Establishing aerosol exposure concentrations for inhalation toxicity studies

Area of Science:

• Toxicology
• Pulmonary Medicine
• Environmental Health

Background:

• Inhalation studies for chemical toxicity and carcinogenicity often set maximum aerosol concentrations based on technical feasibility.
• Accumulating evidence suggests pulmonary burden of deposited particles affects particle clearance rates.
• Lung clearance decreases significantly with increased particulate burden, potentially ceasing at high exposure levels.

Purpose of the Study:

• To discuss criteria for selecting aerosol concentrations in inhalation toxicity studies.
• To provide guidelines for designing inhalation studies with a focus on lung retention.
• To address the impact of particle burden on lung clearance mechanisms.

Main Methods:

• Review of concepts from a National Toxicology Program-sponsored meeting on aerosol inhalation study design.
• Focus on major determinants for establishing maximal aerosol concentrations.
• Emphasis on experimental design features to assess lung retention.

Main Results:

• Technological feasibility is not always the optimal basis for maximum aerosol concentrations.
• Pulmonary particle burden significantly influences particle clearance from the lungs.
• Lung clearance impairment is concentration-dependent, with potential for near-complete cessation.

Conclusions:

• Guidelines are proposed for selecting aerosol concentrations in inhalation toxicity studies.
• Experimental design should prioritize assessing lung retention and the impact of particle burden.
• These guidelines aim to improve the conduct and interpretation of inhalation exposure studies.