The Arrow Award Committee is proud to acknowledge the authors of this innovative, timely and informative paper on the effect of pollution on health. In more detail, the study examines the causal effects of air pollution (exposure to acute fine particulate matter, PM 2.5) on mortality, health care use, and medical costs among the elderly population in the US. The authors make creative use of instrumental variables by instrumenting air pollution with changes in local wind direction, and develop a new approach based on machine learning to estimate the life-years lost due to pollution exposure. The authors find that higher air pollution, as measured by a 1 microgram per cubic meter (10 percent of the mean) increase in PM 2.5 exposure for one day, causes 0.69 additional deaths per million of elderly individuals over a three-day window, and causes the loss of about 3 life-years per million beneficiaries. The mortality effects are concentrated in about 25 percent of the elderly population. The same increase in air pollution also increases emergency room visits by 2.7 per million beneficiaries and inpatient emergency room spending by over $16,000 per million. The estimates on mortality are substantially higher than those reported in previous literature. The results are robust to extending the time window over which to measure mortality from 3 days to 5, 14, or 28 days, suggesting that the main results are not due to short-term mortality displacement. The findings have important implications for both environmental and health policy. We congratulate the authors on the publication of this important paper.