Caution: poisonous vegetables for sale on Yamuna bridge

TERI study finds spinach, cauliflower grown on riverbank contain toxic heavy metals

People stopping by on the Nizamuddin bridge to purchase seemingly fresh vegetables on their return from work is a common sight in east Delhi. Little do they realise that these vegetables are full of poisonous heavy metals, which have a long adverse health impact, particularly on children and the elderly.

When researchers from The Energy and Resources Institute (TERI) tested vegetables grown on the floodplain -- spinach, cauliflower and radish – they found that concentration of heavy metals was the highest in spinach, followed by cauliflower and the least in radish. 

“This suggest that leafy vegetables are high accumulators of heavy metals. These vegetables become the carriers of heavy metals in our food chain,” said the TERI Yamuna study that examined the level of heavy metals in Yamuna water and their percolation to the vegetables.

Toxic metals

Nickel, lead, manganese, chromium, mercury, zinc – were found in water at several locations.At one particular spot, lead levels were found to be 10 times more than elsewhere in the river, whereas at a point near a thermal power plant, mercury concentration was 200 times higher than the levels determined by United States Environmental Protection Agency (USEPA). 

“This reinforced the need for stricter norms to control effluents discharged by industries, power plants, and other sources of pollution as well as regular monitoring of heavy metal levels in vegetables,” TERI researcher Meena Sehgal who led the study, told Deccan Herald.

The two main source of pollutants are Najafgarh drain and Shahdara drain that release loads of untreated waste water in Yamuna killing the river.  CAG report

A report of the Comptroller and Auditor General presented in the Parliament in December, 2011 made clear that Yamuna was dead by the time it left Delhi.

The dissolved oxygen level in Yamuna is zero which means the river cannot harbour any aquatic life. 

The biological oxygen demand is seven times than the normal level, indicating very high level of organic pollution, according to the CAG report, underlining the fact that rampant industrial pollution and untreated sewage were choking the river.

Water samples

The TERI study suggests the city generates 650 million gallons of sewage per day against an installed capacity of 512 million gallons.

However, only 350 million gallons of sewage reaches the treatment plants. A deadline of 2012 has been set to ensure no untreated sewage goes into the river. 

For the survey, TERI researchers collected water samples from 13 locations, every two kilometres from the Wazirabad barrage and covered a stretch of 22 km of Yamuna flowing through Delhi. 

Soil samples were collected from agricultural fields on the Yamuna floodplain at different depths - 15, 25, 60 cm as well as 250 and 500 meter away from the river - to study the exposure levels of plants at different root lengths.

Similar samples were also collected from Dayalpur and Chandawali villages in the Ballabgarh district of Haryana, 25 km from Delhi to judge the extent of contamination.

“Heavy metals were much higher in Yamuna floodplain than rural areas,” said Sehgal.