Why do RI (or ExCR) and CI results differ for volatile substances?

For volatile chemicals, there are a number of conditions which can result in a RI (or ExCR) which is more stringent than CIindoor air. Situations were CI is more stringent than RI (or ExCR) are explained in a separate FAQ.

  • RItotal ≠ RIinhalation although the only exposure route is inhalation
    For threshold effects, S-Risk also accounts for background exposure. RItotal reflects total local (through air) and total background (through air, drinking-water and food) exposure; RIinhalation reflects local and background exposure through inhalation only.
  • RIinhalation or ExCRinhalation leads to a more stringent result than CIindoor air and indoor exposure dominates inhalation exposure
    There are a number of reasons why this kind of results is obtained (typically in residential scenarios).
    • RIinhalation or ExCRinhalation takes into account the higher inhalation rate per unit of body weight of children relative to adults, whereas the CI value only compares concentrations in air,
    • RIinhalation or ExCRinhalation is calculated using a health-based value (Tolerable Concentration in Air), while CIindoor air is calculated using a legal limit (if available) or the same health-based value. If a legal limit is used, which is higher than the health-based value, CI results will be less stringent.

last modified on 09/09/2016 - 12:45

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