Use of Photochemical Ozone Creation Use of Photochemical Ozone Creation Potential as a means of evaluating the Potential as a means of evaluating the

contribution of volatile organic contribution of volatile organic compounds to ground-level ozone compounds to ground-level ozone

concentrationsconcentrations

Christine StevensChristine StevensMike ThelenMike Thelen

Nicole VerbieseNicole Verbiese

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Presentation OutlinePresentation Outline

What are the drivers for increasing restrictions on Volatile Organic What are the drivers for increasing restrictions on Volatile Organic Compounds (VOCs)? Compounds (VOCs)?

Role of VOCs in the ozone formation mechanismRole of VOCs in the ozone formation mechanism VOC legislation in Europe; existing legislationVOC legislation in Europe; existing legislation What is Photochemical Ozone Creation Potential (POCP)?What is Photochemical Ozone Creation Potential (POCP)? Use of the Photochemcial reactivity concept to gain exemption of Use of the Photochemcial reactivity concept to gain exemption of

Volatile Methyl Siloxanes (VMS) from US EPA VOC classificationVolatile Methyl Siloxanes (VMS) from US EPA VOC classification POCP values of typical VMSPOCP values of typical VMS Why is it important that POCP becomes recognised as a means of Why is it important that POCP becomes recognised as a means of

evaluating VOCs in Europeevaluating VOCs in Europe ConclusionsConclusions AcknowledgementsAcknowledgements

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What are the drivers for increasing What are the drivers for increasing restrictions on VOCs?restrictions on VOCs?

Primary driver is to prevent the formation of ground-level ozonePrimary driver is to prevent the formation of ground-level ozone

Ozone can damage health & vegetation at high concentrationsOzone can damage health & vegetation at high concentrations

Air Pollution by Ozone Directive (92/72/EEC) passed in 1992. Air Pollution by Ozone Directive (92/72/EEC) passed in 1992. Updated by Directive 2002/3/EC which sets a more stringent Alert Updated by Directive 2002/3/EC which sets a more stringent Alert Threshold to replace the Warning Threshold used in Directive Threshold to replace the Warning Threshold used in Directive 92/72/EEC and sets 120 92/72/EEC and sets 120 µµg/mg/m33 as long term objective as long term objective

Population Information Threshold (1 h average): 180 Population Information Threshold (1 h average): 180 µµg/mg/m3 3

ozoneozone Population Alert Threshold (1 h average): 240 Population Alert Threshold (1 h average): 240 µµg/mg/m3 3 ""

Vegetation protection: 200 Vegetation protection: 200 µµg/mg/m3 3 ““

VOCs in conjunction with oxides of nitrogen are a precursor for VOCs in conjunction with oxides of nitrogen are a precursor for formation of ground-level ozone in the presence of sunlight formation of ground-level ozone in the presence of sunlight

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Role of VOCs in the ozone formation mechanismRole of VOCs in the ozone formation mechanism

Biogenics± 31%

Solvents± 22%

“Mobile”± 24%

Others± 23%

TroposphereOzone

Stratosphere Ozone mixingSunLight

50 km

10-16 km

0 km

SUNLIGHT

UV: 200-330 nm

UV: > 330 nm:penetration toEarth’s surface

Sea level

NO2 + O2 NO + O3 +otherphotochemicalreactantsVOC + O2

AIR QUALITY

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European areas exceeding Ozone Thresholds in June 2002 (from European Centre on Air & Climate Change)

Key:

•Yellow area – Concentrations exceed 180 µg/m3 Ozone Information Threshold

• Orange area – Concentrations exceed 240 µg/m3 Ozone Alert Threshold

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Ozone concentrations in Ozone concentrations in summer 2005summer 2005

EU countries exceeding the Alert Threshold (240 EU countries exceeding the Alert Threshold (240 µµg/mg/m33)):: Austria, Belgium, Czech Republic, Estonia, Macedonia, Poland, Austria, Belgium, Czech Republic, Estonia, Macedonia, Poland,

Portugal, Slovak Republic, Slovenia, UKPortugal, Slovak Republic, Slovenia, UK

EU countries exceeding the Information Threshold (180 EU countries exceeding the Information Threshold (180 µµg/mg/m33):): France, Germany, Greece, Netherlands, Spain, SwitzerlandFrance, Germany, Greece, Netherlands, Spain, Switzerland

Most EU countries are exceeding Information Threshold limits Most EU countries are exceeding Information Threshold limits during summer months. during summer months.

Trend over recent years for average concentrations of ground-Trend over recent years for average concentrations of ground-level ozone to increaselevel ozone to increase

Global warming is expected to accelerate this trendGlobal warming is expected to accelerate this trend

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Other driversOther drivers

Clean Air for Europe (CAFE) programme – the objective is to protect Clean Air for Europe (CAFE) programme – the objective is to protect against adverse effects of air pollution on human health and the against adverse effects of air pollution on human health and the environment. Included in 7environment. Included in 7thth Framework Programme Framework Programme

SCALE (Science, Children, Awareness-raising, Legislation and SCALE (Science, Children, Awareness-raising, Legislation and Evaluation) programme) focuses on protecting children’s health. Evaluation) programme) focuses on protecting children’s health. One of the main concerns is exposure to pollutants, including VOCs One of the main concerns is exposure to pollutants, including VOCs within buildings.within buildings.

INDEX (Indoor Exposure Limits for Priority Pollutants) EU INDEX (Indoor Exposure Limits for Priority Pollutants) EU progammeprogamme

German NIK (Niedrigste Interessierende Konzentration) German NIK (Niedrigste Interessierende Konzentration) standard for emission limits from building materials (thereby standard for emission limits from building materials (thereby having influence on indoor air) having influence on indoor air)

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VOC legislation in EuropeVOC legislation in Europe Integrated Pollution Prevention & Control (IPPC) Directive Integrated Pollution Prevention & Control (IPPC) Directive

(96/61/EC) sets emission limits for various pollutants (96/61/EC) sets emission limits for various pollutants including organic carbon from large installationsincluding organic carbon from large installations

Solvents Emissions Directive (1999/13/EC) (usually referred Solvents Emissions Directive (1999/13/EC) (usually referred to as the VOC Directive) limits solvent emissions in a number to as the VOC Directive) limits solvent emissions in a number of industrial sectors, but does not limit their useof industrial sectors, but does not limit their use

National Emissions Ceilings Directive (2001/81/EC) sets National Emissions Ceilings Directive (2001/81/EC) sets emission limits for each Member State for four pollutants emission limits for each Member State for four pollutants responsible for acidification, eutrophication & ground-level responsible for acidification, eutrophication & ground-level ozone pollution, namely, VOCs, sulphur dioxide, nitrogen ozone pollution, namely, VOCs, sulphur dioxide, nitrogen oxides, and ammoniaoxides, and ammonia

VOCs in Paints, Varnishes and Vehicle Refinishing Products VOCs in Paints, Varnishes and Vehicle Refinishing Products Directive (2004/42/CE) Directive (2004/42/CE)

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What is Photochemical What is Photochemical Ozone Creation Potential?Ozone Creation Potential?

POCP is an indicator of the ability of a VOC to contribute to POCP is an indicator of the ability of a VOC to contribute to photochemical ozone formationphotochemical ozone formation

A measure of the reactivity of an organic compound with hydroxyl A measure of the reactivity of an organic compound with hydroxyl radicals & subsequent formation of ozoneradicals & subsequent formation of ozone

VOCs vary in their reactivity & therefore contribute differently to the VOCs vary in their reactivity & therefore contribute differently to the formation of ozoneformation of ozone

Concept developed by Derwent and Jenkin in 1990’s who Concept developed by Derwent and Jenkin in 1990’s who incorporated POCP into photochemical trajectory modelsincorporated POCP into photochemical trajectory models

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Use of the POCP concept by Use of the POCP concept by Regulatory Authorities in Regulatory Authorities in other geographic areasother geographic areas

Used by the US Environmental Protection Agency as a Used by the US Environmental Protection Agency as a basic measure to compare reactivities of volatile basic measure to compare reactivities of volatile compounds compounds

Maximum Incremental Reactivity (MIR) – scheme Maximum Incremental Reactivity (MIR) – scheme developed in the US & used by California Air Resources developed in the US & used by California Air Resources Board (CARB); calculated for reference scenarios based Board (CARB); calculated for reference scenarios based on:on:

Specified meteorological conditionsSpecified meteorological conditions Initial pollutant concentrationsInitial pollutant concentrations Emission rates of NOEmission rates of NOXX & VOC & VOC

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Use of POCP concept to gain exemption Use of POCP concept to gain exemption of Volatile Methyl Siloxanes (VMS) from of Volatile Methyl Siloxanes (VMS) from

US EPA VOC classificationUS EPA VOC classification US EPA definition of a VOC is any carbon compound, which reacts US EPA definition of a VOC is any carbon compound, which reacts

photochemically in the atmospherephotochemically in the atmosphere**. Methane & ethane which have . Methane & ethane which have negligible photochemical reactivity are the base line for comparison.negligible photochemical reactivity are the base line for comparison.

As volatile methyl siloxanes (VMS) do not deplete stratospheric As volatile methyl siloxanes (VMS) do not deplete stratospheric ozone, Dow Corning successfully petitioned US EPA in 1994, for an ozone, Dow Corning successfully petitioned US EPA in 1994, for an exemption of VMS from US VOC regulations for use as exemption of VMS from US VOC regulations for use as chlorofluorocarbons (CFCs) substitutes (specifically precision & chlorofluorocarbons (CFCs) substitutes (specifically precision & electronic cleaning applications)electronic cleaning applications)

Subsequent to this, VMS were exempted from regulation as VOCs, Subsequent to this, VMS were exempted from regulation as VOCs, permitting their use as replacements for CFCs in a range of permitting their use as replacements for CFCs in a range of industrial and consumer productsindustrial and consumer products

* This differs fundamentally from the EU definition defined in the Solvents * This differs fundamentally from the EU definition defined in the Solvents Directive where a VOC is any organic compound with a vapor pressure Directive where a VOC is any organic compound with a vapor pressure ≥ ≥ 0.01 kPa at 20ºC, i.e. no account is taken of reactivity0.01 kPa at 20ºC, i.e. no account is taken of reactivity

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Volatile Methyl Siloxanes – Volatile Methyl Siloxanes – smog chamber studysmog chamber study

Environmental chamber experiments performed by University of Environmental chamber experiments performed by University of California (Atkinson, 1991; Carter,1992)California (Atkinson, 1991; Carter,1992)

Studies consisted of 6 h irradiation of smog precursors with & Studies consisted of 6 h irradiation of smog precursors with & without VMS in the presence of high & low concentrations of NOwithout VMS in the presence of high & low concentrations of NOXX

VMS tested:VMS tested: Hexamethyldisiloxane (HMDS)Hexamethyldisiloxane (HMDS) Octamethylcyclotetrasiloxane (D4)Octamethylcyclotetrasiloxane (D4) Decamethylcyclopentasiloxane (D5)Decamethylcyclopentasiloxane (D5) Pentamethyldisiloxanol (hydroxylated degradation product of Pentamethyldisiloxanol (hydroxylated degradation product of

HMDS)HMDS) VMS were found to make no contribution to photochemical ozone VMS were found to make no contribution to photochemical ozone

formation formation

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Incorporation of POCP values for Incorporation of POCP values for VMS into European VMS into European

Photochemical Trajectory ModelPhotochemical Trajectory Model POCP Trajectory model developed by Derwent and Jenkin (1990, POCP Trajectory model developed by Derwent and Jenkin (1990,

1991) used to predict POCP values of VMS for three trajectories 1991) used to predict POCP values of VMS for three trajectories over Europeover Europe

Trajectory 1: traverses southern England and simulates 1 day’s Trajectory 1: traverses southern England and simulates 1 day’s photochemistry across downwind of London, travelling in a photochemistry across downwind of London, travelling in a westerly direction westerly direction

Trajectory 2: traverses Germany, Belgium, UK and Ireland, Trajectory 2: traverses Germany, Belgium, UK and Ireland, simulating 4 days’ photochemistry, travelling in a westerly simulating 4 days’ photochemistry, travelling in a westerly directiondirection

Trajectory 3: traverses France, Belgium, Netherlands, Trajectory 3: traverses France, Belgium, Netherlands, Germany, Denmark & Sweden, simulating 4 day’s Germany, Denmark & Sweden, simulating 4 day’s photochemistry, travelling in a northerly directionphotochemistry, travelling in a northerly direction

POCP values calculated by Derwent and Jenkin vary from -1.6 to 0, POCP values calculated by Derwent and Jenkin vary from -1.6 to 0, and the results were compared with ethylene (on a scale where and the results were compared with ethylene (on a scale where ethylene = 100)ethylene = 100)

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POCP values of VMS expressedPOCP values of VMS expressed relative to ethylene* relative to ethylene*

Traject-Traject-oryory

Southern Southern EnglandEngland

GermanyGermany→Ireland→Ireland FranceFrance→Sweden→Sweden MeanMean

DayDay 11 11 22 33 44 11 22 33 44

EthyleneEthylene 100100 100100 100100 100100 100100 100100 100100 100100 100100 100100

HMDSHMDS -0.3-0.3 -0.2-0.2 -0.1-0.1 -0.3-0.3 -0.1-0.1 -0.1-0.1 -0.3-0.3 -0.2-0.2 -0.2-0.2 -0.2-0.2

D4D4 -0.6-0.6 -0.3-0.3 -0.4-0.4 -0.6-0.6 -0.3-0.3 -0.2-0.2 -0.5-0.5 -0.5-0.5 -0.3-0.3 -0.4-0.4

D5D5 0.00.0 0.00.0 0.00.0 0.00.0 0.00.0 0.00.0 0.00.0 0.00.0 0.00.0 0.00.0

MDOHMDOH -0.2-0.2 -0.1-0.1 -0.1-0.1 -0.2-0.2 -0.1-0.1 -0.1-0.1 -0.1-0.1 -0.1-0.1 -0.1-0.1 -0.1-0.1

* Ethylene is a very strong precursor for the formation of ground-level * Ethylene is a very strong precursor for the formation of ground-level ozoneozone

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Why is it important that POCP Why is it important that POCP becomes becomes

recognised as a means of recognised as a means of evaluating evaluating

VOCs in EuropeVOCs in Europe Despite the introduction of legislation limiting VOC emissions in Despite the introduction of legislation limiting VOC emissions in Europe, average ozone levels are gradually increasing. Europe, average ozone levels are gradually increasing.

The focus by the EU Commission is therefore shifting to consumer The focus by the EU Commission is therefore shifting to consumer market segments as illustrated by the recent Directive (2004/42/CE) on market segments as illustrated by the recent Directive (2004/42/CE) on VOCs in Paints, Varnishes and Vehicle Refinishing Products Directive VOCs in Paints, Varnishes and Vehicle Refinishing Products Directive & the ongoing review by IVAM (Netherlands) on use of VOCs in & the ongoing review by IVAM (Netherlands) on use of VOCs in personal care products.personal care products.

The use of low-POCP VOCs is a more focused approach which can The use of low-POCP VOCs is a more focused approach which can be used in order to meet the increasingly stringent regulations on be used in order to meet the increasingly stringent regulations on ozone, while at the same time permitting the continued use of valued ozone, while at the same time permitting the continued use of valued consumer products in the market place.consumer products in the market place.

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ConclusionsConclusions Current “mass-based” legislation in Europe does not Current “mass-based” legislation in Europe does not

distinguish between the reactivity of different VOCs in distinguish between the reactivity of different VOCs in terms of ozone creation potentialterms of ozone creation potential

If further VOC reduction measures are to be considered, If further VOC reduction measures are to be considered, then replacing highly reactive VOCs with less reactive then replacing highly reactive VOCs with less reactive VOCs could be a more focused, cost-effective approachVOCs could be a more focused, cost-effective approach

In the US, the use of volatile methyl siloxanes was In the US, the use of volatile methyl siloxanes was successfully used as an alternative to reduce the successfully used as an alternative to reduce the regulated VOC content of a productregulated VOC content of a product

The use of volatile methyl siloxanes with zero (even The use of volatile methyl siloxanes with zero (even negative) Photochemical Ozone Creation Potential negative) Photochemical Ozone Creation Potential should be considered as one means of meeting ever should be considered as one means of meeting ever more stringent ground-level ozone regulations in Europemore stringent ground-level ozone regulations in Europe

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AcknowledgementsAcknowledgements

This work was sponsored by Dow Corning This work was sponsored by Dow Corning CorporationCorporation