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Should Environmental Engineers Trust Risk Assessments?

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1996 Annual Conference


Washington, District of Columbia

Publication Date

June 23, 1996

Start Date

June 23, 1996

End Date

June 26, 1996



Page Count


Page Numbers

1.387.1 - 1.387.6

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Paper Authors

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Joel S. Hirschhorn

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

1 Session 3251


Joel S. Hirschhorn Hirschhorn & Associates

Risk assessment is no panacea for making ditllcuk decisions about the priority, extent, and objectives of cleanups - of hazardous waste sites. Whenever critics of cleanup programs, such as the federal Superfbnd prograq seek changes, they inevitably focus on using more risk assessment in decision making. Yet for several decades risk assessment has been used without consistent and widely supported results. In particular, risk assessments have been routinely petiormed for hundreds of Superiimd cleanups, where the interests of companies paying for cleanups, government agencies, and community groups representing affected people are usually di&erent and confi-ontationa~ because of dtierent priorities and objectives. Ultimately, risk assessment does not do a very good job of satis&ing diverse stakeholders about what is or is not a “safe” level of contamination or exposure, either before or after cleanup.

There have been two diiRerent applications of risk assessments for Superfimd cleanups. First, the government must make the case for taking remedial action. Under the National Contingency Plan regulations, EPA has considerable flexibility, because it can choose to take action ifrisks to public health exceed 1OE-6 and must take action if risks exceed 10E-4. For the vast majority of Superfimd decisions, EPA has used the traditional one in a million excess deaths ( 1OE-6) risk leve~ but more recently it has placed increasing emphasis on the one in ten thousand ( 1OE-4) risk level. However, actions by the ten EPA regional offices, which have the maximum discretion in implementing the Superiimd prograq are ofl.en inconsistent.

The second main Superfimd application occurs when EPA defends specific numerical cleanup goals or standards that are selected for a site remedial action. There are usually few federal or state numerical standards under other environmental programs, making it necessary to use a risk assessment approach to derive numerical cleanup standards. Here too, EPA can choose to base cleanup standards over the risk range of 10E-6 to 1OE-4.


Based on the author’s experience with many Superfimd sites since the program’s inception in 1980, the following technical issues are used to illustrate what have surfaced to be significant problems with relying on risk assessments for hazardous waste cleanup sites.

Indicator chemicals

Over time it has become common practice for parties conducting site studies to define some short list of site contaminants that are used in risk assessments. The inevitable issue is whether such indicator chemicals or chemicals of concern fairly represent the fill range of site contaminants and whether estimated risks are

~’~g~~ 1996 ASEE Annual Conference Proceedings ‘..,yyyL:

Hirschhorn, J. S. (1996, June), Should Environmental Engineers Trust Risk Assessments? Paper presented at 1996 Annual Conference, Washington, District of Columbia.

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