Competency #7: Perform exposure calculations.

Purpose

After completing Competency #7, you will understand how to calculate oral and inhalation exposures and how to calculate cancer risk estimates based on previous decisions about potential contaminants of concern, exposure units (EUs), and exposure pathways.

A father and son looking at a power plant in the distance

Courses and Training Videos

Modules

  • Online Public Health Assessment Training (PHAT) - In this series of eight online and interactive modules, you will learn the fundamentals of the public health assessment (PHA) process. For Competency #8, please review PHAT Module 7: Perform Exposure Calculations. This module will provide you with an in-depth look at calculating exposure doses and air concentrations, comparing those levels to health guidelines, and deciding if harmful effects might be possible. PHAT Module 7 will also cover how to calculate cancer risk.

Webinars about PHAST and the SHOWER Model

  • Public Health Assessment Site Tool (PHAST) - These webinars will show how to use PHAST to screen contaminants, calculate exposure, and locate health guideline information. You can find the following webinars on the PHAST resource page under "PHAST Training".
  • PHAST V 2.0 Webinar Air Pathway Demonstration - This webinar will show you the air pathway module within PHAST and how you can use the module to calculate default and site-specific adjusted EPCs, hazard quotients, and cancer risks for air pathways.
  • Shower and Household Water Use (SHOWER) Model
    • ATSDR SHOWER Model - This webinar shows you how to run default and site-specific residential scenarios to generate daily exposure concentrations and dermal doses for households using household water contaminated with volatile chemicals.
    • PHAST Calculator for the SHOWER Model - In this webinar, you will learn how to bring data from a SHOWER model run into PHAST. Once imported, PHAST will calculate default and site-specific doses, air concentrations, hazard quotients, and cancer risk estimates for you.

Webinars about EPC and PAHs

  • EPC Guidance for Discrete Samples - In this webinar, you will learn about ATSDR's guidance for using discrete samples to calculate the EPC. You will understand what EPCs are, the types of statistics used to calculate them, and how to select EPCs based on exposure. Additionally, you will learn how to calculate 95UCLs when appropriate.
  • ATSDR Exposure Point Concentration Tool - In this webinar, you will learn how to use the exposure point calculations (EPC) tool. The webinar details each step for handling discrete sample data from importing data into the tool, trouble-shooting data errors, calculating the EPC, and interpreting EPC results.
  • ATSDR Exposure Point Concentration (EPC) Tool: Common Issues with Data Inputs - This webinar will teach you about the EPC tool, covering each step from importing data and troubleshooting errors to calculating the EPC and interpreting results for discrete sampling data. Additionally, you will learn how to apply the EPC tool for benzo(a)pyrene (BaP) and dioxin samples.
  • EPC Guidance for Non-Discrete (Composite) Sampling - In this webinar you will be introduced to the guidance for determining the EPC when using non-discrete (composite) samples.
  • Polycyclic Aromatic Hydrocarbons - ATSDR Guidance for Calculating Benzo(a)pyrene (BaP) Equivalents for Cancer Evaluations of PAH. In this webinar, you will learn the steps for calculating benzo(a)pyrene (BaP) equivalents to effectively screen chemicals and identify potential contaminants of concern.

Guidance

Public Health Assessment Guidance Manual (PHAGM)

PHAGM describes methods and resources that you can use to evaluate environmental exposures associated with environmental contamination. For Competency #7, please review the following sections within PHAGM's Section 6 (Conducting Scientific Evaluations).

  • EPCs and Exposure Calculations - Here you will learn how to estimate oral, inhalation, and dermal doses from exposure various contaminated medium, such as water, soil, sediment, air, and biota.
  • In-Depth Toxicological Effects Analysis - In this section you will learn how to evaluate chemical exposures when the doses and concentrations at a specific site exceed health guidelines, such as ATSDR's minimal risk levels. Your goal in conducting this additional toxicological evaluation is to determine the adverse health effects that might occur and to characterize the cancer risk estimates for carcinogens.

Discrete and Non-Discrete Sampling Guidance

SHOWER Model Guidance

  • SHOWER Model Guidance – This guidance document describes how to evaluate inhalation and dermal exposure to chemicals that occur when people use water indoors for showering, hand washing, and other activities. When people use water indoors, volatile and semi-volatile chemicals in the water will volatilize to indoor air. Inhalation exposure results from people breathing the chemicals in indoor air, and dermal exposure results from skin contact with the chemicals in water. The guidance covers residential and non-residential scenarios.

Chemical-specific Guidance

Dioxin and Dioxin-like Compounds

Naphthalene
Interim ATSDR Cancer Risk Evaluation Guidance Value for Inhalation Exposures to Naphthalene

Polycyclic Aromatic Hydrocarbons
Guidance for Calculating BaP Equivalents for Cancer Evaluations of PAHs - Refer to this document to learn ATSDR's approach for calculating BaP equivalents from samples with a mixture of carcinogenic PAHs.

Per and Polyfluoroalkyl substances (PFAS)

Cancer

  • National Toxicology Program in the U.S. Department of Health and Human Services,
  • U.S. Environmental Protection Agency

Exposure Dose Guidance (EDG) Documents

Review the following EDG documents to learn about the parameters for different age groups, like body weight, that are required to calculate doses for different media, such as drinking water or soil ingestion. Note that EDGs also exist for life expectancy and for determining exposure factors, particularly for intermittent exposures.

  • Body Weight EDG - The body weight EDG is an updated exposure dose guidance (EDG) on the use of appropriate body weights for health evaluations.
  • Inhalation EDG - The inhalation exposure dose guidance (EDG) explains how to estimate air-related exposures to contaminants of concern based on a variety of exposure scenarios including residential, workplace, and school.
  • Life Expectancy and Exposure Factor EDG - This is an updated exposure dose guidance (EDG) on the appropriate life expectancy values and exposure factors (EF) to be used in health evaluations.
  • Soil and Sediment Dermal Absorption EDG - This is an updated soil/sediment absorption EDG on how to estimate dermal absorption of contaminants in soil and sediment.
  • Soil and Sediment Ingestion EDG - This is an updated soil/sediment EDG on how to estimate soil- and sediment- ingestion doses to contaminants of concern.
  • Surface Water Dermal and Ingestion EDG - This is an updated guidance on how to estimate exposure from ingesting and contacting contaminants in surface water.
  • Water Ingestion EDG - This is an updated water EDG on how to estimate water-ingestion related exposures to contaminants of concern.

Tools

Exposure Point Concentration (EPC) Tool

EPA Tool - Use ATSDR's EPC Tool to calculate EPCs using the procedures identified in ATSDR's EPC Guidance for Discrete Sampling. A special Excel template is required to load environmental data into the calculator. Once calculated, you can enter the EPC into PHAST.

EPC Tool User's Guide - Use this guide for a step-by-step explanation of how to use the EPC tool to generate EPCs. You can find the guide on the PHAST resource page in the "Exposure Point Concentration Guidance" subcategory. To gain access to the EPC Tool User's Guide, send a request to phast@cdc.gov.

Public Health Assessment Site Tool (PHAST)

Use ATSDR's PHAST, a web-based application. To evaluate environmental data and perform complex dose calculations. In PHAST, you will find calculators for drinking water, soil/sediment ingestion, biota intake, and inhalation exposures. You will find a module that you can use to screen contaminants using ATSDR CVs. It contains a database with health guideline information, such as minimal risk levels, reference doses, and reference concentration. Lastly, you will also find a resource page that includes training videos, guidance documents, and tools that you can use as you go through the PHA process. To gain access to PHAST, send a request to phast@cdc.gov.

  • PHAST User Guide. You can find this guide on the PHAST resource page. It describes how to use all aspects of PHAST.

Shower and Household Water-Use Exposure (SHOWER) Model

Use the ATSDR's SHOWER model, an exposure assessment tool, to evaluate inhalation and dermal exposure to volatile chemicals when using contaminated water at home. You can import the results from the SHOWER model into PHAST to generate hazard quotients and cancer risk estimates for inhalation and dermal exposures. You can request a copy of the SHOWER model by emailing showermodel@cdc.gov.

  • User's Guide for the SHOWER Model V. 4.0 - Study the User's Guide document to learn how to:
    • Install and use ATSDR's SHOWER model
    • Engage with the model,
    • Read the output generated by the model, and
    • Import the results of the SHOWER model into PHAST to calculate hazard quotients and cancer risk.
Print
Content Source:
Agency for Toxic Substances and Disease Registry