Alaska (Cont.)

differences between chemical toxicity to biota and to humans. At this point, if no

organic chemicals of concern are present or the concentration of inorganic

elements is at or below "background," the site does not need to be assessed

further.

If the assessor decides to continue the evaluation, a biological characterization

of the site is conducted. The assessor visits the site and identifies habitats and

"special species" of concern. Next, exposure pathways are identified. The authors

use a "habitat approach as a basis for identifying potential exposure pathways

between the areas of contamination and specific species or habitats which occupy,

or potentially could occupy, the site." The authors suggest that contact between

biota and COCs in media such as soil, air, water, and biota, and by direct and

indirect routes be considered.

The product of this assessment is a qualitative evaluation of the threat to

nonhuman receptors. The authors suggest that a qualitative statement of the

magnitude, duration, and frequency of exposure to receptors to each contaminant

or area of contamination be included in the risk assessment report. The minimum

requirements for figures, tables, and data are also given in this document. At the

end of Phase I, the assessor must also submit a Work Plan Outline to the DTSC.

The required contents of this outline are also specified in this guidance document.

Document:

"Supplemental guidance for human health multimedia risk

assessment of hazardous waste sites and permitted facilities"

(California EPA/DTSC 1996).

The California DTSC has a guidance manual on human health risk assessment

which supplements the USEPA's "Risk assessment guidance for superfund,

Volume I, Human health evaluation manual (Part A) and USEPA Office of Solid

Waste and Emergency Response directives. This manual provides

recommendations on specific technical or scientific issues that may be

encountered when preparing human health risk assessments. The document

generally follows USEPA guidance and provides specific information on:

a. Default Exposure Parameters.

b. Use of soil concentration data in exposure assessment.

c. Selection, use, and limitations of indicator chemicals for evaluation of

exposure to complex waste mixtures.

d. Assessment of health risks from inorganic lead in soil.

e. DDT in soil: Guidance for the assessment of health risk to humans

f. A toxicity equivalency factor procedure for estimating 2,3,7,8-

tetrachlorodibenzo-p-dioxin equivalents in mixtures of polychlorinated

dibenzofurans.

A17

Appendix A Summary of Federal, State, and Regional Guidance