NEW DELHI: Despite schemes like rainwater harvesting, Delhi’s groundwater quality has only worsened.

According to the recently released ‘Ground Water Year Book 2011-12’ by the Central Ground Water Board has found that Nitrate concentrations in some parts of the city are as high as 1500 mg/l. This can have grave health impacts as the concentrations are several times higher than the prescribed safe limit. The permissible limit for Nitrate as per Bureau of Indian Standards (BIS) is only 100 mg/l and the Maximum Contaminant Level (MCL) according to the US Environment Protection Agency (EPA) is just 10 mg/l.

One of the main reasons for Nitrate pollution in Delhi according to the study is contamination from sewage, run off from landfills, pesticides from agricultural fields and open drains.

“Data indicates that higher concentration of nitrates are found at the places where domestic effluent is discharged into open unlined drains and usually these places are thickly populated,” it says. The study also found that Delhi’s ground water has more nitrate at shallow levels, deeper wells may have lower concentrations. High nitrate levels are known to cause methemoglobinemia, or “blue baby” disease. In adults it may not have a direct impact but is indicative of the fact that toxic pesticides may be contaminating the water. Places around Indirapuri Market, Inderlok Temple, Chattarpur temple and Chawala have been found to have particularly high levels of Nitrate.

Fluoride concentrations are also high in about 30% of the samples collected by CGWB. While the permissible limit for Fluoride according to BIS is 1.5 mg/l but in many parts of Delhi the Fluoride levels are between 1.5 mg/l to 5 mg/l and in some parts they are about 10 mg/l. High Fluoride levels can cause dental and skeletal flurosis sometimes leading to bone deformities even adults. South-West and North-West districts of Delhi have been found to have higher fluoride concentrations.

Another disturbing finding is that ‘electrical conductance’ which is measured to understand the extent of mineralization of ground water was seen to be high in 42 out of 124 water samples across Delhi. The EC value is in the range of 2000 to 16,700 s/cm. The EC value also gives an idea of total dissolved salts in a water sample. Most of the higher values are falling in western part of Delhi, especially West of Delhi Ridge. “The area of Najafgarh and Kanjhawala Block, Bhalsawa, Burari, Dhirpur and Jagatpur are showing exceptionally high EC Values, even in shallower depth of tube wells,” concluded the report.