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Direct Ecotox Testing of Leachates as an Alternative to

PEC/PNEC Comparison

Hans-Werner WegenICI DESOWAG GmbH & Co. KG

International Woodcare Development Centre

Xantener Strae 235

D-47495 Rheinberg

Abstract

As an alternative approach to the application of the PEC/PNEC consideration for an

environmental risk assessment of treated wood direct ecotoxicological testing of leachates is

presented. Leachates from solvent based preservatives treated timber were used as example.

Daphnids as very sensitive bioindicators exhibited differences due to the included biocides of

the preservative formulation tested .

The methodology of direct ecotoxicological testing as an alternative to PEC/PNEC

comparison is discussed for suitability in wood preservation.

Introduction

Driven by the implementation of the EU Biocidal Products Directive 98/8/EC (BPD) in theenvironmental risk assessment for treated wood different methodologies and test strategies are

at present under discussion within industry, regulatory authorities and standardising

committees.

For the environmental risk assessment of treated timber in service an approach was presented

by the Environmental Focus Group (EFG) suggesting real exposure conditions and listing

typical exposure scenarios for the different environmental compartments, where treated

timber is used according to hazard classes (DEROUBAIX et al, 2000).

As part of the OECD Biocides Programme OECD workshops on assessing environmental

exposure to wood preservatives dealt with the aspects of emissions of preservatives andtreated timber. For the determination of fate and behaviour thereof various exposure scenarios

were presented as mathematical modelling procedures.

General requirements for presenting realistic leaching test methods are a main topic in the

work of the corresponding European Technical Committee TC 38 working groups.

The EWPMG (European Wood Preservative Manufacturers Group) proposed a protocol

describing a tiered approach as a simple but effective environmental risk assessment as

support of the application for product approval under the Biocidal Products Directive

(BAINES, 2001).

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Estimated emission rates will be used in the exposure scenarios to determine worst case PEC

values (Predictable Environmental Concentration), which will then be adopted via fate and

behaviour models to produce realistic PECS: The PEC values will then be compared with

PNEC values (Predictable No Effect Concentration) in a risk assessment.

Taking into account that leachates of treated timber are complex mixtures, also the possibilityof a direct ecotox testing of leachates as an alternative to chemical analysis, PEC calculations

and PNEC determination is in discussion.

Meanwhile different studies have proven, that an examination of leachates on the

ecotoxicological hazards are practicable and promising (WEGEN et al, 1998; MELCHER u.

WEGEN, 1999; MARCHAL et al, 2000). Using sensitive biotests those studies give useful

information for a risk assessment in wood preservation.

A first laboratory test procedure for the determination of ecotoxicological behaviour of

leachates from superficially treated timber was presented by WEGEN and LUCKS ,1998).

This model follows current standards on testing of wood preservatives (such as EN 84) andexisting ecotoxicological testing of chemicals and wastewater. With some minor

modifications this approach has become a proposal for a test guideline on how to screen

leachates from preservative treated wood surfaces for their ecotoxic potential to aquatic

organisms, published by the German Federal Environmental Agency (LUCKS, 2000).

The paper presented here is a further example of the possibility to use direct ecotoxicological

of emissions for the environmental impact assessment of treated wood.

Materials and Methods

Product types

The product type tested was an example for a typical solvent based preservative for the

treatment of timber according to hazard class 3.

The biocides used were Propiconazole (1,2 %) as fungicide and Cypermethin (0.15 %) as

insecticide. A formulation without biocides at all and one formulation only with the

appropriate Propiconazole content served as references for comparison.

Table 1 gives an overview on the product types used.

Table 1: Product typesFungicide Insecticide

A no no

B 1,2 % Propiconazole no

C 1,2 % Propiconazole 0,15 % Cypermethrin

Test Procedure

In each case, 5 EN 113 pine wood blocks, end grains sealed, were treated by surface

application with the test formulations A , B and C by pipette.

The retention rate was 130 ml/m. The specimens were allowed to dry for 24 hours after thelast treatment.

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Then the leaching procedure was conducted according to the EN 84 standard using

demineralised water as leaching fluid. The first 500 ml leachate samples gained after 2 and 24

hours were combined and used in the ecotoxicological testing.

Direct Ecotox Testing of Leachates

Due to the extremely high sensitivity for water contamination Daphnia magna served as the

model organism in this study.

The determination of the daphnia toxicity of the leachates was conducted in accordance with

DIN 38412 Part 30 ( Determination of the non-acute-poisonous effect of wastewater to

Daphnia by dilution limits). The leachate sample was diluted with test water. As test animals

new borne daphnids, 6 to 24 hours old, were deployed in a number of 5 individuals in 6

parallel tests. The test duration was 48 hours at 20C. After this time the Acute No Effect

Levels of the leachates were determined via dilution factors for the end point criteria of 90 %

mortality.

In comparison the Acute Daphnia toxicity of the formulations was determined according toOECD-Guideline 202(1984) Part I (the 24 h EC 50 acute immobilisation test).

Results

Ecotoxicological Testing

a) Ecotoxicity of formulationsThe results of the acute toxicity of the formulations are presented in table 2.

The samples with biocides exhibited an increase in the acute effect onDaphnia magna incomparison with the sample without any biocides. Due to the higher daphnia toxicity of the

insecticide Cypermethrin, formulation C showed the strongest effect.

Table 2: Acute Daphnia toxicity of FormulationsFungicide Insecticide EC 50 (24 hrs)

A no no 28,0 mg/l

B 1,2 % Propiconazole no 17,4 mg/l

C 1,2 % Propiconazole 0,15 % Cypermethin 11,3 mg/l

b) Ecotoxicity of leachatesThe results of the ecotoxicity testing of the leachates are presented in table 3.

The dilution factors after a test duration of 48 hrs for the formulation without any biocide (A)

and the sample with only 1.2 % Propiconazole (B) were 2. That means that no toxicity of the

leachates could be determined.

The sample with Cypermethrin (C) exhibited a clear effect, which can be related to the

daphnia toxicity of this insecticide.

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Table 3: Acute Daphnia Toxicity of Leachates

Fungicide Insecticide Dilution factors (48hrs)

A no no 2

B 1,2 % Propiconazole no 2

C 1,2 % Propiconazole 0,15 % Cypermethin 32

In table 4 data on the acute daphnia toxicity of some typical biocides used in woodpreservation is summarised. This information is taken from the Material Safety Data Sheets

offered from the suppliers of the actives. Concerning the EC 50 values it can clearly be seen,

that in the test formulation C the ingredient Cypermethrin should be responsible for hazardous

acute effects on daphnids as no target organisms.

Table 4: Acute Daphnia Toxicity of biocides used in wood preservation according to

Material Safety Data sheets

Biocide EC 50 ( 48 hrs )

Propiconazole 10.2 mg/l

Tebuconazole 4,2 mg/l

Tolylfluanid 0,57 mg/l

Dichlofluanid 0,57 mg/l

Cypermethrin 0,15 mg/l

Permethrin 0,6 g /l

Flufenoxuron 0,05 g/l

Discussion and Conclusions

PEC/PNEC Approach:

Concerning the approval of chemicals and pesticides the environmental risk assessment is

based on the determination of the PEC/PNEC ratio. The estimation of the PEC (Predictable

Environmental Concentration) is based on emission values of the chemicals, which can be

used in mathematical models to calculate a predicted environmental concentration. The PEC

for a particular chemical depends on its physico-chemical properties and on the properties of

the receiving compartment.

The PNEC (Predictable No Effect Concentration) is determined by ecotoxicological tests on

non target organisms representing the receiving environmental compartment.

Then the ratio of these two estimated values (PEC/PNEC) is considered. If the ratio is less

than 1, the use of the chemical and its emission is an acceptable risk for the environment. The

ratio being greater than 1, it is considered that there could be a higher or perhaps unacceptable

risk for the environment. More data and more testing is required to refine the PEC or PNEC

values and to carry out a more refined risk assessment.

This methodology is clearly applicable for example for pesticides used in agriculture or plant

protection, where chemicals are directly applied into the environment.

The PEC/PNEC comparison is a well adopted approach in the risk assessment of chemicals,

especially for agrochemicals and biocides. It compares predictable concentrations of these

substances with predictable effects on non target organisms.

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Direct Ecotox Testing

In comparison to the PEC/PNEC Comparison the approach of Direct Ecotox Testing of

Leachates is very pragmatic. The test methodology can be used in any suitable equipped

laboratory either by government, institutes or industry.

The main aspects to find an acceptable standardisation are size and kind of timber or the

leaching procedure itself.

The EN 84 deals with the accelerated ageing of treated wood prior to biological testing on

efficacy. It is primarily of use to determine a possible decrease in the efficacy of a wood

preservative. In the case of wood preservation, the leached wood blocks serve for the testing

of the efficacy against wood destroying organisms according to given standards, like EN 84 in

connection with EN 113.

The testing of the combined 2 and 24 hours leachate is suited as a worst case consideration.

The advantages of direct Ecotoxicological Testing are summarised in table 5:

Table 5:Advantages of Direct Ecotox Testing

1 No analytical determination is necessary

2 Real effects can be determined directly

3 Total parameter testing

4 Time and cost effective

5 Suitable foundation for approvals and regulations

No analytical determination is necessary. This can be of interest in cases where analytical

test methodology is not yet available, or analytical determinations are difficult and can onlybe conducted with a very high effort.

Real effects can be determined directly. According to the bioindicator used direct

information on the influence of contamination of the environmental compartment of concern

is possible.

Total parameter testing : Testing of leachates therefore is not a simple testing of dilutions of

composites of the recipe of the preservative . As wood preservatives normally are

formulations of more than one biocide, additive and/or synergistic effects of all leachable

active ingredients and also of other compounds or metabolites are considered in one single

step.

As the ecotoxicological testing follows existing standards the use of acute Daphnia toxicity

studies is recommended. In respect to their high sensitivity these test organisms can be

principally used as bioanalytical apparatus. As link between fish and algae in the aquatic

food chain daphnids are direct bioindicators for the quality of the compartment water.

Time and cost effective: The ecotoxicological test are designed as short term tests. They are

time sparing and cost effective in relation to the expense of analytically checking emissions

for all parameters of concern.

Such determinations of emission rates will also be invaluable in the development of new

products because they enable the researcher to identify early in the development of theproduct potential environmental problems of the treated timber in service.

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Suitable foundation for approvals and regulations: This test approach does not give

automatically data to be directly used in mathematical modelling for chemicals or pesticides.

But measuring the acute effect as an endpoint of the study, it allows a definitive answer on the

hazard possibly arising from treated timber.

The NOEL determined according to this test pragmatic approach is only related to acuteeffects. But it offers sufficient information on the impact of treated timber in service and

ecotoxicological effects thereof at an early stage of product development.

Direct Ecotoxicologial Testing of leachates can simply be used in risk assessment, if an

agreement on practicable laboratory test parameters for a reasonable worst case scenario is

conducted. A no effect level can be obtained by diluting the leachate samples. The dilution

factorservesas a kind of safety factor. Therefore this approach could be a suitable foundation

for approvals and regulations of preservatives and treated timber.

Literature

DIN EN 84 (1997):Wood preservatives. Accelerated ageing of treated wood prior to

biological testing. Leaching Procedure. Ref. No. DIN EN 84:1997-05 , Beuth Verlag GmbH,

Berlin

DIN 38412 Teil 30 (1989) : Testverfahren mit Wasserorganismen (Gruppe L). Bestimmung

der nicht akut giftigen Wirkung von Abwasser gegenber Daphnien ber Verdnnungsstufen(L30).

DIRECTIVE 98/8/EC (1998) of the European Parliament and the Council of 16 February

1998 concerning the placing of biocidal products on the market. Official Journal L 123 ,

24-04-1998, pp. 01-63

BAINES, E.F; DAVIS, S.J (1998) : Environmental Risk Assessment of Preservative Treated

Wood . 4th

International Symposium The Challenge Safety and Environment in Wood

Preservation, Cannes-Mandelieu, France, 2-3February 1988

BAINES, E.F (2001): The EWPMG Proposal for the Environmental Risk Assessment of

Wood Preservatives . Symposium Environment and Wood Preservation,

Cannes-Mandelieu, France, 5-6 February 2001

DEROUBAIX, G. et al (2000): Environmental Risk Assessment of Treated Timber in

Service: The Environmental Focus Group Approach. The International Research Group on

Wood Preservation, IRG/WP 00-50162

LUCKS, J-U. (2000): Specifications in the application form for environmental assessment of

wood preservatives. UBA Texte 32/00. Umweltbundesamt, Berlin

MARCHAL, P.; WEGEN, H.-W.; VAN ACKER, J; MELCHER, E.; PEEK, R.D.;

HOMAN, W.J.; ASTON, D.; RUDOLPH, D; BAINES, E. (2000) : Alternative

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MELCHER, E.;WEGEN, H-W.(1999): Biological and chemical investigations for the

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Research Group on Wood Preservation. IRG/WP 99-50127

OECD Guideline 202 (1984): OECD Guidelines for Testing Chemicals : Daphnia sp. Acute

Immobilisation Test and Reproduction Test. Part I. The 24h EC acute immobilisation test-

WEGEN, H.-W.; PLATEN, A.; VAN EETVELDE, G; STEVENS, M.( 1998): An

appraisal of methods for environmental testing of leachates from salt-treated wood (2), The

International Research Group on Wood Preservation, IRG/WP 98-50110

WEGEN,H-W; LUCKS, U-J. (1998): Ecotoxicological behaviour of leachates from

superficially treated timber as an approach for a test strategy of environmental risk assessment

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50101