1 Introduction
Industrial wastewaters are considered as the major sources of heavy metal pollution in
the environment (Goutam et al. 2018; Bharagava et al. 2017a, b, c; Gautam et al. 2017;
Saxena and Bharagava 2015). Contamination of heavy metal in the environment has
become a serious global problem due to their nondegradation and persistence in the
ecosystem leading to accumulation in different parts of the food chain (Saxena et al.
2019; Saxena and Bharagava 2017; Saxena et al. 2016; Chandra et al. 2015; Igwe et al.
2005). Cadmium (group IIB of the periodic table of elements) is considered one of the
most toxic elements in the environment, posing severe risks to human health and a
long elimination half-life. Weathering of cadmium-rich rocks, volcanic activities,
mining, smelting, industrial processes (as an anticorrosive agent, as a stabilizer in
PVC products, as a color pigment, in nickel-cadmium batteries, etc.), and overuse of
phosphate fertilizers to agricultural soils contribute to aggravate the situation by
increasing the levels of cadmium (Zoffoli et al. 2013). The worldwide production of
cadmium in 2005 was estimated to be 20,000 metric tons. Exposure to cadmium
occurs primarily through ingestion of contaminated water and food and to a significant
extent through inhalation and cigarette smoking. Cadmium poses a great health risk to
humans and animals even at very low concentrations in the body because the metal
cannot undergo metabolic degradation to less toxic species and its excretion is poor as
therapeutically effective chelating agents to enhance excretion of cadmium are
lacking. The target organs for cadmium toxicity in animals include the liver, kidney,
lungs, testes, prostate, heart, skeletal system, nervous system, and immune system
(Waalkes 2003). The International Agency for Research on Cancer (IARC 1993)
classified cadmium as a human carcinogen (group I). In plants Cd toxicity causes
inhibition of photosynthesis, mineral nutrient imbalance, reduced growth, and oxidative stress (Khan et al. 2007; Feng et al. 2010). In recent years, the removal of toxic
metals from soil and water poses a great challenge. Several types of chemical and
mechanical treatments have been established, but these are not cost-effective and have
less public acceptance. The use of microorganism such as algae, fungi, bacteria, and
yeasts for the removal of heavy metals like cadmium from contaminated soil and water
has a low cost, is efficient, and has greater acceptability from the public.
Phytoremediation is the use of plants to clean up contamination from soils, sediments,
and water. An attempt has been made in this chapter to review the challenges of
cadmium toxicity in humans and plants and to discuss the most promising and
alternative methods for remediation of cadmium from contaminated sites.
2 Cadmium and Its Properties
Cadmium was discovered in 1817 by German chemist Friedrich Stromeyer. Cadmium
is an odorless, soft, bluish-white malleable transition metal having atomic number
48 and belongs to group IIB of the periodic table. It shows resemblance with zinc in
many of its physical and chemical properties (Hiatt and Huff 1975; IARC 1993).
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S. Saini and G. Dhania
Industrial wastewaters are considered as the major sources of heavy metal pollution in
the environment (Goutam et al. 2018; Bharagava et al. 2017a, b, c; Gautam et al. 2017;
Saxena and Bharagava 2015). Contamination of heavy metal in the environment has
become a serious global problem due to their nondegradation and persistence in the
ecosystem leading to accumulation in different parts of the food chain (Saxena et al.
2019; Saxena and Bharagava 2017; Saxena et al. 2016; Chandra et al. 2015; Igwe et al.
2005). Cadmium (group IIB of the periodic table of elements) is considered one of the
most toxic elements in the environment, posing severe risks to human health and a
long elimination half-life. Weathering of cadmium-rich rocks, volcanic activities,
mining, smelting, industrial processes (as an anticorrosive agent, as a stabilizer in
PVC products, as a color pigment, in nickel-cadmium batteries, etc.), and overuse of
phosphate fertilizers to agricultural soils contribute to aggravate the situation by
increasing the levels of cadmium (Zoffoli et al. 2013). The worldwide production of
cadmium in 2005 was estimated to be 20,000 metric tons. Exposure to cadmium
occurs primarily through ingestion of contaminated water and food and to a significant
extent through inhalation and cigarette smoking. Cadmium poses a great health risk to
humans and animals even at very low concentrations in the body because the metal
cannot undergo metabolic degradation to less toxic species and its excretion is poor as
therapeutically effective chelating agents to enhance excretion of cadmium are
lacking. The target organs for cadmium toxicity in animals include the liver, kidney,
lungs, testes, prostate, heart, skeletal system, nervous system, and immune system
(Waalkes 2003). The International Agency for Research on Cancer (IARC 1993)
classified cadmium as a human carcinogen (group I). In plants Cd toxicity causes
inhibition of photosynthesis, mineral nutrient imbalance, reduced growth, and oxidative stress (Khan et al. 2007; Feng et al. 2010). In recent years, the removal of toxic
metals from soil and water poses a great challenge. Several types of chemical and
mechanical treatments have been established, but these are not cost-effective and have
less public acceptance. The use of microorganism such as algae, fungi, bacteria, and
yeasts for the removal of heavy metals like cadmium from contaminated soil and water
has a low cost, is efficient, and has greater acceptability from the public.
Phytoremediation is the use of plants to clean up contamination from soils, sediments,
and water. An attempt has been made in this chapter to review the challenges of
cadmium toxicity in humans and plants and to discuss the most promising and
alternative methods for remediation of cadmium from contaminated sites.
2 Cadmium and Its Properties
Cadmium was discovered in 1817 by German chemist Friedrich Stromeyer. Cadmium
is an odorless, soft, bluish-white malleable transition metal having atomic number
48 and belongs to group IIB of the periodic table. It shows resemblance with zinc in
many of its physical and chemical properties (Hiatt and Huff 1975; IARC 1993).
358
S. Saini and G. Dhania