Overview
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Key numbers
The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:
- Department of Public Health, Live fish comprising of 17 catfish and 33 tilapias were purchased from 15 fish farmers with 31(62%)
- Department of Animal (p>0.05). Fish obtained from earthen ponds recorded a higher mean concentration of the three heavy
- Veterinary Medicine, University Mercury concentration in fish muscles was slightly higher than European Union limits (0.1 Mg/Kg) but
- of Nairobi, Kangemi Nairobi, lower than codex alimentarius (0.5 Mg/Kg) limits.
- metals of selected fish ponds in the two sub-counties to ml of potassium permanganate solution (6% v/v) were added.
- persulphate (5% solution w/v). The sample was left with the
- Fish tissue samples (n=50) were collected from all purchased hydrochloride solution (20% m/v) was carefully added to
- microwave vessels. One (1) ml of de-ionized water was then different fish species. Different range tests were deployed to
- microwave vessels were then heated gradually to 180oC for The heavy metal concentration detected ranged between
- 10 minutes after which the microwave automatically begins to cadmium and 0.026-0.134 Mg/Kg for mercury, respectively.
- complete. After cooling, the samples were quantitatively Mg/Kg), mercury (0.306 Mg/Kg) and cadmium (0.134
- placed into 100 ml volumetric flasks and topped to the mark Mg/Kg) in the muscles compared to catfish. Data obtained
- with de-ionized water. The samples were analyzed using an showed that lead had the highest mean concentration of 0.326
- instrument utilizing the Graphite Furnace Atomic Absorption Mg/Kg followed by mercury (0.165 Mg/Kg) and cadmium
- Stock solutions for each metal were prepared by dissolving 1g Fish obtained from earthen ponds recorded a higher mean
- of pure lead and cadmium metal strip in 1:1 nitric acid and concentration (lead 0.346 Mg/Kg; mercury 0.171 Mg/Kg;
- diluted to 1 liter to give a stock solution of 1000 ppm. For cadmium 0.083 Mg/Kg) compared to fish from liner ponds
- each of the stock solutions working standards of 1 Mg/Kg, 5 (lead 0.302 Mg/Kg; mercury 0.158 Mg/Kg; cadmium 0.051
- Mg/Kg, and 10 Mg/Kg were made and calibration curves Mg/Kg). Cadmium ion concentration varied significantly
- curve generated using 1 Mg/Kg, 5 Mg/Kg, and 10 Mg/Kg, significant difference between lead (p=0.206) and mercury
- Table 1: Levels of lead, cadmium and mercury concentration in fish muscles from two fish species and pond types in Tetu and Nyeri Central
- Discussion The mean cadmium concentration in fish muscles (0.069
- Fish muscle tissues were analyzed for the presence of three ppm) was lower than that observed by (22) of 1.79 ppm or (20)
- heavy metal elements namely lead, cadmium and mercury. of 1.66ppm in Kiambu and 1.12 ppm in Machakos. The mean
- Lead had a mean concentration of 0.326 ppm (range 0.092- cadmium concentrations in this study slightly exceeded the
- 0.659 ppm) followed by mercury 0.165 ppm (0.061-0.306 maximum permissible limits stipulated by (19) of 0.05 ppm but
- ppm) with cadmium having the lowest mean concentration of were within codex alimentarius (0.3 ppm) and European
- 0.069 ppm (range 0.026-0.134 ppm). The most likely source Union (0.1 ppm) limits.
- runoffs and drainage which may enter into water bodies like heavy metal concentration (lead 0.346 ppm; mercury 0.171
- rivers that serve as fish pond water sources. ppm and cadmium 0.083 ppm) compared to fish from lined
- The highest concentration of lead (0.679 ppm), mercury ponds (lead 0.302 ppm; mercury 0.158 ppm and cadmium
- (0.306 ppm) and cadmium (0.134 ppm) was observed in 0.051 ppm). Cadmium ion concentration varied significantly
- The mean lead concentration in fish muscles (0.326 ppm) was Nyeri Central is an urban sub-county and effluent from the
- of 0.5 ppm for lead but within European Union and codex fish ponds. This is unlike Tetu which is a rural sub-county.
- alimentarius limits of 0.3 ppm. (20) reported a mean
- compared to reports by (21) that indicated mean lead lead concentration was within European Union and codex
- concentrations of 30.7 mg/L in sediments in Tanzania. (22) alimentarius limits in farmed tilapia and catfish from Nyeri
- no significant difference (p=0.120) in the mean lead metals especially mercury in farmed fish tissues in Nyeri
- The mean mercury concentration in fish muscles (0.165 ppm)
- stipulated by European Union of 0.1 ppm but lower than 0.5 The authors are grateful to the United States Agency for
- ppm codex alimentarius limits. (23) in Croatia reported International Development (Peer Science Project) for
- mercury concentrations ranging from 0.024 to 0.308 ppm. financial support. We also thank the Nyeri fisheries officers
Methods (brief)
- Faculty of Veterinary Medicine, muscle tissue samples for analysis for levels of lead, mercury and cadmium residues using the Flame
- University of Nairobi, Kangemi Atomic Absorption Spectrometry.
- School of Agricultural Sciences Studies to analyze presence of heavy metals and chemicals in fish tissue samples have been
- Tetu and Nyeri Central sub-counties are in the agro-ecological milliliter of de-ionized water was then added and the sample
- some or all of these rivers thus polluting them. The same automatically begins to cool the sample until it indicates when
- water may end up into the ponds. cooling process is complete. After cooling, the samples were
- persulphate (5% solution w/v). The sample was left with the
- Fish tissue samples (n=50) were collected from all purchased hydrochloride solution (20% m/v) was carefully added to
- metal residues. This was done using the Flame Atomic was added to bring the sample volume to 100 mls. The
- method (Graphite Furnace Atomic Absorption Spectrometry). using 1 Mg/Kg, 5 Mg/Kg, and 10 Mg/Kg, and the results were
- added and the sample left to react for approximately 6 compare means of parameters between different pond types
- cool the sample until it indicates when cooling process is Tilapia accumulated higher concentrations of lead (0.679
- complete. After cooling, the samples were quantitatively Mg/Kg), mercury (0.306 Mg/Kg) and cadmium (0.134
- with de-ionized water. The samples were analyzed using an showed that lead had the highest mean concentration of 0.326
- instrument utilizing the Graphite Furnace Atomic Absorption Mg/Kg followed by mercury (0.165 Mg/Kg) and cadmium
- Vapour Atomic Absorption Technique). One gram of fish Nyeri Central Sub-county recorded a slightly higher lead and
- Opportunities for Future Development. Journal of plasma-optical emission spectrometry (ICP-OES) in
- EPA Method 3051A. Microwave assisted acid digestion
Implications
This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.
Wiki pages this source may touch
- Fish — marine, non-predatory (sardines, anchovies, salmon, cod)
- Shellfish (shrimp, crab, lobster, clams, oysters, mussels)
- Mercury
- Cadmium
- Lead
- Nickel
- Chromium
Verification notes
- Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing
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- HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.
Update history
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