Iron and iron oxides are natural components of the earth's crust. Iron oxides are extracted from iron ore and can then be converted to iron. Both iron and iron oxides are used in numerous applications both in nanoscale and in larger form. Therefore, there are different ways of release into the environment.

 

Print toner powder contain iron nanoparticles which can be released unintentionally © Diegofamu/ Fotolia.comPrint toner powder contain iron nanoparticles which can be released unintentionally © Diegofamu/ Fotolia.com

In the environment, it is difficult to distinguish between the natural occurrence of iron and iron oxide nanoparticles and the released nanomaterials generated by human activities. The release of the nanoparticles into air, water and soil is possible. In addition to iron oxides from the earth's crust, insoluble iron oxides also occur in natural waters, e.g. when released by ore mining activities. For example, coalmine wastewater contains many naturally occurring iron nanoparticles [1].

Iron and iron oxide nanoparticles are used in environmental technology for the remediation of groundwater pollutants After the degradation of the harmful chemicals, the nanoparticles remain in the aquifer. Due to the nanoparticles low mobility, it is assumed that they remain at the place of use (see cross cutting text – nanomaterials for environmental remediation) [2,3].

 

Due to their magnetic properties, iron oxide nanoparticles (such as magnetite) are suitable as carrier materials for catalytically active coatings in wastewater treatment. Since the iron oxide nanoparticles are firmly incorporated into the coating or can be magnetically separated from the water after the treatment, it is unlikely that they will be released into the environment [4].

Unintentional release of iron nanoparticles e.g. into the air via diesel exhaust gases or into the environment from medical applications via wastewater may occur. Iron and iron oxide nanoparticles can also be released into the air from toner dust or printing ink. This takes place mostly in closed buildings, from which, however, a part can escape into the ambient air [5].

Currently it is not possible in the environment to distinguish between technically produced iron and iron oxide nanoparticles and the materials’ natural background thereby hindering the measuring of a corresponding environmental concentration. Consequently, such environmental concentrations were calculated using different computer models including the different release scenarios (see cross cutting topics - Estimating the occurrence of nanomaterials in the environment). These estimated environmental concentrations of iron and iron oxide nanoparticles are much lower than the concentrations that can cause harmful effects in environmental organisms [6].

 

Engineered iron and iron oxide nanoparticles are released into the environment from various applications. They are difficult to distinguish from the naturally occurring particles of the material. Using computer models, iron and iron oxide nanoparticles pose only a low risk to the environment according to the current state of knowledge.

 

 

Literature arrow down

  1. Matthies, R et al.(2012), J Environ Monit, 14:1174-1181.
  2. Phenrat, T et al. (2009), Environ Sci Technol, 43(1): 195-200.
  3. Phenrat, T et al. (2007), Environ Sci Technol, 41(1): 284-290.
  4. Hildebrand, H et al. (2009), Environ Sci Technol, 43(9): 3254-3259.
  5. Liati, A et al. (2013), Environ Sci Technol, 47:14495-14501.
  6. Wang, Y et al. (2016), Nanotoxicology, 10(10):1743-5404.

 

 

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