Drinking water contamination by chromium and lead in industrial lands of Karachi.
OBJECTIVE
To identify and quantify chromium and lead as contaminant in water sources of Karachi.


METHODS
This water assessment survey was conducted from June 2007 to February 2008 in all the 18 towns of Karachi. In total 216 water samples were collected from ground (n=108) and surface water sources (n = 108). Water samples were collected in a liter polyethylene acid resistant bottle with extreme care to prevent contamination and concentrations of heavy metals (chromium and lead). Metallic ion contents were estimated by Atomic Absorption Spectrophotometer. Statistical analysis was done by applying T-test and chi-square for continuous and categorical variables respectively at 95% confidence level; Pearson correlation was also determined between chromium and lead concentrations.


RESULTS
A total of 187 water samples had lead concentration higher than the maximum acceptable concentration (MAC) in drinking water, established by WHO (10 PPB) and lead contaminated sources were in significantly higher proportion than chromium contaminated water samples (n = 49) [chi2 = 128; P- < 0.001]. Mean chromium concentration in ground water was (micro = 49; SE = 3.8) was significantly higher than mean chromium concentration (micro = 33, SE = 3.5) in surface water (P = 0.003). There was a significant and positive correlation between chromium and lead concentrations in ground water (P = 0.04) however Pearson correlation was not significant for surface water (P = 0.6). Industrial towns (Korangi, Landhi and SITE) had significantly higher concentration of chromium (micro = 82.4; SE = 8.9) in their ground and tap water as compared to the mean chromium concentration (micro = 33; SE = 2.2) in the water samples of rest of the towns of Karachi (P < 0.001).


CONCLUSIONS
Chromium and Lead levels are high in almost all ground water sources, however extremely high concentrations were found in industrial areas. Presence of any one of the heavy metal contamination necessitate the need for the estimation of other heavy metals as significant positive correlation was found between chromium and lead concentration, indicating the possibility of similar contamination sources in Karachi.
Department of Biochemistry, Dow International Medical College, Dow University of Health Sciences, Karachi, Pakistan.
Nadeem-ul-Haq
Mubashir Aslam
MA
Arain
Zeba
Z
Haque
Nasira
N
Badar
Noman
N
Mughal
D002857:Chromium / Q000032:analysis*; D016001:Confidence Intervals; D006801:Humans; D007220:Industrial Waste; D007221:Industry; D007854:Lead / Q000032:analysis*; D010154:Pakistan; D016012:Poisson Distribution; D013054:Spectrophotometry, Atomic; D014877:Water Pollution, Chemical / Q000032:analysis*; D014881:Water Supply / Q000032:analysis*
D007220:Industrial Waste; D002857:Chromium; D007854:Lead