Hidden in the flow: Microplastics detected in Karnataka’s groundwater

BENGALURU: A study by researchers from Indian Institute of Science (IISc) and Vellore Institute of Technology has detected microplastics in groundwater at depths of 60 to 100 metres in eastern Karnataka, raising concerns about contamination in rural water sources.

Published in Current Science on March 25, the study found microplastics circulating through fractures in hard rock formations such as granites and gneisses. The particles appeared as fragments, filaments, and prisms, with concentrations of up to three particles per litre.

The research team sampled borewell water from villages in Tumakuru, Ballari, Raichur, Chikkaballapur, Koppal, and Kolar districts. In Nov 2024, one-litre samples from 11 locations showed microplastics in 10 sites. A second round in Feb 2025, covering 14 locations, found particles in fewer sites, indicating that contamination levels vary over time.

Larger sample volumes revealed higher contamination. At Ganjigunte and Mudimadugu, 20-litre samples contained significantly more particles and a wider range of plastic types compared to the one-litre samples, suggesting that smaller samples may underestimate the extent of pollution.

Analysis identified multiple polymers, including polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET), commonly used in packaging and agricultural materials. Most particles were smaller than 1,000 micrometres and their linear shapes likely enabled them to move through narrow rock fractures and enter groundwater.

The study attributes the contamination largely to domestic and agricultural waste, along with freshwater fishing activities. Common sources include plastic carry bags, multilayered packaging, pipes, mulch films, and fishing gear.

Researchers estimate that people in these villages may ingest around 1,100 microplastic particles annually through drinking water, or about three per day. However, the study notes that drinking water alone is not currently a major source of exposure, as many villages use reverse osmosis systems that can filter out microplastics if properly maintained.

The findings underline the need for better management of plastic waste in rural areas, particularly in agriculture and inland water bodies, to prevent further contamination of groundwater.