40 Years On: SEPA peatland radiation risk from wind farms

• 26 April 2026
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Today marks 40 years since the Chernobyl nuclear disaster.

On 26 April 1986, the Chernobyl nuclear disaster released significant quantities of radioactive material into the atmosphere. This material travelled across Europe and was deposited across the United Kingdom, including Scotland. The distribution of this fallout was not uniform. Upland areas, particularly in the Highlands and Islands, received higher levels due to rainfall occurring as the radioactive plume passed over.

Among the radionuclides released, Caesium-137 (Cs-137) is the most relevant to long-term environmental conditions in Scotland. This is due to its half-life of approximately 30 years and its behaviour in soils and biological systems. As a result, a proportion of the original fallout remains present in the environment today.

This is not a matter of debate. It is reflected in long-term environmental monitoring and in the historical management of agricultural land. Following the Chernobyl incident, restrictions were placed on livestock movement in parts of the UK due to contamination entering the food chain. In Scotland, these restrictions remained in place until 2010. This demonstrates that Cs-137 deposited in upland environments was capable of transferring into biological systems under real-world conditions.

Cs-137 in Scottish Peatlands: Established Environmental Behaviour

Peatland environments play a significant role in the long-term retention of contaminants. Due to their high organic content, waterlogged conditions, and low levels of disturbance, peat soils can act as sinks for substances deposited from the atmosphere, including radionuclides.

Cs-137 binds strongly to organic matter and is typically retained within the upper layers of peat. Measurements in upland environments have shown that concentrations remain present within surface and near-surface soils. The key point is not the exact concentration at any single location, but the established fact that Cs-137 has persisted in these environments for decades.

Under undisturbed conditions, this contamination remains relatively stable. However, this stability is dependent on the physical and chemical structure of the peat remaining intact. Where that structure is altered, the behaviour of contaminants can change.

This is a well understood principle in environmental science. Contaminants that are stable in situ can become mobile when soils are disturbed, aerated, or subject to changes in water flow. This principle applies broadly across environmental regulation and is not unique to radiological substances.

Peatland Development and Ground Disturbance

Modern energy infrastructure developments in Scotland, including wind farms and associated transmission works, frequently take place in upland peatland areas. These developments involve groundworks that include excavation, trenching, drainage, and the construction of access tracks and foundations.

These activities directly affect the same soil layers in which Cs-137 is known to be present. Excavation exposes peat to air, drainage alters water tables, and mechanical activity breaks down soil structure. These are not unusual or extreme conditions. They are standard elements of construction in peatland environments.

The relevance of this is straightforward. Where a contaminant is present in soil, and where that soil is subject to disturbance, there is a requirement to consider whether that disturbance could alter the behaviour of the contaminant.

This does not require an assumption of harm. It requires recognition of a known condition and a known process.

SEPA’s Position in Context

The Scottish Environment Protection Agency (SEPA) has published its position on this issue, concluding that the disturbance of peatlands during wind farm construction does not represent a realistic risk to human health. This conclusion is based on radiological dose modelling, which assesses whether exposure pathways could lead to the public dose limit of 1 millisievert per year being exceeded.

It is important to accurately reflect what this conclusion means.

SEPA’s position does not state that Cs-137 is absent from peatlands. It does not state that disturbance cannot occur. It states that, based on modelling assumptions, the resulting exposure is unlikely to exceed a specific regulatory threshold.

This is a narrow and specific conclusion. It addresses one aspect of risk, namely the likelihood of exceeding a defined dose limit. It does not address the broader question of whether radiological contamination should be assessed where it is known to exist and where disturbance is proposed.

That distinction is central to understanding the issue.

Environmental Pathways: What Is Known, Not Assumed

The behaviour of Cs-137 in the environment has been extensively studied since 1986. Its movement through environmental systems follows established and well-documented pathways. These pathways do not rely on speculation. They are grounded in observed processes.

The first pathway is soil disturbance and particulate movement. Cs-137 binds to fine soil and organic particles. When peat is excavated, dried, or mechanically disturbed, these particles can be mobilised. This includes the generation of dust during construction activity. The existence of particulate transport as a mechanism for contaminant movement is widely accepted in environmental science and is not specific to radiological materials.

The second pathway is water transport. Changes to peatland hydrology, including drainage and excavation, alter natural water flow. Cs-137 can move in association with suspended sediments or dissolved fractions into surface water systems. Once in watercourses, it can be transported beyond the original point of disturbance. This process has been observed in multiple environmental contexts, including post-Chernobyl monitoring.

The third pathway is biological uptake. Cs-137 behaves chemically in a similar way to potassium, which allows it to be taken up by plants. This mechanism is well established and was a key factor in the historical transfer of contamination into grazing livestock following Chernobyl. It is also recognised in fungi, which can accumulate Cs-137 at higher concentrations than surrounding soils.

These pathways are not theoretical constructs. They are the same processes that led to measurable environmental and agricultural impacts in the years following the original fallout.

What the Current Assessment Does Not Address

SEPA’s assessment focuses on whether these pathways, if activated, would result in radiation doses exceeding the public limit of 1 millisievert per year. This is a valid regulatory metric, but it is not the only relevant consideration.

There are three areas where the current approach is limited.

First, it does not require site-specific measurement of Cs-137 prior to development. Peatland environments are variable. Fallout deposition was influenced by local rainfall patterns, meaning that concentrations differ across locations. Without direct measurement at development sites, it is not possible to determine the actual conditions present.

Second, it does not include pathway-based assessment within Environmental Impact Assessments. Standard environmental practice requires that where contamination is known or suspected, its potential movement through environmental systems is assessed. In the case of peatland developments, this step is not routinely undertaken for radiological contamination.

Third, it does not consider cumulative disturbance across multiple developments. Energy infrastructure in Scotland is not limited to individual projects. It involves multiple sites and extensive linear works across upland regions. The combined effect of repeated peatland disturbance is not addressed within a framework that evaluates projects individually against a fixed threshold.

These are not speculative gaps. They are identifiable features of the current approach when compared with standard environmental assessment practice.

Established Regulatory Principles

Environmental regulation operates on consistent principles across different types of contamination.

Where a substance is known to be present, and where an activity has the potential to disturb or mobilise that substance, the expectation is that the risk is assessed before the activity proceeds. This includes identifying the presence of the contaminant, understanding how it may move, and determining whether mitigation is required.

This principle is applied routinely to chemical contamination, land quality, and water pollution. The same logic applies to radiological contamination.

The presence of Cs-137 in Scottish peatlands is established. The disturbance of those peatlands is planned and ongoing. The mechanisms by which disturbance can lead to mobilisation are understood. Under standard regulatory practice, these factors are sufficient to justify assessment.

The requirement for assessment does not depend on demonstrating that harm will occur. It depends on recognising that a credible pathway exists.

The Role of Evidence

It is important to be clear about what is being asserted.

There is no evidence presented that current peatland developments in Scotland are causing widespread radiological harm. That claim is not made.

What is established is that:

– Cs-137 remains present in peatland environments
– Peatland disturbance occurs as part of development
– Known environmental processes can mobilise contaminants under such disturbance

The question is therefore procedural, not speculative. It is whether these conditions require assessment within the regulatory process.

The absence of evidence of harm is not evidence that assessment is unnecessary. It may simply reflect that the relevant measurements have not been undertaken.

A Matter of Completeness, Not Alarm

This issue should not be framed as an immediate hazard. It is a question of completeness in environmental assessment.

Radiological contamination is one of several environmental factors that may be relevant to peatland development. Others include carbon release, hydrological change, and ecological impact. Each of these is typically assessed as part of the planning process.

The treatment of Cs-137 differs in that it is acknowledged as present but not routinely assessed in the context of disturbance. This creates an inconsistency in how environmental risks are handled.

Addressing this does not require a change in regulatory thresholds. It requires the inclusion of radiological considerations within the same assessment framework applied to other forms of contamination.

Cumulative Effects and Long-Term Considerations

Peatland disturbance associated with energy infrastructure does not occur as a single, isolated event. Across Scotland, developments include wind farms, substations, access tracks, and transmission corridors, often located within the same upland regions. Each project involves excavation, drainage, and ground alteration. When considered collectively, this results in repeated disturbance of peatland systems over large areas.

The concept of cumulative impact is a standard component of environmental assessment. It recognises that individual activities, each with limited impact when considered alone, can together produce a materially different outcome. In the context of peatland disturbance, this means that the frequency and scale of groundworks increase the likelihood that environmental processes capable of mobilising contaminants are activated across multiple locations.

This is not a claim of widespread impact. It is a recognition of scale. Where multiple developments occur within areas known to contain Cs-137, the probability of disturbance interacting with that contamination increases. Assessing projects individually against a fixed threshold does not capture this broader context.

There is also a long-term dimension. Changes to peat structure and hydrology can persist beyond the construction phase. Drainage systems alter water movement, excavated areas may remain exposed, and compacted soils can behave differently under rainfall and erosion. These conditions can influence the movement of particles and water over time.

Environmental processes such as heavy rainfall, surface runoff, and seasonal drying cycles continue to act on disturbed peatlands. These processes are capable of transporting soil and associated contaminants within catchments. The timescale over which this occurs extends beyond the period typically considered in construction-phase assessments.

The relevant point is that environmental systems do not reset once construction is complete. Where conditions are altered, those changes can influence behaviour over extended periods. This is a recognised principle in land and water management.

Monitoring and Evidence Gaps

A consistent theme throughout this issue is the absence of site-specific data.

At present, there is no requirement within standard development processes for developers to undertake baseline measurement of Cs-137 in peatland soils. Without this, there is no direct evidence of conditions at individual sites prior to disturbance.

This has two implications.

First, it limits the ability to assess whether particular locations may differ from generalised assumptions. As established, Cs-137 deposition varies spatially. Without measurement, this variability is not captured.

Second, it prevents any meaningful comparison after development. If monitoring is not undertaken before disturbance, it is not possible to determine whether changes have occurred as a result of construction activities.

SEPA has indicated that a limited sampling programme is being undertaken. While this provides useful background data, it is not equivalent to site-specific investigation. A small number of samples cannot represent the range of conditions across multiple development sites.

In environmental regulation, baseline data is fundamental. It provides the evidence needed to inform assessment and to support any subsequent monitoring or mitigation. The absence of such data does not demonstrate that conditions are safe. It demonstrates that they have not been measured.

Consistency with Environmental Practice

The treatment of radiological contamination in peatland developments can be compared with how other environmental factors are managed.

Where chemical contamination is known or suspected, developers are required to undertake site investigations. Where hydrological impacts are possible, detailed modelling is carried out. Where ecological effects may arise, surveys and assessments are standard practice.

These processes are not triggered only when harm is certain. They are triggered when there is a reasonable basis to consider that an effect could occur.

Applying the same principle to Cs-137 does not introduce a new regulatory burden. It aligns radiological considerations with existing environmental assessment practices.

The current position, in which Cs-137 is acknowledged but not routinely assessed at the project level, represents a divergence from this approach.

What This Means in Practice

The issue does not require a change in the scientific understanding of Cs-137. Nor does it require a revision of dose limits or regulatory thresholds.

It requires that where:

– a contaminant is known to exist
– development involves disturbance of the medium containing that contaminant
– and established processes exist by which it could be mobilised

…then that interaction is included within the assessment process.

In practical terms, this would involve:

– identifying whether Cs-137 is present at a development site
– considering how construction activities may affect its behaviour
– and determining whether any monitoring or mitigation is appropriate

This is consistent with standard environmental assessment methodology.

Conclusion: A Procedural Requirement

Forty years after Chernobyl, the presence of Cs-137 in Scotland’s peatlands is a matter of record. The development of energy infrastructure in those same environments is also a matter of record.

The interaction between these two facts is the issue.

SEPA’s current position addresses one aspect of risk, namely the likelihood of exceeding a defined dose threshold. It does not fully address the procedural requirement to assess known contamination where disturbance is proposed.

This is not a question of whether significant harm is occurring. It is a question of whether the regulatory process is complete.

Environmental assessment is designed to identify and consider relevant factors before development proceeds. Where a known contaminant is present, and where development activities directly interact with the environment containing it, inclusion within that process is consistent with established regulatory principles.

The position set out here is therefore limited and specific.

It does not assert that peatland developments are causing radiological harm.
It does not dispute that overall exposure levels may remain low.

It establishes that:

– Cs-137 is present
– peatland disturbance occurs
– known processes can mobilise contaminants

…and that these factors meet the threshold for assessment.

On the 40th anniversary of the Chernobyl disaster, this is a matter of applying established environmental principles to current conditions.