Heavy metals, chemicals choke Cauvery river: Study

As governments continue to gloss over the massive pollution load in the Cauvery river, the Union government’s Wildlife Institute of India has found copper, mercury and lead exceeding permissible levels in the river’s sediment. Phthalates, the chemicals which disturb the endocrine system, were “most abundant” in the water.

The study, involving 19 researchers, looked into the ecological status of the 805 km-long river that feeds crores of people in Karnataka, Tamil Nadu and Kerala. They studied an 85-km stretch by dividing the river into upper, middle and lower zones. Segments of 5 km were picked from each zone in 17 stretches, covering about 10% of the river’s total length.

Increased human activities contributed to high pollution in middle and lower zones. Samples of water and sediment were collected separately before and after the monsoon. Test of sediments established high concentration of heavy metals while fish samples showed a mix of phthalate esters as well as heavy metals that can accumulate over time and cause major health problems.

The water samples, not from dry seasons, showed modest levels of heavy metals. At least one sediment sample showed lead, a highly toxic substance, at 59.75 mg/kg, nearly double the 35 mg/kg maximum limit set by the Canadian Sediment Quality Guidelines.

Copper, which damages liver and kidney, was at 97 mg/kg against the permissible level of 36 mg/kg while mercury, which primarily harms nervous system, was 0.37 mg/kg compared to 0.17 mg/kg.

In the water samples, chromium (44 microgram/litre) came closer to the World Health Organisation’s safety limit of 50 microgram/litre while zinc and cadmium levels exceeded the Canadian Water Quality guidelines.

However, both the sediment and water had “abundant” levels of the endocrine-disrupting chemicals (EDCs) which cause infertility and cancer.

Phthalate esters at 17,793 nanogram/litre, Bisphenol A at 336.27 nanogram/litre, Polychlorinated biphenyl at 64.64 nanogram/litre, organochlorine pesticides at 94.11 nanogram/litre and Organophosphorus at 104.67 nanogram/litre among others were listed as major contaminants.

Notably, the samples were not picked during February-May months, when the concentration of the contaminants are much higher and exposes both people and wildlife to deadly cocktail of heavy metals and chemicals. During the remaining seasons, the flow of waters would dilute the concentration. To a question, lead author of the report Syed Ainul Hussain from WII noted that it was a “torch-bearer study” that points both academics and policymakers to what needs to be done.

“What we need are studies covering the entire stretch of Cauvery. The study provides an opportunity to state and the Union governments to prioritise river conservation,” he said.

Ruchi Badola from WII, the co-author of the study, said they will propose next phase of the study to understand the impact of the contaminants on wildlife. “We have sought extension of the current study so that we can coordinate with stakeholders. We will also propose to study the impact of contaminants on wildlife in the next phase,” she added.

Nirmala Gowda of Mapping Malnad, who had studied the contamination of Cauvery’s tributaries, noted that even when measured in non-summer months, the contaminants are high: “Of specific concern is the finding of copious EDCs, including the triclosan that interferes with the hormonal system even at low concentrations and affects reproductive health, menstrual cycles, and fetal development. Many countries have already phased out triclosan from many products. We continue to lag behind.”

She said a major shortcoming of the study, however, was its failure to capture toxic compounds like dioxins and furans that are formed during burning of waste.