Study on arsenic pollution was conducted in Onitsha town in Anambra State, Nigeria to examine the pollution status of surface and subsurface water. Arsenic concentration in surface water within Onitsha metropolis ranged from 0.2001 mg/L (River Niger upstream) to 1.5883 mg/L (River Niger central drainage surface), while concentration in boreholes lies within the range of 0.0000 mg/L (22.2% of boreholes) and 1.2507 mg/L (creek road), respectively. Arsenic concentration in sampled water from river sources is above the WHO standard (0.01 mg/ L) while 87.8% of Arsenic concentration in boreholes adjacent and closest to these rivers and creek is also above the world Health Organization standard (WHO, 2011) of 0.01 mg/L. it is discovered that pollution of surface water is greater than that of the groundwater sources. Major sources of arsenic in Onitsha are refuse dumps, effluent from industries and sewage amongst other sources. Arsenic is known to be the most poisonous metal in existence on earth’s surface, its production should be carefully monitored and effluents treated before discharge into the environment.
Key words: Arsenic, water, health.