Organochlorine pesticides in rain, rivers and groundwater in the Lake Naivasha basin and implications for their management

Abstract

Organochlorines (OCs) have a high persistence in the environment and toxicity to humans and wildlife. Despite their ban in several countries, they are still found in agricultural areas. Their presence in drinking water resources (rivers, rain and groundwater) in Lake Naivasha area, which has had a booming horticultural industry in the last three decades was investigated. Twenty-two water samples from the rift floor around Lake Naivasha were collected in June 2017 and analysed for organochlorines. Findings show that all the water samples are contaminated with various organochlorine pesticides and metabolites. The abundance of OCs in water resources can be ranked as follows, rain> river >groundwater in which 18 compounds were identified; alpha, beta, gamma and delta HCH, endrin, aldrin, heptachlor, chlordane, b-endosulfan, methoxychlor, p,p′-DDE, p,p′-DDD, endrin aldehyde, endosulphan sulphate, p,p′-DD and endrin ketone. Their concentrations range from 0.1 to1 μg/L. The OCs with high concentrations are aldrin, endrin aldehyde and endosulphan sulphate. Twelve banned compounds were found present, several decades after their ban (1986 - 2014) shows either occasional usage in the region or the residues drift from use elsewhere. Despite the low concentrations, many of these pollutants can exceed acceptable daily intake (ADI) for humans. Thus, the National Environment Management Authority, Kenya needs to set OCs guidelines on drinking water quality and concerted efforts with agriculture, water and health ministries is needed to ensure public health safety.