Hafnium [Hf, 72]
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19.5 PLANTS
The common range of Hf in plants is 0.01–0.4 mg/kg. Although Hf is slightly available to plants, plants growing in soils amended with sewage sludge contain elevated
amount of Hf, up to, on an average, 3 mg/kg. This may suggest its higher uptake, or
impact of soil dust with its higher concentration. Hafnium uptake from aerial sources
may also explain its higher amounts, up to 11 mg/kg, in spruce bark (Reimann and
de Caritat 1998).
Hafnium has no known metabolic role in plants, and has a very limited ability to
travel up with the food chain. This is the reason why Hf concentrations for most food
samples were below the detection limit. The highest levels of Hf were observed in red
kidney beans, 0.006 mg/kg (Howe et al. 2005). According to Szefer and Grembecka
(2007), Hf occurs in plant food in low levels, from 0.00001 to 0.01 mg/kg FW, in
vegetables and vines, respectively.
Mean contents of Hf in cereal grains range from 0.04 to 0.06 mg/kg, in wheat and
barley, respectively (Eriksson 2001a).
19.6 HUMANS
Hafnium does not normally cause any health problems; nevertheless, all its compounds should be regarded as toxic, although it has no known toxicity. No signs and
symptoms of chronic exposure to Hf have been reported in humans.
The metal dust presents a fire and explosion hazard. It is completely insoluble in
water, saline solutions, and body chemicals. Exposure to Hf can occur through inhalation, ingestion, and eye or skin contacts. Overexposure to Hf and its compounds
may cause mild irritation of the eyes, the skin, and mucous membranes.
Hafnium oxide nanoparticles were reported to be used in the radiotherapy, as a
promising anticancer agent for human patients (Maggiorella et al. 2012).