Evaluating the impact of long-term exposure to fine particulate matter on mortality among the elderly
Xiao Wu et al.
Science Advances, June 2020
Many studies link long-term fine particle (PM2.5) exposure to mortality, even at levels below current US air quality standards (12 μg/m3). These findings have been disputed, with claims that the use of traditional statistical approaches does not guarantee evidence of causality. Leveraging 16 years of data — 68.5 million Medicare enrollees and 570 million observations — we provide strong evidence of the causal link between long-term PM2.5 exposure and mortality under a set of assumptions necessary for causal inference. Using five distinct statistical approaches, we found that a decrease of 10 μg/m3 PM2.5 leads to a statistically significant 6%–7% decrease in mortality risk. Based on these models, lowering the air quality standard to 10 μg/m3 would save 143,257 lives (95% confidence interval 115,581–170,645) in one decade. Our study provides the most comprehensive evidence to date of the link between long-term PM2.5 exposure and mortality, even at levels below current standards.
Causal Effects of Air Pollution on Mortality in Massachusetts
Yaguang Wei et al.
American Journal of Epidemiology, forthcoming
Air pollution epidemiology studies have primarily investigated long- and short-term exposures separately, have used multiplicative models, and have been associational studies. Implementing a generalized propensity score adjustment approach with 3.8 billion person-days of follow-up, we simultaneously assessed causal associations of long- (one-year moving average) and short-term (two-day moving average) PM2.5, O3, and NO2 exposures with all-cause mortality on additive scale among Medicare beneficiaries in Massachusetts, 2000–2012. We found long- and short-term PM2.5, O3, and NO2 were all associated with increased mortality risk. Specifically, per 10 million person-days, each 1 μg•m-3 increase in long- and short-term PM2.5 were associated with 35.4 (95% confidence interval [CI]: 33.4, 37.6) and 3.04 (95% CI: 2.17, 3.94) excess deaths, respectively; each 1 part per billion (ppb) increase in long- and short-term O3 were associated with 2.35 (95% CI: 1.08, 3.61) and 2.41 (95% CI: 1.81, 2.91) excess deaths, respectively; and each 1 ppb increase in long- and short-term NO2 were associated with 3.24 (95% CI: 2.75, 3.77) and 5.60 (95% CI: 5.24, 5.98) excess deaths, respectively. Mortality associated with long-term PM2.5 and O3 increased substantially at low levels. The findings suggest air pollution was causally associated with mortality, even at levels below national standards.
Humanity’s Fundamental Environmental Limits
Seth Binder et al.
Human Ecology, April 2020, Pages 235–244
Models and estimates of Earth’s human carrying capacity vary widely and assume, rather than solve for, binding environmental constraints (the process or resource in shortest supply relative to human biological needs). The binding constraint, and therefore the true upper bound on the number of humans that Earth could sustain indefinitely, remains unknown. We seek to resolve this uncertainty by considering a full range of technological possibilities and incorporating a potential stoichiometric constraint not previously explored. We find that limits to photosynthesis constrain population before micronutrients become limiting unless technological capabilities for utilizing nutrient resources lag far behind other technologies. With ideal technology, human carrying capacity runs into the tens of trillions, while with currently demonstrated technology Earth could support more than 200 billion humans. These numbers reflect neither a desirable nor a natural equilibrium population level, but represent a rough estimate of the maximum number of humans Earth could sustain.
The Employment Impact of Green Fiscal Push: Evidence from the American Recovery Act
David Popp et al.
NBER Working Paper, June 2020
We evaluate the employment effect of the green part of the largest fiscal stimulus in recent history, the American Recovery and Reinvestment Act (ARRA). Each $1 million of green ARRA created 15 new jobs that emerged especially in the post-ARRA period (2013-2017). We find little evidence of significant short-run employment gains. Green ARRA creates more jobs in commuting zones with a greater prevalence of pre-existing green skills. Nearly half of the jobs created by green ARRA investments were in construction or waste management. Nearly all new jobs created are manual labor positions. Nonetheless, manual labor wages did not increase.
The effect of clean air on pharmaceutical expenditures
Alexander Rohlf et al.
Economics Letters, forthcoming
Airborne emissions are detrimental to health. Low emission zones (LEZs) that restrict pollution-intensive vehicles from entering are popular measures to curb local emissions such as particulate matter. We evaluate how LEZs impact defensive pharmaceutical expenditures. To this end, we use the complete medical histories of 2.7M individuals insured with Germany’s largest public health insurer AOK. We identify causal effects exploiting the quasi-experimental, staggered introduction of LEZs in 49 cities. We find that LEZs reduce annual pharmaceutical expenditures for heart and respiratory diseases by 15.8M€, representing a significant fraction of policy costs.
The Changing Risk and Burden of Wildfire in the US
Marshall Burke et al.
NBER Working Paper, June 2020
Recent dramatic and deadly increases in global wildfire activity have increased attention on the causes of wildfires, their consequences, and how risk from fire might be mitigated. Here we bring together data on the changing risk and societal burden of wildfire in the US. We estimate that nearly 50 million homes are currently in the wildland-urban interface in the US, a number increasing by 1 million houses every 3 years. Using a statistical model that links satellite-based fire and smoke data to pollution monitoring stations, we estimate that wildfires have accounted for up to 25% of PM2.5 in recent years across the US, and up to half in some Western regions. We then show that ambient exposure to smoke-based PM2.5 does not follow traditional socioeconomic exposure gradients. Finally, using stylized scenarios, we show that fuels management interventions have large but uncertain impacts on health outcomes, and that future health impacts from climate-change-induced wildfire smoke could approach projected overall increases in temperature-related mortality from climate change. We draw lessons for research and policy.
Characterizing disproportionality in facility-level toxic releases in US manufacturing, 1998–2012
Mary Collins et al.
Environmental Research Letters, May 2020
The relationship between economic activity and environmental pollution is a topic of extensive research. Although a proportional relationship between the two is often the default assumption, emerging scholarship suggests that polluting releases are disproportionally distributed across units of production. This paper examines if proportionality or disproportionality best characterizes the production of toxic pollution in US manufacturing from 1998 to 2012. Examining US Environmental Protection Agency Toxics Release Inventory data from over 25 000 facilities in 322 industries, we find consistently high levels of disproportionality across facility-level toxic releases within industries, even when controlling for facility size. Moreover, high levels of within industry disproportionality are remarkably stable over the fifteen-year study period. In other words, year by year a small handful of egregiously polluting facilities account for the vast majority of toxic releases within a given industry. Our findings suggest that disproportionality should be understood as the default pattern of pollution generation rather than an exceptional case and that policymakers should seek to reduce pollution via carefully considered targeting strategies rather than broad-stroke decision making.
Conservation Co-Benefits from Air Pollution Regulation
Yuanning Liang et al.
NBER Working Paper, June 2020
Massive wildlife losses over the past 50 years have brought new urgency to identifying both the drivers of population decline and potential solutions. We provide the first large-scale evidence that air pollution, specifically ozone, is associated with declines in bird abundance in the United States. We show that an air pollution regulation limiting industrial emissions during summer ozone seasons has generated substantial benefits in conserving bird populations. Our results imply that air quality improvements over the past four decades have substantially slowed the decline in bird populations, preventing a loss of 1.5 billion birds, approximately 20 percent of current totals. Our results highlight that in addition to protecting human health, air pollution regulations have previously unrecognized and unquantified conservation co-benefits.
Dust pollution from the Sahara and African infant mortality
Sam Heft-Neal et al.
Nature Sustainability, forthcoming
Estimation of pollution impacts on health is critical for guiding policy to improve health outcomes. Estimation is challenging, however, because economic activity can worsen pollution but also independently improve health outcomes, confounding pollution–health estimates. We leverage variation in exposure to local particulate matter of diameter <2.5 μm (PM2.5) across Sub-Saharan Africa driven by distant dust export from the Sahara, a source uncorrelated with local economic activity. Combining data on a million births with local-level estimates of aerosol particulate matter, we find that an increase of 10 μg m–3 in local annual mean PM2.5 concentrations causes a 24% increase in infant mortality across our sample (95% confidence interval: 10–35%), similar to estimates from wealthier countries. We show that future climate change driven changes in Saharan rainfall — a control on dust export — could generate large child health impacts, and that seemingly exotic proposals to pump and apply groundwater to Saharan locations to reduce dust emission could be cost competitive with leading child health interventions.
The Price Elasticity of African Elephant Poaching
Quy-Toan Do et al.
World Bank Economic Review, forthcoming
The objective of this paper is to provide an estimate of the elasticity of elephant poaching with respect to prices. Ivory being a storable commodity subjects its price to Hotelling’s no-arbitrage condition, hence allowing identification of the supply curve. The price of gold, one of many commodities used as stores of value, is thus used as an instrument for ivory prices. The supply of illegal ivory is found to be price inelastic with an elasticity of 0.4, with changes in consumer prices passing-through to prices faced by producers at a rate close to unity. Estimations based on a number of alternative estimation approaches all confirm the conclusion that supply is inelastic. The paper ends with a brief discussion on what such a finding implies for elephant conservation policies.
Do Pilot and Demonstration Projects Work? Evidence from a Green Building Program
Christopher Blackburn et al.
Journal of Policy Analysis and Management, forthcoming
Pilot and demonstration (P&D) projects are commonly deployed to catalyze early adoption of technology but are poorly understood in terms of mechanism and impact. We conceptually distinguish unique functions of pilots and demonstrations, then examine whether they accelerate adoption in the case of green building technology. To identify effects on adoption, we develop a difference‐in‐difference‐in‐differences strategy, exploiting variation in timing, location, and technologies of green building P&Ds. Results indicate local quarterly green building adoption rates double following completion of a P&D project. Further analyses examine mechanisms driving this effect. The results suggest green building demonstration projects create learning externalities, proliferating technology diffusion in local markets and through building owner networks. Together, these results suggest that investments in P&D projects by public and private actors can lower costs for subsequent adoption.