ARSENIC LEVELS IN GROUNDWATER AND ITS ASSOCIATED HEALTH PROBLEMS IN SELECTED COMMUNITIES IN NIGERIA

Abstract

Studies carried out in various countries have shown that the presence of arsenic (As) in groundwater poses a major public health problem. In Nigeria, little is known about the extent of contamination of groundwater with arsenic and the associated problems. This study therefore aimed at identifying arsenic-rich water points in selected communities in Nigeria and assessed its impact on the population. The first stage of this study involved a descriptive cross-sectional and laboratory analysis using three stage sampling technique. Three hundred and fifty-five water points made up of 184 boreholes (BH) and 171 deep wells (DW) spread across the six geopolitical zones were collected. In the second phase of the study, a total sample of consenting 170 and 127 persons from arsenic-rich and non-arsenic rich communities respectively was taken from whom blood and urine samples were obtained. The samples were analyzed to detect arsenic using Graphite-furnace Atomic Absorption Spectrometry. Other physico-chemical parameters including Total solids and pH of water were measured. The levels of association between arsenic levels in water and perceived health problems were computed at 5% confidence level. In addition, a questionnaire survey was carried out to obtain relevant arsenic-related morbidity data from the human subjects. A sanitary status assessment of the water points was also carried out using environmental hygiene indices. Data were analysed using descriptive and Chi square statistics. Forty-three percent of the water samples contained arsenic within the WHO's safety level of 0.05mg/l. The remaining 57.0% contained arsenic in excess of the Maximum Concentration Level. Water arsenic(W-As) ranged from 0.00mg/I to 2.42mg/l. Mean arsenic in BH and DW were 0.40mg/l and 0.53mg/l respectively with no significant difference between the two types of water source. Poor sanitary factors were found to be playing major role in elevating the levels in groundwater. Urine-Arsenic(U-As) in both As rich and non As rich communities ranged from 0.01mg/l to 4.9mg/l while blood arsenic (B-As) levels ranged from 0.00 to 2.85mg/l among the respondents that consented to having their blood and/or urine specimen taken. A significant relationship exist between high arsenic levels in water and lower pH of water(p<0.05). There was also a significant relationship between evidence of skin rashes and high blood and urine arsenic (p<0.05). However, no significant relationship was found between high blood and urine arsenic levels and reported cases of fetal malformation. Total solids levels in water were not significantly associated with high arsenic levels in both BH and DW respectively. Awareness of arsenic and its associated health problems was generally low among the study populations as only 16.5% of the respondents could related arsenic problems with groundwater contamination. Arsenic is present in appreciable amount in ground water in Nigeria and there is evidence of its effects on the health of exposed population. Planned mitigation approaches such as continuous monitoring of groundwater points and community-based health education are needed to address the problem.