Analyzing Particle Size Distribution of Over-the-Counter (OTC) Topical Spray Drug Products to Inform Inhalation Exposure Risk Assessments

LUCY NANDY, Xiaofei Liu, Robert Bahde, U.S. Food and Drug Administration

     Abstract Number: 754
     Working Group: Aerosol Exposure

Abstract
Some of the aerosol particles produced by over-the-counter (OTC) topical spray drug products under standard usage have the potential to penetrate deeply into the lungs after being inhaled. Respirable particles may cause inhalation toxicity depending on their chemical properties as well as their dosage. This study evaluated the particle size distribution of such topical spray products after they were actuated from their spray can. Laser diffraction (LD) was used to measure particle size distribution, and therefore, assess the potential inhalation exposure from drug products that become airborne under typical usage. 19 sunscreen spray products were studied for which the average aerosol delivery rate was ~1 g/s, as measured. It was found that less than 5% of the particle mass concentration consisted of particles smaller than 10 µm. However, the measurements did not consider the reduction in particle size after evaporation or breakage of bigger droplets into smaller ones. For a better evaluation, the mass concentration of respirable particles was evaluated with respect to time in a typical indoor environment using an evaporation model. It was found that for particles with an aerodynamic diameter less than 10 µm, the particle mass concentration increased and remained suspended in the air for up to an hour with no ventilation. The result was based on evaluating particles of diameter less than 40 µm assuming non-evaporative chemical composition to be a typical 24 – 28% by mass (weight percent of chemical UV filters/active ingredients in the test sunscreen products), negligible volatile components, and stationary state evaporation process of water. Further work is needed to evaluate potential inhalation dosage of fine particles that remain post evaporation after one typical usage of the product. Such data may help inform future requirements aimed at limiting unintended inhalation exposure from spray drug products.