Texas

If there is no potential for risk, according to these criteria, then there is no

further action or investigation is warranted.

The Oregon DEQ is currently working on a probabilistic risk assessment

guidance document for human health risk assessment. The draft is currently being

reviewed locally and should be available for wider review by the end of August

1997 (Oregon DEQ 1998). The State currently uses the EPA's CERCLA

documents for human health risk assessments.

Texas

Document:

"Texas Risk Reduction Program." Prepared by Texas Natural

Resources Conservation Commission. (TNRCC 1996a).

Contact:

TNRCC, Office of Waste Management, Austin, TX.

The Texas Risk Reduction Program for evaluation of human health risks

follows the risk-based corrective action (RBCA) process developed by the

American Society for Testing and Materials (ASTM). This document uses a tiered

approach to determine risk-based concentration levels for certain contaminant

levels at a hazardous waste site. These risk-based concentration levels are

protective of human health. Also, the document specifies three "remedy

standards" (risk management options) are given. The three options are:

1. Unrestricted Land Use - Permanent Remedy.

2. Restricted Land Use - Remedy with Controls.

3. No Active Land Use - Remedy with Controls.

The risk-based concentration levels are applied to one of these remedy

standards to assess the risk to human health posed by a particular site. Three

sections of this document (TNRCC 1996a) discuss procedures regarding

determination of human health risk.

Section 4.4 describes how to determine human health risk limits and risk

characterization.

The points of exposure (air, soil, groundwater, surface water) for each remedy

standard are discussed in Section 5.4.

Section 7.1 explains the tiered process for the development of human health-

based protective concentration levels.

In this tiered approach, the type of land use, remedy standards, and

groundwater class specific to a site are first determined. The next step is a Tier I

screening level evaluation. At each tier, exposure pathways and chemicals of

concern, site parameters, protective concentration levels (PCLs) and PCL

exceedance are determined. If a risk assessor cannot rule out the potential for

harm to human health at the site in Tier I, he or she proceeds to a site-specific,

A26

Appendix A Summary of Federal, State, and Regional Guidance