Air pollution and economic mobility

Welcome to Science Sessions, the podcast of the proceedings of the National Academy of Sciences, where we connect you with Academy members, researchers, and policymakers. Join us as we explore the stories behind the science. I'm Paul Gabrielson. Fine particulate matter air pollution, or PM 2.5, consists of particles with a diameter less than 2.5 microns. This small size allows the particles to reach deep in the lungs and adversely affect a person's health. Can PM 2.5 air pollution also adversely affect a person's economic future? In a recent PNAS article, Luca Merlo of the European University of Rome, Francesca Duminici of the TH Chan School of Public Health at Harvard University, and Harvard Undergraduate Sophie Ann Kingsbury Lee, studied air pollution and upward economic mobility in counties across the United States. They found that exposure to air pollution and childhood was associated with lower economic upward mobility and adulthood. Luca, why did you choose to study the link between air pollution and economic mobility? The impact of fine particulate matter on human health are nowadays well established. There is a flourishing literature on this topic. However, we recognize that the impact of PM 2.5 on economic opportunities is less well understood. Therefore, we thought that it was therefore crucial to investigate further this topic and address and study what are the exploratory factors that are potentially associated with reduction in future job prospects and earning potential. We therefore filled this knowledge gap by gathering a naturally representative sample of the United States at the census tract level, where we employed around 86% of all the US census tract and examined the association between childhood air pollution exposure and a measure of our mobility, accounting for several confounders, methodological variables, as well as economic and socio-economic background of the families. How did you define and measure upward mobility? There are different ways one can measure upward mobility. In general, intergeneration mobility seeks to measure the degree to which child's social and economic opportunities depend upon his parent income or the social status. Absolute upward mobility is formally defined as the mean income rank at altitude, which is composed of the earning of the child and the spouse earning, measured as the average earning between 2014 and 2015, for those children who are parents are in the bottom half of their own national income distribution. And in particular, the outcome is measured on children born between 1978 and 1983, where born either in the US or from authorized immigrants, and those children came to the US in childhood, which means that the upward mobility measure is measured when they are between 31 and 37 years of age between 2014 and 2015. At the end given that our analysis is conducted at the census tract, we basically aggregated the individual estimate at the census tract, by taking the average of all those children living in a given tract. Francesca, what did you find? Were really interesting to assess as well, the kids that were breathing this high level of fine particle matter basically didn't do as well with respect to their parents as we were expecting to do, right? Now what did we find? Well, what we found is on average, by combining information across 86% of our census tract in the United States, so we found the statistic significance relationship between a child or the exposure to fine particle matter and diminished economic mobility in households. How did the relationship vary across counties and across regions? Because we have the observation at the census tract level, we were able to also assess whether the relationship between PM2.5 and economic mobility is the same across the US or could vary across counties. And so what we found was that this relationship, it's not the same across the US, that there is actually heterogeneity on the strengths of the relationship. PM2.5 can be more or less detrimental to upper mobility, depending on where you live in the United States. And what we found that this relationship is particularly stronger in counties located in the Midwest and in the south of the United States. We have to think that there are a multitude of factors that could influence the strengths of a relationship between exposure to fine particle matter and economic mobility in households. And what we found is that counties that have higher proportion of black and Asian residents and counties that have a lower median household income have a stronger relationship between PM2.5 and upper mobility. Even after you have control for socioeconomic status at the census tract level, if you are living in a county that has higher proportion of black American and in general a median household income, breathing higher pollution level in childhood, you have a stronger effect on compromising your upper mobility. We cannot really pinpoint what is the causal mechanism. But I think what he's saying is children growing up in places in the US that tend to be more vulnerable and more marginalized, right? And we are politicized, although we cannot really test that these are areas where there is lower access to healthcare, the socioeconomic status of their parents is lower, there is less opportunity to better education. So there's a vulnerable area, clearly, there is almost like a double penalty, right? Where you breathing high pollution level class, you don't have ability to recover from that. And so that's where you see that the negative effect of our pollution on upper mobility is even stronger. What are the caveats or limitations of the study? The first one reflects the presence of unmeasured confunders. What we mean by a measure confunder, we mean that our results may be influenced by the presence of characteristics at either the census tract level or at the county level that we didn't account for our analysis. But in our study, what we've done to mitigate this issue, while we conducted additional sensitivity analysis to enable it if our results were indeed robust to the presence of unmeasured confunders, we can confidently say that there is a high level of robustness with respect to unmeasured confunders. But having said that this is a problem that affect all observational studies. The second limitation of the study is that our study design does not allow for direct exploration of the causal mechanism and align the relationship between childhood, active at-matter exposure and our at-convireable up for a mobility. What do these results mean for policymakers and for the public? There are at least three important messages for policymakers. So one is clearly childless exposure to our pollution in addition of compromising your health. It affects you in so many ways that it has a verse-long term economic outcomes. If furthering force, they need to pass regulation to lower the national ambient or quality standard for PM2.5. Fortunately, the Biden administration last February did pass and accepted to make the safety standard for fine particular matter even more stringent than what was before. The second message is you can see with some visualization, a give you specific information of which counties are more a race where the relationship between PM2.5 and upper mobility is even stronger. And so I think for policymakers, it's not only we need to regulate PM2.5, but also we need to really pay attention to these particular counties because then these are counties where the situation can be even worse, where the negative economic impact on PM2.5 is even higher. And then the third policy message which I think is really important right now in the Edochlanar change, it's very important to keep in mind that the same sources of fine particular matter are the same sources of Green Ascastas emission. And so by regulating fine particular matter, we're going to target fossil fuel combustion and fossil fuel combustion are also the major sources of Green Ascastas and so it's also another way indirectly to really try to tackle the health and economic crisis of climate change. So we hope that this would be an important evidence for policymakers to really advance our understanding of how to prevent the negative societal consequences of exposure of our pollution and climate change. And helping us spread the word.