The concentration of lead (Pb) in the soil samples ranged from 50-590 ppm.
42% of the samples had levels above 400 ppm and only one sample had Pb levels
at 50 ppm (reference standard in the Netherlands and Taiwan), with the rest above
60 ppm. Samples from within the waste dump manifested a value of 13,500 ppm
and this is a clear indication that the dumpsite is the major source of high lead levels
found in the surrounding environment. Mean concentrations of lead in soil samples
from the dumpsite were over seven times more than those found in Waithaka.
For mercury (Hg), samples collected from the waste dump exhibited a value
of 46.7 ppm while those collected along the river bank registered a value of 18.6
ppm. Both of these values greatly exceeded the WHO acceptable exposure level of
2 ppm. The rest of the samples were inconclusive due to the fact that the analytical
method used was only capable of detecting high levels of mercury (15 ppm and
above).
Mean concentrations of cadmium (Cd) in the soil samples adjacent to the
site were eight times higher than those prescribed by the Dutch and Taiwanese
authorities (5 ppm). High concentrations were found in both surface and subsurface
soil levels. Waithaka soil samples had copper (Cu) concentrations that were
below the detection limit of 15 ppm (EDXRF System) while concentrations from
the Dandora dumping site greatly exceeded the prescribed standard values as well
as the natural range and registered between 7 and 80 ppm. Mean chromium (Cr)
concentrations were slightly above the critical standard soil levels hence had no
major negative impact on the environment. Zinc (Zn) concentrations from Dandora
soils were four times greater than those from Waithaka and these values exceeded
the recommended standard levels as well.