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Fattorini

and relatively low toxicity. Other surfactants include Corexit dispersants were also used after the
ethoxylated fatty acid esters (nonionic surfactants Deepwater Horizon disaster (2010). This event saw
that provide emulsion stability), sulfosuccinates (e.g., unprecedented use of dispersants, both on the surface
sodium dioctyl sulfosuccinate, an anionic surfactant and, for the 1 time, on a large scale, directly at the
st
with emulsifying properties), organic sulfonic acids source of the release at depth. Nearly seven million
and their salts (anionic surfactants aiding wide oil liters of dispersants were applied, primarily Corexit
dispersion), and alkoxylated alcohols or ethoxylated 9500A and Corexit 9527A. This practice helped reduce
alkylamine (nonionic surfactants). 48 the amount of oil at the surface, mitigating the impact on
As additional components, solvents help transport seabirds, marine mammals, and shorelines. Underwater
and distribute the surfactants, keeping them in the dispersal was intended to prevent large quantities of
solution and facilitating their penetration within the oil oil from reaching the surface, but significant concerns
slick. Dispersant solvents usually consist of hydrotreated were raised. Although dispersants reduced the visibility
light oil distillates and hydrocarbon-based substances of oil at the surface, they introduced oil (and the
with low or absent aromatics to reduce toxicity. Other dispersants themselves) into the deep-water column,
common solvents are glycols (e.g., propylene glycol, where their persistence, fate, and effects on marine life
propylene glycol ethoxylate, and 2-butoxyethanol) were less understood and remain the subject of intense
that are less volatile and potentially less toxic than research. 28,46 The combined toxicity of oil and dispersant,
the aromatic solvents used in early generations of the formation of “marine oil snow” that carried oil to the
dispersants. However, the use of selected glycol ethers seafloor, and the health effects of cleanup workers were
and 2-butoxyethanol has recently been the subject of critical debate points. Some studies have suggested that
concern for their potential adverse effects. 48 underwater dispersal did not significantly reduce the
The first massive use of dispersants dates to the overall amount of oil reaching the surface but altered its
accident of the supertanker Torrey Canyon in 1967, distribution. 28,46,48,103
which caused the spill of approximately 120,000 tons During the Prestige oil tanker spill (2022), given
of crude oil off the coast of Cornwall, United Kingdom. the type of oil and the adverse weather conditions that
The chemical dispersants were used extensively and characterized the initial stages of the accident, the use of
unprecedentedly; over 10,000 tons of these substances, chemical dispersants was controversial and ultimately
such as BP 1002 containing non-ionic surfactant limited, deemed ineffective in containing the crude oil
detergents, were sprayed on floating oil and contaminated spill. For instance, dispersants work best on low viscosity,
beaches. These “first-generation” dispersants were lighter oils, which can be easily emulsified. In contrast,
highly toxic and contained aromatic solvents, such the Prestige’s heavy oil was inherently difficult to disperse
as benzene and xylene. Studies have determined that chemically, due to its elevated viscosity. In addition to
the oil/dispersant mixture was more harmful to the adverse weather conditions, rough seas and strong winds
environment than the oil alone. Numerous seabirds further complicate any attempts to effectively apply
died from lungs clogged by detergent foam, leading to dispersants. While rough seas can promote some natural
increased awareness of the risks of dispersants and the dispersion, they also hinder the targeted application and
development of less toxic formulations. 103 effectiveness of dispersants, which require a certain
During the Exxon Valdez Disaster in 1989, Corexit amount of contact and mixing time to work. In practice, the
chemical dispersants were tested on a limited scale dispersants failed to fulfill the desired role of containing
immediately after the spill. Although the composition and dispersing the spill. The oil largely reached the coasts
of Corexit is not publicly available, it may contain of Galicia and subsequently France and Portugal, causing
substances, such as butoxyethanol bisulfonate, an devastating environmental and economic damage. 48,80-82,103
additional organic sulfonate, and small concentrations The Prestige accident and other spills have elicited
of propylene glycol. Weather conditions and the international debate on the efficacy and potential
viscosity of the oil did not favor significant dispersion, ecotoxicological impacts of dispersants. Concerns include
and the quantities of dispersant available and applied their effectiveness in the field and the combined toxicity
were insufficient to address the scale of the disaster. of the dispersant and the dispersed oil on marine life. For
Some studies suggested dispersants may have formed the Prestige oil, which contained high levels of PAHs,
chemically enhanced, potentially more toxic oil dispersion could have carried these toxic compounds
particles. Much of the cleanup subsequently focused on deep into the water column, potentially exposing benthic
physical methods and biostimulation. 26,48,77,103 organisms and other species. 80-82

Volume 22 Issue 6 (2025) 38 doi: 10.36922/AJWEP025290224