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Environmental fate & pathways

Bioaccumulation: terrestrial

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bioaccumulation: terrestrial
Type of information:
experimental study
Adequacy of study:
weight of evidence
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference Type:
Contamination of terrestrial gastropods, Helix aspersa maxima, with 137Cs, 85Sr, 133Ba and 123mTe by direct, trophic and combined pathways
Madoz-Escande C, Simon O
Bibliographic source:
Journal of Environmental Radioactivity 89, 30-47

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
No standard guideline is applicable for this type of research work
GLP compliance:
no guideline study, but it is expected that GLP-principles were respected

Test material

Details on test material:
Radio-labeled Te

Results and discussion

Bioconcentration factor
Key result
Remarks on result:
other: no fixed BCF-value can be determined for Te; data are used in a weight of evidence approach

Applicant's summary and conclusion

Gastropods were contaminated by radioactive aerosols which were assumed to be representative of those that would be released during a nuclear accident occurring in a PWR, includsing Tellurium. The radionuclides were mixed and associated with stable elements. Three contamination pathwayswere studied: the direct pathway (direct deposition of radioactive aerosols), the trophic pathway (ingestion of flour contaminated by the same aerosols) and a combined exposure (deposition of aerosols followed by ingestion of contaminated flour). The contamination period was followed by a depuration period (ingestion of uncontaminated flour).
During the observation period, there was no significant difference in the growth or in the mortality of the samples betweenthe 3 groups of contaminated snails and the reference group. Following a contamination by the radionuclides, the distribution through the total body of snails depends on the radionuclides and on the exposure pathway. The target tissues for tellurium was: the shell for a direct exposure and the soft tissues for a trophic pathway (digestive system).
The bioaccumulation factors calculated after 21 days of contaminated food ingestion that are found in the shell and musche was 0.003.

At the end of the depuration period (21 days), the cumulated faeces reduced tellurium by about 30% (combined pathway) to 80% (trophic pathway). However, the retention coefficient (calculated as being the relationship between specific activity in an organ on a date of depuration and that corresponding to the end of the period of exposure) remains high, even after 21 days of depuration.
Executive summary:

137Cs, 85Sr, 133Ba and 123mTe contaminations of terrestrial gastropods, Helix aspersa maxima, by direct deposition, labelled food ingestion or combined (trophic and direct pathways) exposure were carried out under laboratory conditions. The aim of this study was to compare the three contamination pathways: direct, trophic and combined, in terms of individual mortality, radionuclide uptake, depuration and distribution in the tissues.

An initial group of 30 snails (2 years old) was exposed to radioactive aerosols during a 20h period. These aerosols were assumed to be representative of those that would be released during a nuclear accident occurring in a PWR. A second group of 50 snails (same age) was submitted to an ingestion of commercial food contaminated by the same aerosols, twice a week for 21 days (flour at a feeding rate of about 0.2 g). A third group of 40 snails was submitted to a combined exposure: exposure to radioactive aerosols (20 h), followed by ingestion of flour contaminated by the same aerosols, twice a week for 21 days. No significant difference between the three groups and a reference group of 10 snails was observed, neither in growth nor in mortality. Concerning the direct pathway, at the end of direct deposition (about 1 day after the beginning), cesium was the most bioavailable element, distributed rather homogeneously throughout the whole body (13% of the total Cs in all organs excepting the digestive system and 28% in the muscle). Tellurium was mainly present in the shell (70%) and in the digestive system (20%). After 21 days of depuration, the faeces eliminated 42% of the Te. As for contamination by ingestion, Te mainly accumulated in the digestive system (72% of Te present in the total body). Concerning contamination by combined pathways, at the end of the 21-day exposure, the 4 radionuclides had the same tendency as direct deposition. However, the effect of the trophic pathway was significant: it causes an 18% increase of Sr in the shell and an 7% in- crease of Cs in the digestive system in comparison to direct deposition, resulting in a final 86% in the shell and 27% in the digestive system.