Guidebook for Assessing Airport Lead Impacts (2016)

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1 1.1 Health Impacts from Lead Exposure Exposure to lead (also known by its chemical symbol Pb) can lead to a variety of adverse health impacts, including neurological effects in children that lead to behavioral problems, learning deficits, and lowered IQ (U.S. EPA 2011). Lead accumulates in the body in blood, bone, and soft tissue because it is not readily excreted. As a result, lead affects the kidneys, liver, nervous system, and blood-forming organs; the EPA also considers lead to be a probable human carcinogen. Human exposure to lead occurs primarily through inhalation and ingestion, with the health effects being same regardless of the route of exposure. People can be exposed to aircraft lead emissions from both the inhalation pathway and from ingestion of aircraft lead that deposits to surfaces and is inadvertently transferred by hand-mouth activity. The concentration of lead in blood (PbB) is the metric generally used to define exposure to lead. Research has shown that PbB is significantly associated with mean ambient lead concentrations (Bierkens et al. 2011, Brunekreef 1984). Historical studies have shown that the use of leaded gasoline accounted for more than 50 percent of PbB in children and that the concentration of lead in gasoline was directly proportional to PbB (Hayes et al. 1994, Schwartz and Pitcher 1989). The Centers for Disease Control and the World Health Organization have identified PbB concentrations of 10 micrograms per deciliter or higher as a “level of concern” to human health (Centers for Disease Control 1991, World Health Organization 1995). CDC has also introduced a new reference level, which is set at 5 micrograms per deciliter (Centers for Disease Control 2012). 1.2 Addition of Lead to Gasoline The use of lead, primarily in the form of tetraethyl lead (TEL), as a gasoline additive began in the 1920s. TEL increases the octane rating of gasoline (Midgley and Boyd 1922). The availability of higher octane gasoline allows for the design of high compression ratio engines which provide greater power and fuel efficiency compared to engines with lower compression ratios. Use of TEL as a gasoline additive was transformative to the transportation engine and fuel industries during the twentieth century (Additive Technical Committee 2013). Using a gasoline with a lower octane rating than the engine was designed to use causes improper combustion—commonly known as “knock”—which can result in engine damage or failure. C H A P T E R 1 Background