Acute Effects Of Single And Mixed
Polycyclic Aromatic Hydrocarbons
Associated To Oil Spills On The
Copepod Oithona Davisae .
Carlos Barata1, Albert Calbet 2, Enric Sainz 2,
Laura Ortíz 3, Josep Maria Bayona 3.
1 Laboratory of Environmental Chemistry, UPC, Terrassa
2 Dept. Biologia Marina i Oceanografia, CMIMA, CSIC, Barcelona
3 Dept of Environmental Chemistry, IIQAB-CSIC, Barcelona
Acknowledgements
Financial Support:
• MEC Spanish project PETROZOO (VEM200320037).
•MEC R y C contract to Carlos Barata and Albert
Calbet
Objectives
Develop a modelling framework to predict the
toxicity of mixture combinations of petrogenic
PAHs in copepod species
Overview – in brief
Effects of crude oil spills in marine
planktonic food webs???
zooplankton species constitute the major food source for
larval fish
Overview – in brief
Polycyclic aromatic hydrocarbons (PAHs)
Environmental fate
1. Most toxic and persistent components of class 2 fuel oils (Prestige)
Toxicity by non-polar narcosis
1.Toxicity = F (1/log Kow)
Effect
2.Toxicity complex mixtures is additive
Toxicity – EC50
2. Occur in complex mixtures
Log Kow
PAHs
Methods
Test Species: Oithona davisae
Chemicals:
Naphthalene, 1-methylnaphthalene, 1,2-Dimethylnaphthalene
Phenanthrene,1-methylphenanthrene,3,6-dimethylphenanthrene
Fluorene, Dibenzothiophene, Pyrene
Analysis: SP -HPLC-UV
Measured variables:
Lethal , Narcosis– after 48 h (%)
Experimental design
Exposure scenarios
Individual exposures 10 PAHs
Mixture combination of only 9 PAHs using an
equitox ratio
Ci = EC50j / n ; n= 9; Cj = 1/9 TUj
Experimental conditions:
No food supply, filtered sea water (38 0/00) 20 oC
Data analysis
Modeling % responses:
Allosteric decay function
Survival
% Mobile = mobile control 
100
50
0
PAHs (mmol/L)
i
EC50
i
EC50 + [ PAH
]i
Data analysis
Modelling single and mixture toxicities (EC50) of PAHj:
1
Log
EC 50
= a  log K owj + b
j
EC50
Single - Quantitative Structure Activity Relationship (QSAR)
Mixture - Concentration Addition model
n

j = 1
c j
ECx j
= 1, For cj = EC 50j /n; 1 = 50%
Kow
Results- Single solutions
Naphthalenes (% mobile vs Control)
Narcosis, survival
N
100
N1
50
0
0
20
40
60
0
80
10
N2
100
50
0
0
5
10
PAHs (mmol/L)
15
20
30
40
Results- Single solutions
Phenanthrenes (% mobile vs control)
Narcosis, survival
P
100
50
0
0
3
6
9
P1
100
50
0
0
1
2
PAHs (mmol/L)
3
Results- Single solutions
Rest of PAHs (% mobile vs control)
Narcosis, survival
F
100
DBT
50
0
0
2
4
6
8
10
0
2
4
Ft
100
Py
50
0
0.0
0.3
0.6
0.9
PAHs (mmol/L)
0.0
0.2
0.4
0.6
Results- QSAR
Survival
EC 50( mmol/L)
0.5
1.0
1
Log
EC 50 j
Narcotization
= 1 log K owj - 5
Ft
Py
DBT
2.0
N2
P
F
5.0
P1
N1
20.0
N
R2 =0.9
60.0
3.0
3.5
4.0
Log K ow
4.5
5.0
5.5
Results- Mixtures
(% mobile vs control
Mixture of 9 PAHs at their EC50/9
Survival
125
Narcotization
EC 50 = 1.1 (0.9-1.3)
100
75
50
25
0
0
1
2
Toxic Units = 1 =
3
9

j = 1
EC50 j
9
Conclusions
1. Allosteric decay function predicted accurately
acute responses
2. Acute responses were inversely related to log Kow
QSAR 9 PAH = Daphnia magna QSAR >100 non polar narcotics
3. Mixture toxicity of PAHs was additive following
the CA model.
Risk Assessment Implications
EC 50 (m g/L)
Naphthalene
Alkylated Naphthalenes
1000
Highest
100
Prestige
10
1
0.1
Background
1
10
100
1000
Number Mixture components
Future Work
1. Derive QSAR models for sublethal responses
Clearance rates (feeding)
1
Log
EC 50 j
= 0.9 log K owj - 2.9
N2
14
50
Prestige
N
182
3
4
5
6
Kow
2 . How toxicity of real samples (elutriates or water
–accommodated fractions of fuel Oil) can be
predicted from Chemical analysis using QSAR
models
Thanks
END
Environmental Toxicology and Chemistry. Volume 24, No. 11, November 2005.