College of Biological and Physical Sciences

No Abstract!

Soil samples were collected from six locations representative of the Nyando River catchment area of the Lake Victoria over a period of two years. Sampling was done four times in the year in February, May, September and December 2005 and 2006 in farms where maize, tea, sugar cane, coffee, rice and vegetables have been grown over the years. This coincided with the effects of different seasons and farming activities on residue levels of the pesticides in use. The objective was to investigate levels and distribution of organochlorine pesticides that have either been banned or are restricted for use in Kenya. Organochlorine pesticides investigated were DDT, lindane, aldrin, dieldrin, heptachlor, endrin, endosulfan (both α- and β- isomers and endosulfan sulphate), the sum is called “total” or Σendosulfan and methoxychlor. Prior to the ban or restriction in use, these pesticides had found wide applications in public health for control of disease vectors and in agriculture for control of crop pests. The analysis revealed presence of all the targeted pesticides with the highest mean concentrations for methoxychlor 138.97±1.517 μg/kg, Σendosulfan (30.267±2.098μg/kg), aldrin (18.317±0.276 μg/kg), respectively. The results show the presence of these pesticides in soils in the basin and this could be impacting negatively on the ecosystem health of the area.

No Abstract!

No Abstract!

A study was done to determine the influence of Acacia senegal variety and var.kerensis on quality of gum arabic in solit, kapkun, kimorok and maoi, Marigat division, baringo District. Soil and gum arabic samples were collected, dried and analysed to establish their chemical characteristics. Gum nitrogen from A. senegal variety senegal in kapnun and solit was negatively correlated to soil nitrogen (r=-0.28), while gum nitrogen from variety kerensis at kimorok and Maoi was positively correlated to soil nitrogen (r=0.16), respectively. High nitrogen content in soils was significantly correlated to high content of nitrogen (0.30%) in gum arabic obtained from A.senegal varieties. Gum copper was highly correlated to soil copper (r=0.09;p<0.01), soil iron was highly correlated to gum iron (r=0.09; p<0.05) and soil manganese and gum manganese was negatively correlated (r= -0.08; p<0.05). Gum zinc from A. senegal variety senegal at kapkun and Solit was negatively correlated to soil nitrogen and (r=-0.15), respectively. Nitrogen, iron, manganese and zinc contents in gums from A.senegal varieties fell within the ranges of the international standard specifications (0.26 to 0.39% N, iron (730 to 2490 ppm), manganese (69 to 117 ppm) and zinc (45 to 111ppm), respectively. A.senegal variety senegal in Solit and kapkun produced better quality of gum arabic than A. senegal variety kerensis in kimorok and Maoi.

Grazing cattle in the tropics and especially in Uasin Gishu district depend on a variety of plant species for their mineral supply. One area of concern is that the grazing cattle may be experiencing mineral imbalances due to lack of proper mineral mapping of the region to ascertain the levels of imbalance. A study conducted in the Uasin Gishu region revealed severe deficiencies of mainly Cu (3.30 ± 0.90) and Zn (6.70 ± 0.40) in soils, the elements Na (1.00 ± 0.39), K (11.80 ± 5.00), Ca (0.57 ± 0.19), Mg (1.35 ± 0.72), P (6.34 ± 3.22), Fe (56.00 ± 0.53), Cu (5.32 ± 2.84), Zn (19.50 ± 8.20) in pasture species and the elements Fe (2.43 ± 1.53), Mn (0.26 ± 0.14 ), Cu (0.60 ± 0.17), Mg (0.02 ± 0.01) in animal blood. The study recommends immediate mineral supplementation schemes to grazing cattle in the region and encouragement of certain pasture species in the region.

Livestock industry is one of the major contributors to the country's GDP and provides one third of the total available food in the country. Mineral deficiencies and imbalances in soils and forages can be a challenge in relation to production in grazing cattle in developing countries. A number of factors influence the availability of such minerals in terms of proper growth and development of cattle. The study was done in selected parts of Uasin Gishu and revealed severe nutritional deficiencies in soils and forages. The study also revealed a number of factors that influenced mineral concentration in the region. The study has suggested recommendations to help identify and alleviate any constraints on animal health and production.
Key words Livestock industry, mineral deficiencies, soils, animal health and production

A study was conducted to assess the physical properties of gum arabic obtained from two Acacia Senegal varieties (var.Senegal and Mar.kerensis). in Marigat division, Baringo district. Gum arabic samples from the experimental sites at Solit, Kapkun, Kimorok and Maoi were collected, dried and analysed to establish their physical characteristics. Moisture content in gum arabic obtained from variety kerensls in Kimorok and Maoi (17.5 ± 1.00 and 15.4 ± 0.50%) were significantly higher (P < 0.05) than those of variety Senegal in Solit and Kapkun (15.0 ± 0.50 and 14.9 ± 1.80%), while internal energy (33.4 and 33.76%) were not significantly different (P > 0.05) from those of variety Senegal found in Kapkun and Solit (33.0 and 32.96%), respectively. Ash content in gum arabic from variety Senegal in Solit and Kapkun (2.94 and 3.16%) was higher (P < 0.05) than those of variety kerensis found in Kimorok and Maoi (2.88 and 2.72%). In Kapkun, volatile matter in gum arabic from variety Senegal (64.2%) was higher (P < 0.05) than the quantities of variety kerensis found in Kimorok, Solit and Maoi (63.8, 63.7 and 63.6%), respectively. Moisture content in gum arabic from variety Senegal in Solit and Kapkun (15.0 ± 0.40 and 14.9 ± 1.80%) fell within international specifications (13 to 15%), while variety kerensis in Kimorok and Maoi (17.5 and 15.4%) fell outside the specifications. Moisture, ash and volatile matter contents in gum arabic from A. Senegal variety Senegal were 14.9, 3.16 and 64.24%, while A. Senegal variety kerensis had 15.2, 2.88 and 63.8%, respectively. Moisture content in gum arabic from A. Senegal variety Senegal fell within international specifications while A. Senegal variety kerensis fell outside the specifications. Ash, volatile matter and internal energy contents in gum arabic from A. Senegal variety kerensis and variety Senegal fell within the specifications. The gum arabic from A. Senegal variety Senegal in Solit and Kapkun was of better quality than that of A. Senegal variety kerensis in Kimorok and Maoi.

No Abstract!

No Abstract!

Abstract. A study was conducted in which samples ol soil. forage, as well as serum, bone, kidney, and liver of waterbuck were collected from Lake Nakuru National Park. The objective was to determine the ecosystem health status in older to establish the causes of animal health problems previously re¬corded in some sections of the Paik. Trace element analysis in serum indicated occurrence ol copper (Cu) deficiency in the north and eastern sections of the Park where mean values were marginal (range: 0.36-0.81. mean: 0.62 mg/1) compared to concentrations recorded in the western part of the Park (range: 0.69 1.48. mean: 1.22 mg/l). Bone analysis on dry matter basis (DM) indicated higher (p < 0.01) levels of cadmium (Cd. 0.437 nig/kg), fhioride (F, 3178 mg/kg). and lead (Pb. 20.62 mg/kg) in animals from the east compared to those from the west (0.002. 1492, 4.87 mg/kg. respectively), suggesting heavy exposure. In addition, samples from the east had much lower than normal calcium (Ca)-to-phosphorus (P) ratios (mean: 1.9:1) compared to those recorded in the west (2.2:1). suggesting poor bone minerali/ation There was a higher concentration of Cd in the kidney (16.24 mg/kg. p < 0.05) and Pb in the liver (58.3 mg/kg. /; < 0.01) in animals from the east compared to those in the west (12.92 and 36.2 mg/kg, respectively), but the converse was true of Cu The liver Cu status was better in animals from the west with, concentrations (mean: 21.7 mg/kg) being about twice those recorded in the east (11.9 mg/kg DM). Forage analysis revealed prospects of Ca, P, and Cu deficiencies in the entire Park. However, in the northeastern section of the Park (measuring 50 ha) where waterbuck residence times are high, forage concentrations of Cd (0.31 mg/kg DM), molybdenum (Mo. 7.20 mg/kg DM). Pb (2.88 mg/kg DM), and /inc (7.n. 126 mg/kg DM) were an order of magnitude greater (p < 0.01) than the levels recorded in the rest of the Park (ranges: 0.133 0.165, 3.69 5.61. 0.485 0.621. 11.6 17.4 mg/kg DM, respectively). These disparities were attributed to a higher soil concentration of CM (2.77 mu/ku DM). Pb (85.1 msi/k DM) and 7,n (1414mg/kg DM i n this section compared lo the rest of the Park (ranges; 0 Id o 15. 5.02 6.26. 1,49 5.44 mg/kg DM. respec¬tively), and su»ngly suggest heavy metal contamination as the source ol annual health problems in the Park.

INTRODUCTION
Kenya strives to move along the path of sustainable development to meet the needs of the present generation without compromising the ability of the resource base to meet those of future generations. However, the development process in the country is at a stage at which land use interests such as agriculture, tourism, ranching, wildlife management, forestry, water conservation, mining, manufacture development are often conflicting. This is excercabated by the mismatch between population and economic growth together with inadequate policies governing land use. Additionally, existing policies and programmes are either poorly implemented or lack harmonization and coordination. These inadequacies especially those governing management of the resource base have resulted in widespread environmental degradation and subsequent threat to ecosystem health.
Some of the threats to ecosystem health can be attributed to poor effluent treatment and disposal of toxic waste and obsolete pesticides (commonly
referred to as persistant organic pollutants, POPs) in the environment. These
* ,
pollutants include polychlorinated piphyeyls (PCBs), aldrin diedrin, DOT, endrin, chlordane, hexachlorobenzene, minex, toxaphene, heptachlor, dioxins and furans.

KENYA COUNTRY PAPER: UNIDO-RENPAP WORKSHOP, BOGOR INDONESIA 18"1 - 20'" SEPTEMBER, 2006

SUMMARY
The total Dioxins (PCDD) and Furans (PCDF) release in Kenya is estimated to be 4,740 g TEQ per annum. The Uncontrolled Combustion Processes category generates 4,304 g TEQ which is the highest of all the categories that were identified, amounting to 91% of the total national release. Waste Incineration generated 249.4 g TEQ equivalent to 5% of the total national release, while Disposal/Landfilhng category has a notable contribution of 106 g TEQ which amounts to 2% of the total national release. Ferrous and non ferrous metal production contributes 12.8 g TEQ which is equivalent to 0.3% of the total national release. Releases from the remaining categories are not significant when compared to the ones already mentioned. However, this does not in anyway underrate their importance, especially in instances where total elimination by application of Best Available Technologies (BAT) and Best Environmental Practices (BEP) can be achieved. These results are summarised in Table Tl and Figures Fl and F2.
Uncontrolled domestic waste burning, a subcategory under the Uncontrolled Combustion Processes category, is the single most significant source of PCDD/PCDF. It generates 2168 g TEQ, which is equivalent to 45.7% of the total national releases. Landfill fires sub category is the second significant source of release, contributing 2126.3g TEQ which is equivalent to 44.8% of the total national release.
With regards to vectors, air receives the bulk of the PCDD/PCDF amounting to 3,103 g TEQ which is equivalent to 66% of the total national release. The bulk of this release comes from the Uncontrolled Combustion Processes, amounting to 2854g TEQ, which is equivalent to 92% of the total national release to air. Release to residues amounts to 1,614 g TEQ which is approximately 34% of the total national release, with the main contributor to this being Uncontrolled Combustion Processes, These results are summarised in Figure F2.
Uncontrolled Combustion Processes category therefore requires significant attention because of the great impact it may have in the country. Policies to govern the management of solid waste are necessary and would go along way in minimizing this impact. Similar efforts to address medical waste would also have a significant impact on the releases in the country. The release of PCDD/PCDF to water also needs to be addressed seriously considering the fact that a significant percentage of the country's population relies on surface water for domestic use.
There are no municipal waste incinerators in Kenya but there are isolated hazardous waste incinerators. However, the inventory has established that the medical waste accounts for the bulk of releases for this category. This is because majority of the government district hospitals and institutions operate the De Mont fort type incinerators. Only two major hospitals operate commercially acquired incinerators. However, most of the incinerators do not have effective air pollution control systems (APCs). To a large extent many of The medical facilities either openly bum their waste or have installations called incinerators which in effect are open burners. The total release from this category averages 249.4 g TEQ.
Hazardous wastes or waste oil are not currently used as fuel for firing cement kilns for fear of compromising on cement quality.

The use of most organochlorine pesticides has been banned or restricted in the republic of Kenya under the Rotterdam and Stockholm convention due to high levels of persistence in the environment and toxicity to nontarget organisms. Studies conducted in some parts of the country have revealed that residue levels of these compounds are still in the environment. However, the residues of these compounds have not been exhaustively studied in the Lake Victoria catchment area. This study was set to investigate the residues levels of p,p-DDT, o,p'-DDE, p.p-DDD, g-HCH, D-HCH, a-HCH, Aldrin, and Dieldrin, in water samples from Lake Victoria catchment. Samples were collected during the short rain, dry and wet seasons and analysed using gas chromatography equipped with electron capture detector. Residue levels ranging from below detection limit (BDL)-0.44 ug/l in river Nzoia water, between BDL-0.34 ug/l in river Sio water, BDL- 0.26 ug/l in water from Sio Port, and between BDL-0.31 ug/l in water from lake Victoria at Marenga Beach were detected.
Key words: Organochlorine, residues, Lake Victoria

No Abstract!

ABSTRACT
Thirty-four HIV/AIDS patients at various stages of disease progression volunteered to manage their health using a nutritional supplement that contained several micronutrients that included a 15 nig daily dose of elemental zinc. This initial publication only focuses on trends in the serum zinc levels and the observed biochemical changes following intervention, considering the critical role this trace element plays in human immunity. At baseline and after 30 months of follow-up, the patients' serum zinc levels were determined as was their clinical status. Four women who were found to be HIV negative at baseline and who had lost their husbands to HIV/AIDS, yet they had regularly had un-protected sex with them, had a mean serum zinc level of 116.2 ± 32.7 meg/100 ml. The serum zinc levels of asymptomatic, moderately symptomatic and severely symptomatic HIV/AIDS patients in the cohort reduced from baseline to post intervention levels of 92.5+12.1 to 78.0 + 8.2 meg/100 ml (P = 0.056); 81.9+ 17.6 to 73.2 + 12.2 meg/100 ml (P = 0.267) and 72.7+ 8.0 to 66.8 + 14.3 meg/100 ml (P = 0.022), respectively, all being far below the mean serum zinc level of 120.0 + 22.0 meg/100 ml reported in normal control subjects in Western literature. For all patients combined, the serum zinc levels fell from 79.2 + 14.5 to 71.0 + 13.0 meg/100 ml (P= 0.016) notwithstanding that the patients had used zinc supplements at recommended daily allowances (RDA) over a period of 30 months. Notably, micronutrient zinc sufficiency plays a key role in promoting cell-mediated immunity and it is probably partly due to this reason that the high-risk women in this study, who also had comparably high serum zinc levels fell from 79.2 +/-14.5 to 71.0 +/-13.0 mcg/100 ml (p=0.016) notwithstanding that patients had used zinc supplements at recommended daily allowances (RDA) over a period of 30 months. Notably, micronutrient zinc sufficiency plays a key role in promoting cell -mediated immunity and it is probably partly due to this reason that the high risk women in this study, who also had comparably high serum zinc levels, remained negative for HIV antibodies despite repeated exposure to the virus. thus from this preliminary data shows HIV/AIDS patients to be deficient in zinc in a manner consistent with their status of disease progression and considering that this trace element is recognized to possess antiviral and antibacterial properties, it is now apparently evident that zinc supplementation may play a key role in the fight against HIV/AIDS not only in Kenya but also in other African countries where the disease has reached epidemic proportions against a background of rampant malnutrition

Key words: Micro nutrient zinc, underutilized arsenal, combating, hiv/aids, SUB-SAHARAN Africa

No Abstract!

Studies were conducted on the distribution, fate and metabolism of DDT in a model ecosystem simulating a tropical marine environment of fish, Gabions nudiceps, Leihrinuf haruk, Cohious keineiis, Gnhiota nebutosis and white shrimp iPanaeus seliferus), show that DDT concentration in the water decreases rapidly within the first 24 h. Rapid accurr. • ution of the pesticide in the biota also reaches a maximum level in 24 h before graJuiiiy declining The bioaccumulution factors calculated for the fish specie.! (G. keinesis) and white shrimp '(P. Stiiferu!) were 270 and 351, respectively, after 24 h There was a steady build up of DDT residues in the sediment during the first 24 h which continued to a maximum concentration of 6 66 ng g in the sea-water fish sediment ecosystem after 3 weeks and 5.27ngg in the seawater/shrimps/sediment ecosystem after 2.7 days The depuration of the accumulated pesticide was slow with only 54% lost in G. nudiceps within 3 days of exposure in fresh sea water. By contrast, depuration was fast in the while shrimp, which lost 97% of the accumulated pesticide under the same conditions. DDT was found to be toxic to two of the fish species, (G. nebulmis and /_. huruk) and to white shnmp, and the degree of toxicity was dependent on the particular species. The 24 h LCyj al room temperature lor the fish species G. nebulous and white shrimp was found to be 0.011 and O.I 16mg kg. respectively. These levels are comparable to the ones recorded for the temperate organisms. Degradation of DDT to its primary metabolites. DDE and DDD. uas found in all the compartments of the ecosystem with DDE being the major metabolite in the fish, shrimps and sediment, while in se.iwater. DDD dominated as the major metabolite.

No Abstract!

Chlorpyrifos, O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothioate, is one of the most widely used organophosphorous pesticides worldwide due its high efficacy (Carvalho et al. 1992; Liu et al. 2001, Meikle and Youngson 1978). In Kenya, Dursban formulations are mainly used for protection of horticultural fruits and vegetables (Lalah 1994), Because of its low water solubility (0.4 mg/L) and high hydrophobicity (log Kow of 5.27), it is believed that chlorpyrifos would be able to partition easily onto aquatic sediments and macrophytes where it can pose dangers to benthic organisms (Ronday et al. 1998). It is also quite a volatile toxicant due to its low vapour pressure (2.5 mPa at 25 °C) and low air-to-water partition coefficient (8.9 10"4 at 25 °C) and its residues have been detected in air and rainwater samples (Liu et al. 2001).Increasing use of chlorpyrifos also causes a lot of anxiety to environmentalists and toxicologists because it is toxic to both humans and wildlife. As an irreversible inhibitor of acetylcholinesterase, it can cause impairment in mammalian brain cell development (Lund et al. 2000; Jeanty et al 2001; Jett et al 1999; Slotkin et al. 2001). Widespread use of this compound is therefore considered to be of great danger particularly to pregnant women and children Some of its reported toxicities to aquatic organisms include 96 hr LCNo of 0.13 |.ig/L and 96 hr LC?o of 0.035 Ug/L in adult Neomysis integer and Americamysis bahia, respectively (Roast et al. 1999). Although its toxicity in mammalian and aquatic organisms has been well documented, its fate and effects on aquatic ecosystems in tropical conditions where it is expected to degrade and dissipate faster (Carvalho et al 1992) are little known. In a laboratory model aquarium simulating a tropical marine environment, we studied the persistence and accumulation of HC-chlorpyrifos in sediment, fish and oysters. The results obtained from these studies are reported in this paper.

No Abstract!

Fluxes of dissolved inorganic nutrients: NH+4, NO-2, N-3, PO34 and Si(OH)4 from near shore sediments of Gazi Bay were measured in situ within mangrove, sea grass and coral reef biotopes using benthic flux bell-jar chambers of cross-sectional area 0.066 m2 and volume 0.0132 m3. The objectives were: (1) to determine the influence of benthic fluxes, fluvial discharge and seasonal variations on the nutrient budget in the Bay waters; (2) to determine the effect of tidal and spatial variations on nutrient loads in the water column and (3) to establish the relative importance of the nutrient sources with regard to total community production of the Bay.
The directly measured fluxes ranged from -270 to +148 µmol NH+4-N/m2/h; -60 to +63 µmol NO-2-N/m2/h; -79 to +41 µmol N-3-N/m2/h; -79 to +75 µmol PO34-P/m2/h and +30 to +350 µmol Si(OH)4-Si/m2/h for and respectively. It was established that benthic fluxes are the major sources of dissolved inorganic NH+4, NO-2and Si(OH)4 while fluvial sources are important for N-3 and PO34into Gazi Bay waters. Seasonal variations had an appreciable effect on the PO3-4, fluxes, N:Si ratio, river nutrient discharge, plankton productivity and important environmental factors such as salinity and temperature. Tidal and spatial variations had no significant effect on nutrient concentrations and net fluxes within the water column. The results imply that benthic fluxes are largely responsible for the nutrient dynamics of the near shore coastal ecosystems especially where direct terrestrial inputs do not contribute significantly to the nutrient budget.
© 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Gazi bay; Nutrient sources; Benthic fluxes; Fluvial discharge; Community production; Coastal ecosystems

Accumulation, distribution and metabolism of ring labelled, "C-1,1,1, - trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT) in a model marine aquatic ecosystem consisting of sea water, sediment, oysters (Isognomonon alatus) and Humbug fish (Dascillus aruanus) were studied in the laboratory. "C-p,p'-DDT distributes rapidly in the ecosystem immediately after application on the water surface with reduction of its concentration in the water phase from 1.18 ng g"1 to 0.71 ng g'after 2 hours and an increase in its content in the sediment and oysters. The bioconcentration factor reached a maximum of 19x 10* in oysters, and 1657 in Humbug fish after 24 hours. The sediment concentration reached 117 ng g"1 after 168 hours from start of application. A peak bioconcentration factor of 111 x 103 was calculated after 120 hours when 0.24 mg kg"1 of '^>p,p'-DDT was maintained through dosing every 24 hours with 0.002 mg kg' of a mixture of labelled and non-labelled pesticide. The rate of depuration of accumulated "C-p,p'-DDT sediment residues was up to 78.3% after 24 hours while oysters lost only 14.0% during the same period. The loss in Humbug fish was only 22.2% in three days. Volatilisation and sorption losses from seawater alone (without sediment/biota) were found to be very high in the range of 73.8 - 91.5% over 24 h for p,p'-DDT in aerated and non-aerated ecosystem. Gas chromatograph and TLC analysis of water, sediment and oyster samples revealed presence of p,p'-DDT and substantial amounts of p,p'-DDE and p,p'-DDD three days after pesticide dosage.

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'-DOT 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 'mSiganus rivulatus.

Introduction
The use of free ranging mammals in monitoring ecosys-tem health has been suggested (Costanza, Norton & Haskell, 1992). In Lake Nakuru National Park of Kenya, a high frequency of dental abnormalities has been reported in the waterbuck (Foley & Atkinson, 1984). This was attributed to inbreeding and increased homozyg-osity, which led to a higher frequency of genetic abnor¬malities. It was also noted that waterbuck in the north¬eastern part were in poorer body condition than in other parts of the park (Kock et al, 1994). Maskall & Thornton (1989) carried out a study of the mineral status of soils in the park, which showed some def¬iciencies. Because the waterbuck is territorial and has a small feeding range, an environmental factor, amongst others, might also play a role in the poor health status of the antelope in the north-eastern part of the park.
The purpose of the present study was to correlate the mineral status of the waterbuck to its health status in lake Nakuru National Park. A comparison was also made with waterbuck around Lakes Elementaita and Naivasha, which are located in the same region. Furthermore the study would be useful in assessing the suitability of Lake Nakuru National Park for rearing endangered species.

PREFACE
To reap the full benefit of any product available in the market, consumers should know the types of raw materials in the products, the way in which the products perform their job, and the precautions that need to be taken when using the products. With some basic knowledge of chemistry, the small print on the label becomes important to the consumer and may lead to a better selection and use of the product purchased.
The first chapter of this book deals primarily with the chemical nature of both living and non-living things. Chapter Two places emphasis on the innate curiosity of man and his use of experimentation in the evolution of important chemical transformation processes that bring about changes in matter. These reaction processes are employed in the chemical industries discussed in the subsequent chapters; their inclusion therefore seeks to bring the study of chemistry into focus in the student's life.
The rest of the text material, which can be built on a very thoughtful analysis of chemical theory or a simple notion of atoms, molecules and a few molecular geometries and interactions, enlightens the student on the many ways in which chemical knowledge has been applied to solve practical problems. An innovative approach to the problem of teaching students something about the chemical processes which touch upon their daily lives is discussed under various chemical aspects including: isolation of metals from their ores and salts and their uses, nuclear processes and their applications, the manufacture of soaps and detergents, synthetic fibres and surface-coating products, beauty aids, perfumes and flavouring agents, foods, agrochemical and animal health products, fermentation reaction products and medicines, environmental chemical pollution, chemical poisons and their basis of toxicity, the role of chemistry in industrial and economic development (with a discussion on some critical industries) and, finally, safety precautions against chemical hazards.
Although some of the exercises provided at the end of each chapter are meant to test the reader's understanding of concepts, a few open-ended questions have been added to stimulate the bright student and to involve him or her in some of the inevitable controversies of chemical science. A few references have been provided to encourage the enthusiastic student to develop a taste for studying in depth a particular point of interest.

The annual domestic consumption levels and patterns of various common biofuels in Kenya were surveyed. The main fuelwood sources were farmland trees, indigenous forests, woodlands and timber off-cuts from plantations. In 1997, about 15.4 million tonnes of firewood (air-dried) were consumed and an equivalent of 17.1 million tonnes round wood wet weight (w/w) was converted to charcoal. In the same year, 1.4 million tonnes of a variety of crop residues were also consumed as domestic fuel. Biofuel availability was the major factor influencing the reported annual spatial species use and consumption patterns. Competing demand for the commonly-used tree species (mainly eucalyptus trees) for commercial and other purposes accounts, to a large extent, for the reported dwindling amounts. Communities in various regions have responded by gradually shifting to other available types including those in gazetted forests. Such a response strategy has implications on the long-term spatial and temporal biofuel use patterns. © 2001 Elsevier Science Ltd. All rights reserved.

Abstract
A questionnaire survey was conducted in rural and urban Kenya to establish biofuel consumption rates and patterns. The survey targeted households, commercial catering enterprises and public institutions such as schools and colleges. Firewood was the main biofuel used, mostly by rural households, who consumed the commodity at average consumption rates in the range 0.8-2.7 kg cap"1 day~'. Charcoal was mostly consumed by the urban households at weighted average rates in the range 0.18-0.69kgcap~' day"1. The consumption rates and patterns for these fuels by restaurants and academic institutions, and those for crop residues are also reported. The rates largely depended on the fuel availability but differed significantly among the three consumer groups and between rural and urban households. Other factors which may have influenced consumption rates are discussed. Although good fuelwood sufficiency was reported in the country in 1997, there were increasing difficulties in accessing these resources by most households, a situation having both short- and long-term implications for biofuel consumption rates and patterns. © 2001 Elsevier Science Ltd. All rights reserved.

Keywords: Biofuels; Per capita consumption; Kenya

Emission ratios (ER) of CO and NO relative to CO2 are reported from real time emission measurements on biofuel fires in Kenya. The experiments were based on available fuels burning in local popular traditional and improved stoves. The mean dCO/dCO2 ratios were 71, 79 and 74 mmol molt-1for firewood, charcoal and agricultural residues, respectively, while the corresponding mean d/NO/d/CO2 ratios for these fuels, in the same order, were 1.8, 2 and 2.2 mmol molt-1, respectively. Whereas stove design characteristics largely influenced the dCO/dCO2 ratios, the fuel nitrogen content was the major factor determining the dCO/dCO2 ratios. The dCO/dCO2 ratio for fuel derived NO is not affected by fire temperature but linearly depend on the fuel nitrogen content. Other important fuel parameters that influenced the observed emission ratio patterns include fuel moisture content, size and volatile matter content in the case of charcoal. In comparison to savanna and forest fires, biofuel fires tend to favour formation of reduced or partially oxidised compounds. It is clear that a change in energy preference up the "energy ladder" leads to a reduction in the CO ER, an important result for emission mitigation policy design.
© 2001 Published by Elsevier Science Etd.
Keywords: Trace gases: Emission ratios; Biofuels; Stoves; Biomass burning

This study provides a means for the evaluation of cleaner manufacturing and the provision of cost-effective worker health improvements in developing nations. Individual worker exposure to volatile organic compounds was measured in the paint manufacturing plants of Nairobi, Kenya. A variety of different paint production jobs were monitored, including laboratory researchers, mixers, tinters, fillers, cleaners, raw materials deliverers, and resins producers.
Exposure levels were calculated based on a time-weighted average over an entire 8-10 hour workday. The paint solvents used can cause both acute and chronic health problems for the workers exposed. For example, over half of the or-ganics monitored, i.e. benzene, styrene, and xylene, exhibit carcinogenic properties. The lifetime cancer risk from exposure to these paint solvents was estimated utilizing published cancer potencies, and the risks range from 1.90 x 10-4for raw materials deliverers to 2.60 x 10-2for cleaners.
The highest exposure tasks included cleaning the mixing vats and mixing the paint product, ranging from risks of 8.5 x 10-4 to 2.6 x 10-2, providing evidence that solvent exposure occurs due to point sources. Because of this, simple and inexpensive technologies should significantly reduce the excess exposure of workers in these manufacturing facilities. The cost of minor innovations in the plants themselves, such as fans, drum and mixing vat covers, and respirators, could amount to as much as five times less than the estimated cost of treating workers who develop cancer due to paint solvent exposure.
Keywords Benzene Exposure, Developing Countries, Kenya, Occupational Exposure, Paint Manufacturing, Risk As-assessment, Volatile Organic Compounds

PREFACE To reap the full benefit of any product available in the market, consumers should know the types of raw materials in the products, the way in which the products perform their job, and the precautions that need to be taken when using the products. With some basic knowledge of chemistry, the small print on the label becomes important to the consumer and may lead to a better selection and use of the product purchased. The first chapter of this book deals primarily with the chemical nature of both living and non-living things. Chapter Two places emphasis on the innate curiosity of man and his use of experimentation in the evolution of important chemical transformation processes that bring about changes in matter. These reaction processes are employed in the chemical industries discussed in the subsequent chapters; their inclusion therefore seeks to bring the study of chemistry into focus in the student's life. The rest of the text material, which can be built on a very thoughtful analysis of chemical theory or a simple notion of atoms, molecules and a few molecular geometries and interactions, enlightens the student on the many ways in which chemical knowledge has been applied to solve practical problems. An innovative approach to the problem of teaching students something about the chemical processes which touch upon their daily lives is discussed under various chemical aspects including: isolation of metals from their ores and salts and their uses, nuclear processes and their applications, the manufacture of soaps and detergents, synthetic fibres and surface-coating products, beauty aids, perfumes and flavouring agents, foods, agrochemical and animal health products, fermentation reaction products and medicines, environmental chemical pollution, chemical poisons and their basis of toxicity, the role of chemistry in industrial and economic development (with a discussion on some critical industries) and, finally, safety precautions against chemical hazards. Although some of the exercises provided at the end of each chapter are meant to test the reader's understanding of concepts, a few open-ended questions have been added to stimulate the bright student and to involve him or her in some of the inevitable controversies of chemical science. A few references have been provided to encourage the enthusiastic student to develop a taste for studying in depth a particular point of interest.

A number of diseases and production problems have been observed in grazing ruminants in many countries around the I world Some of these problems and health effects have been attributed to dietary imbalances in mineral supply and appear \ to be geographically distributed. Grazing cattle require different levels of minerals in their diet depending on the stage of class of development; young and growing, lactating or pregnancy. Common findings indicate that the lactating and young} and growing animals are the most vulnerable to mineral problems, thus providing a sufficient ground for their choice in\ experimental studies. In this preliminary review of the project, the nutritional status of cattle grazing on a range of farms in \ Irons Nzoia District are assessedfrom the mineral content of blood from young and growing as well as lactating animals] sampled during the dry and wet seasons of the study period. Data -will be evaluated in terms of established criteria normality.

EXECUTIVE SUMMARY
An environmental impact assessment study was carried out in the area covering the proposed National Oil Corporation of Kenya (NOCK) truck loading facility which is located in Nairobi's industrial area. The main objective of the study was to assess the state of the environment before the development and commissioning of the facility, in order that the design of the facility can objectively take into account the minimisation of the risk of possible negative environmental impacts that may be generated by activities at the facility, and that a baseline of the current environmental state in the area be provided for monitoring such changes in the future.
This environmental impact assessment study included: a geological/geophysical survey to establish the geology and structures of the proposed construction site; establishment of baseline levels of groundwater and existence of water wells within the area; determination of current levels of pollution in air, soil and groundwater by chemical analysis of samples collected in the area; qualitative investigation of noise pollution status; assessment of existing factory activities in the vicinity of the site vis a vis their effect on the environment and complementarity of the proposed facility; determination of possible effects of various pollutants on human settlements adjoining the area; and rating the potential health risk to workers within the truck loading facility.
Black cotton soils with a thickness of about 70cm overlie relatively thick (51m) phonolites which characterise the geology of the area. There are a number of fractures/cracks traversing the area in a nearly north-south direction. These are believed to be shallow fractures, and it is recommended that pits be dug 3 to 4 m deep to establish the depth of the fractures. Beneath the phonolites (>51m depth) are the Athi tuffs and lake beds where most of the groundwater in the area occurs. This is consistent with water strike levels in boreholes drilled in the Industrial Area. Given the thickness and impermeability of the phonolites and shallow depth of the fractures, contamination of groundwater (>52m depth) by infiltration of pollutants from the surface is most likely insignificant. Groundwater quality in the area does, however, not appear to be suitable for drinking due to its high Fl and Fe content, but is suitable for other domestic and factory use. Heavy metal analysis of the soils reveals that the only metal that could threaten ground water quality in the area is lead, which appears to come from automobile exhaust emissions and atmospheric loading and fall-out of the volatile gasoline additive, lead tetraethyl. This may contaminate the transient (seasonal) groundwater that accumulates in the near surface zone (weathered, fractured phonolite and soil <8m deep) during the rainy seasons, and dries up soon after the rains.
Analysis of organic volatiles reveals the presence of hydrocarbons (hexane, benzene and xylenes) which are components of petrol. The source of these hydrocarbons appears to be the Kenya Pipeline Company pumping station to the West and Shell, Caltex and Mobil loading facilities to the East of the proposed site. Although the concentrations are not of serious concern, it is recommended that frequent monitoring be done to check any danger that might be posed to the new facility. The air concentrations of sulphur dioxide, hydrogen chloride, ammonia and nitrogen-dioxide suggest a low acid and base deposition in the area. Nitrogen
dioxide levels are, however, close to critical limits. Concentrations of the various air pollutants warrant further monitoring, to check the likely risk on human health within the facility. The nearest human settlements are located at least two kilometres to the North and East of the area, so air pollutants and noise that may emanate from the facility are unlikely to pose a threat to them.
The overall finding of the environmental impact assessment study is that the site is suitable for development of a truck loading facility as proposed by National Oil Corporation of Kenya. It is, however, strongly recommended that this baseline study should form the basis for monitoring and evaluation of the environmental conditions as site development proceeds, and when the facility is operational.

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|7 Skulls of the waterbuck (kobus ellipsiprynnus defassa) ithree lake systems of the central Kenyan Rift Valley (viz. tfakuru, Elementaita and Naivasha) were examined for bnormalities, as a result of chronic signs of ill health, in ome of the animals in the region. The waterbuck were ulled randomly and weighed. Several parameters were leasured. A post mortem examination was carried out on ach of the animals culled. Bone samples were stripped F all tissue by boiling. The skulls were weighed and amined for any abnormalities. The teeth were used for eing the animals.
lemean age of the waterbuck was 5.1±1.7 years. 67% of Bimals in poor body condition showed skeletal normalities including pathological eruption and growth • wear of teeth. The teeth had black stains along the gual and buccal surfaces but no evidence of fluorosis. |je abnormalities observed in the skulls could be uted to mineral imbalances in some of the areas in the al Kenyan Rift Valley region. Abnormal eruption of i could in turn play a role in poor feeding of the affected als thus contributing to poor health.

Statement of the Problem
\
Atmospheric concentrations of greenhouse gases have been increasing rapidly (IPCC 1994). This increase has been attributed mainly to human activities. The composition of the atmosphere has thus changed considerably and will continue to do so in future. Such changes are capable of affecting the surface climate of the earth and can have possible consequences on both natural and man-made resources, thereby threatening both marine and terrestrial ecosystems. Deleterious effects of these consequences will affect the well-being of man through impacts on important sectors such as health, agriculture, transport, industry, and water resources (IPCC 1990; 1995). To these sectors, energy is crucial for their development but energy itself is also vulnerable to the effects of climate change. Negative changes in energy production will therefore seriously affect global industrialization programs as well as national economies considering that global demands for energy have been rising at an annual rate of 2% (IPCC, 1995).
Kenya, like most developing countries relies on biomass (mostly woodfuel and charcoal^as the biggest source of energy, contributing about 73% of the total energy requirements. It is used by over 80% of the rural population, mostly for cooking and heating. In addition to biomass, the other two major sources of energy in Kenya are petroleum and electricity. The domestic sector is the largest consumer (59%), followed by industry (15%), transportation (11%), agriculture (10%), and commercial (5%) sectors (Kenya/Canada Energy Advisory Project, 1991).
When considered in terms of social-economic development, human settlement infrastructure, as well as manufacturing, electricity is the most important form of energy in Kenya Currently, it is generated from several sources including hydropower, gas turbines, geothermal power and diesel engines. Of the total amount generated, hydropower contributes over 76%.
Hydroelectricity generation depends on availability of water, which in turn depends on the prevailing climate. Fluctuations in rainfall and temperature can affect evapotranspiration rates which in turn can determine the channel flow and power generation rates. In this regard, the hydro-power source of electricity becomes the most vulnerable to climate change effects. This study therefore focuses on hydro-power development in Kenya in relation to the impacts of climate change that are anticipated in future.

NON-DESTRUCTIVE ANALYSIS OF MERCURY BY THE ENERGY DISPERSIVE X RAY FLUORESCENCE TECHNIQUE IN BEAUTY CREAMS SOLD IN KENYA.
Analysis of mercury in 100 different beauty creams by the energy dispersive X ray fluorescence technique is described. Each sample was brought to a melt by warming on a water bath at 40-50eC, and then poured onto a 2.5 cm diameter Mylar backed aluminium ring so as to acquire the configuration of a homogeneous pellet when cooled. No other physical or chemical treatments were applied to the sample. The results of our mercury level measurements and analysis (u,g/g) showed that: (a) the detection limit for the detector system was 3.3; (b) 'Madonna' (green) (n= 10) had the highest level of mercury: 29 000 + 2800; (c) 'Madonna' (red) (n = 10) had a level of 18 000 ± 1700; (d) 'Pimplex' cream (« = 10) had 6800 ± 690; (e) 'Shirley' (original) (n = 10) registered 14 000 ± 1100; (0 'Bestlady' cream registered 13 000 ± 1300; (g) 'Topsine' (n = 10) had 1600 ± 150; (h) 'Fennel' (n = 10) had 4300 ± 430; (i) 'Shirley' (new), 'Dermovate' and 'Topshirley' creams (n = 10 each) registered mercury levels below the detection limit; (j) there was a significant difference (p < 0.001) in the results for 'Madonna' (red), 'Pimplex' and 'Shirley' (original) for batches bought during March and September 1995. The health implications of some of these high levels of mercury present in some beauty creams in Kenya are discussed.

Kenya's fast growing human population is expected to reach 35 million by the year 2000. In order to cope with such a rapid rate of growth, efforts must be directed towards adequate agricultural and livestock production to counter the disproportionate increase in demand for food. To provide sufficient animal protein (milk and beef products) attempts must be made to eliminate the current constraints hindering livestock production and expansion in Kenya (KARI,1989). One such constraint (in terms of both health effects and economic losses) is the presence of several important infectious diseases affecting cattle, characterized by the occurrence of parasites in the animal's blood (haemoparasites) (Mutugi et al, 1989).
There are two major groups of haemoparasitic diseases that occur in Kenya: tick-transmitted, and tsetse and non-tsetse transmitted (trypanosomiasis) diseases. Tick-borne diseases are considered to be the most important animal health problem in the high potential areas, while trypanosomiasis is a major threat in the low potential range lands (Mutugi, 1986). These diseases restrict introduction of higher producing but susceptible stock in certain areas of the country; inflict high mortalities in susceptible stock; lead to productivity losses in recovered animals; and necessitate exclusion of highly productive breeds of livestock from locations where there is an outbreak (FAO, 1984).
Tick-borne diseases frequently encountered in Kenya are theileriosis, anaplasmosis, cowdriosis and babesiosis. Theileriosis comprises a group of protozoan parasites of the genus Theileria, which are transmitted by the ixodid ticks. Four different species of this genus are recorded in cattle; clinical theileriosis is associated with one species, Theileria parva transmitted by the brown ear tick, Rhipicephalus appendiculatus. This species causes the notorious East Coast Fever (ECF), a highly fatal disease of cattle. A closely related form, corridor disease (T.parva Tawrencei infection) transmitted by the same tick is a buffalo derived parasite that causes very high mortalities in infected cattle (Mutugi et al, 1989). In Western Kenya, both ECF and anaplasmosis are common practical animal health problems that are seriously affecting the livestock industry. Outbreaks of these diseases are frequent and have continued to pose great challenges in terms of control for over 80 years.

Currently, the most conventional method of controlling ECF and anaplasmosis in cattle involves the use of acaricides. In Western Kenya, many types of acaricides are available but presently, the most commonly used chemical is chlorfenvinphos (ILRAD, 1991). It is frequently applied on cattle either through plunge dips or sprays. Little, however, is known about the fate of this compound and its residual effect in milk and beef. A recent survey in Kenya (KEMRI,1988) suggests that chronic or acute exposure to chlorfenvinphos can result in serious health effects in humans. Residue levels exceeding 8jug/kg of butterfat in cow's milk are currently regarded as dangerous for human consumption (Codex Alimentarius,1993), although concentrations as high as 20/ig/kg have been reported in Australia (Shell, 1969).
The purpose of this project was to establish the levels of chlorfenvinphos typically occurring in Kenyan cow's milk; and to determine the influence of season (climate changes) variation in butterfat content, and method of acaricide application (plunge dip or spray) on the residue content in milk sampled at a range of sites in Western Kenya.

Correspondence to: I. O. Jumba

Abstract: The influence of botanical (pasture species), geographical (altitude) and pedological (bedrock type, soil pH and extractable mineral concentration) factors on mineral concentrations in dry season pasture was studied in samples of topsoil and herbage from 135 sites on 84 farms in the Mt Elgon region of western Kenya. Of the four major elements measured in herbage, only S was affected by geology, low values being found above Tertiary volcanic (TV) and metamorphic gneiss (MG) bedrocks. By contrast, only P was not affected by species, Setaria being low and Kikuyu grass usually high in macro minerals. Of the seven trace elements analysed in herbage, geology influenced only one: Cu; low values were again found above TV and MG but Cu availability to grazing ruminants would be relatively high because of the associated low S values. By contrast, only Se was unaffected by species, Kikuyu grass being high in all but Mn. Soil bedrock had a greater influence on soil composition but correlations between extractable soil and herbage mineral concentrations were poor for all elements, even within botanical species after correction for soil pH and soil contamination. Concentrations of Ca, P, Mg, S, Cu and Zn were often less than tabulated requirements for grazing livestock. However, risks of deficiency could not be predicted from the pedological factors measured.

A survey of the macro-mineral concentrations in herbage in the Mt Elgon region of western Kenya is described. A total of 135 samples of dry-season herbage from 84 farms covering 30 000 km2 was analysed for calcium (Ca), phosphorus (P), magnesium (Mg), and sulphur (S). Mean (±standard deviation) concentrations were Ca, 1.5 (0.52); P, 1.4 (0.76); Mg, 1.6 (0.53); S, 1.5 (0.59) g kg'1 dry matter. Calcium, P, and Mg concentrations were low compared with surveys in other tropical countries but this may partly reflect the mature stage at which herb¬age was sampled. Comparisons with recent estimates of the mineral requirements of ruminants indicated that most of the samples were deficient in Ca and P while a minority was deficient in Mg and S. However, such deficits are not synonymous with constraints upon livestock pro¬duction, and supplementation trials with grazing livestock should be conducted.
Keywords: Calcium; Phosphorus; Magnesium; Sulphur; Tropical pasture

A survey of trace mineral concentrations in herbage in the Mt Elgon region of western Kenya is described. A total of 135 samples of mature herbage from 84 farms covering 30 000 km2 was analysed for cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), sele¬nium (Se), and zinc (Zn). Mean (±standard deviation) concentrations [mg kg'1 dry matter (DM)] were Co, 0.2 (0.16); Cu, 4.0 (1.6); Fe, 300 (169); Mn, 220 (128); Mo, 1.1 (0.23); Se, 0.1 (0.03); Zn, 23.6 (9.4). Copper and Zn concentrations were low compared with surveys in other tropical countries but this may partly reflect the mature stage at which herbage was sampled. Comparisons with recent estimates of the mineral requirements of ruminants indicated that most of the samples were deficient in Cu. A minority of the pastures contained less Se and Zn than ruminants are thought to require, but deficiencies of Co, Fe, and Mn were rare. Iron may be more significant as an antagonist of Cu but Mo rarely reached concentrations high enough to be antagonistic to Cu. The possibility of constraints upon livestock production should be inves¬tigated by supplementation trials with grazing livestock beginning with Cu.

Abstract
A number of diseases and production problems have been observed in grazing ruminants in many countries around the I world Some of these problems and health effects have been attributed to dietary imbalances in mineral supply and appear \ to be geographically distributed. Grazing cattle require different levels of minerals in their diet depending on the stage of class of development; young and growing, lactating or pregnancy. Common findings indicate that the lactating and young} and growing animals are the most vulnerable to mineral problems, thus providing a sufficient ground for their choice in\ experimental studies. In this preliminary review of the project, the nutritional status of cattle grazing on a range of farms in \ Irons Nzoia District are assessedfrom the mineral content of blood from young and growing as well as lactating animals] sampled during the dry and wet seasons of the study period. Data -will be evaluated in terms of established criteria normality.

SUMMARY
Kenya is a land of contrasts, having a variety of ecological and climatic zones, and many soil types of different characteristics and composition. In view of the adequate data available, the sensitivity of Kenyan ecosystems to acidic deposition needs to be reviewed and vulnerable areas properly delineated. The 1996 SEI map therefore needs to be re-assessed.
Where land use is the most important activity, consideration needs to be made of socio-economic and demographic factors when creating boundaries. Reduction in the already staggering soil fertility and an imbalance in soil mineral composition and organic matter could bring about negative changes in crop yields. Consequently insufficient food supply, poor incentives, unemployment, decreased foreign exchange earnings and a search for areas with richer soils will ensue. The overall effects will be population shifts and accelerated deforestation and soil degradation. We consider this to be the greatest problem that would be caused by acidic deposition in Kenya.
Geological influences on land use are important since soil type, soil pH and to some extent C.E.C. depend on the underlying parent rock. The present map might be altered if geology is considered as a factor.
Data needs to be analysed at regional level (or on a district basis) to aid validation of the map. This will further refine the boundaries of sensitivity classes, especially if emphasis is placed on soil type, soil buffering ability and base saturation.
Regular monitoring of possible sources of acidic gas emissions, if undertaken, should take into account wind speed, wind direction and wind strength in addition to rainfall regimes and average humidity in each study area. In Kenya, sulphur dioxide emissions by some industries might in the near future be a great threat to a variety of ecosystems.

Samples of topsoil (0-30 cm) and dry season herbage from 135 sites in the Mt Elgon region of Kenya were classified according to farm (n = 84), site altitude, underlying soil bedrock (6 types) and botanical composition (6 classes). Effects on pasture concentrations of Ca, P, Mg and S were determined using a mixed model for unbalanced data sets and the Wald (W) statistic to assess the significance of fixed effects. Associated effects on pH, plus extractable Ca and P concentrations in the topsoils were also evaluated.
Soil bedrock influenced herbage concen-trations of S (P < 0.001) but not those of Ca, P or Mg. Mean herbage S concentrations were lowest on volcanic and metamorphic gneiss associations (1.2 g/kg DM) but only extreme values would be inadequate for grazing livestock. Altitude appeared to affect the concentration of P (P < 0.01) and not those of Ca, Mg and S in herbage but the effect on P was dependent on soil P. Geological and topographical maps cannot be used to predict macro-mineral disorders in live¬stock in the Mt Elgon region.
Herbage species differed markedly in their concentrations of S (P < 0.001), Ca (P < 0.001) and Mg (P < 0.05) but not P. Ca deficiency may arise on setaria, S deficiency on some napier grass pastures and P deficiency on some dry season pastures irrespective of botanical compo¬sition.
Low herbage P concentrations may reflect advanced maturity rather than low soil P status (mean value 20 mgP/kg DM). The correlation between soil P and herbage P was significant (r = 0.595), and similar in slope and intercept for all herbage classes but not strong enough to predict deficient Ijerbages. Herbage Ca was not corre¬lated with soil Ca.

Samples of topsoil and herbage from 135 sites in the Mt Elgon region of Kenya were classified according to farm, site altitude, underlying soil bedrock (6 types) and botanical composition (6 classes). Effects of altitude, bedrock and species on pasture concentrations of Co, Cu, Fe, Mn, Mo, Se and Zn were determined using a mixed model for unbalanced data sets and the Wald statistic (W) to assess statistical significance. Extractable concentrations of each element in the soil were measured at each site except for Se where total Se was used.
Cu values were particularly low in forages associated with tertiary volcanic bedrock (3.8 ± 0.34 mg/kg DM), but even the maximal values (5.4 ± 0.34 mg/kgDM on metamorphosed sedi¬mentary material) were marginal for ruminants. Se and Cu concentrations were usually low at low altitudes but no other significant effects of alti¬tude or geology on herbage trace element concen¬trations were found. For Cu and Se alone, geological and topographical maps may help to delineate areas where risks of deficiency are high or low. Herbage composition was poorly corre¬lated with total (Se) or extractable (other trace elements) concentrations in the soil.
Species differences were important for all Clements except Se, with kikuyu grass (Pennis-etum clandestinum) the richest in all but Mn. For Cu and Zn, deficiencies were most likely to occur with rhodes grass (Chloris gayana) with 3.5 mg Cu and 19.5 mgZn/kg DM and setaria (Setaria sphacelata) with 3.9 mg Cu and 17.7 mg Zn/kg DM. Species differences in Mo were within a low range of values (derived means < 1.6 mg/kgDM) but may, in combination with S, influence Cu availability. The lowest mean Se value (0.047 mg/ kgDM in setaria) was inadequate for ruminants. Species variation in Co, Fe and Mn was signifi¬cant but values were consistently above animal requirements and for Co and Fe were probably influenced by soil contamination.

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ABSTRACT
In a preliminary study, 135 samples of mature forages from 84 livestock farms (farm size 10 • 6000 acres) in Bungoma and Trans Nzoia districts were assessed for both macro (Co, S, Mg and P) and trace elements (Co, Cu, Se, Mo, Zn, Fe and Mn) using a variety of chemical techniques. Mean concentrations of these elements were low compared with surveys in other tropical countries. Comparison with recent estimates of the mineral requirements of cattle and sheep indicated that 70 -98 % of the forages were deficient in Co, P and Cu. Several pastures contained less Mg, S, Zn andSe than ruminants are thought to require but deficiencies of Co, Mn and Fe were rare. Re-assessment of the data for Cu availability using two derived prediction equations, one for hay: Cu (%DM)=8.9 -0.7logtMo - 2.61logc S and the other for grass: Cu (%DM) = 5.72 - 1.2975 • 2.785hgf Mo + 0.227 Mo X S showed that forage Mo and S rarely reached concentrations high enough to be antagonistic to Cu. However, Fe concentrations were sufficiently high to implicate this element as an independent Cu antagonist. Since forage mineral deficits are not synonymous with constraints upon livestock production, the possibility of such constraints should be further investigated, first through blood analysis and then by supplementation trials with grazing animals beginning with Cu.

The prediction of mineral deficiencies in grazing livestock requires good correlations between convenient markers of mineral status and animal health or productivity. Correlations are likely to become weaker in moving from animal to pasture to soil in pursuit of a predictor because of the many factors which influence mineral uptake at each interface. However, soils are the easiest to characterize and correlations might be improved by removing the effects of known sources of variation. The influence of botanical (pasture species), geographical (altitude) and pedological (bedrock type, soil pH and extractable mineral concentration) factors on mineral concentrations in dry season pasture was therefore assessed. Samples of topsoil and herbage were gathered from 135 sites on 84 farms in the Mt Elgon region of W. Kenya between January and March, 1987. The underlying parent bedrock was determined from 1:125,000 Geological survey maps and altitude from topographical maps. Botanical composition of the pasture sample was recorded. Soil pH and total (Se) or extractable (not Se) mineral concentrations were determined by standard methods as were total mineral concentrations in unwashed herbage. Distribution of principle botanical species and all bedrock types amongst the sample sites are indicated in Tables 1 and 2 respectively, together with the analytical results. Statistical analysis used a residual maximum likelihood (REML) model for unbalanced data sets.
Pasture concentrations of Ca, P and Cu were generally below the requirement of ruminants, Zn and Se were marginal while Co, Fe and Mn were adequate. Soil bedrock had little influence on herbage composition. Of the four macro-elements, only S was affected by geology, low values being found above TV and MS bedrock. By contrast, only P was not affected by species, Ss being low and PC usually high in macro minerals. Of the seven trace elements analysed, geology influenced only one (Cu); low values were again found above TV and Mfi but Cu availability to grazing ruminants would be relatively high because of the associated low S values. By contrast, only Se was unaffected by species, PC being rich in all but Mn. Soil bedrock had a greater influence on soil composition but correlations between soil and herbage usually accounted for less than 10% of the variation in pasture composition (max r value 0.5 for P): correlations within species were equally poor. The influence of species on herbage Co disappeared if herbage Fe was used as a covariate, suggesting that contamination by soil Co varied between species: however, the correlation with soil Co remained weak. Soil pH was generally low and its use as a covariate did little to improve soil/plant relationships. Herbage Cu increased and Se decreased in curvilinear relationships with altitude.
Mineral deficiencies were therefore likely to occur in grazing livestock, risk being influenced by botanical and topographical but not pedological factors.

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Clonal teas have different aluminium content increasing with age of leaf. Although aluminium andfertilizernitrogen enhance teagrowth andteayields, respectively, field trials have shown no relationship between total aluminium content in the leaf and clonal tea yields. Higher aluminium concentrations were found in the dust grades of black tea than in the large size grades. However, aluminium levels decreased in the tea liquor from dust grades compared to the large size grades. Only up to 40% of the total aluminium in tea was infused into tea liquors; the amounts infused varied with clones and grading (sorting). Aluminium content of black tea was lowered by increasing rates of nitrogenous fertilizers, more frequent fertilizer application, and application of NPK 20:10:10 as opposed to NPKS 25:5:5:5.

flame-less atomic absorption spcctropholometry technique lias been used to determine mercury concentrations in 14 skin-lightening creams and soaps commonly sold in the Kenyan market and 10 in the Norwegian market. The use of borohydride or stannous chloride as the reducing agents for mercuric salts gave different results. When slannous chloride was used as the reducing agent the range of mercury content was 222 to 4920 jjg/kg. When borohydride was used as the reducing agent the range of mercury content was 0.95 to 1121.86 |jg/kg. The difference in results has been attributed to the difference in digestion modes and the ability of the boric acid to encapsulate the mercuric salts. In general the Kenya products had slightly higher mercury content.

Conditions of analyses of copper, lead, cadmium and zinc content in human hair using differential pulse anodic stripping voltammetry (DPASV) and hanging mercury drop electrode (HMDE) have been established. Sample digestion using the mixture HC1; H2O2:HNO3 in the ratio 2:1:40 by volume gave the best wet-ashing procedure. The peak currents and peak potentials of zinc, cadmium and lead, copper were maximum at pH 6-7 and 1-3 respectively, when excess H2O2 was eliminated with subsequent addition of hydroxyamine hydrochloride. Matrix concentration effects were minimized by digesting weights not exceeding 50 mg per sample. The effect of selenium (IV) was negligible and was ignored. The detection limit of 0.0036 ng/cm3 for Cd+2 was obtained while the values for zinc, lead and copper were 0.0230, 0.0287 and 0.0269 ng/cm3 respectively, at the 95% confidence limit. The observed DPASV conditions of analysis of these metals are useful for routine determination of the metals in human hair and should complement the conventional flame atomic absorption spectrophoto-metry methods

SUMMARY
An intercomparative analysis of the concentration of heavy metals: zinc, cadmium, lead, copper, mercury, iron and calcium in head hair of a randomly selected sample of Kenyan people using the techniques of atomic absorption spectrophotometry (AAS) and differential pulse anodic stripping voltammetry (DPAS) has been undertaken. The per cent relative standard deviation for each sample analysed using either of the techniques show good sensitivity and correlation between the techniques. The DPAS was found to be slightly more sensitive than the AAS instrument used.
The recalculated body burden ratios of Cd to Zn, Pb to Fe reveal no unusual health impairment symptoms and suggest a relatively clean environment in Kenya.

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