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EPA Issues Advance Notice of Proposed Rulemaking on Lead Emissions from Leaded Aviation Gasoline, Seeks Public Comment

The increasing contribution of lead from avgas to the total inventory of lead emissions. The total lead inventory for 2008 will be available in 2010. Source: EPA. Click to enlarge.

EPA has issued an Advance Notice of Proposed Rulemaking (ANPR) on lead emissions from piston-engine aircraft using leaded aviation gasoline (avgas). EPA is describing and inviting comment from all interested parties on the data available for evaluating lead emissions, ambient concentrations and potential exposure to lead from the use of leaded aviation gasoline in piston-engine powered aircraft.

Aviation gasoline is utilized in general aviation aircraft with piston engines—which are generally used for instructional flying, air taxi activities, and personal transportation. Lead is not used in jet fuel, the fuel utilized by most commercial aircraft. Emissions of lead from piston-engine aircraft using leaded avgas represent approximately half of the national inventory of lead emitted to air.

Lead in Avgas
In 1996, EPA promulgated regulations that banned the use of leaded gasoline in highway vehicles; the addition of lead to fuel used in piston-engine powered aircraft was not banned in this action.
Lead is added to fuel for piston-engine aircraft in the form of tetraethyl lead (TEL). This lead additive helps boost fuel octane, prevents knock, and prevents valve seat recession and subsequent loss of compression for engines without hardened valves.
The concentration of lead in avgas can be one of four levels (ranging from 0.14 to 1.12 grams of lead per liter or 0.53 to 4.24 grams of lead per gallon) as specified by the American Society for Testing and Materials (ASTM).
The most common avgas currently supplied is “100 Low Lead” or 100LL which has a maximum lead concentration specified by ASTM of 0.56 grams per liter or 2.12 grams per gallon.
A fraction of lead is retained in the engine, engine oil and/or exhaust system, which EPA currently estimates at 5%.

There are about 20,000 airport, heliports, and similar facilities nationwide that use leaded gasoline. EPA estimates that approximately 14.6 billion gallons of leaded avgas were consumed between 1970 and 2007, emitting approximately 34,000 tons of lead. Airport-specific lead inventories for 2008 are currently undergoing review by state, local and tribal authorities and will be completed in 2010.

Since 1980, US lead emissions have decreased by more than 90%. EPA also recently issued national air quality standards for lead that are 10 times tighter than the previous standards. There is no known safe level of lead in the body. Lead exposure is of special concern with young children because it puts them at risk for a wide range of health impacts, including lowered IQ and behavioral disorders.

Lead concentrations in air increase with proximity to airports where piston-engine aircraft operate, EPA says. Lead emitted in-flight is expected to disperse widely in the environment because lead is emitted as a small particle and can travel widely before depositing to soil, water, vegetation or other surfaces.

Approximately 16 million people live within one kilometer of the approximately 20,000 airport facilities in the US, and more than 3 million children attend school within one kilometer of the approximately 20,000 airport facilities.

The advanced notice of proposed rulemaking describes the data that are currently available and being collected that would help evaluate health impacts from piston-engine aircraft emissions. This action describes considerations regarding emission engine standards and requests comment on approaches for transitioning the piston-engine fleet to unleaded gas.

The action is one of the steps EPA is taking in response to a petition submitted by Friends of the Earth (FOE) requesting that EPA find endangerment from and regulate lead emitted by piston-engine aircraft, or if insufficient information exists, to commence a study.

This action will be open for a 60-day comment period upon publication in the Federal Register. EPA will review comments and make a determination as to whether aircraft lead emissions cause or contribute to air pollution, which may reasonably be expected to endanger public health or welfare. By law, EPA in consultation with the Federal Aviation Administration would be required to issue standards if a positive finding were made.



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