Oil companies are being urged to help Norwegian authorities track down the source of high toxin levels in fish in the country's waters, with illegal dumping of plastic waste decades ago the prime suspect.

Oil and gas groups Equinor, Aker BP and Wintershall Dea are among the companies the Norwegian Environment Agency has approached for assistance uncovering the unusually high levels of mercury and other toxins among some species in the Norwegian Sea.

Gas system operator Gassco and geo-data specialist Fugro have also been approached for help in unravelling a mystery that, as of now, has not implicated the oil or gas sector.

Norwegian authorities are concerned that high levels of mercury, dioxin and PCB (polychlorinated biphenyl) in halibut from the Sklinnabanken fishing grounds may be related to leakage from barrels of toxic waste dumped in this area in the 1960s and 1970s.

Illegal dumping

In 1971, a Dutch vessel was intercepted attempting to dump barrels containing 600 metric tons of toxic chlorinated aliphatic hydrocarbons from a Dutch plastics producer at Sklinnabanken.

After the incident was exposed, the practice stopped. However, the Norwegian Environment Agency has, after reviewing media reports from the 1970s, estimated that as much as 50,000 barrels of toxic waste from Europe's plastics industry may have been dumped on the Norwegian continental shelf.

A spokesperson for the agency told IntraFish sister publication Upstream it had contacted the mentioned oil industry players but added that so far no dumped material has been found in the area.

Vast area to cover

The agency hopes that the oil and gas companies can uncover barrels of dumped waste during their seabed surveys before drilling operations begin.

However, since the area is approximately 6,000 square kilometers — equivalent to 840,000 football fields — it will not be possible to investigate the whole area, the spokesperson said.

Wintershall Dea is one of the operators with several licenses in the area. A Wintershall Dea spokesperson told Upstream it has so far found nothing of note in relation to the agency's request.

According to the Norwegian Environment Agency, the barrels may be difficult to detect since they will be covered by sediments.

However, the Wintershall spokesman said the company is very thorough when preparing a drill site.

“For our areas of operation and where we put down facilities, we would most likely find things like drums of toxic waste and we would definitely report this,” he said, adding that seabed survey reports are are very detailed, frequently reporting plastic waste, helmets, whale bones and other items.

The spokesperson said that when the company is gearing up to drill a prospect, it will first survey the area with a side-scan sonar sensor.

"This technique is good at picking out hard objects from the seabed. This initial scan is used to identify rocks and boulders and potential hard coral communities on the seabed,” he explained.

Simultaneously, a multi-beam echo sounder sensor is also used, giving more information about the changing depths on the seafloor.