J. O. Lalah

Carbofuran and its Toxic Metabolites Provide Forensic Evidence for Furadan Exposure in Vultures ( Gyps africanus ) in Kenya

Forensic analysis of carbofuran residues in weathered tissue samples for evidence of Furadan exposure in vultures (Gps africanus) by HPLC gave concentration (mg/Kg dry tissue weight) ranges of bdl – 0.07 (carbofuran), bdl – 0.499 (3-ketocarbofuran) and 0.013–0.147 (3-hydroxycarbofuran) in beaks, bdl–0.65 (carbofuran), 0.024–0.190 (3-ketocarbofuran) and 0.017–0.098 (3-hydroxycarbofuran) in feet, 0.179–0.219 (3-ketocarbofuran) and 0.081–0.093 (3-hydroxycarbofuran) in crop content, 0.078–0.082 (3-ketocarbofuran) and 0.091–0.101 (3-hydroxycarbofuran) in muscle of a laced carcass and 0.006–0.014 (carbofuran), 0.590–1.010 (3-ketocarbofuran) and 0.095–0.135 (3-hydroxycarbofuran) in soil sampled from a poisoning site. These compounds were confirmed by GC-MS. The results showed that HPLC combined with GC-MS is suitable for forensic analysis of carbofuran residues in bird tissue samples and that forensic investigation should include its two toxic metabolites, 3-hydroxycarbofuran and 3-ketocarbofuran.

Soil and water contamination with carbofuran residues in agricultural farmlands in Kenya following the application of the technical formulation Furadan.

This study was undertaken to determine the concentrations of carbofuran residues in water, soil and plant samples from selected sites in the farmlands in Kenya and to demonstrate the impact of Furadan use on the local environment. Soil, water and plant samples obtained from agricultural farmlands where the technical formulation Furadan has been used extensively showed high environmental contamination with concentrations of carbofuran and its two toxic metabolites 3-hydroxycarbofuran and 3-ketocarbofuran, separately, ranging from 0.010–1.009 mg/kg of dry surface soil, 0.005–0.495 mg/L in water samples from two rivers flowing through the farms and bdl-2.301 mg/L in water samples from ponds and dams located close to the farms. Maize plant samples contained these residues in concentrations ranging from 0.04–1.328 mg/kg of dry plant tissue. The significantly high concentration levels of carbofuran and its metabolites, 3-ketocarbofuran and 3-hydroxycarbofuran, found in various matrices demonstrate that Furadan was used extensively in the two areas and that there was environmental distribution and exposure of residues in water which posed risks when used for domestic purposes or as drinking water for animals in two wildlife conservancies where the dams and ponds are located. Surface soil contamination was also high and posed risks through run-off into the dams and rivers as well as through secondary exposure to small birds and mammals.

Copper, lead and cadmium concentrations in surface water, sediment and fish, C. Carpio, samples from Lake Naivasha: effect of recent anthropogenic activities

Following recent concerns of chemical pollution around Lake Naivasha, especially originating from recent agricultural activities in the catchment, samples of water, sediments, and fish Common carp (Cyprinus carpio) were collected from the Hippo Point, Kasarani, Mouth of Malewa River, Mouth of Karati River, Crescent Island, Sher Karuturi Discharge outlet and Oserian Bay for analysis of Cu, Cd and Pb by FAAS. The mean heavy metal levels ranged from 5.12–58.11 (Pb), 1.06–1.73 (Cd), and <0.03–2.29 (Cu) mg/kg wet weight in C. carpio muscle, <100–179.83 (Pb), <10.00–10.06 (Cd) and <30.00–32.33 (Cu) μg/L in surface water, and 17.11–53.07 (Pb), 1.18–5.58 (Cd) and 3.00–8.48 (Cu) mg/kg dry weight in sediment and showed a wide variation within and between samples with relatively high concentrations in sediments and fish muscle tissues. The results indicate that Lake Naivasha, in some parts, is polluted with these heavy metals of which relatively higher concentrations are found at the discharge outlets near Sher Karuturi and Oserian Bay. This indicates possible contribution from surrounding horticultural/floricultural activities and the Mouths of the Rivers Malewa and Karati which flow from it’s upper catchment.

The major environmental factors that influence rapid disappearance of pesticides from tropical soils in Kenya

Results of field and laboratory studies on adsorption/desorption, leaching, dissipation, bound residue formation and metabolism of DDT, DDE, lindane, parathion, malathion, dimethoate and carbofuran in tropical soils in various regions in Kenya are summarized in this paper. Based on reported half‐lives of dissipation in temperate soils, DDT, DDE and lindane were found to dissipate much more rapidly in tropical soil conditions with half‐lives of dissipation of 64.5–245.6, 145 and 5–8 days, respectively. Carbofuran (t 1/2 = 66–115.5 days), malathion (t 1/2 = 36.7–770 days), parathion (t 1/2 = 48days) and dimethoate (t 1/2 = 72 days) were also less persistent. The major environmental factors, wind, rainfall, solar radiation intensity and soil moisture content that contributed to this rapid disappearance are presented, explaining also the influence of important soil characteristics such as pH, % organic carbon, texture and microbial activity on pesticide distribution and degradation in soil.

The dissipation, distribution and fate of a branched 14C-nonylphenol isomer in lake water/sediment systems

A single tertiary isomer which is believed to be one of the major branched isomers of the isomeric nonylphenol was synthesized for use in investigations on its metabolism and estrogenicity in aquatic organisms. The physico-chemical properties of the isomer were determined to enable the prediction of its behaviour in aquatic environments. From laboratory investigations on its dissipation and distribution in lake water, which are reported in this paper, it was found that it had a half-life of dissipation of 38.1 days and 20.1 days in an open lake water and in an open lake water/ sediment system, respectively, and to be rapidly partitioned in to sediment giving a high concentration factor of 1.76 after 28 days with an initial dose concentration of 2.52 ppm. The main dissipation route was found to occur through volatilization and co-distillation. The isomer was, however, found to be resistant to biodegradation in both the lake water and sediment, showing only a slight 9% loss (after 56 days) and 4.2% loss (after 28 days), of the 14C-residues in lake water and lake water/sediment systems, respectively, by microbial activity. Transformation to other more polar metabolites possibly by hydroxylation was also found to be minimal in both lake water and sediment samples after 14 days by HPLC analysis. After 7 days, only 2.25 and 7.4% transformation to a more polar metabolite was detected in lake water and sediment samples, respectively.

The effect of boiling on the removal of persistent malathion residues from stored grains

Abstract This study aimed at finding the fate of malathion in maize grains and beans stored in a tropical laboratory for 12 months at temperatures of 20–24°C, relative humidity of 42–80% and grain moisture contents of 11.7–12.5% in maize grains and 14.1–15.3% in beans. Malathion and its degradation products malaoxon, malathion α-monocarboxylic acid and β-monocarboxylic acid were found in stored maize grains and beans treated with a mixture of pure radiolabelled malathion and 2% malathion dust after 12 months of storage. A significant percentage of these residues were removed from the grains by cooking in boiling water. Though malathion and its polar metabolites, malathion α- and malathion β-monocarboxylic acids were completely eliminated by boiling, malaoxon was still detected in quite high quantities in the solvent extracts of cooked beans and maize. Addition of NaCl to the grains increased the rate of removal of the residues from both maize grains and beans by boiling water. The data obtained clearly showed a distinction in persistence, distribution and metabolism of malathion between the two types of crop, indicating also that more adverse windy, humid and hot tropical conditions contributed to higher rates of metabolism and loss of the pesticide from the grains. The accuracy and ease of using radiolabelled malathion in investigating its fate and behaviour in the two matrices is shown in this study.

The distribution of organochlorine pesticides in marine samples along the Indian Ocean coast of Kenya.

The concentrations of organochlorine residues of lindane, aldrin, ∝- endosulfan, dieldrin, endrin, p,p′-DDE, p,p′-DDD and p,p′-DDT in samples of seawater, sediment, fish and seaweed from different locations along the coast of Kenya are discussed in relation to the geographical location of the sampling sites and potential sources of residue over a period of two years. All sediment samples were found to contain very low levels of organic carbon except those sampled from Sabaki River that had high (4.7%) organic carbon due to greater primary activity. Most of the pesticides residues (112 samples analysed in 1997 and 258 analysed in 1998/99) were detected in fish, water, sediments and seaweed. The concentration of some residues was higher during the wet season than the dry season in 1997, but no marked seasonal variation was observed in 1998/99. Lindane, aldrin, p,p′-DDT and p,p′-DDE were the most frequently observed residues in all samples while ∝-endosulfan, dieldrin, p,p′-DDD and endrin were either present in low concentrations or absent in most samples. Water samples had the lowest concentrations of residues (range 0.503 - 9.025 ng g−1). Sediments had the second highest levels of pesticides residues with a range of 0.584 - 59.00 ng g−1 while fish lipid content had the highest levels of residues in 1989/99 with p,p′-DDT concentration of 1011 ng g−1 and 418 ng g−1 p,p′-DDD in Siganus rivulatus.

Water quality and trace metal distribution in a pristine Lake in the Lake basin in Kenya.

Water and surface sediment samples taken from various locations within Lake Kanyaboli in the Lake Victoria basin were analysed to determine the concentration and distribution of heavy metals. There were wide ranges in concentrations of the metals among the sampling points analysed. Sediment concentrations (μg/g dry weight) ranged from n.d.–2.54 (Ag), 0.25–1.08 (Cd), 0.89–1.64 (Co), 3.7–7.73 (Cr), 1.80–30.27 (Cu), 1073–2627 (Mn), 22.61–55.60 (Ni), 11.42–153.9 (Pb), 40.46–154.7 (Sn) and 65.0–146.5 (Zn). Dissolved metal concentrations (μg/L) ranged from n.d.–9.22 (Ag), n.d.–5.54 (Cd), n.d.–8.30 (Co), 5.26–60.82 (Cr), 10.96–43.11 (Cu), 184.7–375.9 (Mn), 1.84–38.3 (Ni), 5.98–47.77 (Pb), n.d.–540.6 (Sn) and 14.5–55.9 (Zn). Compared with WHO standards and other freshwaters worldwide, this lake was found to be unpolluted, with all metals, except Mn, being detected at concentrations lower than the highest desirable levels and maximum permissible levels. Some of the toxic metals, Cu, Zn, Pb and Cd (in sediment) and Ag, Co and Pb (in water) were detected at lower concentrations than those found in the polluted Kisumu Pier in Winam Gulf in the Lake basin, which confirms the anthropogenic influence on the latter.

Variation in indoor levels of polycyclic aromatic hydrocarbons from burning various biomass types in the traditional grass-roofed households in Western Kenya

Biomass burning as fuel in the traditional grass-roofed rural households of Western Province of Kenya in open fire places, in poorly ventilated conditions, lead to accumulation of soot under the roofs. This study characterized and quantified the polycyclic aromatic hydrocarbons (PAHs) in accumulated soot in these households and determined the variation in PAHs concentrations with fuel biomass type. Soot samples collected from the households were extracted, cleaned and analysed by gas chromatography. The PAHs were identified using retention times, verified by gas chromatographic mass spectral analysis and quantified from peak area responses using the internal standard method. The PAHs levels significantly varied (P ≤ 0.05) with biomass type in the order: dung ≥ indigenous trees ≥ exotic trees ≥ shrubs and crop residues. Use of dung and wood from indigenous trees as fuel should be discouraged since they are higher emitters (P ≤ 0.05) of carcinogenic PAHs.

The Persistence and Fate of Malathion Residues in Stored Beans (Phaseolus vulgaris) and Maize (Zea mays)

Two experimental models simulating the traditional storage conditions prevalent in Kenya, i.e. the open basket model and the modern wooden box model, were used to study the rate of dissipation and fate of malathion residues in maize grains and beans stored for periods of up to one year at ambient temperatures averaging 23°C. The grain samples were initially treated with 10.36 mg kg -1 of radiolabelled malathion dust prior to storage and portions analysed at regular intervals for malathion, malaoxon and the transformation products isomalathion, malathion α-monocarboxylic acid and malathion β-monocarboxylic acid using a combination of chromatographic, radioisotopic and mass-spectrometric techniques. The findings showed a gradual penetration of malathion into the grains in amounts which were slightly higher in maize than in beans irrespective of the method of storage. After 51 weeks of storage, 34-60% of the initial residues persisted in all the grains. The total residual levels were slightly higher in beans than in maize irrespective of the storage methods though the persistence was a little higher in the wooden box than in the open basket. The rates of dissipation of the pesticide from the grains decreased with storage time and followed a biphasic pattern. Applying first-order reaction kinetics, the following half-lives were obtained : maize grains stored in open basket : 194 days ; maize grains stored in closed wooden box : 261 days ; beans stored in open basket : 259 days ; beans stored in closed wooden box : 405 days. Beans stored in the wooden box had higher levels of bound residues than those sampled from the open basket. This trend was similar in maize grains although the concentrations were lower. The analysis of malathion metabolites confirmed the degradation trend of the residues.