Page 220 - Soil Degradation, Conservation and Remediation

6.2 Sources of Soil Pollutants 209

Table 6.10 Toxicities of heavy metals to human
Heavy metals Common toxicities of heavy metals in human
a
Arsenic Arsenicosis is the most common disease caused by drinking
As-contaminated water for a long time. Inorganic arsenic compounds are
“known to be human carcinogens.” Arsenic may cause cancers of the
bladder, kidney, skin, liver, lung, colon, and lymph. Darkening of the
skin and the appearance of small “corns” or “warts” on the palms, soles,
and torso
a
Cadmium The well known itai-itai disease was caused by the consumption of rice
grown by irrigating with Cd-contaminated river water in Japan after
1945. Cd toxicity causes renal tubular dysfunction, high blood pressure,
lung damage, and lung cancer. Acute Cd inhalation may lead to
pneumonitis and pulmonary edema. Chronic exposure via inhalation may
cause emphysema. One of the most widely known toxic effects
manifested by Cd poisoning is nephrotoxicity
Chromium b Impaired growth, altered immune function, disturbances in aortic plaque and
size, corneal lesion formation, and decrease in reproductive functions;
both Cr(III) and Cr(VI) are potent human carcinogens. The major target
organ for Cr(III) and Cr(VI) is the respiratory tract. Classical symptoms
are perforations and ulcerations of the septum, bronchitis, decreased
pulmonary function, and pneumonia
b
Copper Copper is an essential element. Cu toxicity in humans is very rare and is
usually associated with long-term intake of cow’s milk or with severe
malnutrition in infants and young children
Lead a Lead damages the central nervous system, kidneys, and lungs. It causes

anemia; nausea, anorexia, and abdominal cramps; muscle aches and joint

pain; difficulty in breathing, asthma, bronchitis, and pneumonia; and
damage to the fetus and miscarriage. Children are more vulnerable to Pb
poisoning than adults. Pb may cause male infertility
a
Mercury Severe mercury poisoning occurred in Minamata of Japan from
contaminated fish and in Iraq from contaminated wheat. Wheat was

sprayed with MeHg fungicide. In the outbreak more than 6,000 children
and adults had been poisoned, with nearly 500 deaths. Symptoms include
paresthesia, ataxia, dysarthria, and deafness. Chronic Hg poisoning may
result from exposure to small amounts of Hg over long periods;
symptoms include salivation, loss of appetite, anemia, gingivitis,
excessive irritation of tissues, nutritional disturbances, and renal damage
accompanied by proteinuria. Exposure to Hg may cause nausea, severe
gastrointestinal irritation, and abdominal pain
Molybdenum b Toxic effects of Mo include increased blood xanthine oxidase, increased
concentrations of uric acid in blood and urine, and a high incidence of
gout
a
Nickel Exposure to nickel sulfate and nickel chloride can cause vomiting and
headaches and the metal can cross human placental barrier, affecting the
fetus. Ni-sensitive individuals often develop contact dermatitis.
Inhalation of Ni compounds has been considered responsible for lung,
sinonasal, and laryngeal carcinomas. Other illnesses include
pneumonoconiosis and emphysema. Ni may cause kidney cancer.
Among different types of Ni compounds, crystalline nickel subsulfi de is
carcinogenic, whereas amorphous NiS is not
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