| dc.description.abstract | Although fish is an important source of food in Kenya,
limited information is available on fluoride in Kenyan fish.
Fluoride is accumulated by aquatic organisms living in high
fluoride environment. It was therefore found relevant to
undertake a more extensive investigation of the fluoride levels
in Kenyan lake water and fish, and also to study various factors
related to the accumulation of fluoride in fish.
Water samples were collected from Lakes Nak uru ,
Bogoria, Baringo, Naivasha, Elementaita and Magadi and the
pH as well as fluoride concentrations measured with a pH
meter and a fluoride ion specific electrode respectively. Water
from all the lakes were alkaline with pH ranging from 8.4 to
10.7. The fluoride levels of water from Lakes Naivasha.
Magadi, Nakuru, Elementaita, Bogoria, and Baringo were 2.4.
84, 344, 463, 738, and 5.4 mg F/1 respectively.
After addition of decomplexing agents, TISi\B .(Total ionic
strength adjustment buffer - Orion) II or TISAn III, the pH of
water samples from lakes Naivasha, and Baringo were within
the recommended pH range for fluoride analysis (5.0-5.5),
while water samples from lakes Magadi, Bogoria and
Elementaita had pH values above 5.5. It was therefore found
relevant to study how dilution and addition of decomplexing
solutions, affect the fluoride measurements in water from
Lake Magadi.
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Dilution of the water did not alter the pH before addition
of buffer hence interfering ions could be responsible for the
problem encountered in fluoride analysis in the alkaline water.
Hence the commonly used methods for fluoride analysis in
water, might give erroneous or unreliable results when used
in the analyses of water with high pH as found in some of the
lakes of the Rift valley.
A total of 320 fish samples from Lakes Naivasha, Bnrtrigo
and Magadi were analysed for fluoride concentration in fillet
skin. gills and bones using fluoride ion selective electrode
methodology after extraction from tissues.
The recovery of fluoride at various spiking levels were as
follows (mean ± SEM %): blanks 99.6 ± 2 %. fillet 87.4 ± 4 %.
skin 101 ± 16 %, gills 105 ± 6 % and Bones 109 ± 3%.
Fluoride concentration in fish tissues were as follows (mean ±
SEM mg Fjkg): Lake Magadi fish; fillet 68 ± 12. skin 809 ±
140, gills 1366 ± 40 and 1661 ± 49 for bones. Lake Naivasha
fish:Oreochromis ieucostictus, fillet 11 ± 1. skin 18.2 ± 2, gills
571 ± 36, and 608 ± 22 in. bones; Tilapia zilii, fillet 10 ± 0.4,
skin 18 ± I, gills 435 ± 24 and 455 ± 27 for the bones;
Micropterus salmoides (Black bass). fillet 7 ± 0.6, skin 83 ±
24, gills 251 ± 23 and 338 ± 24 in bones. Lake Baringo: Tilapia
nilotica, fillet 7 ± I, skin 10 ± 1.6, gills 241 ± 20.8 and 268 ±
36 in bone tissues. All the values are on dry weight basis.
Concentration of fluoride in tissues varied according to fish
species (p < 0.05) and perhaps the feeding habit and fish
growth rate.
Lake Magadi Tllapta fish were surviving under a fluoride
concentration of 84 mg F/1 in the water. Therefore the Lake
Magadi Tilapia seems to be adapted to living in high fluoride
environment possibly through an excretion mechanism.
Lake Magadi fish may be unsuitable for human
consumption due to the high fluoride content in the tissue
which could amount to a health risk. Fish from Lakes Nalvashn
and Baringo provide an important source of protein. III
preparation of the fish. no part is removed except the scales
and perhaps the fins. The amount of fluoride released by
bones. gills and skin during the process of cooking is an area
which requires further research.
There is no current concensus on the level of fluoride
acceptable in various foods and beverages consumed on a daily
basis and therefore intensive studies are necessary with
regard to fluoride levels in food and beverages as well as
bioavailability of fluoride. Accordingly. the present findings
indicate that there is a need to carry out fluoride bioavailability
studies in food substances like soups which are prepared
using fillet, skin, gills and bones which may contain high
concentrations of fluoride. | en |
