Chemistry Reference
In-Depth Information
catalytic functions and is important for both man and plants health and growth (Jeffery,
1992). The zinc content of normal plants tissues varies according to plant species, but it is
usually within the range of 5 - 300mg/kg dry matter (Walsh, 1971).
Generally vegetables appear to have the highest and lowest amount of heavy metals
accumulated in their leaves and seed respectively e.g. beans, peppers, tomatoes, melons and
peas show very low intake of heavy metals in their seed. Plant intake of heavy metals varies
with soil P
H
. A study by Echem (2010) on cassava cultivated on oil polluted soil showed that
soil contaminated with heavy metals cause contamination of foodstuffs.
Heavy metals are associated with myriad adverse health effects, including allergic reaction,
nephrotoxicity, and cancer. Humans are often exposed to heavy metals in various ways -
mainly through the inhalation of metals in the workplace or polluted neighbourhoods, or
through the ingestion of food that contains high levels of heavy metals or paint chips that
contain lead Ifon, (1977).
The three heavy metals commonly cited as being of the greatest public health concern are
cadmium, lead and mercury. There is no biological need for any of these three heavy metals.
Exposure to cadmium can result in emphysema, renal failure, cardiovascular disease and
perhaps cancer. The primary adverse health effect from exposure to lead is neurological
impairment (particularly in children). Other adverse health effects associated with lead
include sterility in males and nephrotoxicity.
Heavy metals have been reported to play positive and negative roles in human life (Slavesk
et al., 1998; Divrikli et al., 2003; Dundar and Saglam, 2004). Some heavy metals like
cadmium, lead and mercury are major contaminants of food supply and may be considered
as very harmful to the environment since they do not biodegrade while others like iron, zinc
and copper are essential for biochemical reactions in the body (Zaidi et al., 2005). Jarup
(2003) and Sathawera et al., (2004) have reported that, most heavy metals are not
biodegradable, have long biological half-lives and have the potential for accumulation in the
different body organs leading to unwanted side effects. There is a strong link between
micronutrient of plants, animals and humans, and the uptake and impact of contaminants in
these organisms (Yuzbas, et al., 2003; Yaman et al., 2005).
Research findings by Divrikli et al. (2006) had shown that the concentration of essential
elements in plants is conditional; it is affected by the characteristics of the soil and the ability
of plants to selectively accumulate some metals. Sources of heavy metals for plants include
rainfall in atmospheric polluted areas, heavy traffic as a result of high discharge of exhaust
effluents- indiscriminate disposal of oil or fossil fuels by road side mechanics, - plant
protection chemicals and fertilizers which could be absorbed through leaf blades
(Kovacheva et al., 2000; Lozak et al., 2002; Sobukola et al., 2006).
The aim of this research is to ascertain the level of heavy metals ingested by bitter leaf
grown along heavy traffic routes. It is a well established fact that diesel, gasoline, lubricants,
vehicle parts such as carburettors among others, contain heavy metals. The routes chosen for
this study record the highest traffic density for heavy duty vehicles, lorries, buses and cars
