Options for Reducing Lead Emissions from Piston-Engine Aircraft (2021) / Chapter Skim
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3 General Aviation Lead Emissions and Their Potential Health Impacts
3 General Aviation Lead Emissions and Their Potential Health Impacts
Pages 43-70
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From page 43... ...
by GA aircraft and aircraft activities at airports that contribute to those emissions and nearby ambient lead concentrations. In addition, the chapter discusses various issues related to lead exposures to people in communities around airports as well as worker exposures at those airports.
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. NATIONAL TRENDS IN AIRBORNE LEAD CONCENTRATIONS AND EMISSIONS For decades, lead in gasoline for on-road motor vehicles had been the primary source of environmental lead.
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EPA allowed the continued sale of leaded gasoline for piston-engine GA aircraft. Between 1970 and 2014, estimated nationwide lead emissions decreased by 99.7 percent (about 220,000 tons)
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Responding to the phaseout of lead in gasoline, average airborne lead concentrations decreased by 99 percent from 1980 and 2016 (see Figure 3-4)
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As an example, despite known toxicities documented well before, it was not until 1978 that leadbased paints were banned for residential use in the United States. While it is beyond the scope of this report to provide an exhaustive compilation of the health effects associated with lead exposure, this section provides a broad overview of lead's profound and negative health impacts.
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Atmospheric lead concentrations exceeded 8 mg/m3 in the late 1980s (see Figure 3-4) , while pre-industrial concentrations of airborne lead from natural origins are estimated at 0.0006 mg/m3 (Patterson, 1965)
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. Some investigators observed that criminal behavior in urban cities has dropped in parallel with the reduction of airborne lead following the elimination of leaded fuels for motor vehicles (Nriagu, 1990, Wakefield, 2002)
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LEAD EMISSIONS FROM GA AIRCRAFT Lead emissions from piston-engine GA aircraft at and near airports arise from numerous aircraft activities that can have different contributions to airborne particulate matter containing lead. Ground-level activities include idling at hangars, taxiing, run-up, takeoff roll, after-landing roll, and maintenance operations.
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Finally, the lead content of fuel is estimated using national sales volume for each grade of aviation gasoline (with sales now dominated by 100 octane low lead aviation gasoline [100LL]
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. Those airport emissions estimates are based on aircraft fleet and activity information rather than the volume of avgas combusted, which is the basis used for the aircraft lead emission estimate in Figure 3-3.
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Figure 3-5 shows contours of modeled airborne lead concentrations at Richard Lloyd Jones Jr. Airport in Tulsa, Oklahoma.
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NOTES: Airport property boundaries are designated by a thick black line; dark interior lines indicate runways. 1,000 ng/m3 equals 1 µg/m3.
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Nationwide results were presented as model-extrapolated lead concentrations stratified by LTO ranges across the 13,000 airports, without also identifying how many and which airports fall into each of the LTO ranges. AIRBORNE LEAD PARTICLE SIZES FROM PISTON-ENGINE GA AIRCRAFT EMISSIONS The exhaust of engines burning gasoline consists of gases including carbon monoxide, nitrogen oxide, and carbon dioxide, carbon in the form of soot, and carbonyl hydrocarbons (such as formaldehyde, a known carcinogen)
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reports that exhaust particles collected in flight from a single piston-engine aircraft burning 100LL fuel were found also to consist of 4 nm lead-dibromide beads embedded in a hydrocarbon matrix. However, the particles in the aircraft exhaust were found to be much smaller (13 nm average diameter)
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. NOTES: The left chart shows size distribution of automotive and aircraft particles, showing the much smaller size of the aircraft exhaust particles.
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Therefore, particle number concentrations may be a more meaningful metric than mass concentration for health studies of particle exposures less than 100 nm. ENVIRONMENTAL DYNAMICS OF PARTICULATE MATTER LEAD EMISSIONS Both airborne concentrations and particle deposition locations depend on the emission height and particle size.
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The agency chose a distance of 500 meters because at that distance EPA estimated that airborne lead concentrations, averaged over 3 months (the averaging time used for the lead NAAQS) , diminished to local background concentrations.
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attributable to leaded avgas consumption to be at least $10 per gallon. WORKER EXPOSURES AT AIRPORTS In occupational settings at airports, workers can be exposed to inorganic lead through inhalation and ingestion of dibromide particles emitted from the combustion of leaded avgas.
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Taking the TEL vapor pressure at 25°C and the high end of this dosing rate, the headspace concentration is 0.036 mg/gallon for Grade 100LL avgas.12 Using a 1:1 molar ratio dosing 9 Reid Vapor Pressure (RVP) Control Periods for California Air Basins and Counties are provided at https://ww3.arb.ca.gov/fuels/gasoline/rvp/rvp_controlperiod.pdf.
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at RVP (psi) Saturation Saturation Saturation Saturation 5.5 24.7% 2.60 0.036 2.05 7.1 31.9% 3.35 0.036 2.05 NOTE: EDB = ethylene dibromide; psi = pounds per square inch; TEL = tetraethyl lead; VOC = volatile organic compound.
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has published some excellent general reference materials that provide information on occupational lead exposures.16,17 The Occupational Safety and Health Administration (OSHA) occupational exposure standards and related requirements (29 CFR § 1910)
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and has very detailed and specific requirements. At a minimum, an employer is required to carry out an initial exposure determination for each employee or group of similarly exposed employees in the workplace to assess whether any employee may be exposed to airborne lead concentrations at or above an action level.
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. EPA should conduct more targeted monitoring and enhanced computa tional modeling of airborne lead concentrations at airports of potential concern, as indicated by its recent screening study, to evaluate aircraft operations that are main contributors to lead hot spots and design
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In addition to airports found to have airborne lead concentrations exceeding the concentration of the lead NAAQS, additional monitoring and modeling should include air ports found to have lead concentrations that are lower, but approach ing, the NAAQS concentration (Recommendation 3.1)
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2003. Intellectual impairment in children with blood lead concentrations below 10 micro gm per deciliter.
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2020a. Model-Extrapolated Estimates of Airborne Lead Concentrations at U.S.
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2011. A geospatial analysis of the effects of aviation gasoline on childhood blood lead levels.
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2017. The effect of leaded aviation gasoline on blood lead in children.
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