| dc.description.abstract | For a long time, the toxicity of metals was
considered as an occupational hazard.
Industrialization, urbanization, increased
vehicular traffic and use of fertilizers and
pesticides in agriculture have resulted in
increased contamination of environment by
heavy metals. The toxicity of metals in the
environment is becoming a matter of concern
for the general population. It has been observed
that the toxic metals, attributed to vehicular
emissions, such as Lead, arc deposited at
relatively short distances from the road. Hay
(1984) has reported that about 2OOO tons of
lead is deposited on the earth annually due to
the use of tetra-ethyl lead and tetra-methyl lead
in fuel. Studies on the toxicity and essentiality
of toxic trace elements have been carried out by
several researchers (Nelson, 1991; Reichlnayr-Lais
& Krichgebner, 1991; Mukhtar et al.,
1991; Duane et al., 1996; Hong & Ha, 1996;
Oluwole et al., 1994; Ostachowicz...et al., 1995;
Murti Krishna & Viswanathan, 1991; (heavy
metal task force, 1991). At the same time, all
mineral elements are essential to the
environment, human beings and animals but
their excess 'may lead to serious health hazards.
Kinyua et al. (1991, 1993) have reported the
concentrations of mercury, lead, cadmium,
copper, manganese and iron in water and fish samples from Nairobi-Athi river, and Naivasha
area in Kenya, respectively. The study of the
levels of mercury in water, fish, sediments and
blood samples from different regions of Kenya
have been done by Kamau et al. (1991).
The adjacent lands along most major
highways of Kenya are left as open spaces, or
used for small scale farming and grazing of
cattle and livestock. Some grass and plants are
expected to have high levels of lead and other
toxic metals. So far, no study has been carried
out to determine the concentrations of toxic
metals in soil samples along Thika and
Mombasa highways of Kenya. This work will
be important and essential to study the impact
of pollution on the health and environment. | en_US |
