Chemical and other stress in deb 5 extrapolations
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Chemical (and other) stress in DEB 5: extrapolations. Tjalling Jager Dept. Theoretical Biology. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A A A A A A A. Contents. Extrapolations Why extrapolation? Examples of extrapolation. Why extrapolation.

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Chemical and other stress in deb 5 extrapolations

Chemical (and other) stress in DEB5: extrapolations

Tjalling Jager

Dept. Theoretical Biology

TexPoint fonts used in EMF.

Read the TexPoint manual before you delete this box.: AAAAAAA


Contents

Contents

Extrapolations

  • Why extrapolation?

  • Examples of extrapolation


Why extrapolation

Why extrapolation

“Protection goal”

Available data

??

  • different exposure time

  • different temperature

  • different species

  • time-varying exposure

  • species interactions

  • populations

  • other stresses

  • mixture toxicity


Contents1

Contents

Example life-cycle dataset

  • Bindesbøl et al (2007), re-analysed in Jager and Klok (2010)

  • copper in Dendrobaena octaedra

  • size, survival, cocoons over 20 weeks

  • here, only [Cu] > 80 mg/kg


Deb analysis of data

40

9

35

8

30

7

25

6

cumulative offspring per female

20

5

body length

15

4

10

3

5

2

0

0

50

100

150

1

time (days)

0

50

100

150

time (days)

DEB analysis of data

Assumption

  • copper leads to a decrease in ingestion rate

80

80

120

120

160

160

200

200

Jager and Klok, 2010


Parameter estimates

internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

Parameter estimates

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

to population model …


Population effects

Population effects

  • Type of information that risk assessors should be most interested in ...

  • Popular endpoints

    • intrinsic rate of increase

    • toxicant concentration where this rate is zero

    • (or multiplication factor lambda, and where it is one)

  • Popular (simple) approaches

    • matrix models

    • Euler-Lotka equation

    • ...


Matrix models

Matrix models

  • In combination with DEB(tox)

    • Klok & De Roos (1996), Lopes et al (2005), Klanjscek et al (2006), Smit et al (2006), Liao et al (2006)

  • Discrete time and discrete stages ...

    • one state variable (size or age) for the organism …

    • DEB generally requires more ...

1

2

3

4


Euler lotka equation

Euler-Lotka equation

  • In combination with DEB(tox)

    • Kooijman & Metz (1984), Jager et al (2004), Alda Álvarez et al (2005, 2006) ...

  • Continuous time and continuous states ...

    • straightforward for DEB animals

    • only for constant environment ...

  • In constant environment, populations grow exponentially


Individual based models

Individual-based models

  • Follow all individuals seperately …

  • Full flexibility for dynamic environments

    • but calculation intensive …

    • see Martin et al (subm.)

Kooijman (2000)


Population effects1

no-effects

Population effects

But, this is extinction at:

  • abundant food

  • no predation

  • no disease

  • optimal temperature

  • low competition

0.025

0.02

0.015

population growth rate (d-1)

0.01

0.005

0

60

80

100

120

140

160

180

200

concentration (mg/kg soil)

Jager and Klok, 2010


Extrapolation food

internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

Extrapolation: food

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

less food in environment


Energy budget

feeding

5%

reproduction

maturation

maintenance

Energy budget …

ad libitum

growth


Energy budget1

reproduction

50%

maintenance

Energy budget …

feeding

limiting

maturation

growth


Food limitation 90

Food limitation (90%)

40

9

35

8

30

7

25

6

cumulative offspring per female

20

5

body length

15

4

10

3

5

2

0

0

50

100

150

1

time (days)

0

50

100

150

time (days)

80

80

120

120

160

160

200

200


Food limitation

Food limitation

0.025

0.02

food 100%

0.015

population growth rate (d-1)

0.01

food 90%

0.005

0

60

80

100

120

140

160

180

200

concentration (mg/kg soil)

Jager and Klok, 2010


Extrapolation chemicals

internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

Extrapolation: chemicals

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

other compounds (related)


Process based qsar

Process-based QSAR

Jager and Kooijman, 2009


Extrapolation mixtures

internal

concentration

in time

internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

external

concentration

(in time)

toxico-

kinetics

Extrapolation: mixtures

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

other compounds (mixtures)


Mixtures

internal

concentration

A in time

internal

concentration

B in time

DEB

parameters

in time

external

concentration

B (in time)

external

concentration

A (in time)

Mixtures

toxico-

kinetics

growth

DEB

model

toxico-

kinetics

life-history

traits

theory implies interactions …


Mixtures1

internal

concentration

A in time

internal

concentration

B in time

DEB

parameters

in time

external

concentration

A (in time)

external

concentration

B (in time)

Mixtures

??

toxico-

kinetics

DEB

model

toxico-

kinetics

life-history

traits


Simple mixture rules

compound

‘target’

metabolic process

assimilation

maintenance

Simple mixture rules

toxicity parameters linked (compare CA)


Simple mixture rules1

Simple mixture rules

compound

‘target’

metabolic process

assimilation

maintenance


Simple mixture rules2

Simple mixture rules

compound

‘target’

metabolic process

assimilation

maintenance

toxicity parameters independent (compare IA)


Visual representation

Visual representation

  • For binary mixture, model represents surface that changes in time …

Baas et al (2007)


Pahs in daphnia

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)

Jager et al (2010)


Chemical and other stress in deb 5 extrapolations

same target

costs reproduction

(and costs growth)


Iso effect lines

Iso-effect lines

for body length <50% effect


Extrapolation species

internal

concentration

in time

DEB

parameters

in time

external

concentration

(in time)

Extrapolation: species

?

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

other (related) species


Experiments nematodes

Experiments nematodes

Species

  • Caenorhabditis elegans and Acrobeloides nanus

    Chemicals

  • cadmium, pentachlorobenzene and carbendazim

    Exposure

  • in agar

    Endpoints

  • survival, body size, reproduction over full life cycle

  • analysed with extended DEBtox

Studies published as: Alda Álvarez et al.,

2005 (Func. Ecol.), 2006 (ES&T), 2006 (ET&C)


Pecb in a nanus

A. nanus

PeCB in A. nanus

Effects on assimilation


Pecb in c elegans

C. elegans

PeCB in C. elegans

Costs for growth and reproduction


Physiological moa

Physiological MoA


Physiological moa1

Physiological MoA


Physiological moa2

Physiological MoA


Physiological moa3

Physiological MoA


Species differences

toxicant

target site

toxicant

target site

maintenance

maintenance

reproduction

reproduction

Species differences?

Species A

Species B


Species differences1

Species differences?

toxicant

target site

maintenance

reproduction


Extrapolation exposure

internal

concentration

in time

metabolic

processes

in time

external

concentration

(in time)

Extrapolation: exposure

TK pars

tox pars

DEB pars

toxico-

kinetics

DEB

model

life-history

traits

time-varying concentrations


Time varying exposure

Time-varying exposure

Specifically relevant for risk assessment

  • Such as:

    • accidental spills

    • plant-protection products

    • industrial chemicals; batch production

  • Impractical and costly to test each scenario experimentally


Fate modelling

pesticide fate modelling

oil-spill modelling

Fate modelling


Time varying exposure1

environ. conc.

time

Time-varying exposure


Time varying exposure2

environ. conc.

time

time

Time-varying exposure

Assumption

  • toxicokinetics follows first-order, one-comp. model

internal conc.


Time varying exposure3

environ. conc.

NEC

time

time

Time-varying exposure

Assumption

  • effects on energetic processes are reversible

blank value

assimilation eff.

internal conc.


Time varying exposure4

cumul. reproduction

body length

time

time

Time-varying exposure


Experimental validation

Experimental validation

Daphnia magna and fenvalerate

  • modified 21-day reproduction test

  • pulse exposure for 24 hours

  • two (more or less) constant food levels

Pieters et al (2006)


Pulse exposure

Body length

Cumulative offspring

Fraction surviving

High food

Low food

Pulse exposure

mode of action: ‘assimilation’

  • Insights

  • tox. parameters independent of food

  • chemical effects fully reversible

  • reproduction rate slows down …


Summary

Summary

  • Extrapolation is crucial for environmental management

    • extrapolation requires mechanistic theory

    • DEB provides a framework for extrapolation

  • But, hypotheses for toxicant effects must be ‘correct’

  • More work is needed, e.g.,

    • starvation responses and interaction with toxicants

    • patterns in DEB parameter values between species

    • patterns in toxicity parameters (species and chemicals)

    • reversibility of toxic effects

    • interactions between chemicals in a mixture

    • etc. etc. ...


Outlook

biochemistry

DEB theory

species specific

Outlook

  • number of chemicals and species is very large …

  • but number of target sites and DEB parameters is limited!

toxicant

target site

DEB

parameters

DEB

model

?

effect on

life cycle


Chemical and other stress in deb 5 extrapolations

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  • PhD position at SCK-CEN in Mol (Belgium): radiation effects on duckweed (Lemna minor) with DEB

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

    And:http://www.bio.vu.nl/thb/users/tjalling/debtox_papers.htm

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