp; [62]): Hg 0.078 to 0.083; Cd 0.025 to 0.03; Pb 0.060 to 0.068.

Lake Balkyldak, North Kazakhstan (Pavlodar chlor-alkali plant, in operation 1975–1993): Hg in fish 0.16 to 2.2 mg/kg in 2001–2002 (ref [55]); 1 to 1.5 mg/kg in 2006–2007 (ref [56]). Both ranges exceed the Eurasian Customs Union maximum permissible concentration of Hg in freshwater fish (0.3 mg/kg) for the majority of fish in those samplings.

Fish and seafood consumption (Table 3, kg/year/capita)

Kazakhstan: 3.68 (FAOSTAT 2021, general population); 6.4 (university students, questionnaire); 27.4 (males, Temirtau district, high Hg-pollution area, questionnaire); 14.6 (females, Temirtau); 37.6 (fishermen, Temirtau); 17.9 (non-fishermen, Temirtau); 4.5 (Almaty children 9–10 years, normal weight, 24-h recall); 3.1 (Almaty children 9–10 years, obesity, 24-h recall).

Uzbekistan: 3.86 (FAOSTAT 2021); 1 (Tashkent general population); 0.5 (Khorezm general population).

Tajikistan: 0.63 (FAOSTAT 2021). Ministry of Health recommendation 10 kg/year/capita; only 3.9% of women of childbearing age consumed fish in a recent study.

Kyrgyzstan: 0.86 (FAOSTAT 2021).

Turkmenistan: 2.51 (FAOSTAT 2021); 3.28 (Mary City).

Comparative context: highest-consumption countries (Maldives, Iceland, Macau) exceed 70 kg/year/capita; Tajikistan’s 0.63 is among the lowest globally, surpassed downward only by Ethiopia (0.53) and Afghanistan (0.36). Kazakhstani fishermen survey (Hsiao et al.): fish consumption 103 g/day for fishermen and 49 g/day for non-fishermen (721 and 343 g/week respectively). Jia et al. reported per capita Kazakhstan fish consumption of 9.59 kg/year (184 g/week) from national statistics.

Human biomonitoring

• Children, Aralsk vs Akchi (Kazakhstan; Erdinger et al.): urinary Hg 0.94 µg/L (Aralsk) vs 0.29 µg/L (Akchi); urinary As 6.4 µg/L (Aralsk) vs 9.6 µg/L (Akchi). Both groups’ Hg levels below the 25 µg/L health-based guidance value.
• Children, Pavlodar: hair Hg 0.44 ± 0.5 mg/kg, up to 0.7 mg/kg in districts close to the industrial zone.
• Anemic children, Kazakhstan/Kyrgyzstan/Uzbekistan (Brázdová et al., ref [80]): hair Pb 0.02 to 36.0 µg/g (Kazakhstan); 1.13 to 27.40 µg/g (Uzbekistan); 2.71 to 50.10 µg/g (Kyrgyzstan — particularly high). Hair Cd and Hg highest in Uzbekistan: Cd 0.01 to 1.41 µg/g; Hg 0.02 to 2.90 µg/g.

Methods (brief)

Narrative literature review, not a primary measurement study and not a PRISMA-protocol systematic review. The authors searched PubMed, Web of Science, and Scopus for scientific articles and reports on As, Hg, Cd, and Pb in waters and foods of Central Asia, both per-toxic-metal and per-country/city, without language restrictions. Google Scholar searches were used for combinations with few publications, with keywords in English, Russian, and Central Asian languages. No PRISMA flow diagram, no inclusion/exclusion criteria disclosed, no quality assessment of cited studies.

The review tabulates per-study fish-tissue concentrations (Table 2; mg/kg, mean ± SD or range), per-country fish-consumption estimates (Table 3), and Eurasian Customs Union maximum permissible concentrations (Table 1, “On Food Safety” TR CU 021/2011). The review does not separate inorganic from total arsenic in any fish-tissue value, nor methylmercury from total mercury — values are reported as totals throughout. The introductory text notes the speciation distinction conceptually (As primarily organic in fish and seafood with arsenobetaine the major compound; methylmercury comprises up to 100% of total Hg in seafood) but the tabulated occurrence values are not speciated.

Analytical methods used in the cited primary studies are not summarized in this review. Limits of detection are referenced indirectly via “below LOD” entries in Table 2 but no LOD values are tabulated.

Funded by CENAKVA-South Bohemian Research Centre of Aquaculture and Biodiversity of Hydrocenoses, grant LM 2023038.

Implications

Certification: Establishes that toxic-metal contamination of fish across Central Asia is generally below Eurasian Customs Union maximum permissible concentrations for the broad lake-and-river survey data, but with two important exceptions: (a) Hg in fish from Lake Balkyldak in Pavlodar, where the chlor-alkali-plant legacy has driven fish-tissue Hg to 0.16–2.2 mg/kg, repeatedly exceeding the 0.3 mg/kg fish-flesh limit; and (b) elevated Hg in Issyk-Kul Lake fish (0.026 to 0.066 mg/kg, with pike perch in Lake Tuzkan reaching 0.138 mg/kg as a range maximum). These are localized industrial-legacy hotspots, not regional baselines. Per-country fish-consumption data shows that Central Asian intake is generally well below FAO/WHO recommendations, so population-level exposure to fish-borne metals is constrained primarily by low consumption rather than low contamination. The Kazakhstan fisherman cohort (37.6 kg/year/capita in a high-Hg-pollution district) represents the highest-exposure subgroup identified in the review.

Courses: Demonstrates how regulatory frameworks (Eurasian Customs Union TR CU 021/2011) operate alongside literature-derived occurrence data; how industrial legacy contamination (Pavlodar Hg-cell chlor-alkali plant, Karbide chemical plant on River Nura, Semipalatinsk nuclear test site) creates persistent geographic hotspots; and how to interpret population-level risk through the lens of per-capita consumption rather than concentration alone. Useful for teaching the geographic-and-historical dimension of metal exposure: most fish in Kazakhstan are below limits, but specific Soviet-era industrial point sources still drive elevated tissue concentrations decades after closure.

App: Contextual signal that Central Asian freshwater fish, on average, present low metal exposure relative to fish-consumption-dominant geographies (Maldives, Japan, coastal Europe). The exception is fish sourced from Lake Balkyldak, Issyk-Kul Lake (Kyrgyzstan), and the River Nura / Intumak Reservoir corridor, where Hg risk is elevated. Saltwater fish are largely absent from local supply (the region is landlocked).

Wiki pages this source may touch

• arsenic-total
• mercury-total
• cadmium
• lead
• fish
• freshwater-fish
• seafood
• water
• fresh-fish
• fish-freshwater

Verification notes

• Speciation: the review’s tabulated fish-tissue values are all totals (As, Hg, Cd, Pb) with no inorganic/total or methyl/total separation in Table 2 or surrounding text. This page uses tAs and tHg accordingly per CLAUDE.md Part 14. The introductory speciation discussion (organic As / arsenobetaine in fish; MeHg comprising up to 100% of total Hg in seafood) is conceptual context, not measured speciation.
• Eurasian Customs Union limit values for Hg in freshwater non-predatory vs predatory fish (0.3 vs 0.6 mg/kg) preserved verbatim from Table 1; the “predatory fish 0.6” figure is the source’s own designation and applies to species like pike perch, walleye, pikeperch in the Customs Union framework.
• Folder placement (03_Marine_Predatory) is a mismatch for the actual paper scope. Central Asia is landlocked (the Aral and Caspian seas are inland salt seas, not connected to global oceans); the fish data in Table 2 is overwhelmingly freshwater (crucian carp, tench, perch, roach, common carp, silver carp, pike perch in freshwater, rainbow trout, goldfish). The paper’s only “marine” references are the regulatory framework (Eurasian Customs Union categories include “saltwater fish” and “tuna, swordfish, and beluga”) and brief introductory mentions of marine vs freshwater toxicology. Frontmatter products list fresh-fish and fish-freshwater accordingly, not the marine subcategories.
• The Allen et al. Pb-in-Shardara-Reservoir value is reported in the source as “0.1 to 3.8 µg/g wet weight” (= mg/kg wet weight, since 1 µg/g = 1 mg/kg); preserved in source units throughout.
• Lake Balkyldak Hg ranges (0.16 to 2.2 in 2001–2002 and 1 to 1.5 in 2006–2007) are reported per the source’s exact figures from refs [55] and [56]; the source notes that “the Hg levels were slightly lower” in 2006–2007 but the range minimum (1) is actually higher than the 2001–2002 minimum (0.16), reflecting that the later sampling did not capture as much variability rather than a true narrowing of the distribution.
• Tajikistan FAOSTAT consumption (0.63 kg/year/capita) is reported as among the lowest globally; the review’s claim that it is surpassed downward only by Ethiopia and Afghanistan is the source’s own framing, preserved verbatim.
• The Hsiao et al. Kazakhstani fisherman cohort 27.4 / 14.6 / 37.6 / 17.9 kg/year/capita values in Table 3 are tagged “Temirtau district” — a district of North Central Kazakhstan flagged elsewhere in the review as a high-Hg-pollution zone — preserved with the district attribution.
• The Brázdová et al. hair Pb range for Kyrgyzstan (2.71 to 50.10 µg/g) is the highest of the three Central Asian countries surveyed in that study; the source frames this as “particularly high,” preserved as a paraphrase tied to the figures.
• This is a B-tier narrative review with no PRISMA protocol; values are tabulated per cited primary study without pooling, meta-analysis, or quality scoring. The page is a literature entry point into the regional primary studies (refs [48], [54]–[62]) rather than an independent evidence source on its own.
• Source-internal species-naming inconsistency in Table 2: the Issyk-Kul Lake row labels Perca schrenkii as “pike perch,” but Perca schrenkii is Schrenk’s perch (Balkhash perch); “pike perch” is the conventional common name for Sander lucioperca, which the same Table 2 uses correctly for the Lake Tuzkan and Kairakkum reservoir rows. The page preserves the source’s labeling verbatim rather than silently relabeling, but the species attribution should be read as the source intends (the Perca schrenkii fish from Issyk-Kul, regardless of common-name disagreement).
• Audit subagent (2026-06-03) verdict PROMOTE, 5/5 checks clean. One ⚠️ polish suggestion (the species-naming inconsistency above) applied; the other ⚠️ flags (Lake Balkyldak “North Kazakhstan” loose geography, Temirtau “North Central Kazakhstan” descriptor, Erdinger 25 µg/L Hg threshold framing) were verified as faithful source-text reproduction and left as-is.
• No brand names appear in the source pertaining to contamination values; the only named manufacturer is the Karbide chemical plant on the River Nura and the Pavlodar chlor-alkali plant, both named as point sources of industrial Hg release (regulatory-event subject context, not brand ranking).

Page history

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