Grainger College of Engineering, All Events

Evaluating the Emission Rates, Chemical Composition, and Oxidative Potential of Particulate Matter in Indoor Environments

Advisor: Professor Vishal Verma

ABSTRACT

Exposure to particulate matter (PM) is known to have an adverse health effect on human health, leading to increased mortality globally. The airborne transmission through PM is also an important pathway in the spread of infectious diseases. Oxidative potential (OP), which quantifies the ability of PM to induce oxidative stress, has emerged as an alternative metric that may better represent PM-induced toxicity than particle mass concentrations (PMC) alone. As people spend over 85% of their time indoors, a vast proportion of infectious disease transmission, as well as exposure to PM, occurs indoors. However, the OP of indoor PM and the contribution of respiratory and non-respiratory sources towards human-generated aerosol emissions indoors are relatively unknown.

We evaluated human-generated particle emissions during different human activities in a controlled-chamber and quantified the environment the influence of human occupancy on concentrations of indoor PM in real-world environments. Results from this work demonstrated that human-generated aerosols predominantly comprise emissions from non-respiratory sources (>55%) and that indoor particle concentrations are driven by human occupancy.

Next, we quantified the OP of PM emissions from commonly used indoor sources spanning different emission mechanisms in a chamber environment. We found that the intrinsic (mass-normalized) OP of emissions from several indoor sources was comparable to or exceeded those of ambient PM2.5. An exploratory exposure assessment revealed certain sources (i.e., incense, cigarettes, and toasters) could result in occupants being exposed to higher OP in less than 1 h of indoor operation than that resulting from inhaling typical ambient PM2.5 in the US over an entire day. Collectively, these results demonstrate the importance of indoor emissions, emphasizing the need for comprehensive health impact assessments to mitigate indoor PM exposure.

Subsequently, we collected PM samples from occupied residences in the Champaign-Urbana Region and measured their composition and OP. Results from this work revealed that building and source use characteristics played a role in discerning residential exposure to PM and OP.

Finally, we quantified the time- and size-resolved emission rates of PM mass, chemical constituents, and OP from indoor sources to enhance our understanding of the dynamics of OP evolution indoors and its respiratory deposition. The results from the time-resolved experiments revealed limited temporal variation of intrinsic OP across an emission experiment. Results from the size-resolved emission experiments demonstrated that particle size affected both the chemical composition and intrinsic OP of indoor emissions. Respiratory deposition assessments revealed that only a fraction of the inhaled particles eventually gets deposited in the respiratory tract, and that the deposited PM disproportionately comprises Quazi-ultrafine particles.