Steps in the PHA Process

Diagram showing the steps in the PHA Process

The steps in the PHA Process are done in the following order:

Initiate site scoping

Define roles and responsibilities

Establish communication mechanisms

Develop a site strategy (including a site conceptual model)

Collect site information

Select sampling data

Conduct scientific evaluations to include:

Exposure pathways (define exposure units*)


EPCs and exposure calculations

In-depth toxicological effects

Summarize findings and next steps


*Based on site-specific information, health assessors may define an exposure unit (if appropriate) before or after the screening analysis. Health assessors will use professional judgement to determine when to define exposure units; however, they must define them before determining EPCs.

Page last reviewed: April 14, 2022