Fig. 1.
Sources of sheep’s exposure to poly- and perfluoroalkyl substances
Table 1.
Key characteristics of the Kyrgyz Republic regions from which sheep hair was sampled for poly- and perfluoroalkyl substance determination
| Region name | Alamedin | Sokuluk |
|---|---|---|
| Area (km2) | 1,503 | 2,550 |
| Human population in 2024 (in thousands) | 180.6 | 250.6 |
| Human population density (thousands/km2) | 0.120 | 0.098 |
| Administrative centre | Lebedinovka | Sokuluk |
| Distance in the straight line from the centre of Bishkek to administrative centre of the region (km) | 9.50 | 22.29 |
| Population concentrations | 51 settlements in 17 rural communities | 1 town and 68 settlements in 19 rural communities |
| Number of sheep and goats in 2015 1, 2 | 123,019 | 51,033 |
| Wool production in 2024 (in tonnes) | 158 | 329.1 |
12 – more recent data concern larger administrative areas: the Alamedin and Sokuluk regions are located in Chui Oblast, in which the number of sheep and goats amounted to 660,049 animals in 2022. The origin of the data is the National Statistical Committee of the Kyrgyz Republic (https://stat.gov.kg/ru/statistics/selskoe-hozyajstvo/)
Table 2.
Optimised tandem mass spectrometry parameters for multiple-reaction monitoring (MRM) analysis of Kyrgyz Republic sheep hair sampled for poly- and perfluoroalkyl substance determination
Table 3.
Linear range, method detection limits (MDLs), method quantification limits (MQLs), recovery and precision of the selected poly- and perfluoroalkyl substances analysed in hair samples of Kyrgyz Republic sheep
| Compound | Linear range (ng/g) | MDL (ng/g) | MQL (ng/g) | Recovery (%) | Inter-day precision (RSD %) | ||
|---|---|---|---|---|---|---|---|
| Low level | Medium level | High level | |||||
| PFBuA | 0.9–100 | 0.3 | 0.9 | 96 ± 3 | 99 ± 3 | 100 ± 4 | 4 |
| PFPeA | 0.6–100 | 0.2 | 0.6 | 93 ± 5 | 93 ± 7 | 97 ± 5 | 3 |
| PFHxA | 0.6–100 | 0.2 | 0.6 | 88 ± 7 | 92 ± 8 | 92 ± 5 | 5 |
| PFHpA | 0.6–100 | 0.2 | 0.6 | 87 ± 6 | 86 ± 6 | 90 ± 6 | 3 |
| PFOA | 0.6–100 | 0.2 | 0.6 | 91 ± 2 | 90 ± 2 | 95 ± 2 | 4 |
| PFOS | 0.6–100 | 0.2 | 0.6 | 83 ± 7 | 88 ± 5 | 89 ± 4 | 5 |
Table 4.
Concentration levels (ng/g), frequency of detection (%), method detection limit (MDL (ng/g)) and method quantification limit (MQL (ng/g)) of poly- and perfluoroalkyl substances (n = 50) – cumulative data from hair samples of Kyrgyz Republic sheep
| Compound | Range | Arithmetic mean | Geometric mean | 25th percentile | Median | 75th percentile | Samples >MDL (%) | MDL | Samples >MQL (%) | MQL |
|---|---|---|---|---|---|---|---|---|---|---|
| PFBuA | 0.95–14.18 | 2.24 ± 2.34 | 1.79 | 1.25 | 1.54 | 2.30 | 100 | 0.30 | 100 | 0.90 |
| PFPeA | 0.99–27.90 | 5.55 ± 4.54 | 4.50 | 3.33 | 4.18 | 5.85 | 100 | 0.20 | 100 | 0.60 |
| PFHxA | < MQL–3.87 | 1.06 ± 0.78 | 0.82 | <MQL | 0.88 | 1.44 | 100 | 0.20 | 70 | 0.60 |
| PFHpA | <MQL–4.32 | 1.02 ± 0.76 | 0.78 | <MQL | <MQL | 0.95 | 100 | 0.20 | 64 | 0.60 |
| PFOA | <MQL–2.67 | 0.87 ± 0.68 | 0.65 | <MQL | 0.80 | 1.21 | 100 | 0.20 | 52 | 0.60 |
| PFOS | <MQL–3.36 | <MQL | <MQL | <MQL | <MQL | <MQL | 100 | 0.20 | 4 | 0.60 |
Fig. 2.
Mean concentration levels (± standard deviation) of perfluorobutanoic acid (PFBuA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA) and perfluorooctanoic acid (PFOA) in sheep hair samples from the Kyrgyz Republic Alamedin (1) and Sokuluk (2) regions. * – P-value < 0.05; *** – P-value < 0.001; **** – P-value < 0.0001
Table 5.
The poly- and perfluoroalkyl substances observed in selected previous hair sample studies and included in this Kyrgyz Republic sheep hair sample study
| Substance | n | Range (pg/mg) | Median/mean (pg/mg)1 | Frequency detection2 | Reference |
|---|---|---|---|---|---|
| Human hair | |||||
| Belgium | |||||
| PFPeA | 114 | <MQL | <MQL/- | 6.1 | (4) |
| PFHxA | <MQL–2.4 | <MQL/- | 18.4 | ||
| PFHpA | <MQL–1.4 | <MQL/- | 4.4 | ||
| PFOA | <MQL–3.4 | <MQL/- | 86.8 | ||
| PFOS | <MQL–11.3 | <MQL/- | 0.9 | ||
| China | |||||
| PFBuA | 28 | ND | - | 0 | (7) |
| PFPeA | ND–326 | -/31.7 | 40 | ||
| PFHxA | ND–201 | -/29.2 | 73 | ||
| PFHpA | ND–68.5 | -/12.6 | 33 | ||
| PFOA | 18.3–1390 | -/277 | 100 | ||
| PFOS | 1.01–51.0 | -/6.76 | 100 | ||
| South Korea | |||||
| PFPeA | 94 | ND–0.75 | <MDL/0.48 | 16 | (14) |
| PFHxA | ND–0.14 | <MDL/0.13 | 2 | ||
| PFHpA | ND–0.28 | <MDL/0.14 | 26 | ||
| PFOA | 1.3–9.8 | 3.2/3.6 | 100 | ||
| PFOS | 0.69–15 | 4.2/4.8 | 100 | ||
| Spain | |||||
| PFBuA | 42 | 5.8–15.5 | 7.8/8.9 | 14 | (20) |
| PFPeA | 4.6–13.3 | 6.8/7.4 | 26 | ||
| PFHxA | 2.0–10.6 | 8.9/8.1 | 26 | ||
| PFHpA | 0.6–10.1 | 2.4/3.1 | 86 | ||
| PFOA | 0.6–9.5 | 1.4/2.0 | 57 | ||
| PFOS | 0.7–11.0 | 1.9/2.7 | 76 | ||
| Dog hair | |||||
| Poland | |||||
| PFBuA | 30 | 0.98–26.6 | 9.66/11.2 | 100 | (18) |
| PFPeA | <0.14–15.6 | 4.39/5.31 | 96.7 | ||
| PFHxA | <0.14–18.9 | 5.92/7.45 | 96.7 | ||
| PFHpA | <0.14–13.2 | 1.35/2.10 | 86.7 | ||
| PFOA | 1.51–66.7 | 17.4/21.2 | 100 | ||
| PFOS | <0.14–1.63 | 0.70/0.76 | 86.7 | ||
| Sheep hair | |||||
| Kyrgyz Republic | |||||
| PFBuA | 50 | 0.95–14.8 | 1.54/2.24 | 100/1002 | This study |
| PFPeA | 0.99–27.90 | 4.18/5.55 | 100/1002 | ||
| PFHxA | <MQL–3.87 | 0.88/1.06 | 100/702 | ||
| PFHpA | <MQL–4.32 | <MQL/0.87 | 100/642 | ||
| PFOA | <MQL–2.67 | 0.80/0.87 | 100/522 | ||
| PFOS | <MQL–3.36 | <MQL/<MQL | 100/42 | ||