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In Vitro Inhalation Testing:
Revolutionizing Inhalation Product Safety

In the world of product safety and environmental health, assessing potential risks associated with inhalable products has always been a complex challenge. Commercial nebulizer applications, used for various purposes like disinfection and scenting, release potentially harmful aerosols into the air. Understanding the possible adverse acute inhalation effects of these aerosols is crucial for ensuring consumer safety. A recent study by Ritter et al (2023) explores an innovative in vitro inhalation approach to estimate potential adverse acute inhalation effects of aerosols from commercial nebulizer applications.

The study aims to characterize aerosols, estimate exposure, and evaluate acute biological effects through in vitro inhalation. The key objective is to generate dose-response data that allows for the determination of in vitro lowest observable adverse effect levels (LOAELs) and correlate them with estimates of human lung deposition. This quantitative in vitro to in vivo extrapolation approach (QIVIVE) seeks to bridge the gap between laboratory testing and real-world exposure scenarios.

To demonstrate the feasibility of this approach, a case study was conducted using two realistic test materials commonly used in commercial nebulizers, despite limited knowledge of their composition. The study employed an acute in vitro inhalation setup with air-liquid interface A549-cells within the optimized exposure system known as the expoCube®. This innovative approach aimed to expose cells to aerosols and analyze relevant biological effects, including cell viability, mitochondrial membrane potential, stress levels, and IL-8 release.

The case study yielded dose-responsive effects in a sub-toxic dose range, attributed primarily to the main component of one of the test materials and its presence in the aerosol phase. QIVIVE calculations indicated a factor of at least 256 between the in vitro LOAEL and the estimated acute human lung exposure for this test material. In essence, this approach allowed for the quantification of potential adverse effects associated with aerosol exposure, even when detailed knowledge of material composition was limited.

Figure 1 – expoCube

This publication highlights the value of a non-target in vitro inhalation testing approach, especially in situations with limited knowledge of complex product composition. It emphasizes the potential of these methods in advancing product safety and environmental health assessments, enabling researchers to gather vital information on biological effects, in vivo relevance, and individual aerosol compound contributions. The study suggests that accumulating knowledge from diverse applications will refine in vitro to in vivo predictions, further improving study design and result interpretation.



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