Occurrence Of Select Heavy Metals In Groundwater Sources And Potential Health Risks Among Residents In Informal Settlements Of Kisumu East County, Kenya

Abstract

Groundwater contamination with heavy metals is a global problem with millions of people at risk. Exposure to even low concentration of heavy metals through long term ingestion of contaminated water is responsible for various non-communicable diseases. In developing countries like Kenya, groundwater supplements water supply due to limited or unreliable piped water in informal settlements. Contamination of groundwater in these settlements due to uncontrolled human activities and infrequent monitoring is a concern considering that Kisumu County is highly reliant on groundwater. In addition, there are limited studies relating to heavy metal contamination, which is a concern with the cognizance of development of non-communicable as a result of exposure to heavy metals in the environment. The study aimed to determine levels of select heavy metals (arsenic, cadmium, lead and mercury) in groundwater sources used for drinking water and the potential health risks from exposure in the informal settlements of Kisumu East County. This was a cross-sectional study among informal settlements of Kisumu where 355 households selected using stratified random sampling technique between 5th and 17th December 2017. `Ethical approval was granted by the KNH/UoN ERC(P352/07/2017) and NACOSTI (P/18/3232/2089A) structured questionnaire captured socio-demographic details, anthropometric measurements and exposure assessment in relation to groundwater use. Groundwater samples were collected from 37 water points in the month of May 2018 and analyzed for levels of heavy. Carcinogenic and non-carcinogenic risk assessment was performed according to the USEPA methodology for both adults and children. Occurrence of heavy metals followed the order; As>Cd>Pb>Hg, and were within WHO and KEBS.limits. Groundwater was used for both drinking and domestic purposes. Prevalence of chronic disease was low at (4% n=50)) with hypertension and diabetes as the main conditions. An increase in age (p=0.001) and gender (p=0.05) were statistically significant factors with presence of chronic disease among the residents using groundwater. Health risk values were within acceptable levels (HQ/HI ˂1) with a higher value in children compared to adults, making them susceptible to heavy metal exposure. Despite the health risk and results of heavy metals indicating minimal anthropogenic activities in the area, a significant number of households (80%n=257)) did not maintain recommended distance of waste sites to groundwater sources and are therefore a potential source of future groundwater contamination. Regular monitoring of groundwater and strict adherence of pollution policies in the informal settlements can remarkably reduce the risk of ingesting heavy metal