Fresh, green spinach leaves that Delhiites put on their plates contain more than just nutrients. A recent study conducted by The Energy and Resources Institute (TERI) indicates the presence of heavy metals in the vegetables that are grown with water from the Yamuna, making them potentially hazardous to health.
The study also found the levels of metals, like nickel, manganese and lead, in the river water to be higher than the international aquatic water quality criteria for fresh water.
Titled “Yamuna, the poisoned river”, the two-year-long study was conducted with the intention of ascertaining the concentration of heavy metals in water used for irrigation and drinking purposes, and metal contamination in crops grown on the Yamuna basin that are irrigated with these waters.
The study claims that despite interventions by the government, the river continues to remain polluted and is being “chocked” by “rampant industrial pollution and untreated sewage”.
“Despite government norms, the sewage treatment plants continue to be underutilised. In fact, the toxins have polluted the ground water and soil. It has entered our food chain through the vegetables grown on the banks and continues to affect the people living on the banks,” the study adds.
The city generates 650 million gallons of sewage per day against an installed capacity of 512 million gallons, but only 350 million gallons of sewage reaches the treatment plants, the study claims.
To highlight the seriousness of the contamination, the study cites, at one particular location, lead levels found to be 10 times higher than elsewhere in the river. At another point, near a thermal power plant, the mercury concentration was 200 times higher than the levels determined by the United States Environmental Protection Agency (USEPA).
For the study, water samples were taken from 13 locations every 2 km from the Wazirabad barrage and covering a stretch of 22 km of the river flowing through Delhi.
Soil samples were collected from agricultural fields on the Yamuna flood plains at different depths -- 15, 25, 60 cm as well as 250 and 500 metres away from the river, to study the exposure levels of plants at different root lengths.
The soil samples collected from the river bank showed very high quantities of nickel and chromium and lead levels ranged from below detection to 40 times over the permissible limits. Mercury concentration too was much higher than the permissible standard at all locations, the study says.
“Wazirabad and Okhla barrage showed high levels of different metals. A possible reason for this is the industrial effluents. While the Wazirabad section of the river receives wastewater from Najafgarh and its supplementary drains, the Shahdara drain releases its load downstream at the Okhla barrage. During the monsoon season, the river water floods the land and contaminates reach the soil,” it cites.
The study further claims that vegetables that are grown in the contaminated soil absorb the contaminants. “Vegetables grown in the flood plains namely -- spinach, cauliflower, and radish were tested for the contaminants. The concentration of heavy metals was found to be highest in spinach, followed by cauliflower and the least in radish. These vegetables become the carriers of heavy metals in our food chain.”
The study shows a higher concentration of lead, nickel, and chromium in the bloodstream of inhabitants of the Yamuna bank when compared with village women and children.
Having identified the sources of pollution, the study has also put forth suggestions to prevent the harmful contaminants from entering the food chain.
The study recommends regular bio-monitoring of different environmental compartments and of the population living in areas threatened by contaminants. “The pollutants must be treated at various sources – both industrial and domestic wastewater. Safer technologies are needed to reduce release of heavy metals in air and waste-water. Pollution control and waste management agencies need to adopt a strong role in controlling environmental exposure.
It also recommends developing guideline values and regulations to monitor levels of heavy metals in agricultural soil, surface water and farm produce.