Medical Advisory Services (MAS) provides medically-based occupational, environmental and public safety services to protect people through science, experience, and practical solutions. People are the most important asset:  in societies, in corporate organizations, and in ensuring the sustainability of our environment.  The current Gulf of Mexico oil spill is wreaking havoc on the citizens of the world, and the environment in which we live.  This is a very complex, intricate and difficult situation.

Dr. Tee L. Guidotti, a pre-eminent physician with extensive experience in the oil and gas industry, explains the toxicology and human health impact associated with the Gulf of Mexico oil spill based on the facts disclosed to date.  Using our medically-based Enterprise Risk Management approach, we work to develop emergency preparedness and sustainability protocols that enables us to fulfill our commitment to ensure the health, safety, and productivity of people, while protecting environmental and fiscal assets.

Public attention is focused on the implications of the oil release for the environment, as it should be. Leaders and local residents are concerned about the economic impact of the release. There is outrage at what has happened and anger directed at BP.

Corners cannot be cut in this industry without placing lives at risk. Upstream oil and gas (the part of the industry from exploration to a producing well to the refinery) is an intrinsically hazardous industry as a whole. The offshore oil and gas industry is one of the most hazardous subsectors in the economy, but it has a remarkable safety record overall (despite high-profile incidents). The reason we do not hear more about these hazards is that the oil and gas industry has the resources and infrastructure to prevent hazard from translating into risk, by investing in controls, training, engineering, emergency response, and safety management systems. And yet, it happened, and to one of the companies seemingly best equipped to deal with what might go wrong.

What is the prospect for future human health risk from this fiasco? We can already identify several risk drivers: occupational hazards associated with exposure and cleanup, community exposure, community and ecosystem disruption, and psychogenic effects.

Crude oil is much less toxic, overall, than its refined products but there are constituents with significant toxic properties. Crude is a mixture of hydrocarbons, mostly straight and branched-chain alkanes, some more complicated hydrocarbon structures (such as ringed alkanes and some aromatic compounds). Dissolved in it, and readily coming out when the pressure drops, are varying amounts of hydrogen sulfide, carbon disulfide, and mercaptans; these sulfur compounds, particularly hydrogen sulfide, make the difference between “sweet” and “sour” oil and gas. The crude that is gushing from the BP well is sweet, so there is little hydrogen sulfide in it. There are also trace amounts of metals in crude, including mercury, and some radionuclides (“naturally-occurring radioactive materials”, called NORM in the industry). As a mixture, crude oil is irritating to skin but much more toxic to animals (especially birds and invertebrates) than human beings, who have used it on occasion as medicine (it is an effective but disgusting laxative).  On a relative scale of similar mixtures based on experimental induction of skin cancer, it ranks low. So crude oil, on the whole, is not a big risk for human toxicity.

Individual constituents of crude oil can be highly toxic, of course, but the exposure risk needs to be understood in the context of this unusual situation. The most toxic fraction of crude oil is the “volatile” fraction, consisting of low molecular-weight compounds that, as the name implies, evaporate quickly and are primarily (but not exclusively) a hazard through inhalation. The highest cancer risk is associated with benzene. The highest toxicity risk otherwise is probably n-hexane, which is the only highly toxic straight alkane. The combined effect of mixed volatiles may be similar to but probably less than petroleum distillates (a refined product of crude capturing lighter fractions, used in many industry applications as a vehicle or solvent), the most important of which is to depress the central nervous system, like an anesthetic, when inhaled in very high concentrations.  

Although these compounds are individually toxic, the potential for exposure is much less in this situation than usual for a well blowout. The reason is that the oil reservoir is under enormous pressure and the well is releasing oil into a deep-water column with a pressure of more than 150 atmospheres (1500 decibars, as the underwater engineers prefer), which means that volatile compounds in crude would not outgas as readily as on the surface. They are likely to dissolve quickly in ocean water so many of the more water-soluble compounds (like benzene) may not make it to the surface.

The high molecular-weight, asphalt-like brown viscous “mousse” that rises to the surface is a gooey semi-liquid that is likely to be irritating but not highly toxic on skin contact with humans, although it has not been much studied. This material has devastating ecological toxicity, however. In the form of droplets in water, it fouls the filter systems of invertebrates, changes the taste of seafood, poisons wildlife that preen and lick it off (thereby ingesting very large quantities), and interferes with flight and the natural oils that make sea-going birds water resistant. The potential for endocrine disruption effects and other ecotoxicological effects is not known, however, surveillance activities related to this spill will give us the answer..

The products used to manage the oil present another class of risk. There are only so many ways to clean up an oil spill or release,:

• contain the oil (with booms, floating risers, containment apparatus),
• absorb the oil (using hair or polymer materials),
• remove contaminated soil and vegetation (which is very disruptive ecologically and carries the occupational risks of any big construction project),
• burn the oil that is combustible (which can only be done when it is fresh, causes air pollution, and releases combustion products that are generally more toxic than the crude or mousse),
• disperse the oil (using dispersant / detergent chemicals), and, perhaps most important,
• giving ecological systems time to degrade the oil and repopulate the ecosystem (with sickening consequences in the meantime and possibly permanent loss of diversity in the long term).

Dispersant chemicals, which are surfactants, are used to emulsify the oil to make it more amenable to bacterial degradation. (This action may also increase the problem of exposure of invertebrates to suspended droplets in ocean water but this is not a human toxicity issue.) Surfactants, which are basically detergents, are low in toxicity as a class although they can be irritating. The chemicals that are used as vehicles for the dispersants may be more toxic in concentrated form than the active ingredients, as at least one formulation is blended with petroleum distillates, which, as noted above, are at least as toxic as the volatile fraction of crude.

It is unclear what the future will hold. The psychological consequences to the people who live in Gulf communities, the loss of income and the social disruption that follows, the apprehension of offshore workers who are similar rigs, and the grief of the families of the lost workers give this tragic incident emotional depth and impact that goes far beyond the physical and toxic hazards.