Contamination of surface water sources such as rivers due to metals, can often make the water dangerous to drink because of the health hazards associated with consuming toxic metals. The report titled 'Status of trace and toxic metals in Indian rivers' published by the Central Water Commission (CWC), presents the findings of a study conducted by the CWC that evaluated the water quality of all the river basins of the country with regard to the status of trace and toxic metals present.
Type of toxic metals and sources of metal contamination
Primary metals considered to be toxic are lead, arsenic, copper, cadmium, mercury and nickel. These hazardous metals are also referred to as trace elements and are normally found in low concentrations in the environment and can create health problems if their concentration increases in the food and the water chain. Contamination of surface water sources due to metals can occur due to a number of industrial processes such as:
- Mining
- Discharge of industrial effluents containing metallic solutions into the water. These include effluents discharged from battery and paint manufacturing, electroplating, viscous-rayon manufacturing, copper picking and galvanizing & rubber processing industries.
- Dumping of solid wastes which contain metal salts
- Agricultural practices that introduce toxic metals to water
Health impacts of toxic metals
Heavy metals may enter the human body through food, water, and air, or even absorption through the skin. This may be due to the contact of humans with these metals in agriculture, manufacturing, pharmaceutical, industrial, or residential settings. Though several adverse health effects of heavy metals are known, people's exposure to these metals continues to increase in some parts of the world. Large amounts of any of these metals can cause:
- Acute or chronic toxicity/ poisoning resulting in damaged or reduced mental and central nervous functions
- Changes in the blood composition and damage to the lungs, kidneys, liver, and other vital organs
- Physical, muscular, and neurological degenerative processes that are similar to Alzheimer’s disease, Parkinson’s disease, muscular dystrophy, and multiple sclerosis
- Cancer
- Risk of allergies
Keeping these hazards in mind, agencies like the Bureau of Indian Standards (BIS) and Indian Council of Medical Research (ICMR) have formulated drinking water standards for trace and toxic metals for humans as well as for livestock and irrigation use in India.
Findings of the study
A total of 355 water quality stations and 32 gauge stations covering all the river basins from the East to the West and North to the South were studied. It found the following:
Arsenic
- Maximum arsenic concentration was observed at Sundergarh water quality monitoring station on Ib River, a tributary of the Mahanadi.
- Arsenic concentration in all the other rivers was within acceptable limits of the BIS and no toxicity was observed in the rivers during the study period.
Cadmium
- Cauvery, Pennar, Yamuna and Hindon rivers were found to be contaminated with cadmium at 7 water quality monitoring stations.
- The highest cadmium concentration was observed on the Delhi railway bridge and Mathura water quality monitoring station at the Yamuna river.
Chromium
- 11 major Indian rivers were found to have chromium concentration exceeding tolerance limits.
Copper
- Maximum copper concentration was observed at Regauli water quality station on Rapti river.
- Ganga, Gomti, Kwano, Ramganga, Rapti, Sarju were among the rivers where two or more water quality monitoring stations were contaminated with copper.
Iron
- Iron concentration was found to exceed limits at more than two water quality stations at the Barak, Brahamputra, Ganga, Mahi, Narmada, Ramganga, Rapti, Seonath, Subarnarekha, Teesta and Yamuna rivers.
- Iron concentration was reported to be maximum at Srikakulam water quality station on Nagavali River.
Lead
- Lead concentration was maximum in the water sample from Moradabad water quality station on Ramganga River.
- Many water quality monitoring stations were found to be contaminated with lead near the Brahamani, Ganga, Ghaghra, Gomti, Mahanadi, Ramganga, Rapti and Yamuna rivers.
Mercury
- Mercury concentration was within the acceptable limits of the BIS and no toxicity due to mercury was observed in the Indian rivers during the study period.
Nickel
- Nickel concentration at Fatehgarh water quality station on the Ganga was reported to be the maximum.
- Baitarni, Ganga, Gomti, Hasdeo, Mahanadi, Narmada, Purna, Seonath, Subarnarekha, Tel, Wainganga and Wardha were the rivers where 2 or more water quality monitoring stations were observed to be contaminated with Nickel.
Zinc
- In all the water samples, zinc concentration was well within the acceptable limits of the BIS and no toxicity was observed in the Indian rivers during the study period.
Please download the complete report below.