such as amino acids, nucleic acids, vitamins, fatty acids, and phosphoric acid,
leading to physiological dysfunction of the body and eventually causing lesions
(Shi 2013). Different forms of danger are posed by HMs by its reactivity in plants,
animals, humans, and ecosystems. All need micronutrients such as copper and zinc
in small quantities, but their excess leads to poisoning; exposure to even smaller
quantities of As, Hg, Pb, and Cd may cause lethal toxicities as these metals are not
required by biosystems. Cadmium is one of the most toxic and mobile HM elements,
which ensures its availability for plants under acidic pH ranges (Felix-Henningsen
et al. 2010). It is considered that cadmium can lead to damage of the kidney and even
death if the intake is too great at one time. Zinc, with characteristics similar to
cadmium, can also contribute to acute gastrointestinal and respiratory problems
(Anderson et al. 2005). Lead, known to cause severe cognitive dysfunction, neurological damage, behavioral disorders, renal impairment, and also hypertension in
humans, can remain in soil and bioavailable for thousands of years because of its
stable nature (McLaughlin 2002; Flora et al. 2012).
(i) Lead
Lead (Pb) is ubiquitous by nature but is an element considered to be not
biologically useful because the facile interference of Pb
2+ with several biological
enzymes can be toxic. Its toxicity thus poses severe health issues in many body
functions such as reproduction and by causing muscular, neural, gastrointestinal,
genetic, and even behavioral changes. It also threatens the environment by its
unknown fate.
(ii) Cadmium
Cadmium is a metal well known to be carcinogenic, inducing mutations in
humans. It influences the metabolism of calcium by altering its availability, causing
problems associated with kidney functions such as hypercalciuria and kidney failure;
it also alters the blood hemoglobin level, resulting in anemia and other related
problems (Awofolu 2005).
(iii) Chromium
Complications of anosmia and alopecia are caused by exposure to chromium
(Salem et al. 2000).
(iv) Zinc
Zinc is an essential element for organisms, but fatigue and even dizziness can be
caused by exposure to a high concentration (Hess and Schmid 2002).
(v) Copper
Many of the metabolic enzymes require copper for activation; thus, copper is
considered to be a vital metal for many living organisms. Although vital, when its
limit is exceeded, impairment in the functioning of brain and kidneys results; this is
also associated with blood hemoglobin level. It can even disturb the digestive
function by causing severe intestinal irritation (Salem et al. 2000).
4 Recent Advances in Phytoremediation of Toxic Metals from Contaminated. . .
87
leading to physiological dysfunction of the body and eventually causing lesions
(Shi 2013). Different forms of danger are posed by HMs by its reactivity in plants,
animals, humans, and ecosystems. All need micronutrients such as copper and zinc
in small quantities, but their excess leads to poisoning; exposure to even smaller
quantities of As, Hg, Pb, and Cd may cause lethal toxicities as these metals are not
required by biosystems. Cadmium is one of the most toxic and mobile HM elements,
which ensures its availability for plants under acidic pH ranges (Felix-Henningsen
et al. 2010). It is considered that cadmium can lead to damage of the kidney and even
death if the intake is too great at one time. Zinc, with characteristics similar to
cadmium, can also contribute to acute gastrointestinal and respiratory problems
(Anderson et al. 2005). Lead, known to cause severe cognitive dysfunction, neurological damage, behavioral disorders, renal impairment, and also hypertension in
humans, can remain in soil and bioavailable for thousands of years because of its
stable nature (McLaughlin 2002; Flora et al. 2012).
(i) Lead
Lead (Pb) is ubiquitous by nature but is an element considered to be not
biologically useful because the facile interference of Pb
2+ with several biological
enzymes can be toxic. Its toxicity thus poses severe health issues in many body
functions such as reproduction and by causing muscular, neural, gastrointestinal,
genetic, and even behavioral changes. It also threatens the environment by its
unknown fate.
(ii) Cadmium
Cadmium is a metal well known to be carcinogenic, inducing mutations in
humans. It influences the metabolism of calcium by altering its availability, causing
problems associated with kidney functions such as hypercalciuria and kidney failure;
it also alters the blood hemoglobin level, resulting in anemia and other related
problems (Awofolu 2005).
(iii) Chromium
Complications of anosmia and alopecia are caused by exposure to chromium
(Salem et al. 2000).
(iv) Zinc
Zinc is an essential element for organisms, but fatigue and even dizziness can be
caused by exposure to a high concentration (Hess and Schmid 2002).
(v) Copper
Many of the metabolic enzymes require copper for activation; thus, copper is
considered to be a vital metal for many living organisms. Although vital, when its
limit is exceeded, impairment in the functioning of brain and kidneys results; this is
also associated with blood hemoglobin level. It can even disturb the digestive
function by causing severe intestinal irritation (Salem et al. 2000).
4 Recent Advances in Phytoremediation of Toxic Metals from Contaminated. . .
87