Making sense of sub-lethal mixture effects Tjalling Jager, Tine Vandenbrouck, Jan Baas, Wim De Coen,...

Making sense of sub-lethal mixture effects

Tjalling Jager, Tine Vandenbrouck, Jan Baas, Wim De Coen, Bas Kooijman

Challenge of mixture ecotoxicity

Some 100,000 man-made chemicals Large range of natural ‘toxicants’ For animals, 1.25 million species described Complex exposure situations

Typical approach

A B

Typical approach

Typical approach

Typical approach

wait for 21 days …

Dose-response plot

dose-ratio dependent deviation from CA

dose-ratio dependent deviation from CA

concentration A concentratio

n B

tota

l o

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

dose-ratiodependentdeviation from CA

dose-ratiodependentdeviation from CA

concentration A concentratio

n B

tota

lo

ffsp

rin

g

concentration A concentratio

n B

tota

lo

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

dose-ratiodependentdeviation from CA

dose-ratiodependentdeviation from CA

concentration A concentratio

n B

tota

lo

ffsp

rin

g

concentration A concentratio

n B

tota

lo

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

dose-ratiodependentdeviation from CA

dose-ratiodependentdeviation from CA

concentration A concentratio

n B

tota

lo

ffsp

rin

g

concentration A concentratio

n B

tota

lo

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

dose-ratiodependentdeviation from CA

dose-ratiodependentdeviation from CA

concentration A concentratio

n B

tota

lo

ffsp

rin

g

concentration A concentratio

n B

tota

lo

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

dose-ratiodependentdeviation from CA

dose-ratiodependentdeviation from CA

concentration A concentratio

n B

tota

lo

ffsp

rin

g

concentration A concentratio

n B

tota

lo

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

dose-ratiodependentdeviation from CA

dose-ratiodependentdeviation from CA

concentration A concentratio

n B

tota

lo

ffsp

rin

g

concentration A concentratio

n B

tota

lo

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

dose-ratiodependentdeviation from CA

dose-ratiodependentdeviation from CA

concentration A concentratio

n B

tota

lo

ffsp

rin

g

concentration A concentratio

n B

tota

lo

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on total Daphnia reproduction after 21 days under standard OECD test conditions?”

dose-ratiodependentdeviation from CA

dose-ratiodependentdeviation from CA

concentration A concentratio

n B

tota

lo

ffsp

rin

g

concentration A concentratio

n B

tota

lo

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on Daphnia reproduction after 21 days under standard OECD test conditions?”

dose-ratiodependentdeviation from CA

dose-ratiodependentdeviation from CA

concentration A concentratio

n B

tota

lo

ffsp

rin

g

concentration A concentratio

n B

tota

lo

ffsp

rin

g

What question did we answer?

“What is effect of constant exposure to this mixture on Daphnia reproduction after 21 days under standard OECD test conditions?”

“What is effect of constant exposure to this mixture on Daphnia reproduction after 21 days under standard OECD test conditions?”

Better questions

do we see these time patterns of effects?• can we explain the effects on all endpoints over the life

cycle in one framework?• can we make useful predictions for other mixtures, other

species, and other exposure situations?

externalconcentration

B (in time)

externalconcentration

A (in time)

effectsin time

Process-based

externalconcentration

B (in time)

externalconcentration

A (in time)

toxico-kinetics

toxico-kinetics

toxico-kinetics

toxico-kinetics

Process-based

internalconcentration

A in time

internalconcentration

B in time

survival as achance process

effectsin time

Tolerance distribution• McCarty et al (1992)• Lee & Landrum (2006)Stochastic death• Ashauer et al. (2007)• Baas et al. (2007, 2009)

Tolerance distribution• McCarty et al (1992)• Lee & Landrum (2006)Stochastic death• Ashauer et al. (2007)• Baas et al. (2007, 2009)

Sub-lethal endpoints …

growth

reproduction

feeding

maintenance

maturation

Sub-lethal endpoints …

growth

reproduction

feeding

maintenance

maturationRules for mass and energy flowsDEB (Kooijman, 2000/2001)

Rules for mass and energy flowsDEB (Kooijman, 2000/2001)

Process-based

externalconcentration

A (in time)

externalconcentration

B (in time)

toxico-kinetics

toxico-kinetics

toxico-kinetics

toxico-kinetics

internalconcentration

A in time

internalconcentration

B in time

metabolicprocesses

in timeDEB

model

DEBmodel effects on

all endpointsin time

assimilationmaintenanc

ematuration

….

theory implies interactions …

growth

externalconcentration

A (in time)

toxico-kinetics

toxico-kinetics

externalconcentration

B (in time)

toxico-kinetics

toxico-kinetics

DEBmodel

DEBmodel

internalconcentration

A in time metabolicprocesses

in timeinternalconcentration

B in time effects onall endpoints

in time

Process-based

assimilationmaintenanc

ematuration

….

Simple mixture rules

assimilation

maintenance

…

compound ‘target’ metabolic process

toxicity parameters linked (compare CA)

Simple mixture rules

assimilation

maintenance

…

compound ‘target’ metabolic process

Simple mixture rules

assimilation

maintenance

…

compound ‘target’ metabolic process

toxicity parameters independent (compare IA)

fluoranthene pyrene

PAHs in Daphnia

Based on standard 21-day OECD test• 10 animals per treatment• length, reproduction and survival every 2 days• no body residues (TK inferred from effects)

0 5 10 15 20

0

0.2

0.4

0.6

0.8

1

frac

tio

n s

urv

ivin

g

0 5 10 15 200

0.2

0.4

0.6

0.8

1

frac

tio

n s

urv

ivin

g

0 5 10 15 20

time (days)0 5 10 15 20

time (days)0 5 10 15 200 5 10 15 20

0

10

20

30

40

50

60

70

80

90

cum

ula

tiv

e o

ffsp

rin

g p

er f

ema

le

0

0.5

1

1.5

2

2.5

3b

od

y le

ng

th (

mm

)

00 (solv.)0.08650.1730.346

0

0.5

1

1.5

2

2.5

3b

od

y le

ng

th (

mm

)

00 (solv.)0.08650.1730.346

00 (solv.)0.2130.4260.853

00 (solv.)0.2130.4260.853

0.0865 0.2130.173 0.4260.260 0.6400.0865 0.6400.260 0.2130.346 0.853

0.0865 0.2130.173 0.4260.260 0.6400.0865 0.6400.260 0.2130.346 0.853

pyrene fluoranthene mixtures

Same target:costs reproduction(and costs growth)

Same target:costs reproduction(and costs growth)

Iso-effect lines

0 0.05 0.1 0.15 0.2 0.25 0.30

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

t = 10

t = 10

t = 14

t = 14

t = 14

t = 14

t = 18

t = 18

t = 18

t = 18

t = 21

t = 21

t = 21

t = 21

pyrene (μM)

flu

ora

nth

ene

(μM

)

50% survival

0 0.05 0.1 0.15 0.2 0.25 0.3

t = 10

t = 14

t = 14

t = 21

t = 21

pyrene (μM)

t = 10

t = 18

t = 18t = 10

50% reproduction

for body length <50% effect

Conclusions PAH mixture

Mixture effect consistent with ‘same target’• as expected for these PAHs• explains all three endpoints, over time

Iso-effect lines are functions of time• which differ between endpoints• in this case: little deviation from CA

Few parameters for all data in time• 14 parameters (+4 Daphnia defaults)

(descriptive would require >100 parameters)

Parameter estimates

externalconcentration

A (in time)

externalconcentration

B (in time) toxico-kinetics

toxico-kinetics

toxico-kinetics

toxico-kinetics

internalconcentration

A in time

internalconcentration

B in time

metabolicprocesses

in timeDEB

model

DEBmodel effects on

all endpointsin time

TK pars tox pars DEB pars

Educated extrapolation

externalconcentration

A (in time)

externalconcentration

B (in time) toxico-kinetics

toxico-kinetics

toxico-kinetics

toxico-kinetics

internalconcentration

A in time

internalconcentration

B in time

metabolicprocesses

in timeDEB

model

DEBmodel effects on

all endpointsin time

TK pars tox pars DEB pars

populations

Educated extrapolation

externalconcentration

A (in time)

externalconcentration

B (in time) toxico-kinetics

toxico-kinetics

toxico-kinetics

toxico-kinetics

internalconcentration

A in time

internalconcentration

B in time

metabolicprocesses

in timeDEB

model

DEBmodel effects on

all endpointsin time

TK pars tox pars DEB pars

other endpoints

other, e.g.,repro raterespiration

Educated extrapolation

externalconcentration

A (in time)

externalconcentration

B (in time) toxico-kinetics

toxico-kinetics

toxico-kinetics

toxico-kinetics

internalconcentration

A in time

internalconcentration

B in time

metabolicprocesses

in timeDEB

model

DEBmodel effects on

all endpointsin time

TK pars tox pars DEB pars

time-varying concentrations

Educated extrapolation

externalconcentration

A (in time)

externalconcentration

B (in time) toxico-kinetics

toxico-kinetics

toxico-kinetics

toxico-kinetics

internalconcentration

A in time

internalconcentration

B in time

metabolicprocesses

in timeDEB

model

DEBmodel effects on

all endpointsin time

TK pars tox pars DEB pars

food limitation

Educated extrapolation

externalconcentration

A (in time)

externalconcentration

B (in time) toxico-kinetics

toxico-kinetics

toxico-kinetics

toxico-kinetics

internalconcentration

A in time

internalconcentration

B in time

metabolicprocesses

in timeDEB

model

DEBmodel effects on

all endpointsin time

TK pars tox pars DEB pars

other narcotic compounds

Educated extrapolation

externalconcentration

A (in time)

externalconcentration

B (in time) toxico-kinetics

toxico-kinetics

toxico-kinetics

toxico-kinetics

internalconcentration

A in time

internalconcentration

B in time

metabolicprocesses

in timeDEB

model

DEBmodel effects on

all endpointsin time

TK pars tox pars DEB pars

other (related) species

Final words

A process-based approach is essential …• to progress the science of mixture toxicity• to make useful predictions for RA

Key elements DEB approach• one framework for all endpoints over time• feasible with ‘reasonable’ data sets• certain interactions are unavoidable …

Of course, more work is needed …• validate predicted interactions and extrapolations• ready to tackle more complex mixtures!

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Vacancies• PhD student, Marie Curie training network (CREAM)

Courses• International DEB Tele Course 2011

Symposia• 2nd International DEB Symposium 2011 in Lisbon

More information: http://www.bio.vu.nl/thb