Exercise: Exposure Assessment

MVEN10 Risk Assessment in Environment and Public Health

Author

Zheng Zhou

Published

September 12, 2025

Part II: Calculating Exposure

This part is to provide hands-on practice in exposure assessment, a fundamental component of human health risk assessment. Students will learn to:

  • Calculate Average Daily Dose (ADD) using real-world data

  • Integrate multiple exposure parameters from different populations

  • Compare exposure scenarios across different countries

  • Interpret results in the context of public health significance

  • Apply statistical programming (R) to exposure assessment problems

Through this exercise, you will develop practical skills in quantitative exposure assessment methodology that forms the foundation of risk characterization in environmental and occupational health.

Submission requirements

  • The sections of the report should be indexed by questions

  • Include proper citations for all data sources

  • Ensure all figures or tables are properly labeled

  • Save the report as a PDF and submit to Canvas

Average daily dose concept and equation

Definition

The Average Daily Dose (ADD) represents the average amount of a chemical substance that an individual is exposed to per unit body weight per day over a specified time period. It is a fundamental metric in exposure assessment used to characterize potential health risks.

Equation

\[ ADD=\frac{C\cdot IR\cdot EF\cdot ED}{BW\cdot AT} \]

Where:

ADD = Average Daily Dose (mg/kg-day)

C = Concentration of the contaminant in the medium (mg/kg for food)

IR = Ingestion Rate (kg/day for food consumption)

EF = Exposure Frequency (days/year)

ED = Exposure Duration (years)

BW = Body Weight (kg)

AT = Averaging Time (days)

Simplified Equation for Dietary Exposure

For this exercise focusing on chronic dietary exposure, we will use a simplified version assuming continuous daily exposure over a lifetime:

\[ ADD =\frac{C\cdot IR}{BW} \]

Case Study: Inorganic arsenic through rice intake

Inorganic arsenic contamination in rice represents a significant global public health concern. Inorganic arsenic is classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC) (IARC 2012). Rice serves as a staple food for over half of the world’s population, making dietary exposure through rice consumption a widespread concern.

The European Commission has established maximum levels for inorganic arsenic in rice products (200 µg/kg for milled rice), and the US FDA has proposed action levels, highlighting the regulatory significance of this contamination issue.

Instructions

  1. Extract data on rice consumption for the US, Swedish and Italian populations. You can find relevant information from the following sources:

The US EPA Exposure factors handbook

Sweden and Italy European Exposure facts.

Notice the data could be reported for different subpopulations. Choose the most representative subpopulation based on the principles of exposure assessment you learnt before. Convert the extract data to average daily rice intake (kg/day).

  1. Extract data on inorganic arsenic concentration in rice from the US, Swedish and Italian markets. You can find relevant information from the following sources:

US FDA Analytical Results from Inorganic Arsenic in Rice and Rice Products Sampling

livsmedelsverket report on Inorganic arsenic in rice and rice products on the Swedish market 2015

Notice the data could be reported for different rice and rice products. Decide based on the principles of exposure assessment you learnt before.

Tenni et al. 2017 Total As and As Speciation in Italian Rice as Related to Producing Areas and Paddy Soils Properties

Notice the data could be reported for different arsenic species and different rice grains. Consider only inorganic arsenic. Convert the extract data to average inorganic arsenic concentration in rice (ug/kg).

  1. Extract data on body weights for the US, Swedish and Italian populations. You can find relevant information from the following sources:

The US EPA Exposure factors handbook

Sweden and Italy European Exposure facts.

Notice the data could be reported for different subpopulations. Choose the most representative subpopulation based on the principles of exposure assessment you learnt before. Convert the extract data to average body weights (kg).

  1. Calculate ADDs using the simplified equation and the extracted data on rice consumption, inorganic arsenic concentration and body weight. Do the calculation for the US, Swedish and Italian population respectively.

  2. Calculate ADDs for the following hypothetical scenarios:

  1. If Sweden had the same rice consumption rate as Italy. Keep Sweden’s original arsenic concentration and body weight data.

  2. If arsenic concentration were regulated uniformly across the EU. Use half of the EU maximum level for inorganic arsenic in rice for both Sweden and Italy, that is 100 ug/kg. Keep original consumption and body weight data for each country.

  3. If Swedish population had the same body weight as the US. Keep Sweden’s original arsenic concentration and rice consumption.

Present all ADD calculations (including the real ones from question 4) in a table for comparison.

You may generate the table in excel and paste into e.g. word.

If using R (e.g. in future examples) you can use a table generator for the QMD file.

  1. The World Health Organization (WHO 2011) determined that the inorganic arsenic lower limit on the benchmark dose for lung cancer was calculated to be 3 μg/kg bw per day and 5.2 µg/kg bw/day for bladder cancer, respectively. The US EPA (IRIS 2025) ruled that the inorganic arsenic lower limit on the benchmark dose for cardiovascular endocrine disruption was calculated to be 6 x 10 -5 mg/kg/day. Compare the real ADDs you calculated for the three populations with these regulatory reference values.

Optional questions for extracurricular activities

The following questions are not required for this report. You are encourage to explore them as extracurricular activities if you are interested.

  1. Extract data on rice consumption, inorganic arsenic concentration and body weight for a different country of your interest.

  2. Calculate the ADD and compare with the ones from question 4. Then compare the ADD with the reference values from question

  3. Based on the ADDs you calculated in question 4 and 5, discuss which parameter (concentration, consumption, body weight) causes the greatest change in ADD when varied between populations?

  4. Based on the results of question 6, discuss if you consider inorganic arsenic in rice require immediate regulatory action for Sweden and Italy. If yes, propose one mitigation strategy for the corresponding country and briefly explain your rationale.

Reference

International Agency for Research on Cancer. 2012. Arsenic and arsenic compound. https://publications.iarc.who.int/Book-And-Report-Series/Iarc-Monographs-On-The-Identification-Of-Carcinogenic-Hazards-To-Humans/Arsenic-Metals-Fibres-And-Dusts-2012

WHO 2011. Evaluations of the Joint FAO/WHO Expert Committee on Food Additives (JECFA). https://apps.who.int/food-additives-contaminants-jecfa-database/Home/Chemical/1863

Integrated Risk Information System. 2025. Arsenic, Inorganic. https://iris.epa.gov/ChemicalLanding/&substance_nmbr=278#values