10
Trace Elements in Abiotic and Biotic Environments
spray, forest fires, and wind-blown dust. Sb anthropogenic emission is mainly from
fossil fuel combustion, incineration of wastes and cement kilns, and various metallurgical industries. It is often fixed by some metallic particles, such as Pb, Cd, and
Zn in aerosols and may be transported over long distances. Sb emission in the region
of Bavaria, Germany, is estimated at 6–8 kt/yr (Wegenke et al. 2005).
2.5 PLANTS
Antimony is relatively easily taken up by plants, when it is present in soluble forms,
although it is not considered to be essential to plants. In contaminated soils, Sb
often occurs in the SbS form, which is easily available to plants. The common range
in cultivated plants is between <1 and 30  μg/kg; however, in roots, it is usually
higher. Spinach grown on Sb-contaminated soil contains this metal up to 1130 μg/kg,
whereas in parsley it is below 420 μg/kg (Hammel et al. 2000). Lowest Sb content is
reported for cereals grains at 0.5–1 μg/kg (Eriksson 2001a). Methylantimony compounds may occur in plants within the range of 100–200 μg/kg.
Pot experiment with high Sb doses (1000 mg/kg) shows that Sb 3+ is more toxic
than Sb 5+ to rice plants (He and Yang 1999).
2.6 HUMANS
Sb amount in the human body (average 70 kg) is approximately 2.0 mg, in the bone,
it is between 0.01 and 0.6; in the tissue, it ranges from 0.01 to 0.21 mg/kg (Emsley
2011); and in the rib bone, it is ≤0.0096 mg/kg (Zaichik et al. 2011). Sb distribution
within the body and its excretion are a function of both the route of administration
and the valence state of Sb. After inhalation, the trivalent form, Sb 3+ , accumulates
more rapidly than the pentavalent form, Sb 5+ , in the liver, whereas pentavalent is
found preferentially in the skeleton. In the blood, the trivalent form is lodged primarily in the red blood cells, whereas the pentavalent form is carried by the plasma.
Therapeutic use of trivalent Sb against parasites leads to its higher accumulation
in the liver, the thyroid, and the heart. Antimony concentrations in breast milk in
Italian women ranged from <0.05 to 12.9 μg/kg, with a mean of 3.0 ± 0.4 μg/kg
(Health Canada 1999). Urinary Sb levels are thought to be a good indicator for the
overall Sb exposure, regardless of the source (Makris et al. 2013).
Sb toxicity is a function of the water solubility and the oxidation state in Sb species. In general, Sb 3+ is more toxic than Sb 5+ , and the inorganic compounds are more
toxic than the organic compounds, with stibin (SbH 3 ), a lipophilic gas, being most
toxic (by inhalation). Soluble Sb salts, after oral uptake, exert a strong irritating
effect on the gastrointestinal mucosa and trigger sustained vomiting. Other effects
include abdominal cramps, diarrhea, and cardiac toxicity (WHO 2003).
Antimony toxicity occurs either due to occupational exposure or during therapy.
Occupational exposure may cause respiratory irritation, pneumoconiosis, antimony spots on the skin, and gastrointestinal symptoms. As a therapeutic, Sb has
been mostly used for the treatment of leishmaniasis and schistosomiasis. The major
toxic side effects of antimonials as a result of therapy are cardiotoxicity (~9% of
patients) and pancreatitis, which is seen commonly in HIV and visceral leishmaniasis