297
11.5.4 Effect of Composition and Crystalline Structure
Toxicity is also influenced by the composition and crystalline structure of nanoparticles. It has been observed that soluble forms of silver and copper nanoparticles
triggered toxicity in various tested organisms like zebrafish, daphnids, and algal
species, whereas TiO 2 of the same dimensions did not cause any toxicity. Thus,
compositions of NPs are integral in determining the toxicities (Griffitt et al. 2008).
Regarding crystal structure, it has been observed that rutile TiO 2 nanoparticles
induce lipid peroxidation, oxidative DNA damage, and micronuclei formation in the
absence of light when compared to the anatase nanoparticles having similar size and
chemical composition (Gurr et al. 2005).
11.5.5 Effect of Aggregation and Concentration
Aggregation and concentration can be regarded as the final aspects regarding the
toxicity of nanomaterials. Among others, the aggregation of ENPs is mainly dependent on the size, surface charge, and composition. Thus, carbon nanotubes induce
cytotoxic effects due to accumulation of aggregates for long span of time (Yang
et al. 2008). Further, the pulmonary interstitial fibrosis is enhanced by agglomerated
carbon nanotubes than well-dispersed carbon nanotubes (Wick et al. 2007).
Regarding the effect of concentration, generally, increase in the nanoparticles concentration leads to decrease in toxicity at higher concentration (Gatoo et al. 2014).
Santos et al. (2010) reported that the nontoxic threshold concentration for thermally
hydrocarbonized and carbonized porous silicon particles was toxic at 2 mg mL
−1
,
whereas for thermally oxidized porous silicon particles, it was 4 mg mL
−1
(Santos
et al. 2010).
11.6 Ecological Accumulation of Engineered Nanoparticles
There are predominantly three aspects that need to be taken care of while evaluating
the impact of engineered nanomaterials in the environmental matrix: (i) their mobility (movement along with transfer) from one place to another or from one recipient
to another (for example, from soil to drinking water or food plants), (ii) the possible
ecotoxicity to living organisms in aqueous environment, sediments and soils that
they likely come into contact, and (iii) to what extent engineered nanomaterials are
altered once they are exposed in the environment along with the mechanism behind
it. Organisms undergo several routes of exposure to pollutants leading to their
uptake. Some of the relevant routes and endpoints are bioavailability, bioconcentration, bioaccumulation, and biomagnification. Table 11.2 enlists some existing and
representative biological accumulation studies of synthesized engineered
nanomaterials using most commonly used organisms and ecologically relevant contact conditions.
11 Environmental Impact and Econanotoxicity of Engineered Nanomaterials
11.5.4 Effect of Composition and Crystalline Structure
Toxicity is also influenced by the composition and crystalline structure of nanoparticles. It has been observed that soluble forms of silver and copper nanoparticles
triggered toxicity in various tested organisms like zebrafish, daphnids, and algal
species, whereas TiO 2 of the same dimensions did not cause any toxicity. Thus,
compositions of NPs are integral in determining the toxicities (Griffitt et al. 2008).
Regarding crystal structure, it has been observed that rutile TiO 2 nanoparticles
induce lipid peroxidation, oxidative DNA damage, and micronuclei formation in the
absence of light when compared to the anatase nanoparticles having similar size and
chemical composition (Gurr et al. 2005).
11.5.5 Effect of Aggregation and Concentration
Aggregation and concentration can be regarded as the final aspects regarding the
toxicity of nanomaterials. Among others, the aggregation of ENPs is mainly dependent on the size, surface charge, and composition. Thus, carbon nanotubes induce
cytotoxic effects due to accumulation of aggregates for long span of time (Yang
et al. 2008). Further, the pulmonary interstitial fibrosis is enhanced by agglomerated
carbon nanotubes than well-dispersed carbon nanotubes (Wick et al. 2007).
Regarding the effect of concentration, generally, increase in the nanoparticles concentration leads to decrease in toxicity at higher concentration (Gatoo et al. 2014).
Santos et al. (2010) reported that the nontoxic threshold concentration for thermally
hydrocarbonized and carbonized porous silicon particles was toxic at 2 mg mL
−1
,
whereas for thermally oxidized porous silicon particles, it was 4 mg mL
−1
(Santos
et al. 2010).
11.6 Ecological Accumulation of Engineered Nanoparticles
There are predominantly three aspects that need to be taken care of while evaluating
the impact of engineered nanomaterials in the environmental matrix: (i) their mobility (movement along with transfer) from one place to another or from one recipient
to another (for example, from soil to drinking water or food plants), (ii) the possible
ecotoxicity to living organisms in aqueous environment, sediments and soils that
they likely come into contact, and (iii) to what extent engineered nanomaterials are
altered once they are exposed in the environment along with the mechanism behind
it. Organisms undergo several routes of exposure to pollutants leading to their
uptake. Some of the relevant routes and endpoints are bioavailability, bioconcentration, bioaccumulation, and biomagnification. Table 11.2 enlists some existing and
representative biological accumulation studies of synthesized engineered
nanomaterials using most commonly used organisms and ecologically relevant contact conditions.
11 Environmental Impact and Econanotoxicity of Engineered Nanomaterials