(Left) The tanker Sanchi billowing smoke off the coast of eastern China on Jan 10. (Right) Six days later, a fuel spill is visible on the East China Sea. NYT PIC

A FIERY collision that sank an Iranian tanker in the East China Sea a month ago has resulted in an environmental threat that experts say is unlike any before: an almost invisible type of petroleum has begun to contaminate some of the most important fishing grounds in Asia, from China to Japan and beyond.

It is the largest oil spill in decades, but the disaster has unfolded outside the glare of international attention that big spills have previously attracted. That is because of its remote location on the high seas and also the type of petroleum involved: condensate, a toxic, liquid by-product of natural gas production.

Unlike the crude oil in better-known disasters like the Exxon Valdez and the Deepwater Horizon, condensate does not clump into black globules that can be easily spotted or produce heart-wrenching images of animals mired in muck. There’s no visible slick that can be pumped out. Experts say the only real solution is to let it evaporate or dissolve. Absorbed into the water, it will remain toxic for a time, though it will also disperse more quickly into the ocean than crude oil.

Experts say there has never been so large a spill of condensate; up to 111,000 metric tonnes have poured into the ocean. It has almost certainly already invaded an ecosystem that includes some of the world’s most bountiful fisheries off Zhoushan, China, the archipelago that rises where the Yangtze River flows into the East China Sea.

The area produced five million tonnes of seafood of up to four dozen species for China alone last year, according to Greenpeace, including crab, squid, yellow croaker, mackerel and a local favourite, hairtail. If projections are correct, the toxins could soon make their way into equally abundant Japanese fisheries.

Exposure to condensate is extremely unhealthy to humans and potentially fatal. The effects of eating fish contaminated with it remain essentially untested, but experts strongly advise against doing so.

“This is an oil spill of a type we haven’t seen before,” said Paul Johnston, a scientist at Greenpeace Research Laboratories at the University of Exeter, England. “Working out the impact is actually a huge task — probably next to impossible.”

For China, the disaster has become a test of its ambitions as a global and regional steward of the seas, especially at a time when it is reinforcing its territorial claims, including disputed territories with Japan in these waters.

Given its proximity, China has taken the lead in investigating the disaster and monitoring the spill, but it has faced some criticism for what some see as a slow and inadequate response thus far.

Officials in Beijing announced on Feb 1 that samples of fish taken within four to five nautical miles of the sunken ship contained traces of petroleum hydrocarbons, suggesting possible condensate contamination; they pledged to expand the range of testing to 90 miles, and closely monitor fish coming into markets.

The threat of contamination has raised anxiety in the ports that cling to the rugged coastlines of Zhoushan’s islands, though such fears are usually expressed with quiet resignation lest one offend the government.

“The quality will go down because of the oil in the water,” said Hai Tao, a fish wholesaler at the International Aquatic Product City in Putuo, a district on Zhoushan’s biggest island, as he watched a ship unload hundreds of crates of mantis shrimp, a delicacy headed to restaurants across China.

The spill began on the evening of Jan 6, when the Sanchi, a Panamanian-flagged, Iranian-owned tanker, collided with a cargo ship in waters roughly 160 nautical miles east of Shanghai. The Sanchi exploded and burned for more than a week before sinking. All 32 crew members are presumed dead.

Katya Popova, a senior research scientist at the National Oceanography Centre in England, said there had not been a sufficiently coordinated international operation, and that was exacerbating the scale of the disaster. The lack of visible devastation has almost certainly dampened public reaction that might have galvanised a more vigorous response.

In Beijing, officials have been eager to demonstrate that the government was doing everything possible first to respond to the disaster and then to protect the health of its economically and politically sensitive fishing industry, which employs 14 million people.

They have issued regular statements and held briefings, showing video of efforts to clean up the condensate and to monitor the sunken wreck, which was located at a depth of 115m, or about 377 feet.

It is believed to still be leaking condensate and other fuels.

Han Xu, deputy director of the fisheries administration bureau of the Ministry of Agriculture, told reporters at a news conference in Beijing late last month that the accident had “a certain impact on the density of fishery resources” in the area, but that the government did not yet know the extent of the threat.

In the meantime, authorities have ordered a ban on fishing in the areas affected.

The spill is already drifting east toward Japan, but winds and currents can be unpredictable. The contamination could even reach waters as far off as Tokyo.

The cause of the disaster remains a mystery. The Sanchi was nearing the end of its voyage to South Korea through one of the most heavily traversed parts of the world’s oceans when it collided with the CF Crystal, a bulk carrier flagged in Hong Kong that was delivering grain to China from the United States. As the Sanchi erupted into flames, the Crystal managed to make harbour — and is now in one of Zhoushan’s many ports. -- NYT

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