Environmental Engineering Reference
In-Depth Information
Lead, in particular, continues to be a signiicant public health problem in developing
Asian countries, and the threat is not only to humans but also to various species of
terrestrial organisms (Hsu et al. 2006 ). Pb is toxic and has no known biological
function in humans. Numerous studies have disclosed that traditional Indian and
Chinese herbal preparations do contain high levels of lead and other toxic heavy
metals. For example, 64% of herbal samples collected in India displayed substantial
amounts of lead and other heavy metal residues (Ernst 2002 ). In addition to Pb, Cd,
and Hg are also known to be toxic to humans, even at very low concentrations, and
these metals are taken up by some medicinal plants from the environment (Chen
1992 ). Although herbal products are preferred by consumers for their “natural ori-
gin,” and are believed to be devoid of harmful effects, some medicinal plants accu-
mulate heavy metals from polluted sources and pose a toxic threat to human
consumption. Although herbal medicines may be as eficient as synthetic ones, they
may be less safe because of the presence of unacceptably high levels of certain
heavy metals (Blicharska et al. 2010 ).
The toxicity to biota of heavy metals has been of interest to scientists for many
years. In recent decades, to assure the quality of herbal medicines, phytopharmaceu-
ticals and herbal medicines have been extensively analyzed by laboratories around
the world for their metal content (Narendhiraknnan et al. 2005 ; Garg et al. 2007 ).
Moreover, the World Health Organization (WHO) and the US Food and Drug
Administration (FDA) have standardized safe limits for the occurrence of certain
metals (e.g., As, Hg, Pb, and Cd) in herbal drugs. However, the WHO has not yet
decided what the permissible limits in medicinal plants are for all metals, because
many of these metals are also essential dietary micronutrients for humans.
An essential element is one that is required for maintenance of life, whose dei-
cient intake consistently results in a functional impairment from some optimal to a
suboptimal level. Supplementation of an essential deicient element to proper physi-
ological levels prevents or cures the impairment (Mertz 1981 ). Certain metals are
among micronutrients that are important for normal functioning of vital organs.
Metals are critical components of many enzymes, e.g., zinc is a cofactor for more
than 100 metalloenzymes (Kosalec et al. 2009 ), and are essential for proper func-
tioning of the biochemical processes in which they participate (Lozak et al. 2002 ).
Nevertheless, at suficient concentrations, several of these essential metals are
potentially toxic (Donkin and Ohlson 2000 ; Obi et al. 2006 ).
Medicinal plants are mainly sourced and harvested from wild habitats, after
which they are delivered to their market, without many questions being asked about
their origins, botanical identity, purity, safety, and eficacy. The main reason that
purchasers lack inquisitiveness is the cost factor. Although harvesting from nature
ensures suficient volumes and low cost of these plants, if the buyer wants to verify
the background and quality of them, the cost increases. At the current time, medici-
nal plants growing in the wild constitutes an important portion of herbal plants that
are traded in Europe (Salgueiro et al. 2010 ). Because of the foregoing points, a fun-
damental issue concerning the medicinal plant industry has to be the quality of these
plants. The safety and beneit of plant products are directly related to the quality of
the raw materials from which they are derived (Salgueiro et al. 2010 ).
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