Radioactive Substances Committee Thematic Assessment

Environmental concentrations of radionuclides in the OSPAR Maritime Area and their radiological impact

The description of the state of the marine environment in relation to radioactive substances is based on the outcome of the OSPAR assessments that cover environmental concentrations, and radiological impact. For environmental concentrations of indicator radionuclides for the nuclear sector there is clear evidence that environmental concentrations in the assessment period are close to or lower than historic levels. The environmental concentrations of indicator radionuclides for the nuclear sector in seawater would not result in a significant radiological impact on humans or the marine environment. In addition, the modelled additional concentrations of indicator radionuclides for produced water from the non-nuclear oil and gas sub-sector in seawater would not result in a significant radiological impact on humans or the marine environment.

Table S.1: Chapter Summary per OSPAR Region
	Arctic Waters	Greater North Sea	Celtic Seas	Bay of Biscay and Iberian Coast	Wider Atlantic
Environmental concentrations
Intensity¹	L	L	L	L	L
Trend since QSR2010²	↓	↓	↓	↓	↓
Trend to 2030	↓	↔	↓	↔	↓
Radiological impact
Intensity³	L	L	L	L	L
Trend since QSR2010²	↓	↓	↓	↓	↓
Trend to 2030	↓	↔	↔⁴	↔	↓

¹ - Intensity of environmental concentrations is based on data reported to OSPAR up to 2018 and published in the Fifth Periodic Evaluation. No Contracting Party reports environmental concentration data to OSPAR for OSPAR Region V, but it is possible to comment on the intensity for OSPAR Region V based on expert judgement and published data from other sources.

² - Trends since QSR 2010 are based on assessments carried out by OSPAR in the Fifth Periodic Evaluation. Trend for OSPAR Region V is based on expert judgement and published data from other sources (see footnote 1).

³ - Intensity of radiological impact is based on the assessments carried out by OSPAR in the Fifth Periodic Evaluation. Radiological impact for OSPAR Region V is based on expert judgement and published data from other sources (see footnote 1).

⁴ - Although activity concentrations of three (H-3, Tc-99 and Cs-137) out of four indicator radionuclides for the nuclear sector are expected to reduce further, the radiological impact from all four indicator radionuclides is expected to be similar due to the remobilisation of Pu-239,240 from the inventory of this radionuclide in sediments as the result of historic discharges and the significant radiological impact it produces.

The levels of radionuclides in the marine environment

From the assessments that OSPAR has carried out on data for the period 1995 to 2018 for environmental concentrations of indicator radionuclides associated with the nuclear sector, there is clear evidence that environmental concentrations in the assessment period are close to or lower than historic levels. In OSPAR RSC sub-region 3, the statistical assessment showed evidence of an increase in environmental concentrations of H-3 in seawater between the assessment and baseline periods which probably reflects the influence of the tritium discharges from the French nuclear fuel reprocessing facility at la Hague in OSPAR RSC sub-region 2. OSPAR has recognised in previous periodic evaluations that the industrial-scale abatement of tritium in the liquid effluent of nuclear power stations and nuclear reprocessing facilities is currently not technically feasible.

Table S.2: Assessment results for H-3, Tc-99, Cs-137 and Pu-239,240 in seawater by OSPAR RSC sub-region and OSPAR Region
OSPAR Region	OSPAR RSC sub-Region	Comparison against historic levels
OSPAR Region	OSPAR RSC sub-Region	H-3	Tc-99	Cs-137	Pu-239,240
Arctic Waters (Region I)	13	-	L	L	L
	14	-	C	L	L
	15	-	C	L	C
Greater North Sea (Region II)	2	L	-	-	C
	3	H	-	-	-
	7	C	-	L	L
	8	C	-	L	C
	9	C	-	L	L
	10	L	L	L	L
	11	-	-	L	C
	12	C	-	L	-
Celtic Seas) Region III	1	C	-	-	-
	4	-	-	L	-
	5	C	L	L	-
	6	L	L	L	C
	7	C	-	L	L
Bay of Biscay and Iberian Coast (Region IV)	1	C	-	-	-

L Lower than historic levels; C Close to historic levels; H Higher than historic levels; - No statistics possible. For further information on the assessment methodology and reasons for why no statistics were possible for some reasons see the Fifth Periodic Evaluation . No data available for Region V.

Table S.3: Assessment results for Tc-99, Cs-137 and Pu-239,240 in seaweed (S), molluscs (M) and fish (F) by OSPAR RSC sub-region and OSPAR Region
OSPAR Region	OSPAR RSC sub-Region	Comparison against historic levels
		Tc-99			Cs-137			Pu-239,240
		S	M	F	S	M	F	S	M	F
Arctic Waters (Region I)	13	L	-	-	L	-	C	-	-	-
	14	L	-	-	C	-	L	-	-	-
	15	L	-	-	C	-	L	-	-	-
Greater North Sea (Region II)	2	-	-	-	L	-	C	-	L	-
	3	L	-	-	L	-	L	-	C	-
	7	L	-	-	L	-	-	-	L	-
	8	-	-	-	-	-	-	-	C	-
	9	-	-	-	-	-	L	-	-	-
	10	L	-	-	L	L	L	-	L	-
	11	L	-	-	L	-	-	-	-	-
	12	L	-	-	L	-	L	-	-	-
Celtic Seas) Region III	1	-	-	-	L	-	-	-	-	-
	4	L	L	-	L	L	-	-	L	-
	5	L	-	-	L	L	L	C	C	-
	6	L	L	L	L	L	L	L	L	C
	7	L	-	-	L	-	-	-	L	-
Bay of Biscay and Iberian Coast (Region IV)	1	-	-	-	L	-	-	-	-	-

L - Lower than historic levels; C - Close with historic levels; - No statistics possible. For further information on the assessment methodology and reasons for why no statistics were possible for some reasons see the Fifth Periodic Evaluation . No data available for Region V.

Figure S.1: Comparison of established OSPAR RSC sub-regions and the five main regions of the OSPAR maritime area. The 15 OSPAR RSC sub regions are: 1. Wider Atlantic, 2. Cap de la Hague Channel, 3. Channel East, 4. Irish Sea (Rep. of Ireland), 5. Irish Sea (Northern Ireland), 6. Irish Sea, 7. Scottish waters, 8. North Sea South (Belgian and Dutch Coast), 9. German Bight, 10. North Sea (NW, SE, and Central), 11. North Sea (Skagerrak), 12. Kattegat, 13. Norwegian Coastal Current, 14. Barents Sea and 15. Norwegian, Greenland Seas and Icelandic Waters.

The radiological impact on humans and the marine environment

OSPAR has carried out assessments to determine the radiological impact of mean values of environmental concentrations of indicator radionuclides for the nuclear sector (H-3, Tc-99, Cs-137 and Pu-239,240) in seawater in the assessment period. In all cases except one the annual doses from the indicator radionuclides would be below the environmental reference levels and the trivial annual dose of 10 µSv. This would not result in a significant radiological impact on humans or the marine environment. This includes the situation in OSPAR RSC sub-region 3 where there was evidence of an increase in environmental concentrations of H-3 in seawater between the assessment and baseline periods. The impact of the environmental concentration of H-3 in the OSPAR Maritime Area is far lower than the trivial dose. The one case where the OSPAR methodology did not conclude that the impact was trivial, was for Pu-239,240 in seawater in OSPAR RSC sub-region 6. However, more focused assessments by the United Kingdom showed that the annual doses to the public from plutonium isotopes in seawater in OSPAR RSC sub-region 6 are approximately 10 µSv and that the maximum dose to the worst affected marine organism (phytoplankton) was approximately 25% of the reference dose value for phytoplankton used in the Fifth Periodic Evaluation. These assessments confirmed that the radiological impacts resulting from Pu-239,240 in seawater in OSPAR RSC sub-region 6 are very low. OSPAR has also carried out assessments to determine the radiological impact of modelled additional concentrations of indicator radionuclides for produced water from the oil and gas sub-sector over the wider OSPAR Maritime Area. In all cases the annual doses from the additional concentrations of these indicator radionuclides in seawater would be below the environmental reference levels and the trivial annual dose of 10 µSv. Again, this would not result in a significant radiological impact on humans or the marine environment.

Table S.4: Statement on confidence assessment for conclusions on the state for environmental concentrations of radioactive substances and radiological impact⁵

Confidence	Arctic Waters (Region I)	Greater North Sea (Region II)	Celtic Seas (Region III)	Bay of Biscay and Iberian Coast (Region IV)	Wider Atlantic (Region V)
Environmental concentrations	Very high	Very high	Very high	Very high	Very high
Radiological impact⁶	High	High	High	High	High

⁵ - Confidence assessments are based on intensity and trends since the QSR 2010 (see summary table) as these are based on environmental concentration data reported by Contracting Parties and assessments carried out by OSPAR in the Fifth Periodic Evaluation. Conclusions made by OSPAR as to whether environmental concentrations are close to (or lower than) historic levels are based on the statistical significance of the assessment methodology.
⁶ - Although OSPAR concludes that in all cases except one the annual doses from the indicator radionuclides would not result in a significant radiological impact on humans or the marine environment, OSPAR recognises that the conclusions are based only on a select number of radionuclides and therefore assigns a confidence assessment of high to these conclusions.

Pressures

Impact