Using the estimates in Table 1 we can estimate the share of the reduction in PM2 _._ 5 levels that is due to increased use of no-till. Collectively the average share of crop pixels in no-till has increased by 9.67 percentage points from the first two years of our sample to the last (Table 2). Average PM2 _._ 5 levels during the tillage period have fallen 3.29 _μg/m_<sup>3</sup> over that same period. Combining our estimates of the impact of increasing no-till with the change in share of cropland in no-till suggests that the increase in no-till management can account for 3.8% of the 3.29 _μg/m_<sup>3</sup> decrease in PM2 _._ 5.

# **2.1 Local air pollutant benefits compared to carbon benefits of no-till**

Whether no-till reduces carbon emissions is controversial. For example, a recent summary of nature-based carbon mitigation approaches<sup>11</sup> intentionally did not include no-till because of questions about its effectiveness in reducing carbon emissions. They argue the available evidence suggests that carbon benefits of no-till only occur when fields have been in no-till management continuously for more than a decade, which is not the case in much of the U.S. Corn Belt.

On the other hand, a global review of studies on low disturbance soil management suggests that the median rate of carbon sequestration that can be achieved after adopting no-till approaches is roughly 0.2 t/ha/yr.<sup>27</sup> Applying global model-based approaches to the U.S. suggests much of the Midwest would have sequestration rates in the range 0.05-0.1 t/ha/yr.<sup>28</sup> A modelbased approach specific to the United States suggests that median accumulation rates are closer to the globally observed 0.2 t/C per ha.<sup>19</sup> Monetizing these various estimates suggests that the annual benefits of carbon reductions, if the entire U.S. Corn Belt adopted no-till, would be roughly 5 billion (USD2020) annually.<sup>19</sup> Using the value of a statistical life used by the U.S. EPA for cost-benefit analysis, adjusted to 2020 dollars, of roughly 9.5 million, the reductions in air pollution from adopting no-till would need to save roughly 500 statistical lives per year to equalize these benefits.

Existing work examining the mortality benefits of reducing PM2 _._ 5 estimates a 1 _μg/m_<sup>3</sup> decrease in annual PM2 _._ 5 results in 7.17 fewer deaths per 100,000 individuals.<sup>29</sup> Scaling this to a single month reduction in PM2 _._ 5 suggests reductions of 1 _μg/m_<sup>3</sup> for a month would save 0.6 lives. There are roughly 33 million individuals in our study area. Full adoption of notill agriculture suggests an increase of 50 percentage points relative to current levels, which suggests a 0.65 _μg/m_<sup>3</sup> decline in PM2 _._ 5 levels across the study area for the month that tillage occurs. Putting all this together suggests a decline of roughly 130 deaths per year. That indicates the air pollution benefits of adopting no-till might be 25% of the carbon benefits or 1.25 billion (USD2020) annually. This ignores any other benefits of reducing pollution, which could be sizeable as reductions in pollution have been shown to have meaningful consequences for students’ academic performance, morbidity, and labor productivity.<sup>30,31,32</sup> 8