AN EFFECT OF CLIMATE CHANGE: INCREASED HEALTH RISKS DUE TO ARSENIC IN DRINKING WATER - THE CASE OF IZMIR, TURKEY
Özet
Our previous research (Kavcar et al., 2009) has shown that tap water arsenic concentrations in the City of Izmir, Turkey, was of concern as arsenic in 15 of 37 (41%) of the tap water samples (collected in the year 2004) exceeded the Turkish drinking water standard of 10 mu g/L (TMH, 2005). The median, mean, and 95(th) percentile concentrations were 2.9, 12.0, and 42.0 mu g/L, respectively. The violations of the standard were in three districts, i.e., Bornova, Cigil, and Karsiyaka, that were served primarily by groundwater sources. The concentrations in other districts were below the standard. However, concentrations less than the standard may be associated with a carcinogenic risk that is greater than the acceptable risk level of one in ten thousand depending on the level of exposure, mainly, daily drinking water intake rate and body weight. This was the case for the City of Izmir as lifetime carcinogenic risks exceeded the acceptable level for 19 of the 37 participants (51%). As the result of the above cited research, the local government has shut-down a number of groundwater wells as a mitigation measure. In turn, the concentrations were brought down to <15 mu g/L in the three districts by increasing the proportion of surface water supplied from Tahtali Reservoir. However, climate change has been affecting the region. The water volume in the resevoir was dropped below 5% in 2008. As a result, the arsenic contaminated wells were brought back into the service, causing a sharp increase in the arsenic concentrations, this time all around the city, measured by the local health authority. Izmirians who can not afford to buy bottled drinking water are (to be) exposed to arsenic concentrations of 30-40 mu g/L until the planned treatment plant is in place. A probablistic risk assessment was conducted to estimate the human health risks for the scenario of no available surface water, in which no treatment and treatment with 90% and 99% efficiencies were assumed for the arsenic contaminated groundwater, based on the concentrations measured by the local health authority. The median carcinogenic risk estimated for the scenario of no treatment for the metropolitan area was approximately eight times the median value estimated when the main source water was Tahtali Reservoir, a surface water dam.
