Evaluation of Environmental and Human Risk From Crude-Oil Contamination
Authors: Sullivan Michael J. 
Published: December 2007

Summary
The presence of petroleum compounds in soils, water, or petroleum compoundsin soils, water, or air does not necessarily result in a risk to populations. This paper presents a method of quantitative risk assessment (QRA) usedsuccessfully to assess, describe, and understand the environmental- andhuman-heath risks found in the oilfield environment.

Introduction
Soil contamination from petroleum hydrocarbons has become an important humanand environmental-health issue in the U.S. over the last decade. Yet, thiscontamination has probably occurred since the use of petroleum becamewidespread during the petroleum became widespread during the early part of thiscentury. The potential exists for humans to be exposed to petroleumconstituents in soils through various pathways. Potential pathways of exposureto pathways. Potential pathways of exposure to petroleum hydrocarbons in soilat a site depend petroleum hydrocarbons in soil at a site depend on the type ofsoil, petroleum, and petroleum constituents present. petroleum constituentspresent. Potential human exposures to petroleum in soils can be evaluatedthrough the use of formal QRA. This method incorporates information about thetoxicity of the petroleum and its constituents. the environmental behavior ofthese agents. and the estimated exposure to these agents to evaluate thepossible health risks to humans exposed to possible health risks to humansexposed to petroleum in soil. petroleum in soil. Crude oil is the naturallyoccurring liquid phase of petroleum. Natural crude-oil seeps are common inregions of petroleumbearing formations. This natural petroleumbearingformations. This natural contamination may result in human exposures to crudeoil and subsequent associated health risks. Risks from natural contaminationsources are often referred to as background risks. Health risks associated withexposures resulting from accidental releases of chemicals into the environmentare referred to as additional or incremental risks. QRA's are used to evaluateincremental health risks from accidental releases of petroleum products intothe environment. For example, if products into the environment. For example, ifa QRA concludes that the presence of crude oil in soil results in exposuresthat may cause adverse effects, then the concentration of the crude in soil mayneed to be reduced to an acceptable level.

Use of Risk Assessment.
Companies use formal health-based risk assessmentfor a variety of reasons, including the need to understand risks and toprioritize the remediation and prevention of risk. Internally, companies wantto understand the potential risks at a given site for decision-making reasonsand for comparison with other sites. The QRA provides information that cananswer a variety of internal questions. For example, how can one company withmultiple sites contaminated with a variety of chemicals prioritize remediationalternatives? How can a company develop a structured enviroinmental program toremediate each of those sites when the given fiscal reality does not permitremediation of all sites in a given year? Companies can use QRA's to prioritizethe sites and clean up the most risky sites first. This equates to a program ofrisk prevention in which the greatest amount of prevention in which thegreatest amount of risk reduction is achieved for every remediation dollarspent. QRA's can also be used to prioritize the remediation within a givensite. The chemical with the highest concentration may not be the chemical withthe highest risk. Use of QRA's within a site allows, first, for the remediationof chemical contaminants that pose the highest risk to the exposed population, with subsequent remediation of the remaining chemical contaminants having lowerrisk. Externally, QRA's are used in a variety of situations, includingregulatory responses and dealings with the public and media. QRA's can providealternative contamination levels or remediation goals at a given site and canbe used to convey the conditions at the site to the public and media. QRA's arescientifically defensible documents, based on the best and most currentunderstanding of the toxicity and exposure data base, that provide a logical, documented transition from site-specific exposure and toxicity data to theestimated risk. As legal documents, QRA's are used in liability cases and inthe defense of product liability suits. QRA's provide a structure to theremediation process and address an endpoint; they can be used to provide analternative remediation goal to one being proposed by regulators-i.e., arisk-driven rather than technology-driven remediation endpoint.

QRA Components.
The principle of risk assessment can be summed up as hazardtimes exposure equals risk.
JPT
P. 14