Physiologically based clearance/extraction models for compounds metabolized in the nose: an example with methyl...

Area of Science:

• Toxicology and Environmental Health
• Physiological Modeling
• Respiratory System Research

Background:

• Nasal airflow and chemical clearance are critical for assessing inhalation exposure risks.
• Physiologically based clearance-extraction (PBCE) models are advanced tools for understanding these processes.
• Previous models lacked detailed physiological and biochemical integration for nasal clearance.

Purpose of the Study:

• To develop and validate physiologically based clearance-extraction (PBCE) models for the human and rat nose.
• To assess the influence of physiological, biochemical, and anatomical factors on airstream clearance.
• To derive accurate dosimetric adjustment factors (DAFs) for extrapolating rodent toxicity data to humans.

Main Methods:

• Derived a generic clearance equation for single airway/tissue compartments.
• Developed a whole-nose PBCE model integrating three nasal tissue regions with four compartments each.
• Utilized a steady-state solution to model methyl methacrylate (MMA) extraction and metabolism.

Main Results:

• The PBCE model accurately described steady-state extraction of MMA and other metabolized vapors.
• Model-derived tissue dosimetry estimates provided DAFs ranging from 1.6 to 8.0 for MMA.
• These DAFs differ significantly from the default value of 0.145, suggesting improved accuracy.

Conclusions:

• PBCE models offer a robust framework for assessing nasal clearance and chemical dosimetry.
• The models provide crucial DAFs for human health risk assessment, enhancing interspecies extrapolation.
• A minimal data set for PBCE model development, including partition coefficients and metabolic data, was defined.