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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

BAF values are not constant across arsenic concentrations in fresh- and saltwater. BAF values from these studies ranged from 2 to 19,000 and appear to be the highest within the range of ambient arsenic concentrations and decline to relatively low values as arsenic water concentrations increase. The median of freshwater BAF values assuming a log-normal distribution is 270 L/kg wet weight (n=91), and this value was selected for the chemical safety assessment. 

Key value for chemical safety assessment

BCF (aquatic species):
270 L/kg ww

Additional information

Summary

Arsenic bioaccumulation depends on various factors, such as environmental setting (marine, estuarine, freshwater), organism type (fish, invertebrate), trophic status within the aquatic food chain, exposure concentrations, and route of uptake. Biomagnification in aquatic food chains does not appear to be significant. Bioconcentration of arsenic occurs in aquatic organisms, primarily in algae and lower invertebrates. An extensive study of the factors affecting bioaccumulation of arsenic in lotic systems found no evidence of biomagnification since arsenic concentrations in organisms tend to decrease with increasing tropic level. Arsenic is mainly accumulated in the exoskeleton of invertebrates and in the livers of fish. No differences were found in the arsenic levels in different species of fish, which included herbivorous, insectivorous, and carnivorous species. The major bioaccumulation transfer is between water and algae, at the base of the food chain and this has a strong impact on the concentration in fish. No differences were found between bottom-feeders and predators in tissue levels of arsenic. BAF values appear to be the highest within the range of ambient arsenic concentrations, and decline steeply to relatively low levels as arsenic concentrations in water increase (according to ATSDR, 2007 and WHO, 2001).

Water:

BAF values are not constant across arsenic concentrations in fresh- and saltwater. BAF values from these studies ranged from 2 to 19,000 and appear to be the highest within the range of ambient arsenic concentrations and decline to relatively low values as arsenic water concentrations increase. Regardless, all BAF values were analysed together in a weight-of-evidence approach for fresh- and saltwater, respectively. The median of freshwater BAF values assuming a log-normal distribution is 270 L/kg wet weight (n=91), and this value was selected for the chemical safety assessment. The median of saltwater BAF values assuming a log-normal distribution is 5866 L/kg wet weight (n=4), and this value was considered for the chemical safety assessment. Biomagnification of arsenic in aquatic food chains does not appear to be significant. On the contrary, the highest BAF values were measured at the lower trophic levels (Tyler et al., 2003).

Sediment:

55 field-measured bioaccumulation data points (BSAFs) were summarised (Anonymous, 1998). The median BSAF value on a dry weight basis for invertebrates was 0.143, indicating that invertebrates in most of the assessed studies did not accumulate arsenic to levels greater than those measured in the associated sediments.The overall median of freshwater BSAF values based on a log-normal distribution is 0.143 dry weight (n=55) and was considered for the chemical safety assessment.