Pollution and Other Flows to Environment

1. Outcome

This Circular provides operational guidance on compiling indicators of pollution and other flows from the economy to the marine and coastal environment, supporting evidence-based decision-making for marine spatial planning, pollution control programs, environmental impact assessment, and SDG 14.1 reporting. Upon completing this Circular, readers will understand how to derive pollution indicators from the residual flow accounts compiled using TG-3.4 Flows from Economy to Environment, construct composite indices for marine pollution assessment, and calculate intensity and efficiency indicators that link economic activity to environmental pressures. The guidance addresses decision use cases including coastal pollution source tracking, nutrient loading assessments for marine spatial planning, SDG 14.1 reporting on marine pollution reduction, environmental impact assessment for development proposals, identification of pollution hot-spots requiring intervention, and evaluation of decoupling between economic growth and pollution pressures.

The Circular presents a systematic compilation procedure for pollution indicators: identify pollutant categories from residual flow accounts, extract relevant entries from physical supply-use tables, attribute flows to marine receiving waters using spatial allocation methods, and compute intensity ratios linking pollution to economic denominators. The accounts-to-indicators workflow draws on the international statistical standards summarised in TG-0.2 Overview of Relevant Statistical Standards and supports the derivation of ecosystem degradation indicators addressed in TG-2.8 Climate Change Indicators. The indicators compiled through this Circular feed directly into environmental policy integration processes described in TG-1.6 Environmental Impact Assessment, enabling assessment of development proposals against pollution thresholds and supporting evidence-based decisions on pollution control measures.

2. Requirements

This Circular requires familiarity with:

• TG-0.1 General Introduction to Ocean Accounts -- for the conceptual framework and key components of Ocean Accounts
• TG-0.2 Overview of Relevant Statistical Standards -- for the methodological foundations provided by SNA 2025, SEEA CF, and SEEA EA that underpin both the residual flow accounts and the indicator derivation methods in this Circular
• TG-3.4 Flows from Economy to Environment -- for the accounting framework and compilation methods for residual flows to the marine environment

3. Guidance Material

The transition from accounts to indicators represents a critical step in making environmental-economic accounting policy-relevant. While the residual flow accounts compiled under TG-3.4 Flows from Economy to Environment organise data on pollution and other flows in a systematic accounting framework, policy makers and analysts typically require derived indicators that summarise environmental pressures, enable trend analysis, support international comparison, and facilitate assessment against targets and thresholds.

The SEEA Central Framework establishes that indicators are derived from accounts through the "combined presentation" approach, which brings together physical and monetary data to enable calculation of ratios and indices^[1]. The Framework for the Development of Environment Statistics (FDES 2013) provides a complementary perspective, organising environmental indicators within a pressure-state-response conceptual framework where residual flows constitute environmental pressures that affect environmental state and trigger societal responses^[2]. This relationship to the DPSIR (Drivers-Pressures-State-Impact-Response) framework is also noted in TG-3.4 Flows from Economy to Environment, which positions residual flows as the "Pressures" component linking economic drivers to environmental state changes. The link between pollution pressures (this Circular) and the resulting changes in marine ecosystem condition is addressed in TG-2.3 Ecosystem Condition, which provides guidance on condition indicators such as dissolved oxygen levels and chlorophyll-a concentrations. Understanding the causal chain from pressure (nutrient loading, chemical discharge) to state (water quality, habitat integrity) is fundamental to interpreting the indicators presented here.

This Circular adopts a systematic approach to indicator derivation, organised around the major categories of residual flows to the marine environment. Each subsection identifies the accounting data required, presents recommended indicator specifications, discusses measurement challenges, and notes relevant international frameworks and reporting requirements.

3.1 Pollution Indicator Framework

The development of marine pollution indicators requires a coherent framework that links accounting data to policy-relevant measures. The SEEA Central Framework supports indicator derivation through combined presentations that juxtapose physical flows with economic data^[3]. For marine pollution, this framework can be extended to address the specific characteristics of ocean-related residual flows.

Figure 2.7.1: Derivation of marine pollution indicators from accounting data^[4]

Typology of pollution indicators

Marine pollution indicators can be classified into several categories:

1. Absolute flow indicators -- total quantities of pollutants discharged or emitted to the marine environment, measured in physical units (tonnes, kilograms). These indicators directly derive from the physical supply tables in residual flow accounts and provide the foundation for assessing total environmental pressure.

2. Intensity indicators -- ratios that relate pollution flows to measures of economic activity, such as emissions per unit of gross value added or waste generated per unit of output. Intensity indicators enable assessment of whether pollution is increasing or decreasing relative to economic scale^[5].

3. Efficiency indicators -- measures of how effectively economic processes convert inputs to outputs while minimising waste generation. These include material productivity (GDP per unit of material consumed) and emission efficiency (output per unit of emissions).

4. Composite indices -- aggregated measures that combine multiple pollution parameters into single indices for communication and monitoring purposes. SDG indicator 14.1.1 (Index of coastal eutrophication and floating plastic debris density) exemplifies this approach^[6].

5. Threshold-based indicators -- measures that assess pollution levels against environmental quality standards or ecological thresholds, enabling assessment of exceedance frequency and magnitude.

Linking accounts to indicators

The derivation of indicators from accounts follows a structured process:

1. Select relevant account entries -- identify the physical flow data from residual flow accounts corresponding to the indicator scope (e.g., nutrient emissions to coastal waters)

2. Determine appropriate denominators -- for intensity indicators, identify the economic or production variable (output, value added, employment) to use as denominator

3. Establish spatial and temporal scope -- define the geographic boundary (coastal zone, EEZ, specific water bodies) and reference period

4. Apply aggregation or weighting -- for composite indices, determine the aggregation method and any weights reflecting relative importance or impact of different pollutants

5. Document metadata and methods -- ensure indicator derivation is transparent and reproducible, supporting quality assessment per TG-0.7 Quality Assurance

The FDES 2013 Basic Set of Environment Statistics identifies specific statistics related to emissions and waste that can inform indicator development, organised under Component 3: Residuals^[7]. These include emissions of greenhouse gases by sector, generation and pollutant content of wastewater, discharge of wastewater to the environment, and generation and management of waste. The FDES 2013 Core Set of Environment Statistics provides a prioritised subset of the Basic Set, and compilers should note which indicators in this Circular align with Core Set statistics, as these represent the priority for international comparability^[8].

3.2 Compilation Procedure: From PSUT to Marine Indicators

The compilation of marine pollution indicators follows a structured workflow that extracts data from physical supply-use tables (PSUT), applies spatial attribution to identify marine-destined flows, and computes indicator values. This section provides step-by-step operational guidance.

Step 1: Identify pollutant categories in residual flow accounts

The SEEA CF physical supply-use table for residuals records flows by substance or material type. For marine pollution indicators, compilers should extract the following categories from the PSUT:

Water emissions:

• Nutrients: nitrogen compounds (nitrates, ammonia), phosphorus compounds
• Organic pollutants: biological oxygen demand (BOD), chemical oxygen demand (COD)
• Heavy metals: mercury, cadmium, lead, copper, zinc
• Persistent organic pollutants (POPs): as listed under Stockholm Convention
• Hydrocarbons: oil and petroleum products

Air emissions with marine deposition:

• Nitrogen oxides (NOx) and ammonia (NH3) -- contributing to marine eutrophication via atmospheric deposition
• Sulphur oxides (SOx) -- affecting ocean chemistry
• Carbon dioxide (CO2) -- driving ocean acidification
• Mercury -- depositing to marine waters and bioaccumulating in food webs

Solid waste to marine environment:

• Plastics: by polymer type where data allow (PE, PP, PS, PET, PVC)
• Marine litter: fishing gear (ALDFG), vessel waste, coastal litter
• Microplastics: primary (industrial pellets, microbeads) and secondary (fragmented waste)

The SEEA CF Table 3.18 provides the general structure for recording solid waste flows by source and destination^[9]. For marine litter accounting, the "waste to environment" category is disaggregated to distinguish waste reaching marine waters from other environmental destinations.

Step 2: Extract flows from PSUT by industry source

The physical supply table records residual generation by economic unit (industries classified by ISIC and households). For each pollutant category, compilers extract:

• Total generation by industry (tonnes per year)
• Industry classification (ISIC Rev.4 or national adaptation)
• Distinction between point sources (identifiable discharge locations) and diffuse sources (distributed over area)

Example extraction for nutrient emissions:

The SEEA CF methodology for attributing residuals to source industries is described in SEEA CF paras 3.268-3.277^[10]. Compilers should apply consistent attribution principles, recording flows to the industry that generates the residual rather than the industry that manages or treats it (unless treatment is incomplete and residuals are released).

Step 3: Apply spatial attribution to identify marine-destined flows

Not all residuals recorded in the PSUT reach the marine environment. Spatial attribution requires:

Hydrological connectivity analysis -- identify catchments that drain to coastal waters; estimate nutrient transport coefficients accounting for in-stream retention:

Marine load = Catchment generation × Delivery ratio

Delivery ratios typically range from 0.05 to 0.40 depending on distance to coast, soil type, vegetation cover, and retention in waterways. The OECD Gross Nitrogen Balance methodology provides guidance on estimating nutrient delivery from agricultural catchments to receiving waters^[11].

Direct discharge identification -- for point sources (wastewater treatment plants, industrial outfalls), use administrative records to identify facilities discharging to coastal waters versus inland waters.

Atmospheric transport modelling -- for air emissions, use atmospheric deposition models to estimate the fraction depositing to marine waters within the EEZ. Where atmospheric models are unavailable, apply simplified coefficients based on distance to coast and prevailing wind patterns.

Marine litter leakage rates -- estimate the fraction of mismanaged waste reaching marine waters using methodologies such as Jambeck et al. (2015)^[12], which incorporates coastal population, waste management infrastructure, and proximity to shore.

Step 4: Compute indicator values

With marine-attributed flows identified, compute indicator values:

Absolute indicators:

Total marine nutrient loading = Sum of N flows to marine waters (tonnes N/yr)

Intensity indicators:

Nutrient intensity = Marine nutrient loading / Ocean economy GVA (kg N per million currency)

The ocean economy GVA denominator is compiled as described in TG-3.3 Economic Activity Relevant to the Ocean, ensuring consistency between the numerator (pollution) and denominator (economic activity driving pollution).

Spatial indicators:

Nutrient loading density = Marine nutrient loading / Coastal zone area (kg N per km2)

Temporal indicators:

Loading change rate = (Current year loading - Base year loading) / Base year loading

Step 5: Quality assessment and uncertainty quantification

Pollution indicators inherit uncertainty from multiple sources: measurement error in residual flow accounts, uncertainty in spatial attribution (delivery ratios, atmospheric deposition fractions), and sampling variability in monitoring data. Compilers should:

• Document methods and assumptions for each step
• Quantify uncertainty ranges where feasible (e.g., confidence intervals for delivery ratios)
• Validate indicator trends against independent monitoring data (e.g., compare estimated nutrient loads with measured concentrations in coastal waters)
• Apply quality flags following TG-0.7 Quality Assurance

The SEEA CF principle of recording flows at the point of generation (rather than point of ultimate environmental impact) means that accounts-based indicators measure pressure rather than state. Compilers should clearly communicate that nutrient loading indicators, for example, represent inputs to marine waters, not resulting water quality. The link between loading (pressure) and concentration (state) depends on hydrodynamic dilution, biological uptake, and other factors addressed in ecosystem condition accounts.

3.3 Marine Pollution Indicators

Marine pollution encompasses a diverse array of substances that enter ocean waters through direct discharge, riverine transport, atmospheric deposition, and other pathways. This subsection addresses indicators for the major categories of marine pollutants: nutrients, chemicals, and hydrocarbons.

Nutrient pollution indicators

Nutrient pollution, particularly nitrogen and phosphorus compounds, contributes to coastal eutrophication--a process whereby excessive nutrient enrichment stimulates algal growth, depletes dissolved oxygen, and degrades marine habitat quality^[13]. SDG Target 14.1 specifically calls for reduction of nutrient pollution, with indicator 14.1.1 including a coastal eutrophication index^[14].

Recommended nutrient indicators:

The OECD/Eurostat Gross Nitrogen Balances and Gross Phosphorus Balances methodologies provide standardised approaches for calculating agricultural nutrient balances that can be applied to coastal catchments^[11:1]. The SEEA Agriculture, Forestry and Fisheries (SEEA AFF) guidance extends these methodologies within an accounting framework^[15].

For compilation, compilers should:

• Distinguish between point sources (industrial and municipal discharges with identifiable locations) and diffuse sources (agricultural runoff, urban stormwater)
• Apply appropriate models or coefficients to estimate nutrient transport from catchments to coastal waters, accounting for in-stream retention and transformation
• Attribute emissions to industries using ISIC classification, enabling analysis of sectoral contributions

The detailed methodology for recording nutrient emissions in residual flow accounts is provided in TG-3.4 Flows from Economy to Environment, Section 3.1 on emissions to water. This Circular addresses the subsequent step of deriving indicators from those accounts. The relationship between nutrient loading indicators (pressure) and marine ecosystem condition indicators such as dissolved oxygen levels, chlorophyll-a concentrations, and habitat quality scores is addressed in TG-2.3 Ecosystem Condition. Understanding this pressure-state linkage is fundamental to interpreting nutrient indicators in a policy context.

Chemical pollution indicators

Chemical pollutants encompass a broad category of substances including heavy metals, persistent organic pollutants (POPs), pharmaceuticals, and other synthetic chemicals. The FDES 2013 identifies the release of chemical substances as a key subcomponent of residuals statistics^[16].

Recommended chemical pollution indicators:

The measurement of chemical pollutants presents significant challenges due to the large number of substances, varying analytical methods, and difficulty in estimating diffuse sources. The European Pollutant Release and Transfer Register (E-PRTR) and similar national registries provide models for point source reporting^[17]. For ocean accounting, priority should be given to chemicals:

• Subject to international regulation (Stockholm Convention POPs, Minamata Convention mercury)
• Of particular concern for marine ecosystems (tributyltin, microplastics)
• With established monitoring and reporting systems

Hydrocarbon pollution indicators

Oil and petroleum products constitute a significant category of marine pollution, originating from vessel operations, offshore activities, land-based runoff, and accidental spills. The International Maritime Organization's MARPOL Convention establishes the regulatory framework for operational discharges from vessels^[18].

Recommended hydrocarbon indicators:

The ratio of accidental spills to total oil transport provides an indicator of maritime safety performance, while the trend in operational discharges indicates progress in compliance with MARPOL regulations.

For offshore petroleum activities, additional guidance on accounting for operational discharges is provided in TG-3.10 Offshore Energy. The broader context of marine litter (including oil-contaminated debris) is addressed in TG-6.12 Marine Litter and Plastics Accounting.

3.4 Marine Litter Indicators

Marine litter--solid waste that enters the marine environment--has emerged as a priority global environmental concern. SDG Target 14.1 addresses marine debris, with indicator 14.1.1 including floating plastic debris density^[9:1]. The Intergovernmental Negotiating Committee (INC) process under UNEA Resolution 5/14 has been working toward a global plastics treaty^[19]. Compilers should monitor the outcomes of INC sessions for potential new mandatory reporting requirements on plastic waste that may affect indicator specifications in future revisions of this Circular.

Plastic pollution indicators

Plastic dominates marine litter by item count and persistence. Indicators should address both the flow of plastic to marine waters and the resulting accumulation in marine environments.

Recommended plastic pollution indicators:

The Taskforce on Nature-related Financial Disclosures (TNFD) framework identifies plastic footprint as a specific disclosure metric, defined as total weight of plastics used or sold, disaggregated by reusable, compostable, and technically recyclable categories^[20].

For practical compilation, the approach developed by Jambeck et al. (2015) provides a methodology for estimating plastic leakage from waste generation, mismanagement rates, and proximity to coastlines^[12:2]. This methodology can be adapted to national contexts using locally-sourced waste statistics.

The treatment of microplastics warrants particular attention. As noted in TG-3.4 Flows from Economy to Environment, the boundary between dissolved/suspended pollutants (addressed under water emissions) and particulate matter such as microplastics (addressed under solid waste) requires clarification. For indicator purposes, microplastics may be reported as either:

• A component of water quality indicators (concentration in water column)
• A component of solid waste indicators (mass of plastic entering marine environment)

Compilers should clearly document which approach is adopted and avoid double-counting. International guidance on microplastics measurement standardisation is under development through bodies including GESAMP and IOC-UNESCO. Future revisions of this Circular may incorporate updated methodological standards as they emerge. The comprehensive treatment of marine litter stock-flow accounts is provided in TG-6.12 Marine Litter and Plastics Accounting.

Other marine debris indicators

Beyond plastics, marine litter includes fishing gear, packaging, and other materials.

Recommended debris indicators:

The SF-MST (Statistical Framework for Measuring the Sustainability of Tourism) provides guidance on tourism solid waste accounting relevant to coastal tourism waste generation^[21].

3.5 Atmospheric Deposition Indicators

Atmospheric emissions that subsequently deposit in marine waters represent an indirect but significant pathway for marine pollution. Key substances include nitrogen compounds that contribute to marine eutrophication, sulphur compounds affecting ocean chemistry, carbon dioxide driving ocean acidification, and mercury entering marine food webs^[22].

This pathway is addressed in TG-3.4 Flows from Economy to Environment, Section 3.1, which notes that "the accounting challenge is to link atmospheric emissions to their marine deposition, which requires integration with atmospheric modelling or use of deposition coefficients." This Circular addresses the indicator derivation aspect of this challenge.

Atmospheric nitrogen deposition

Atmospheric nitrogen deposition provides a supplementary nitrogen load to marine waters beyond direct waterborne discharge. The SEEA Technical Note on Air Emissions Accounting provides guidance on air emissions accounts that form the basis for deposition estimates^[23].

Recommended atmospheric deposition indicators:

The estimation of actual deposition requires atmospheric transport and deposition modelling, which may be beyond the capacity of many national statistical systems. A pragmatic approach is to report emissions from relevant sectors (agriculture, transport, energy) that contribute to deposition, while noting that the relationship between emissions and marine deposition depends on atmospheric conditions and distance to coast.

Ocean acidification indicators

Ocean acidification--the reduction in seawater pH due to absorption of atmospheric CO2--is addressed by SDG Target 14.3, with indicator 14.3.1 tracking average marine acidity measured at representative sampling stations^[24]. While pH measurement is fundamentally an environmental monitoring activity, indicators linking economic activity to acidification drivers are relevant for ocean accounting.

Recommended acidification-related indicators:

The relationship between national emissions and ocean acidification is mediated by global atmospheric mixing, meaning that national emissions contribute to global rather than specifically national marine acidification. Nevertheless, tracking emission trajectories provides accountability for contributions to this global pressure. Carbon accounting for the ocean economy is an evolving area; compilers may draw on the air emissions accounting methodology in the SEEA Technical Note on Air Emissions Accounting^[23:1] and on GHG inventory guidance under the UNFCCC framework. The comprehensive treatment of climate-ocean indicators is provided in TG-2.8 Climate Change Indicators, which addresses ocean acidification indicators in detail in Section 3.3.

Mercury deposition indicators

Mercury enters marine food webs through atmospheric deposition and bioaccumulates in fish, posing human health risks. The Minamata Convention on Mercury establishes international reporting requirements^[25].

Recommended mercury indicators:

3.6 Intensity and Efficiency Indicators

Intensity and efficiency indicators relate pollution flows to measures of economic activity, enabling assessment of decoupling--the dissociation of environmental pressure from economic growth^[26]. The SEEA Central Framework supports this through combined presentations that juxtapose physical and monetary data^[10:1].

These indicators are particularly relevant for ocean economy assessment, linking the economic activity data compiled under TG-3.3 Economic Activity Relevant to the Ocean to the residual flow data compiled under TG-3.4 Flows from Economy to Environment.

Pollution intensity indicators

Pollution intensity indicators express environmental pressure per unit of economic output or activity.

Recommended intensity indicators:

Intensity indicators should be calculated separately for key ocean-related industries as identified in TG-3.3 Economic Activity Relevant to the Ocean:

• Fishing (ISIC 031)
• Aquaculture (ISIC 032)
• Fish processing (ISIC 1020)
• Water transport (ISIC 50)
• Coastal tourism (ISIC 55, 79, 93)
• Offshore extraction (ISIC 06, 09)

Decoupling indicators

Decoupling indicators assess whether environmental pressure is growing slower than (relative decoupling) or declining absolutely while the economy grows (absolute decoupling)^[27].

Recommended decoupling indicators:

The interpretation of decoupling requires time series data. Single-period ratios provide intensity measures, but decoupling assessment requires comparison of percentage changes over multiple periods.

Additional guidance on resource efficiency indicators is provided in TG-2.11 Resource Efficiency.

Combined presentation for indicators

Following the SEEA Central Framework approach, a combined presentation for marine pollution indicators would include^[28]:

From this combined presentation, the following indicator categories can be derived:

1. Pressure indicators: total nutrient discharge, total marine litter, total CO2 emissions
2. Intensity indicators: nutrients per GVA, waste per output, emissions per GVA
3. Efficiency indicators: output per unit waste, GVA per unit emissions
4. Decoupling indicators: change in pressure relative to change in economic activity
5. Response indicators: environmental expenditure as share of output

The structure of this combined presentation aligns with that recommended in TG-3.4 Flows from Economy to Environment, Section 3.4, ensuring consistency between accounting and indicator frameworks.

3.7 Worked Example: Coastal Zone Nutrient Loading Indicator

This section presents a worked example demonstrating the compilation of a nutrient loading indicator for a hypothetical coastal zone, illustrating the step-by-step process from account data to indicator output.

Context

Coastal Zone Alpha is a 50 km stretch of coastline with intensive aquaculture (5 farms producing 8,000 tonnes/year of finfish), one urban wastewater treatment plant serving a population of 120,000, and agricultural catchments draining 15,000 hectares of cropland to coastal waters. The zone experiences periodic algal blooms, and planners require a nutrient loading indicator to support marine spatial planning decisions.

Step 1: Extract nutrient flows from residual accounts

From the national physical supply-use table for water emissions (compiled per TG-3.4), extract nitrogen discharge for Zone Alpha:

Step 2: Apply spatial attribution

Not all generated nitrogen reaches marine waters. Apply delivery ratios:

The agricultural delivery ratio of 0.18 is based on OECD guidance for mixed cropland catchments with moderate riparian buffers. Sensitivity analysis (not shown) indicates delivery ratios ranging 0.12-0.25 depending on rainfall intensity and vegetative cover.

Step 3: Compute indicator values

Absolute loading indicator:

Total nitrogen load to Zone Alpha = 315,700 kg N/yr = 316 tonnes N/yr

Spatial intensity indicator:

Loading per coastline length = 316 tonnes / 50 km = 6.3 tonnes N per km per year

Loading per unit coastal zone area:

Coastal zone area = 50 km × 5 km (avg width) = 250 km2
Loading density = 316 tonnes / 250 km2 = 1.26 tonnes N per km2 per year

Source attribution:

• Aquaculture: 58% of marine load
• Wastewater: 29% of marine load
• Agriculture: 13% of marine load (though 45% of gross generation)

Step 4: Compare to thresholds

OSPAR guidance suggests coastal zones with loading >1.0 tonne N per km2 per year are at elevated eutrophication risk. Zone Alpha exceeds this threshold, indicating policy intervention may be warranted.

Step 5: Link to economic activity

From ocean economy accounts (TG-3.3), Zone Alpha aquaculture GVA is 12.5 million currency units per year:

Aquaculture N intensity = 184 tonnes N / 12.5 million currency = 14.7 kg N per thousand currency GVA

This intensity can be compared across zones or tracked over time to assess whether nutrient loading is decoupling from aquaculture production.

Policy interpretation

The indicator compilation reveals that while aquaculture contributes the majority (58%) of nitrogen reaching coastal waters, agricultural sources represent 45% of gross generation but only 13% of marine load due to retention in the catchment-to-coast pathway. Policy interventions focused solely on aquaculture may achieve 58% reduction potential, while interventions targeting agricultural practices have lower marine impact due to natural attenuation. The indicator supports prioritisation of aquaculture best management practices (reduced feed conversion ratios, improved waste collection) and WWTP upgrades, while agricultural interventions may be warranted for broader environmental benefits beyond marine loading.

This worked example demonstrates the practical application of the compilation procedure described in Section 3.2, showing how account data (physical flows by source) is transformed into policy-relevant indicators through spatial attribution, threshold comparison, and linkage to economic activity measures.

4. Data Sources and Compilation

Compilation of pollution indicators draws on the residual flow accounts established under TG-3.4 Flows from Economy to Environment, supplemented by additional data sources for indicator derivation. TG-4.3 Administrative Data provides detailed guidance on administrative data sources for ocean accounting.

Key data sources for indicator compilation include:

From residual flow accounts:

• Water emissions accounts (nutrients, chemicals, BOD/COD)
• Air emissions accounts (CO2, NOx, SOx, mercury)
• Solid waste accounts (total generation, disposal routes, marine leakage estimates)
• Physical disturbance records (noise, dredging, habitat modification)

Additional data for indicators:

• National accounts (GDP, GVA by industry) for intensity denominators
• Employment statistics for employment intensity
• Spatial data (coastline length, EEZ area, catchment boundaries) for area-based indicators
• Environmental monitoring data for validation and threshold-based indicators
• Survey data (beach litter surveys, at-sea debris surveys) for direct measurement indicators

International reporting frameworks:

• SDG indicator 14.1.1 reporting requirements^[29]
• UNFCCC greenhouse gas inventories
• Minamata Convention mercury reporting
• Regional seas convention pollution protocols

5. Implementation Considerations

Prioritisation

Given resource constraints, compilers should prioritise indicators based on:

1. Policy relevance -- indicators that address national marine policy priorities and international commitments (particularly SDG 14)
2. Data availability -- indicators for which underlying data can be compiled from existing sources
3. Trend monitoring -- indicators that can be compiled consistently over time for trend analysis
4. Sectoral attribution -- indicators that enable identification of industries responsible for environmental pressure

Quality assessment

Indicator quality depends on the quality of underlying data. Key quality dimensions include^[30]:

• Accuracy -- how closely indicators reflect actual pollution levels
• Comparability -- consistency of methods over time and across jurisdictions
• Timeliness -- currency of indicator values relative to reference period
• Coherence -- consistency with related indicators and accounting totals

Further guidance on quality assessment is provided in TG-0.7 Quality Assurance.

International comparability

For international comparison and reporting, indicators should align with:

• SDG indicator metadata and methodologies
• SEEA recommended indicator frameworks
• FDES indicator specifications
• Regional seas monitoring protocols

Indicator presentation and communication

Pollution indicators are frequently presented in dashboards, report cards, and infographics for diverse audiences. Effective communication requires attention to several considerations. Indicators should be presented with clear units and reference periods, enabling unambiguous interpretation. Time series should be displayed alongside contextual information such as targets, thresholds, and policy milestones. Disaggregation by sector, substance, and spatial unit supports targeted policy analysis, while aggregation into headline indices supports high-level communication. The combined presentation table in Section 3.6 provides a template that can be adapted for dashboard and report card formats. Guidance on integrating pollution indicators with other ocean accounting outputs for combined presentation and communication is provided in TG-3.8 Combined Presentations.

6. Acknowledgements

This Circular has been approved for public circulation and comment by the GOAP Technical Experts Group in accordance with the Circular Publication Procedure.

Authors: Gerald Singh, Kirsten Oleson

Reviewers: [To be confirmed]

7. References