Aluminium nitride

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in sediment species: invertebrate

Data waiving:

exposure considerations

Justification for data waiving:

other:

Reference 2

Endpoint:

bioaccumulation in aquatic species, other

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

TOC:

Not reported

Type:

BCF

Value:

>= 65.2 - <= 84.8 L/kg

Basis:

whole body w.w.

Remarks:

snail

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:500 µg/L

Type:

BMF

Value:

>= 0.03 - <= 0.06 dimensionless

Basis:

other: total dw without gill

Calculation basis:

steady state

Remarks on result:

other: Relatively high Al concentrations in gill tissue were probably related to residues from collection sites and particulate food in the water column. Thus gill tissues were not considered for BMF calculations.

Details on results:

1. Al accumulation in L. stagnalis (after 30 d exposure)
- Mean Al concentrations of Al in whole snail soft tissues:
* Group 1 (control): 3.0 ± 1.8 µg/g
* Group 2 (Al): 32.6 ± 4.7 µg/g wet weight
* Group 3 (Al + P): 42.4 ± 8.9 µg/g
* Concentrations were all significantly different from each other.
- Corresponding dry-weight Al concentrations:
* Group 1: 8.2 ± 4.0 µg/g
* Group 2: 206 ± 66.3 µg/g
* Group 3: 291 ± 67.2 µg/g
* Concentrations were all significantly different from each other.
- Tissue concentrations obtained in this test are considered as environmentally realistic

2. Subcellular distribution of Al in L. stagnalis
- 96 ± 6 % recovery of Al from the fractions when compared to the total homogenate
- Partitioning of Al followed the pattern: debris > granules/inorganic material > organelles > heat stable proteins > heat denatured proteins in Al-alone exposed snails, and debris > granules/inorganic material > heat stable proteins > organelles > heat denatured proteins in Al + P-exposed snails
- Highest Al concentration was found in the inorganic (granule) fraction
- A significantly higher proportion of the Al in the Al + P fed snails was found in the granule and heat stable protein fractions together when compared to those in the snails fed on Al alone (39 % vs 26 %);
- Al and P in the water column are likely to interact rapidly and form small but highly stable aluminophosphate species. These would be internalised by the snails – possibly by pinocytosis – in a form that was therefore already non-toxic and then immediately localised to the inorganic granule fraction (considered to be .trophically unavailable)
- A significantly higher proportion of the Al was found in this fraction in the Al + P group compared to the Al-alone group (30 % vs 21 %).

3. Crayfish feeding
- The total amount of Al in the snail tissue given to each crayfish was significantly higher for the Al + P group (mean 255 ± 10 µg vs 205 ± 7 µg Al per crayfish) as was the amount of trophically available Al (187 ± 11 µg and 161 ± 16 µg respectively).
-> This was calculated from the total Al available less the trophically unavailable proportion of Al (i.e. Al in the inorganic granules) derived from the fractionation data.
- The amount of Al that was not consumed was estimated from analysis of the uneaten snail remnants. Crayfish ingested on average 189 ± 13 µg Al per crayfish in the Al-alone group — significantly less than the 216 ± 11 µg Al ingested by the Al + P group, over the course of the experiment. However, the amount of Al consumed that was predicted to be trophically available averaged 149 ± 5 µg per crayfish in the Al-alone group, and 152 ± 8 µg in the Al + P group; these values were not significantly different.

4. Accumulation in crayfish
A) Crayfish fed on control snails:
- Total amounts of Al in crayfish fed on control snails did not differ between the start and end of the experiment: mean 4.8 ± 1.8 µg and 4.8 ± 2.1 µg Al per crayfish
- Gills contained higher concentrations of Al than other tissues (mean 30 ± 12 µg/g and 44 ± 2.7 µg/g dry weight at the start and end of experiment respectively; not significantly different)
> These levels are approximately 40 times lower than concentrations of Al accumulated in crayfish gills when exposed to 500 µg/L Al in the water, so it appears likely that the crayfish came from a minimally polluted site
- Mean total concentration of Al in control crayfish tissues was 12.0 ± 2.5 µg/g (dry weight) per crayfish;
- Mean total Al concentration after subtraction of Al related to gill tissue: 2.4 ± 0.6 µg/g

B) Crayfish fed on Al snails (group 2):
- Mean total concentration of Al in control crayfish tissues was 25.4 ± 10.6 µg/g (dry weight) per crayfish
- Mean total Al concentration after subtraction of Al related to gill tissue: 11.6 ± 5.2 µg/g

C) Crayfish fed on Al+P snails (group 3):
- Mean total concentration of Al in control crayfish tissues was 9.9 ± 5.3 µg/g (dry weight) per crayfish

Comment:
- It is possible that particulate food in the water column could have contributed to Al on the gill surface in the exposed groups, and this, coupled with the high control levels, would suggest that a large proportion of Al associated with the gills was likely to be on the external tissue surface.
- total Al concentrations in remaining tissues (without gill tissues) of crayfish fed on group 2 and 3 snails were significantly higher than in the control group, but not significantly different from each other

5. Crayfish behaviour
There were no significant differences in the behavioural scores of crayfish from different experimental groups at any time point during the experiment.

Reported statistics:

Statistical analyses were carried out using SPSS for Windows (IBM, US) and Prism (GraphPad Software Inc., USA). Due to the small sample sizes, data were analysed using Mann–Whitney U-tests with significance defined as p < 0.05. Multiple comparisons were carried out using a Kruskall–Wallis test followed by Mann–Whitney U with Hochberg's (1988) modified Bonferroni correction procedure to adjust for multiple comparisons. Percentage data was arc-sin transformed prior to analysis. Nominal alpha was set to 0.05. 95 % confidence limits were calculated from the range of values from which means were calculated.

1. Assimilation efficiency of Al by P. lenisculus

There was no significant difference in the total amount of Al accumulated per crayfish when comparing the Al to Al + P fed groups (44 ± 16 µg and 30 ± 9 µg Al per crayfish respectively, minus control values). When gill was discounted, calculated accumulation was 25.0 ± 8.1 µg Al and 24.1 ± 74 µg Al respectively, with the majority in the hepatopancreas. This gave an assimilation efficiency of 13 % of the total ingested Al for the Al-alone fed group, 11 % for the Al + P fed group, and 17 % and 16 % of the trophically available Al ingested.

2. Al in the crayfish faeces

The total amount of Al excreted in faeces by each crayfish was significantly higher in the group fed Al + P snails than those fed Al-alone snails (mean 20.1 ± 4.6 µg and 13.0 ± 3.1 µg respectively). This value is for the entire experiment; Al concentrations in the faeces varied greatly during the experiment depending on the quantity of snail recently consumed by individual crayfish. Control concentrations were significantly lower than for crayfish in both exposed groups when total excretion over the time course of the experiment was considered (controls: 120 ± 25 µg/g dry weight; Al alone: 3580 ± 1340 µg/g; Al + P: 5670 ± 2576 µg/g). Concentrations in the two Al-exposed groups were not significantly different from each other.

3. Al in the crayfish tanks

Water sampled from tanks containing crayfish fed control snails contained, on average, 4.3 µg/L Al. Al concentrations in tanks containing crayfish fed Al-exposed snails varied considerably between time points, but averaged 6.7 µg/L for the Al-alone fed group and 5.7 µg/L for the Al + P fed group. From this it is estimated that 97 µg Al leached or was excreted into the water by each Al-alone

crayfish over the time course of the experiment, and 77 µg Al from the Al + P fed crayfish (all less control values). These amounts are

not significantly different from each other. Al in the uneaten snail tissues was 195 µg/g and 268 µg/g (per unit dry weight) in the Al-alone and Al + P snails respectively. These values are only very slightly lower than the concentrations of Al measured in snail tissues prior to feeding and so leaching of Al from the snail tissues into the water appears to have been minimal. However, the water measurements could have included Al associated with some faecal matter that was too small to collect for analysis.

4. Accounting for the Al

When the Al in water, uneaten snail tissues, and crayfish tissues (all less control values), were combined, 80 % of the Al available to

the crayfish through feeding could be accounted for. The remaining 20 % is likely to have been in tissues such as the nervous system, tissue that could not be separated from the carapace, and the haemolymph which were not analysed. Small pieces of faeces that were impracticable to collect would also contain Al. Of the 80 % of the Al that was accounted for, 23 % and 17 % were found in

the crayfish soft tissues, and 62 % and 48 % in the water column, of the Al-alone group and the Al + P group respectively. The

proportions of Al in the soft tissues and water did not differ from each other between these two experimental groups. However, the

proportion of total Al in the faeces was significantly higher in the Al + P fed group than in the Al-alone fed group (32 % vs 15 %). In the Al-alone fed group, the proportion of Al in the water was also significantly higher than that in the faeces; this ratio was not different

for the Al + P group. In both groups significantly higher proportions of total Al were found in the water than in the soft tissues.

Since approximately 20 % of the total Al was not accounted for at the end of the experiment, the assimilation efficiency of Al by P.

lenisculus may well be higher than the estimated 17 %

Validity criteria fulfilled:

not applicable

Conclusions:

BCF values in the freshwater snail Lymnaea stagnalis exposed to aqueous Al concentrations of 500 µg/L ranged between 65.2 L/kg and 84.8 L/kg.
BMF values in crayfish fed with snails prevoiusly exposed to Al (500 µg/L) ranged between 0.03 and 0.06. Thus the bioaccumulation potential of Al ions is considered to be low.

Executive summary:

In order to investigate the potential for trophic transfer of aluminium (Al), the freshwater snail Lymnaea stagnalis and the predator signal crayfish Pacifastacus leniusculus were used in a bioaccumulation study. Snails were exposed to aqueous Al concentrations of 500 µg/L either in the presence or absence of an inorganic ligand (phosphate (+P); 500 µg/L) for 30 days, or kept as unexposed controls.

Subsequently, exposed and control snails were fed to individually housed crayfish (n = 6 per group) over 40 days. Water samples, uneaten snail tissue and faeces were collected throughout the experiment in order to assess the fate of Al. Behavioural toxicity to the crayfish was assessed at four time points, and tissue accumulation of Al in soft tissues was measured following a 2-day depuration period.

The BCF value for snails exposed to Al + P was 84.4 L/kg vs 65.2 L/kg in the case of Al only exposure.

Crayfish fed snails exposed to only Al or Al+P did not accumulate aluminium. By contrast, aluminium concentrations in crayfish were significantly lower than intheir food under both expposure regimes (BMF = 0.06 and 0.03 for Al and Al+P exposure, respectively).

Relatively high Al concentrations could be measured in gill tissue of crayfish and were probably related to residues from collection sites and particulate food in the water column. Thus, gill tissues were not considered for BMF calculations.

There were no significant differences in behavioural activity between the different groups of crayfish at any time point. Overall, it can be concluded that the bioaccumulation and biomagnification potential of Al ions is low.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Description of key information

According to Annex IX section 9.3.2, column 2 of the REACH Regulation this study does not need to be conducted if the substance has a low potential for bioaccumulation. This endpoint has been waived for ammonia.
Furthermore, BCF values for aluminium were determined in the freshwater snail Lymnaea stagnalis exposed to aqueous Al concentrations of 500 µg/L. BCF was found to range between 65.2 L/kg and 84.8 L/kg.
BMF values in crayfish fed with snails previously exposed to Al (500 µg/L) range between 0.03 and 0.06. Thus the bioaccumulation potential of Al ions is considered to be low.

Additional information

The existing information on aluminium shows the absence of aluminium biomagnification across trophic levels both in aquatic and terrestrial food chains. The existing information suggests not only that aluminium does not biomaginfy, but rather that it tends to exhibit biodilution at higher trophic levels in the food chain.

Ammonia is a naturally-occurring compound and a key intermediate in the nitrogen cycle. Since it is continually recycled in the environment, bioaccumulation is irrelevant.