29 May,2026 09:22 AM IST | Mumbai | Ranjeet Jadhav
Tarballs being washed onto the shore are an annual occurrence in Mumbai. Pics/By Special Arrangement
Every year, as pre-monsoon winds lash Mumbai's coastline, dark sticky tarballs - a visible sign of a recurring seasonal oil spill - begin washing ashore from Juhu to Versova and Aksa to Girgaon, coating beaches, fragile mangroves and rocky shores in toxic petroleum residue. Marine ecologist Shaunak Modi warns that the oily sludge poses a threat to both marine biodiversity and human health.
According to Modi, the sticky black globs are not isolated incidents, but part of a seasonal oil spill affecting India's west coast from April to September. He has raised concerns that while visible tarballs on beaches are cleared, those that land on rocky terrain take months to clear out, often leaching back into the ocean.
6-7kg
Weight of each large tarball
MARPOL - the International Convention for the Prevention of Pollution from Ships - is the primary international treaty developed by the International Maritime Organization (IMO) to protect the marine environment and minimise ocean contamination from routine shipping operations and accidents.
"This seasonal oil spill is happening for over a decade. Kids play barefoot, people walk through it, and sanitation workers collect it without gear. After collection, it is sent to landfills, raising further concerns. Some of this oil may leach back through mangroves into the sea," Modi said.
"It starts towards the end of March. We get strong onshore pre-monsoon winds, and a lot of tarballs start washing ashore across Mumbai," said Shaunak Modi, marine ecologist, and Director of the Coastal Conservation Foundation, and founder of Marine Life of Mumbai.
The impact on wildlife is severe. Floating oil can coat the feathers of seabirds, making flight difficult, while marine animals may mistake tarballs for food. Once ashore, they affect crabs, mussels, shells, and other intertidal species. "The issue extends beyond beaches. Juhu and Girgaum are where we notice it more because tarballs are visible on sand. But rocky shores also get covered. Beaches are cleaned, rocky shores aren't," Modi said. He added that oil on rocky shores such as Bandstand can remain until November or December, contaminating tide pools and marine habitats, until they slowly wash away with the tides.
Tarballs are currently coin-sized, but they grow much larger during peak monsoon. "Between July and September, you start seeing almost basketball-sized tarballs washing ashore. I have documented these 6-7 kg tarballs from Gujarat to Karnataka," he said.
According to Modi, rough seas churn floating oil with sand and seawater, forming tarballs. He said that the sources are allegedly likely linked to a pipeline leakage at Bombay High, and also to ships illegally cleaning oil tanks offshore. "India has signed MARPOL, but unfortunately, enforcement is weak. A lot of times this also comes from ships," Modi added.
