Post on 16-Jul-2020
Deriving bioconcentration factors of constituents of essential oils using in-vivo benchmarked dietary exposure studies
Roxana Sühring, Chang’er L. Chen, Gisela Horlitz, Michael McLachlan, Matthew
MacLeod
Bioconcentration is important…and difficult to measure
𝑩𝑪𝑭 =𝑪𝒇𝒊𝒔𝒉
𝑪𝒘𝒂𝒕𝒆𝒓=𝒌𝟏𝒌𝑻
Variability?
Water-based exposure?
Mixtures?1Arnot & Gobas 20042Arnot & Gobas 2006
kD
k1
k2 kE
kG
kM
𝑑𝐶F𝑑𝑡
= 𝑘1𝐶W + 𝑘𝐷𝐶𝐷 − 𝑘2 + 𝑘𝐸 + 𝑘𝑀 + 𝑘𝐺 𝐶F
Arnot & Gobas, QSAR, 2003,Chen et. al. ES&T 2018, OECD 305 2012 Revisions
Using dietary exposure
𝑩𝑪𝑭 =𝒌𝟏𝒌𝑻
measured
estimated
What is benchmarking and howcan it help?
Benchmarking with a conservative substance
𝑑𝐶
𝑑𝑡⇒𝑑𝐶/𝑑𝐶𝐵𝑀
𝑑𝑡 DaysLn(C
/ n
gg-1
ww
)
No benchmark
Days
Benchmarkd with HCB
3,4
3Xiao et al. 20134Chen et al. 2018
Can we measure the BCF of mixtures?
Benefits
• More representative of the chemical product
• Reducing the number of test animals
Evaluation
• 16 chemicals with published tested and
predicted BCF data for individual substances
• Reported BCFs from < 100 to ~17000
BM-BCF
BCF-literature
BM
-BC
FBCF-literature
Not statistically different
(t-test, p = 0.33)
Threshold benchmarking5
Is the depuration rate faster or slowerthan the benchmark?
5Zou et al. 2015
Ln(C
/ n
gg-1
ww
)
No benchmark
Days
Days
Benchmarkd with PeCB
Very Bioaccumulative
𝑩𝑪𝑭 =𝒌𝟏𝒌𝑻
Mixtures?
Uncertainty of k1 estimate
𝑩𝑪𝑭𝑩𝑴 =𝒌𝟏𝒌𝑻𝑮
Water-based exposure?
Variability?
BCF of Essential oils
Pine oil
• > 60 components• Analytical standards for compounds
> 1% contribution (n = 9)• > 88% of the mixture
Cedarwood oil (virginian)
• ~ 60 components• Analytical standards for compounds > 1%
contribution (n = 7, detected n = 6)• 75% - 80% of the mixture
(depending on batch)
Image from wikipedia.org
Image from wikipedia.org
β-pinene (BPN) Carene (CAN)
Terpinolene (TPN) Borneol (BNL) Bornyl Acetate (BAC) β-caryophyllene (BCP)
Measured pine oil constituents
α-pinene (APN) Camphene (CAM) Limonene (LIM)
Results: Pine oil
Log BCFBM = 0.97 x Log KOW - 0.88
R² = 0.95
B limit
vB limitMedian BCF for BCP meets B criterion
No constituents are B at the 95% confidence level
Thujopsene (Thu)
Cuparene (Cup) Cedrol (CDL) α-Funebrene (aFun)
Measured Cedarwood oil constituents
α-Cedrene (aCed) β-Cedrene (bCed)
Biotransformation of Cedarwood oil?
Log BCFBM = 0.70 x Log KOW + 0.16
R² = 0.94
B limit
vB limit
Biotransformation of Cedarwood oil constituents exceeds biotransformation of the reference substances
BUT: Four out of six constituents are B or vB at the 95% confidence level
Comparison with literature data
Benchmark substancesanalysed in theCedarwood oil study
Benchmark substancesanalysed in thePine oil study
Dichlorobenzene (DiCB)Hexachlorobenzene (HCB)Musk xylene (MX)PCB52Pentachlorobenzene (PeCB)Trichlorobenzene (TrCB)
What about P and T of Cedarwood oil?
Screening T criterion: EC50 < 0.01 mg/L (potential T), < 0.01 mg/L (T)
• Cedarwood oil has applications as natural biocide/insecticide6.
• α-Cedrene EC50: 0.044 mg/L (Daphnia pulex)7
• Cedrol: indications for endocrine disruption8 and gentoxicity9
• No T results for the remaining Cedarwood oil constituents
Readily biodegradable: ≥ 60% degradation in a ready biodegradation test
• α-Cedrene and Cedrol: > 75% biodeg in 28 days (OECD 301 test)10
• Thujopsene: 36 % biodeg in 28 days test, 56 % in 60 days test (OECD 301) 10
• No biodeg test results for the remaining Cedarwood oil constituents
• α-Cedrene: not P, vB, potential T• Cedrol: not P, not B, unknown acute T, publications indicating potential
genotox, ED• Thujopsene: not readily but significant 56% degradation, B, unknown T
• No experimental results for most of the analysed constituents
Thank you for your attention!
Take home messages
• Dietary exposure with internal benchmarking provides a robust method for depuration rate
measurements of complex mixtures in fish
• Results for reference substances match published measurements for individual components
• Number of test animals can be reduced
• Higher biotransformation of Pine oil and Cedarwood oil compared to reference substances
• Pine oil likely contains at least one B constituent but most constituents are not B
• Most measure constituents of Cedarwood oil are B or vB
• More information on NCSs and constituents is needed
References1. Arnot JA, Gobas FAPC. 2004. A food web bioaccumulation model for organic chemicals in aquatic ecosystems. Environ. Toxicol. Chem. 23 (10): 2343−2355.
2. Arnot JA, Gobas FAPC. 2006. A review of bioconcentration factor (BCF) and bioaccumulation factor (BAF) assessments for organic chemicals in aquatic organisms. Environ.
Rev. 14: 254–297.
3. Xiao RY, Adolfsson-Erici M, Akerman G, McLachlan MS, MacLeod M. 2013. A Benchmarking Method to Measure Dietary Absorption Efficiency of Chemicals by Fish. Environ.
Toxicol. Chem. 32 (12): 2695−2700.
4. Chen CL, Löfstrand K, Adolfsson-Erici M, McLachlan MS, MacLeod M. 2018. Deriving in Vivo Bioconcentration Factors of a Mixture of Fragrance Ingredients Using a Single
Dietary Exposure and Internal Benchmarking. Environ. Sci. Technol. 2018, 52, 5227−5235.
5. Zou H, Radke M, Kierkegaard A, MacLeod M, McLachlan MS. 2015. Using Chemical Benchmarking to Determine the Persistence of Chemicals in a Swedish Lake. Environ. Sci.
Technol. 2015, 49, 1646−1653.
6. Kramer A, Guggenbichler P, Heldt P, Juergen K, Ladwig A, Thierbach H, Weber U, Daeschlein G. 2006. Hygenic Relevance and Risk Assessment of Antimicrobial-Impregnated
Textiles. In: Hipler UC & Elsner P. Biofunctional Textiles and the Skin. Current Problems in Dermatology, Vol. 33. ISBN: 3-8055-8121-1. page 94.
7. Passino-Reader DR, Hickey JP, Ogilvie LM. 1997. Toxicity to Daphnia pulex and QSAR Predictions for Polycyclic Hydrocarbons Representative of Great Lakes Contaminants.
Bull. Environ. Contam. Toxicol. 59:834-840.
8. Simon C, Onghena M, Covaci A, VanHoeck E, Van Loco J, Vandermarken T, Van Langenhove K, Demaegdt H, Mertens B, Vandermeiren K, Scippo ML, Elskens M. 2016.
Screening of endocrine activity of compounds migrating from plastic baby bottles using a multi-receptor panel of in vitro bioassays. Toxicology in Vitro 37. 121–133.
9. Mertens B, Simon C, Van Bossuyt M, Onghena M, Vandermarken T, Van Langenhove K, Demaegt H, VanHoeck E, Van Loco J, Vandermeiren K, Covaci A, Scippo ML, Elskens
M, Verschaeve L. 2016. Investigation of the genotoxicity of substances migrating from polycarbonate replacement baby bottles to identify chemicals of high concern. Food
and Chemical Toxicology 89. 126-137.
10. Jenner KJ, Kreutzer G, Racine P. 2011. Persistency assessment and aerobic biodegradation of selected cyclic sesquiterpenes present in essential oils. Environ Toxicol
Chem30:1096 – 1108.
Hexane phase
ACN
Elute with Hex
Ultrasound assisted extraction - Purge & trap – GC-MS
MQ water
hexane
BCF BM-BCF
Target 5th Median 95th 5th Median 95th
α-Cedrene 4600 138000 infinite 6900 11000 23000
β-Cedrene 4400 69000 infinite 6000 9200 20000
Thujopsene 3000 8600 infinite 3600 4800 6900
Cuparene 1900 2900 6900 1700 2100 2600
Cedrol 570 710 940 520 600 720
α-Funebrene 4100 23000 infinite 4400 6900 15000
BMs
TrCB 610 800 1200 650 750 870
PeCB 3500 12000 infinite 3800 5500 9900
HCB 12000 -10615 infinite n.a. n.a. n.a.
PCB3 2800 6900 infinite 2800 4100 7700
Name kT kTG
α-Cedrene 0.001 ± 0.029 -0.012 ± 0.01
β-Cedrene 0.002 ± 0.029 -0.01 ± 0.009
Thujopsene 0.016 ± 0.03 0.004 ± 0.011
Cuparene 0.047 ± 0.027 0.044 ± 0.012
Cedrol 0.195 ± 0.049 0.203 ± 0.036
α-Funebrene 0.006 ± 0.028 -0.004 ± 0.009
BMs
TrCB 0.173 ± 0.053 0.15 ± 0.024
PeCB 0.012 ± 0.027 n/a
HCB -0.013 ± 0.024 -0.025 ± 0.011
PCB3 0.02 ± 0.03 0.01 ± 0.014
Threshold benchmarking
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