The discovery of PCBs at a depth of almost eleven thousand meters below the ocean’s surface is extremely unsettling. Legally, structurally, and institutionally unsettling in a way that the environmental law community has only just started to address, rather than philosophically unsettling, though that is also the case. In June 2017, Chinese researchers on board the R/V Tansuo Yihao collected sediment samples from the southern Mariana Trench without the intention of engaging in a legal dispute. However, that’s basically what they discovered.
The polychlorinated biphenyl concentrations found in those samples, which ranged from 931 to more than 4,000 picograms per gram of dry sediment, were not trace amounts that could be written off as background noise. Certain readings were comparable to contamination levels from semi-industrial coastal areas, such as the Han River in South Korea or Asaluyeh Harbor in Iran. locations with shipping lanes, factories close by, and decades of recorded industrial discharge. There is none of that in the Mariana Trench. After decades of industrial civilization dumping its waste into rivers and skies that eventually feed the sea, it has only what gravity and ocean currents brought, slowly and silently.
Organic pollutants that are persistent do not decompose. That’s exactly the issue, both legally and scientifically. PCBs continue to build up despite being prohibited in the US since 1979 and worldwide by the Stockholm Convention in 2001. Human regulatory frameworks were never intended to match the chemical patience with which they navigate atmospheric and oceanic currents. Tracing them to a particular manufacturer, a particular nation, or a particular industrial operation becomes a matter of forensic conjecture by the time they settle into hadal sediments seven miles below the surface. However, the disappearance of the paper trail does not eliminate the liability issue.
It’s difficult to ignore how advantageous these trenches’ remote location has been for the businesses that made these compounds. Sitting far beyond the jurisdictional clarity of any one country’s courts or enforcement mechanisms, it was out of sight and, until recently, mostly out of scientific reach. Only around 1% of the world’s seafloor is made up of the hadal zone, those V-shaped depressions created where tectonic plates grind against one another. However, it serves as a long-term storage facility for all that humankind has dumped into the water column above. At 11,034 meters, the lowest point on Earth, the Challenger Deep, receives this contamination like a slow, silent ledger of industrial consequences.
The deep ocean’s legal framework is still genuinely precarious. The United Nations Convention on the Law of the Sea, or UNCLOS, states that the high seas and their resources are part of humanity’s shared legacy. That sounds defensive. In actuality, this means that no country has unambiguous enforcement authority over what ends up in hadal sediments. Standing, traceable harm, and an identifiable defendant have historically been prerequisites for environmental litigation against polluters. Contamination that moved through global atmospheric currents and then sank through thousands of meters of open ocean does not neatly map onto any of those conditions.
The biology is what adds complexity and possibly urgency to the situation. Jamieson and associates discovered that the endemic amphipod fauna in the Mariana and Kermadec Trenches, which are unique to the planet, were bioaccumulating these same persistent pollutants. There may be active biological concentration because the toxic load in those organisms was higher than what would be predicted from the surrounding sediments alone. The question of who is accountable for harm done to a species that no jurisdiction formally claims arises when a species that only exists at a depth of eleven thousand meters has industrial-era contamination in its tissue. This question has never been seriously addressed by international environmental law.
Even if it happens gradually, a more comprehensive reckoning is on the horizon. The idea of “common heritage” has begun to be studied by international legal scholars as a framework for liability as well as a resource-sharing principle. If humanity is collectively responsible for the contamination of the hadal trenches, then this responsibility logically extends to the states and industries that contributed the most emissions at some point. The United States, Germany, Japan, and other countries that produced PCBs on a large scale are also signatories to treaties that require environmental remediation and the precautionary principle. Technically, it’s still unclear whether those responsibilities extend seven miles down. It most likely shouldn’t be.
The risk of precedent through inaction is the deeper one. The contamination compounds found in sediments, animals, and the microbial ecosystems that scientists now believe reside in the hadal lithosphere itself are present every year that goes by without a legislative framework for hadal pollution liability. At the bottom of the world, the poisonous dividend of a century of industrial production has been discreetly deposited. Someone will eventually be asked to explain it. When the time comes, will the organizations that can demand accounting exist and have the will to do so?
