ENVIRONMENTAL HEALTH IMPLICATIONS OF PESTICIDE USAGE IN COCOA GROWING AREAS IN SOME PARTS OF SOUTH-WESTERN NIGERIA

Abstract

Applications of chemical pesticides constitute an effective means of controlling pests of cocoa in Nigeria. However, use of chemical pesticides has resulted in many unpleasant environmental and human health consequences. The environmental health impacts of chemical pesticides application were investigated in rivers located in Osun, Ondo and Ekiti states of South-west, Nigeria using aquatic bio-indicators and levels of pollution of the rivers by pesticides derivatives as indices. The present study involved market survey of pesticides, questionnaire administration, and collection of environmental samples (Water, sediment and macroinvertebrates samples) from three rivers; Aponmu, Owena and Oruwo rivers. A total of 305 pesticide brands were surveyed in Ondo State i.e. 147, 140, and 18 pesticide brands in Akure, Ondo town and Igbara-Odo respectively. Akure had the highest number of recorded pesticides brands. Questionnaire survey revealed that the percentage of uneducated, untrained and those who do not read pesticide labels were significantly higher (P< 0.05) than those who are educated, trained and read labels. About 66.3% of the respondents apply pesticides regularly especially in the rainy season to control weed while only 1.8% of the respondents obtain adequate information and guidelines from an Agricultural agency. Analysis of the physicochemical parameters of the three sampled rivers revealed that the mean electrical conductivity, total dissolved solutes, temperature and pH were within permissible limits of Unites States Environmental Protection Agency (USEPA) and National Environmental Safety, Regulatory and Enforcement Agency (NESREA) standards for rivers and lakes except for mean dissolved oxygen (DO) which was below required standards. In addition, there was no relationship observed between DO and pesticides derivatives at Owena river. However, as the concentration of pesticide derivatives increased at Aponmu river, DO decreased. Levels of pesticide derivatives in the sampled rivers were generally observed to increase from April to July. The concentrations of copper obtained at the three rivers sampled were highest in the month of June but declined in the following month. Aponmu and Oruwo rivers had about the same level of Copper; 54.00 ±0.46 mg/l and 54.49 ±1.71 mg/l respectively, while Owena river had the least copper concentration with a value of 46.03 ±0.41 mg/l. Aponmu and Oruwo had equal number of macroinvertebrate taxa (14) while Owena had the highest number of taxa (19). Owena had the highest number of individual organisms (368) followed by Aponmu (340) while Oruwo had the lowest number of individuals. According to the Simpson (0.8977) and Shannon (2.466) index of biodiversity, Owena river was the most diversed followed by Oruwo while Aponmu was the least diversed with respect to species richness. Margalef index has indicated that Owena has the highest species richness (3.047) while Aponmu had the lowest, probably indicating the level of pollution of each environment. The work provides a comprehensive investigation of environmental implications associated with pesticides usage in cocoa farms especially the reducing macroinvertebrates’ abundance observed as levels of pesticides’ derivatives increased.