According to the data shown above, heavy metal pollution is more
prevalent in Asian countries. Rapid population increase and
industrialization have resulted in land-use changes across the Asian
subcontinent, necessitating persistent efforts to improve agricultural
productivity in restricted geographical regions to provide appropriate
quantities of food. Unfortunately, to achieve that goal, wastewater,
treated effluent, and sludge loaded with heavy metals have frequently
been utilized as low-cost irrigation supplies in portions of Asia and
Africa, causing food quality and hence health to suffer. The buildup of
dangerous heavy metals in plants may easily be transmitted to the human
system, resulting in heavy metal bioaccumulation in human tissues. The
outcomes of such might have serious ramifications in the future.
Impact of SS on the Human system
According to existing studies, heavy metals in urban soils can enter the
human body through skin absorption and dust inhalation, among other
routes, and so directly affect, particularly children’s health. The
toxicity levels of several chosen metals in humans are as follows: Co
Al, Cr Pb, Ni Zn, Cu Cd Hg (Mansourri & Madani 2016). The toxicity of
heavy metals in humans is determined by their dose, rate of emission,
and duration of exposure. Hg, Cd, and Pb are three heavy metals that
have attracted more attention in recent decades (Valavanidis, &
Vlachogianni, 2010). In humans, the negative health consequences of Hg
and mercuric compounds include potential carcinogens, brain, lung, and
kidney damage, fetal harm, high blood pressure or heart rate, vomiting
and diarrhea, skin rashes, and eye irritation (Martin, & Griswold,
2009). The US EPA has set a regulatory limit of 2 parts per billion
(ppb) for Hg in drinking water (Martin, & Griswold, 2009).
Chronic Cadmium toxicity in children includes lung, kidney, skeletal,
and cardiovascular system damage, as well as the development of
malignancies of the lungs, kidneys, prostate, and stomach (US-EPA 2010;
WHO 2011). People are exposed to Cadmium via consuming contaminated
food, smoking cigarettes, and working in cadmium-laden environments and
primary metal industries (Paschal 2000).
Lead exposure can occur through the inhalation of contaminated dust
particles and aerosols, as well as through the consumption of
contaminated food and drink. Lead poisoning affects the kidneys, liver,
heart, brain, bones, and neurological system in humans. Headache,
dullness, memory loss, and irritability are some of the initial signs of
lead poisoning (Flora et al., 2006).
Hexavalent Chromium compounds, which include Ca, Zn, Sr, and Pb
chromates, are extremely soluble in water, poisonous, and carcinogenic.
Furthermore, Chromium compounds have been linked to delaying the healing
of ulcers. Chromate chemicals have also been discovered to be capable of
destroying the DNA in cells (Matsumoto, 2006).
Thallium is a soft, tasteless, odorless whitish-blue metal that, when
exposed to oxygen, oxidizes to thallium oxide. Thallium can be found in
electronics, optical glasses, semi-conductors, and mercury lamps, among
other places. Thallium enters the body by eating, inhalation, and
cutaneous contact. Thallium is very poisonous, with a fatal dosage
ranging from 6 to 40 mg/kg. Thallium poisoning causes anorexia,
vomiting, gastrointestinal bleeding, abdominal discomfort,
polyneuropathy, alopecia, renal failure, skin erythema, seizures, mood
disturbances, autonomic dysfunction, cardiotoxicity, and coma, among
other symptoms (WHO 2011).
Humans are exposed to Ni through food, air, and water. Previous research
has shown that ingestion of nickel-contaminated dust was the primary
exposure pathway for local populations, as opposed to inhalation and
cutaneous exposure (Sobhanardakani 2019). Other heavy metals, such as
Arsenic (As), have been linked to dermatitis, bronchitis, and poisoning.
A high Zn content might induce skin rashes and damage to nerve
membranes. Cu may cause intestinal discomfort as well as liver and renal
damage (Singh et al., 2011). The permissible limits of the heavy metal
in the human body & drinking water have been documented below (Table 3)
Table 3: Permissible limit of the heavy metals in the Human body and
Drinking water according to the different regulatory bodies (Source
Singh et al., 2011; Paul 2017)