Effects of the Use of Fungicides in Tomato Farms on Copper Levels in the Environment Within Subukia, Kenya

Tomato farmers in Subukia have often used copper-based fungicide to control parasitic fungi. The parasitic fungi cause a serious problem which makes the farmers spray the plants every 4 days during the wet weather. It is estimated that about 4.44 kg of copper-based fungicide (CBF) per acre per spray is used. This leads to copper accumulation in the plants and soil, and consequently the water system is polluted due to run off storm water. The copper that remains on the ripened tomatoes and the farm soil is a potential hazard to the human life as well as other biota. The farmers grow tomatoes from September to April; a time in which Subukia River and its tributaries have dirty brown waters with a foul smell. The river water is used for domestic purposes and communities living down stream often complain of gastrointestinal tract initation and the disappearance of mudfish, tadpoles among other vertebrates that find the river their habitat. Too much copper causes necrotic hepatitis, headache, nausea, vomiting, gastrointestinal bleeding, heamaturia, methaemoglobinaemia, renal failure and haemolytic anaemia. The purpose of this study was to investigate the effects of CBF used in tomato farms on copper levels in the environment in Subukia with a view of obtaining data which can be used to draw conclusions and recommendations on the pollution levels due to the use of CBF. The farm soil and tomato fruits samples were collected from the various available tomato farms that are adjacent to the river while the river water and sediments samples were fetched in a section of river Subukia for a stretch of 30 km during the dry and wet season. After sample treatment the levels of copper in the soil, sediment, water, and the tomato fruits were determined using atomic absorption spectroscopy and polarographic techniques. The pH of the soils in the tomato farms were found in the range of 4.4 to 7.60 while the pH of the river system was in the range of 6.25 to 7.98. Most copper based fungicide disproportionates to form aqua ion Cu(H20)l62+ which lowered the soil pH. The levels of copper were found in the range of 0.216 to 20.425 ug/g in the soil, 0.697 to 17.522 ug/ml. in the river water, 0.101 to 20.925 ug/g in the river sediments and 0.404 to 16.835 ug/g of the dry matter in the tomato fruits. The labile fraction in the river water was found to be 44% of the total copper level in the water. Based on WHO limits the levels of copper from the CBF have not reached hazardous toxic levels for human beings but the levels of copper are toxic to algae, aquatic invertebrates, and vertebrates and its use should therefore be stopped. Prolonged exposure of these levels of Cu to human being will lead to accumulation effects up the food chain and toxic levels will cumulatively be realized. This study has determined levels of copper that are sufficient to cause death to embryonic and juvenile stages of aquatic vertebrates and invertebrates and inhibit growth and nitrogen fixation of algae and therefore recommends that the use of CBF in tomato farming be substituted with others that do not contain copper. The study recommends that policy makers use the data obtained to develop quality standards which protect aquatic life, reduce pollution, and decrease toxicity to organism, water, soil, fruits and consequently the human beings. (author)