Technologies for assessment of physical, chemical and toxicological characteristics of ambient ultrafine particles.

摘要

Atmospheric ultrafine particles have recently received significant attention because some toxicological investigations have indicated their potential for eliciting adverse health effects. To date there has been limited toxicological and epidemiological evidence linking respiratory health effects and exposures to ultrafine particles primarily due to lack of adequate methods for ultrafine particle sampling and measurement. This thesis is aimed on addressing these issues by developing various technologies to better understand the physical, chemical and toxicological properties of ultrafine particles. An inertial impactor to separate ultrafine from the accumulation mode particles was developed and evaluated. The impactor operates at a substantially high-flow rate under a very low pressure drop and can be used to collect bulk samples of ultrafine particles and also for inhalation studies. The very small mass of ultrafine particles has posed a great challenge in determining their size-dependent chemical composition using conventional aerosol sampling technologies. To overcome this challenge, two technologies-Versatile Aerosol Concentration Enrichment System (VACES) and the NanoMOUDI, a recently developed cascade impactor that classifies particles in 5 size ranges from 10 to 180 nm were used in tandem to sample size-segregated ultrafine PM in a source and receptor site in Los Angeles Basin (LAB). This methodology demonstrates how this technology can be used for future in-depth characterization of the ultrafine PM mode. Differences in the chemical composition and size distribution of ultrafine PM across the LAB can elicit different biological response. To study the effects of these differences, an ultrafine particle concentrator was developed to provide ultrafine PM at concentrations sufficient to perform inhalation toxicology studies. The recently developed VACES were also used to concurrently collect coarse (2.5--10 mum), fine (<2.5 mum) and ultrafine (<0.1 mum) PM in source and receptor sites to perform in vitro bioassay studies. The objectives of this study were to determine whether differences in the size and composition of coarse, fine and ultrafine particulate matter (PM) are related to their uptake in macrophages and epithelial cells and ability to induce oxidative stress.