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MIT team calculates lead emissions from avgas fuel in US contribute to ~$1B in annual damages due to IQ losses

Researchers at MIT have produced the first assessment of the annual costs of IQ losses from aircraft lead emissions in the US. Their study, published in the ACS journal Environmental Science & Technology, found that that atmospheric lead pollution attributable to leaded aviation gas (avgas) contributes to US$1.06 billion (the mean from a range of $0.01–$11.6 billion) in annual damages from lifetime earnings reductions, and that dynamic economy-wide methods result in damage estimates that are 54% larger.

Because the marginal costs of atmospheric lead pollution are dependent on background concentration, the researchers also expect the costs of piston-driven aircraft lead emissions to increase over time as regulations on other emissions sources are tightened.

Master.img-001
Surface atmospheric PM10 lead concentrations attributable to aviation in the continental United States (μg/m3). Credit: ACS, Wolfe et al.. Click to enlarge.

Lead is a persistent toxic pollutant that impacts human health and welfare through inhalation and ingestion pathways. Lead emissions from general aviation (GA) piston-driven aircraft are attributable to the addition of tetraethyl lead (TEL) for the formation of aviation gasoline (avgas). … The lead additive in avgas prevents piston- driven engine knock, improves effective fuel octane, and prevents valve seat recession. While lead used as an antiknock agent in motor vehicles was the largest source of domestic anthropogenic lead emissions from the 1960s through the 1980s, regulations limiting allowable lead concentrations in gasoline in 1985 induced decreases in emissions in the 80s and 90s, and this use of lead was phased out by 1995 in the United States. By 2008, piston-driven aircraft emissions accounted for half of all US atmospheric anthropogenic lead emissions, and were the single largest source of lead emissions to the air.

… Eliminating lead from automobile fuel, new residential paint, and plumbing systems over the past several decades likely contributed to significant economic benefits. IQ-related gains in discounted lifetime earnings from reduced lead exposure due to these regulations for a single year cohort of American children have been estimated to be between $110 and $319 billion relative to peak exposure. The potential nation-wide IQ-related benefits of eliminating lead from aviation fuel have not previously been quantified. Previous aviation studies have focused on avgas’s contribution to elevated lead levels at individual airports or regions, have excluded emissions from GA cruise, and have not calculated monetized damages, focusing instead on lead concentrations in the atmosphere, soil, or in the blood of exposed children. In addition to decreasing cohort-wide lifetime earnings, productivity losses from lead related IQ deficits will affect economic output, but the economic feedbacks of lead exposure have not been quantified. Here, we estimate the costs of leaded aviation fuel on society through IQ-related impacts of aviation lead emissions across the United States.

—Wolfe et al.

The MIT team developed temporally and spatially resolved aviation lead inventories using piston-driven aircraft data for 2008 including emissions from the cruise phase. These have been excluded from prior assessments of aviation-attributable lead concentrations, which only included emissions during takeoffs and landings at specific airports.

They then modeled the impact of the aviation lead inventory on atmospheric concentrations using the community multi-scale air quality model (CMAQ). The researchers then used these concentrations to help quantify the impacts of annual aviation lead emissions on the US population via two methods: static estimates of cohort-wide IQ deficits; and dynamic economy-wide effects using a computational general equilibrium model.

They also examined the sensitivity of these damage estimates to different background lead concentrations, showing the impact of lead controls and regulations on marginal costs.

In Case 1, background concentrations reflect average exposure levels of lead Total Suspended Particulates (TSP); in Case 2, background concentrations reflect measured concentrations from a time before the completed phase out of leaded gasoline; and in Case 3, background concentrations reflect an additional 85% improvement in average air concentration.

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US-wide IQ-related benefit of aviation lead control, measured as increase in lifetime earnings, for three background cases: Case 1: 0.011 μg/m3, Case 2: 0.4 μg/m3, and Case 3: a spatially varying case with mean concentration of 0.0017 μg/m3. Credit: ACS, Wolfe et al. Click to enlarge.

Earnings reductions related to IQ loss are only one effect of lead exposure. High lead levels can lead to damages to the nervous, circulatory, endocrine, and renal systems, which may contribute to health costs and foregone wages. At high blood lead levels, the Centers for Disease Control prescribes medical intervention for heavy metal poisoning that can include oral or intravenous chelation. Lower bound estimates of medical treatment costs from all lead hazards are $11−$53 billion, about 6%−20% of total lead damages. Childhood exposure to lead has also been linked to criminal activity. The environmental hypothesis for crime rates suggests that childhood exposure to lead increases the likelihood of possessing low behavior and cognition self-control and that low-self-control is an important predictor of adolescent and adult criminal behavior. The direct costs of lead-linked crimes in the US in 2006 are estimated at $1.8 billion, and indirect costs, including treatment for psychological and physical damages may contribute to an additional $11.6 billion in damages.

—Wolfe et al.

In response to a 2006 petition by the environmental NGO Friends of the Earth (FoE), the US Environmental Protection Agency (EPA) has been evaluating the impact of lead emissions from aircraft using leaded aviation gasoline in order to make a determination regarding whether aircraft lead emissions cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare.

In April 2010, the US Environmental Protection Agency (EPA) issued an Advance Notice of Proposed Rulemaking (ANPR) on lead emissions from piston-engine aircraft using leaded aviation gasoline (avgas). (Earlier post.)

In 2012, EPA responded to the 2006 petition by describing the analytical work it then had underway to support a sound endangerment determination related to lead emissions from general aviation aircraft. In that response, EPA estimated it would take up to three years—i.e., until mid- to late 2015—to issue a final determination with regard to endangerment from lead emissions of aircraft engines.

In 2014, a petition from FoE, Physicians for Social Responsibility, and Oregon Aviation Watch requested that the EPA Administrator reconsider the 2012 response and requested the regulation of lead emissions from general aviation aircraft.

In 2015, EPA responded to that second petition saying that the necessary analytical work was ongoing. The EPA currently plans to issue a proposed endangerment finding in 2017. This proposed finding will then undergo public notice and comment. EPA currently plans to issue a final endangerment finding in 2018.

Resources

  • Philip J. Wolfe, Amanda Giang, Akshay Ashok, Noelle E. Selin, and Steven R. H. Barrett (2016) “Costs of IQ Loss from Leaded Aviation Gasoline Emissions” Environmental Science & Technology doi: 10.1021/acs.est.6b02910

Comments

HarveyD

Average life expectancy (in good health) in USA has been oing down for 40+ years for many reasons. The cost of trying to keep people alive is going up every year. Air, water and food pollutions seem to be the main reasons.

With over 4000 pollutants, our industries will soon run out of healthy people to sicken.

Brian P

General aviation aircraft engine technology is roughly on par with the old air-cooled VW Beetle. No updated valve seats (that would allow use of unleaded fuel), therefore no catalytic converters, no emission controls at all. If they have fuel injection, it is an old open-loop design. Any change has to get through FAA certification, and the FAA is pretty resistant to change. It's hard to put new aircraft and powertrains on the US market due to the stifling legal environment, so old stuff keeps getting re-used and rebuilt again and again, and it has to run on the same leaded avgas that it always has.

A number of more modern powertrains have been developed for aircraft use, but they have not made it to the end users in appreciable numbers.

Bob Niland

In addition to the points made by Brian P, there's also the question of the GA demographic trend. If the population+active_hours of 100LL powerplants is flat or declining, there are probably bigger fish to fry.

Grounding the whole fleet would also likely have little impact on what Zika is about to do to the IQ trend. And don't get me started on what average diets do to IQ.

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