On Thursday, October 23rd, Michelle Bell presented her research on the relationship between ozone pollution and human mortality at an event hosted by the Yale Bioethics Center. Bell explained that her research contributes answers to three fundamental questions. Does ozone exposure increase the risk of human mortality? Does the effect persist at very low concentrations? How does this risk vary by individual and community?

Bell sought to explore the relationship between ozone exposure and human mortality in two ways. First, she conducted a meta-analysis of 39 time-series studies. Second, she used a multi-city approach, empirically testing the relationship in 95 cities. Both of these studies established a significant relationship between ozone exposure and human mortality. Bell then used an exposure response curve to study the effects of ozone at low concentrations. Four separate models of the data all showed that there is an increased risk of mortality at low ozone concentrations, even down to background concentrations. Bell also concluded that ozone toxicity varies by community. Relevant factors in community variance include air conditioning, unemployment, and racial composition. Bell's work also revealed that possible confounders such as temperature and PM10 do not, in fact, reduce the impact of ozone on human mortality. She also called attention to the fact that her work is one in a number of independent studies which all find a positive relationship between ozone and mortality. This agreement, she contends, has been a key factor in recent policy changes regarding ozone. Further research, she believes, will focus on understanding how particle composition and climate change will affect ozone toxicity.