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Biological Degradability Methods for Testing and Other Aspects

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Title: Biological Degradability Methods for Testing and Other Aspects


1
Biological Degradability Methods for Testing
and Other Aspects
Market Inspection and Surveillance of Detergents
and Cleaning Products in Turkey TAIEX Seminar,
7 May 2008, Ankara Dr. Klaus TaegerProduct
SafetyRegulations, Toxicology and Ecology
2
Presentation overview
  • Development of EU legislation on biodegradability
    of surfactants
  • Methodology principles on biodegradation
  • Definition of the ten days window principle and
    applicability on assessement of surfactants
  • EU legislation on biodegradability testing of
    surfactants
  • Summary and conclusions

3
The detergent problem in the early 1960s
4
Development of the European Detergent Legislation
on Biodegradability requirements
5
Biodegradation principle and analytical
measurements
Oxygen consumption
O2
Organic substance
Biomass growth
CO2
Carbon dioxide evolution
DOC removal
6
Definition of primary and ultimate degradation
pathway of exemplified fatty alcohol sulfate
O-SO3Na
Fatty alcohol sulfate (parent compound)
Primary degradation
Sulfate
OH
Fatty alcohol (primary degration product)
C2
Degradation intermediates
C2
C2
Ultimate degradation
Biomass
CO2 H2O
Final products
7
Surfactants Biodegradation in Screening
Tests Primary degradation vs. ultimate
degradation
Primary degradation (BiAS or MBAS)
Total degradation (DOC removal)
Ultimate degradation (O2 / CO2 minerali- sation)
degradation
Test duration days
8
Methods for Testing Surfactants of the OECD 301
Series
Analytical Parameter
Method
  • Screening Tests
  • Oxygen consumption
  • Carbon dioxide evolution
  • Dissolved organic carbon removal
  • Tests on primary degradation
  • Specific analysis(e.g. HPLC, MBAS, BiAS)
  • gt 60 pass level
  • OECD 301 D, F
  • OECD 301 B, 310
  • gt70 acceptability is limitedOECD 301 A, E
  • gt 80 pass level
  • OECD 301 A, E
  • OECD 303 A

9
Definition of the ten days window principle in
the OECD 301 Series
Why is the 10 day time-window not applicable for
testing surfactants ?
? lt 10 days ?
O2 / CO2
Time duration days
10
Essential conditions for the ready biodegradabilit
y assessment
  • Inoculum / bacteria not adapted
  • Low biomass / bacteria density relation
  • Kinetic term fulfilling the 10 days window
  • Defined pure substance

11
Biodegradation of a typical nonionic surfactant
(1)
Molecular mass distribution at day 0
12
Biodegradation of a typical nonionic surfactant
(2)
Molecular mass distribution at day 6
13
Non-applicability of the ten days principle for
surfactants scientific arguments
  • Biodegradation of surfactants are generally
    characterised by a multiphase kinetics due to a
    multi-component substrate
  • Potential intermediate metabolites may have
    metabolic rates which are different from the
    parent compound
  • Some metabolites interfere with the degradation
    process by inhibiting the transformation of the
    parent molecule

14
Modified Carbon dioxide evolution test with
additional carbon determination - CO2 /
DOC-Combination-Test -
15
Biodegradation and Elimination curve of a
secondary alcohol ethoxylate in the CO2 /
DOC-Combination Test
16
Biodegradation and Elimination curve of a
branched fatty acid in the CO2 / DOC-Combination
Test
17
Limitation of methodical biodegradation testing
  • Bacterial toxicity
  • Volatility
  • Water solubility
  • Mixtures
  • Adsorption / films

18
EU Legislation as a step-by-step testing scheme
(derogation for Industrial Institutional
applications)
Screening tests on readily biodegradability
OECD 301 B, C, D, F OECD 310
above 60 limit
allowed for market
below 60 limit
Primary biodegradability screening
and/or confirmatory
below 80 limit
not allowed for market
pass 80 limit
Simplified complementary Risk Assessment
acceptable risk
allowed for market
19
EU Legislation complementary Risk Assessment
(Annex IV)
  • Identify of the surfactant
  • Exposition Function and expected volume
  • Information about potential metabolites
  • Further biodegradation studies
  • preadapted inoculum
  • verification of inherent biodegradability OECD
    302 A or B including OECD 303 A
  • Toxicity testing of metabolites
  • Information about the potential of
    bioaccumulation of metabolites

20
Aceptance of surfactants biodegradation under EU
legislation
  • Screening tests on readily biodegradability
    according to the OECD 301 Series and OECD 310
    without application of the 10 days window
    principle
  • Acceptability of data based on DOC removal which
    show a definite sigmoid biodegradation curve
  • Read across by interpolation between a similar
    surfactant group
  • Step-by-step testing scheme by derogation for
    Industrial Institutional applications

21
Summary and Conclusions
  • In the 1960 the assessment of the
    biodegradability of surfactants based on the loss
    of surface tension (primary biodegradation)
  • Over decades the EU legislation implemented the
    ultimate biodegradation (mineralisation)
  • The ten days window principle of the readily
    biodegradability screening tests does not apply
    for surfactants, because surfactants are
    multi-component mixtures
  • In cases of failing pass levels a derogation for
    Industrial Institutional applications allowes a
    step-by-step testing scheme of surfactants
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