Environmental Engineering Reference
In-Depth Information
31.6
HaZard idEntification and risk assEssmEnt of nanoparticlEs
prior to studying the impact of nanoparticles on the environment and health, minimal characterization of the engineered
nanoparticles has to be carried out. The physicochemical properties of the nanoparticles must be understood in detail for ana-
lyzing nanoparticle-induced toxicity. As the field of nanotoxicity is emerging and the specific properties of nanoparticles influ-
encing cellular toxicity are still unclear, it is essential to completely characterize nanoparticles [61]. Nanoparticle characterization
involves knowing its chemical composition and purity; particle size and particle size distribution; shape, structure, and specific
surface morphology (crystal phase, form); surface chemistry/coating/charge/area; agglomeration or aggregation state, or par-
ticle size under experimental conditions as appropriate; stability over time; dissolution, water solubility, dosimetry, and uptake.
For assessing the effects of nanoparticles on the environment, the indication of their hazardous effects, the effect of dissolution
in water on thier toxicity, their tendency for agglomeration or sedimentation, their fate during wastewater treatment, and their
stability during incineration need to be understood. Acute toxicity, chronic toxicity, impairment of DNA, crossing and dam-
aging of tissue barriers, brain damage, and translocation and effects of engineered nanoparticles in the skin, gastrointestinal, or
respiratory tract are some of the effects that have to be studied to assess the safety of nanoparticles for human health [6].
Hazard identification and risk assessment of engineered nanoparticles can be briefly summarized as follows. The initial step
is the physicochemical characterization of the nanoparticles. it will involve nanoparticle structure alerts and their behavior in
aerosols and suspensions. This is followed by the identification of structure or composition of the nanoparticle as the main
hazard. The next step is to test the nanoparticles for the production of RoS in a cellular environment. Further, the nanoparticles
have to be tested for genotoxicity, immunotoxicity, skin toxicity, ocular, liver, and kidney toxicity under
in vitro
conditions.
After
in vitro
experiments,
in vivo
tests are carried out for immunotoxicity, organ toxicity, genotoxicity, and reproductive tox-
icity. The nanoparticles showing positive genotoxicity and mutagenicity will be analyzed for carcinogenicity and adverse
effects on reproductive behavior. The risk assessment of nanoparticles involves the evaluation of the magnitude of risk at dif-
ferent exposure levels, setting of the exposure levels, and other regulatory limits, that is, hazard identification, hazard charac-
terization, exposure assessment, and risk characterization. Based on the hazard assessment of nanoparticles, the knowledge on
experimental levels of exposure to nanoparticles and toxic effects induced by nanoparticles will be combined and used to enable
effective management and safer application of nanoparticles [62].
31.7
conclusion
The toxicological effect of nanoparticles on the ecosystem and human health has been of increasing interest. The interaction
between the highly increased reactive surfaces of nanoparticles due to the increased surface-to-volume ratio and the biotic and
abiotic components of the ecosystem constitutes the basis of nanotoxicological studies. The interaction mechanism between
nanoparticles and living organisms is not yet completely understood. Apart from the nanoparticle material, size, shape, surface,
charge, coating, dispersion, agglomeration, aggregation, concentration, and matrix, dosimetrics should also be considered for
toxicological studies. Hazard identification at the
in vivo
level with respect to entry routes and putative targets has been identi-
fied. But there are few epidemiological studies on the long-term exposure to engineered nanoparticles. Therefore, there is a
need for long-term evaluation of the risks associated with nanoparticles before their large-scale production and application for
commercial and medical purposes.
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