The Municipality of Anchorage has concluded a yearlong study examining the levels of lead present in the atmosphere at its Merrill Field Airport, which the U.S. Environmental Protection Agency (EPA) chose as one of 15 airports for a national look at airfields serving large numbers of piston-engine aircraft. The city's Department of Health and Human Services (DHHS) agreed to conduct the study in Alaska on behalf of the EPA.
Lead levels at Merrill Field tested well below national standards. The federal air quality standard for lead is 0.15 micrograms per cubic meter, measured as a rolling three-month average. The highest three-month average measured at the Airport Heights-based airfield, which operates two asphalt runways and one gravel, was 0.07 micrograms per cubic meter, less than half the federal standard.
"This study just informs (the municipality) and shows that we're in compliance with EPA standards," said Steve Morris, DHHS deputy director. It's estimated piston aircraft are responsible for about half of the nation's lead emissions. The aircraft -- planes with one or more piston-powered engines connected to propellers -- still run on fuel containing lead, unlike commercial jets, cars and other motor vehicles. The data collected during this study will be used during a process that may result in regulation of aircraft exhaust emissions, a possibility that has been the subject of discussion among Alaska pilots.
It is difficult to phase out aircraft that use leaded fuels, according to Matthew Stichick, environmental engineer with the DHHS Environmental Health Program, because the lead additive serves two functions. It increases the fuel's octane rating, as well as helps lubricate engine components like valves. Newer planes are also built of stronger alloys that react differently to the lead. Phasing out leaded fuels in automobiles was a gradual process that took some 25 years to complete.
At high levels, lead can have various negative effects on health, particularly among growing children. Depending on the level of exposure, lead could lead to problems with the nervous system, kidney function, immune system, reproductive and developmental systems and the cardiovascular system according to Health and Social Services. Effects on the brain in children and the cardiovascular system in adults have been documented.
Infants and young children are sensitive to even low levels of lead, which can contribute to behavioral problems. Children exposed to higher levels of mercury or lead are three to five times more likely to be identified by teachers as having problems associated with Attention Deficit Hyperactivity Disorder, according to a scientific study published by Environmental Health Perspectives.
Airborne lead concentrations at Merrill Field were highest on days with the most airport activity. During the 60 days samples were collected, total airport operations varied from managing as few as two aircraft to as many as 649, on one sunny day in August. Measurements were taken at the east end of runway 25 where most planes begin takeoff.
The EPA selected the small, Alaska airfield based on simple criteria. On Dec. 14, 2010, the EPA revised the ambient-monitoring requirements for measuring lead in the air. It set the threshold at 0.5 tons per year, reduced from a single ton. Then, it began choosing the 15 airports, opting for locations with one or two runways and with lead levels that fell between the old and new standard. And lead emissions at Merrill Field are estimated to be 0.62 tons per year. Merrill Field largely was chosen because the majority of air traffic uses a single runway, said Stichick.
This study is the first time the Municipality of Anchorage has measured lead levels since the 1980s. The city used to monitor a handful of roadways back when cars ran on leaded fuel. That source of emissions has been virtually eliminated due to federal regulations. Concentrations of airborne lead sharply fell from 1982 to 1987 and monitoring was discontinued. Anchorage's improvement mirrored national trends, Morris said.
The EPA and city have expressed an interest in doing a study at the Ted Stevens Anchorage International Airport, but so far no plans have been made. Morris noted that the majority of planes flying to and from the larger airport are jets, which use fuel that doesn't contain lead. The federal agency isn't interested in looking at airport with jets; they're not a concern, he said. There also are no plans for additional monitoring of neighborhoods surrounding Merrill Field, like Fairview.
The EPA estimates it will take until mid-to late 2015 to determine whether lead emissions from piston aircraft pose a danger to public health.
Contact Jerzy Shedlock at jerzy(at)alaskadispatch.com