Methods and Standard Values to Estimate Human Exposures in MOE, Carcinogenic Potency Project

For each exposure estimate, references are given in the last column of the MOE table.

Exposure estimates assume 100% absorption.

  1. Chemical Consumption in a Single Food

    For consumption of a chemical in a single food, both the average concentration of a chemical in that food and the average US consumption of the food are used. The consumption of the chemical in µg/day is as follows:

    Consumption of the food (gm/day) × Chemical concentration (ppm)

    The amount in µg/day is converted to mg/day, and intake in mg/kg/day is calculated as follows:

    Chemical consumption from the food (mg/day)
    70 kg body weight person

  2. Chemical Consumption in the Total Average Diet

    For chemical intake from consumption of all foods in the average US diet, the value is reported in the reference. The calculation of exposure in mg/kg/day is as follows:

    Chemical consumption in total diet (mg/day)
    70 kg body weight person
  3. Occupational Exposures to Workers

    Average exposures to workers are for inhaled air in a specific occupational category during specific years. Chemical concentrations are reported in the table reference in milligrams per cubic meter of workplace air. To calculate the concentration to a daily dose rate in milligrams per kilogram body weight, an assumption is used that a worker inhales 9.6 m3 of air per 8-hour workday, weighs 70 kg, works 5 days per week 50 weeks per year for 40 years, and has a standard lifespan of 70 years. The calculation of exposure in mg/kg/day is as follows:

    Air concentration (in mg/m3) × 9.6 m3/day
    70 kg body weight person
      ×    5 days/week
    7 days
    ×    50 weeks/year
    52 weeks
    ×    40 years work life
    70 year life
  4. Inhalation of Indoor Home Air

    Average inhalation rates for indoor air are based on the US EPA Exposure Factors Handbook (1997), which reports average breathing rates for various types of activity and the number of hours spent indoors. The values in the MOE table use an estimate of an average adult spending 12 hours per day at home indoors and inhaling 7.72 m3/day. The calculation of exposure in mg/kg/day is as follows:

    Air concentration (in mg/m3) × 7.72 m3/day
    70 kg body weight person

  5. Inhalation of Outdoor Air

    Average inhalation rates for outdoor air are derived from the US EPA Exposure Factors Handbook (1997), which reports average breathing rates for various types of activity and the number of hours spent outdoors. The values in the MOE table use an estimate of an average adult spending 2 hours per day outdoors and inhaling 2.39 m3/day indoors. The calculation of exposure in mg/kg/day is as follows:

    Air concentration (in mg/m3) × 2.39 m3/day
    70 kg body weight person

  6. Drinking Water

    For consumption of a chemical in a single food, both the average concentration of a chemical in that food and the average US consumption of the food are used. The consumption of the chemical in mg/day is as follows:

    Concentration in water (in mg/L) × 1 L/day
    70 kg body weight person

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Last updated: September 25, 2008