302
11.6.3 Bioaccumulation
Bioaccumulation occurs if exposure takes place through contaminated food along
with ambient sources and bioaccumulation endpoint (bioaccumulation factor, BAF)
is defined as the ratio of the concentration of the substance or chemical in an organism (specific genus) (chemical mass per kg biomass) to the exposure concentration
in water (chemical mass per L) (Hou et al. 2013). However, in case of exposure to
soil or a benthic environment, the bioaccumulation endpoint is typically characterized by the ratio of chemical concentration in an organism to that in the sediment
and termed as biota-sediment accumulation factor (BSAF). As per the USEPA
Toxic Substances Control Act (TSCA), bioaccumulative substances have log BCF
values in the range 3–3.7 and those with log BCF values ≥3.7 are considered very
bioaccumulative substances. It has been shown that the bioaccumulation potential
of nanoparticles to fish through oral route or food exposure is relatively low. In case
of earthworms, several reports have revealed that the bioaccumulation potential of
metal oxide or metallic nanoparticles.
11.6.4 Biomagnification
Biomagnification is the accumulation of a toxicant or chemical or pollutant by an
organism due to water and food intake and it results in a concentration higher than that
would have achieved from water contact alone and thus higher than expected from
equilibrium (Hou et al. 2013). The biomagnification end point, the biomagnification
factor (BMF), is the extent to which the concentration increases from one trophic level
to next higher level. More precisely, BMFs are expressed as the ratio of the fugacity
of a chemical entity in the predator to that in the prey, rather than as an expression of
concentrations as discussed just above. In general, a BMF >1 signifies that biomagnification exists in a given food web. The comparatively greater bioaccumulation and
partial depuration of engineered nanomaterials in lower trophic level organisms like
daphnid results into the chance for trophic transfer and biomagnification through the
food chain. Werlin et al. (2011) reported that CdSe QD titer in ciliated protozoa
(Tetrahymena thermophila) is ~5 times higher than that in the bacteria (Pseudomonas
aeruginosa), demonstrating that biomagnification occurs (Werlin et al. 2011). In contrast, due to the lack of QD internalization into bacterial cells, Holbrook et al. (2008)
failed to observe trophic transfer from bacteria (Escherichia coli) to ciliates
(Tetrahymena thermophila)-rotifers (Brachionus calyciflorus) (Holbrook et al. 2008).
The difference would imply that uptake of QDs by bacteria is dependent on microbial
isolates and/or QD exterior functionalization. In the absence of bacteria, QDs could be
uptaken by ciliates and trophic transferred to the predator, rotifers. However, the body
burden in rotifers is less than that in ciliates (BMF = 0.29–0.62), implying no biomagnification. Trophic transfer has also been observed in many high trophic level aquatic
food webs, including QDs and Ag NPs transfer from algae to daphnia, QDs or nTiO 2
transfer from daphnia to fish, clamworm to juvenile turbot.
D. Kundu et al.
11.6.3 Bioaccumulation
Bioaccumulation occurs if exposure takes place through contaminated food along
with ambient sources and bioaccumulation endpoint (bioaccumulation factor, BAF)
is defined as the ratio of the concentration of the substance or chemical in an organism (specific genus) (chemical mass per kg biomass) to the exposure concentration
in water (chemical mass per L) (Hou et al. 2013). However, in case of exposure to
soil or a benthic environment, the bioaccumulation endpoint is typically characterized by the ratio of chemical concentration in an organism to that in the sediment
and termed as biota-sediment accumulation factor (BSAF). As per the USEPA
Toxic Substances Control Act (TSCA), bioaccumulative substances have log BCF
values in the range 3–3.7 and those with log BCF values ≥3.7 are considered very
bioaccumulative substances. It has been shown that the bioaccumulation potential
of nanoparticles to fish through oral route or food exposure is relatively low. In case
of earthworms, several reports have revealed that the bioaccumulation potential of
metal oxide or metallic nanoparticles.
11.6.4 Biomagnification
Biomagnification is the accumulation of a toxicant or chemical or pollutant by an
organism due to water and food intake and it results in a concentration higher than that
would have achieved from water contact alone and thus higher than expected from
equilibrium (Hou et al. 2013). The biomagnification end point, the biomagnification
factor (BMF), is the extent to which the concentration increases from one trophic level
to next higher level. More precisely, BMFs are expressed as the ratio of the fugacity
of a chemical entity in the predator to that in the prey, rather than as an expression of
concentrations as discussed just above. In general, a BMF >1 signifies that biomagnification exists in a given food web. The comparatively greater bioaccumulation and
partial depuration of engineered nanomaterials in lower trophic level organisms like
daphnid results into the chance for trophic transfer and biomagnification through the
food chain. Werlin et al. (2011) reported that CdSe QD titer in ciliated protozoa
(Tetrahymena thermophila) is ~5 times higher than that in the bacteria (Pseudomonas
aeruginosa), demonstrating that biomagnification occurs (Werlin et al. 2011). In contrast, due to the lack of QD internalization into bacterial cells, Holbrook et al. (2008)
failed to observe trophic transfer from bacteria (Escherichia coli) to ciliates
(Tetrahymena thermophila)-rotifers (Brachionus calyciflorus) (Holbrook et al. 2008).
The difference would imply that uptake of QDs by bacteria is dependent on microbial
isolates and/or QD exterior functionalization. In the absence of bacteria, QDs could be
uptaken by ciliates and trophic transferred to the predator, rotifers. However, the body
burden in rotifers is less than that in ciliates (BMF = 0.29–0.62), implying no biomagnification. Trophic transfer has also been observed in many high trophic level aquatic
food webs, including QDs and Ag NPs transfer from algae to daphnia, QDs or nTiO 2
transfer from daphnia to fish, clamworm to juvenile turbot.
D. Kundu et al.