Page 247 - Materials Chemistry, Second Edition

228 Life Cycle Assessment of Wastewater Treatment

organisms. In strongly polluted aquatic locations such as these, flora and fauna
are by and large devastated or totally exposed; consequently, the pollution unfa-
vorably influences aquatic biodiversity. In addition, metals are not subject to bac-
terial degradation and consequently, remain forever in the marine environment
(Woo et al., 2009).
Heavy metal contaminants in aquatic systems stimulate the creation of reactive
oxygen species (ROS), which can harm fish and other oceanic life. When heavy met-
als are amassed by an oceanic life form, they can be exchanged through the hierarchy
of the natural food chain. Carnivores at the highest point of the food chain, includ-
ing people, acquire the greater part of their heavy metal burden from the aquatic
system as food, particularly where fish are available, so there exists the potential for
significant biomagnification. There are five potential ways for a toxin to enter a fish:
through food, non-food particles, the gills, oral intake of water, and the skin. Once
the toxins are consumed, they are transported by the blood either to a storage point
or to the liver for metabolism and disposal. In the event that the contaminants are
metabolized by the liver, they might be stored there, discharged in the bile, returned
to the blood for possible discharge by the gills or kidneys, or stored in fat, which is
an additional hepatic tissue (Ayandiran et al., 2009).

11.3.4 Heavy MeTal ToxiciTy in HuMans
The fundamental dangers to human health from heavy metals are related to exposure
to lead, cadmium, mercury, and arsenic. These metals have been broadly considered
and their consequences for human health consistently surveyed by global bodies, for
example, the WHO. Heavy metals have been used by people for a large number of
years. Although a few antagonistic health impacts of heavy metals have been known
for a long time, exposure to heavy metals persists and is even expanding in a few
parts of the world, specifically in less developed nations; however emissions have
declined in most developed nations during recent years. The use of food harvests
polluted with heavy metals for human consumption is a noteworthy result of the
natural hierarchy.
Living beings require different amounts of heavy metals. Co, Cu, Mg, Mo, and
Zn are required by people. All metals are lethal at higher concentrations. Excessive
levels can harm animals. Other heavy metals, for example, mercury, plutonium, and
lead, are harmful metals that have no known indispensable or useful function in
animals, and their accumulation for some time in the bodies of animals can cause
genuine disease (Singh et al., 2011). The effect of these poisonous heavy metals on
human health is at present an area of serious interest because of the omnipresence of
their introduction. Heavy metals move toward becoming harmful when they are not
used by the body and gather in sensitive tissues. The constant ingestion of dangerous
metals has detrimental effects on people, and the related destructive effects progress
toward becoming noticeable some time after their introduction (Khan et al., 2008).
Heavy metals upset metabolic functions in two ways:

• They accumulate and thus affect the functioning of indispensable organs,
for example, the heart, cerebrum, kidneys, bone, liver, and so forth.