Toxic lakes, poisoned veg farms
Irrigated by sewage-fed lake water, vegetable farms on the city's outskirts are contaminating the food chain with chemicals hazardous to human health.
It is a tough, but heavily loaded question. Loaded, because repeated studies by city-based universities and scientific institutions have clearly indicated heavy metal contamination in vegetables sold in big markets across Bengaluru.
Irrigated by sewage-fed lake water on agricultural land, contamination of the greens has been proved beyond doubt. Analyzing samples of water, soil and crop plants, the tests have shown significant traces of zinc, copper, lead and cadmium in the greens that directly influence our food chain.
Twelve years ago, when the Bellandur lake’s pollution levels were high but not at today’s alarming levels, a Bangalore University study had shown high heavy metal contamination in vegetables grown in the vicinity. The impact of the lake’s polluted water on vegetation was found to be much more than soil.
Incessant flow of untreated sewage from multiple inlets, encroachment and wide-spread development have effectively killed vegetable farming in Bellandur. Cultivation has gradually shifted to Varthur and Hoodi lakebeds on the downstream.
But here lies the big problem: Highly polluted water from Bellandur flows into the downstream lakes, contaminating the ground water as well. It is mostly this water that is being drilled out through borewells by the farmers.
As if this is not hazardous enough, the vegetables are also washed with the lake water before they are loaded onto distribution trucks.
Their produce is supplied to vegetable markets in Marathahalli, KR Puram, Whitefield, HAL and other areas within a 20km radius. At the HAL market, for instance, supplies start at around 3 am. Enquiries reveal that most vegetables are sourced from farms in Hoodi, Kadugodi, Varthur and other areas.
Not many customers are aware of this supply chain, although most retailers feign ignorance about the irrigation methods for fear of losing clients.
Nirupam, a customer, says he has been buying vegetables from the HAL market for nearly a decade. But he admits he had never asked where the greens came from.
In recent years, say the retailers, supplies from Varthur side have been declining as farms are being traded for real estate. Huge apartment blocks and malls have come up on once fertile lands. To compensate the shortfall, supplies often come from KR Market.
Yet, that is not a safe bet. An ongoing study by the Ashoka Trust for Research in Ecology and the Environment (Atree) has already indicated contamination in vegetables grown in the command area of the Byramangala tank on the Vrushabhavathi river.
Over the last three years, tests on water and soil samples collected from the area growing babycorn have shown accumulation of heavy metals, as Atree researcher Priyanka informs. Heavily polluted with industrial effluents and untreated domestic sewage, the Vrushabhavathi river feeds this water directly into the Byramangala tank.
Babycorn cultivation has graduated to tomatoes and other vegetables in recent months. These greens make their way to the KR Market and Kalasipalyam outlets, eventually heading to other vegetable bazaars in the city interior.
Heavy metal contamination of water can be effectively tracked only with 24-hour sampling, says Priyanka.
For the study on Vrushabhavathi, the water was measured day and night. Heavy metal traces were found to peak during the night.
This is a clear indication that industrial effluents are being discharged after dusk to hoodwink the agencies.
Stringent quality tests
The message is clear: The Karnataka State Pollution Control Board (KSPCB) needs to change its water quality monitoring protocol. Atree is now in talks with the Board to make the testing more scientific and stringent. Its data analysis on Vrishabhavathi and Byramangala tank is also being shared with KSPCB.
But water quality monitoring is only a part of the mechanism to prevent health hazards of irrigation with sewage-fed water. Soil and plant quality are equally critical. The University study showed that the presence of cadmium in spinach (4 mg g-1) and radish (2.5 mg g-1) is way beyond the acceptable standards.