Evaluation of sheep exposure to poly- and perfluoroalkyl substances through hair sample analysis

Fig. 1.

Fig. 2.

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

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

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

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

Optimised tandem mass spectrometry parameters for multiple-reaction monitoring (MRM) analysis of Kyrgyz Republic sheep hair sampled for poly- and perfluoroalkyl substance determination

Compound	Precursor ion (m/z)	MRM 1a (m/z)	MRM 2b (m/z)	Fragmentor (V)	Collision energy (eV)
PFBuA	213	169.0	51.6	55	0
PFPeA	263	219.0	89.7	55	0
PFHxA	313	269.0	119.0	60	0
PFHpA	363	319.0	332.8	65	0
PFOA	413	369.0	194.3	62	0
PFOS	499	80.0	51.5	145	40
PFOA-13C4	417	371.9	172.0	77	4