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Great Lakes Binational Toxics Strategy

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Alkyl-Lead Inventory Study:  Sources, Uses and Releases in Ontario, Canada


A Preliminary Review:

Alkyl-Lead

Report on Alkyl-Lead: Sources, Regulations and Options

Report on Alky-Lead: Sources, Regulations and Options

U.S. Environmental Protection Agency
Great Lakes National Program Office
June 2000

 

Executive Summary

On April 7, 1997, Environment Canada (EC) and the U.S. Environmental Protection Agency signed the Great Lakes Binational Toxics Strategy: Canada-United States Strategy for the Virtual Elimination of Persistent Toxic Substances in the Great Lakes (Binational Strategy or BNS) (USEPA, EC, 1997). The Binational Strategy sets reduction goals for Canada and the U.S. to virtually eliminate persistent toxic substances, including alkyl-lead, in the Great Lakes. To guide EC and EPA, along with their partners, as they work toward virtual elimination of the strategy substances, the BNS outlined a four-step analytical framework. This report presents, for alkyl-lead, analysis results related to the first three steps of the BNS four-step process: gathering information, analyzing current regulations, initiatives, and programs, and identifying cost-effective options to achieving further reductions.

Organolead compounds are man-made compounds in which a carbon atom of one or more organic molecules is bound to a lead atom. Of these, the Tetraalkyllead compounds, Tetraethyllead [TEL] and Tetramethyllead [TML] are the most common alkyl-lead compounds that have been used in the past and are still in use today in the United States, primarily as a fuel additive to reduce "knock" in combustion engines. These two alkyl-lead compounds are the focus of this report.

Alkyl-lead is released to the environment primarily through evaporative emissions from unburned gasoline retained in an engine's carburetor or fuel tanks and through evaporative losses during the filling of gasoline tanks, accidental spillages, and releases during production. However, alkyl-lead compounds combine with other compounds during the combustion process to form inorganic lead halides that are subsequently emitted as microparticulates in exhaust. Therefore, the human exposure pathways for alkyl-lead include inhalation of leaded gasoline vapors and dermal exposure to leaded gasoline. Unlike metallic forms of lead, alkyl-lead is easily absorbed through the skin. Additionally, the lead halides exhausted through combustion can be inhaled. Subsequent deposition of these lead halides contributes to exposure to lead through ingestion of lead contaminated soil or dust, and ingestion of lead-contaminated food or water.

The use of alkyl-lead has been prohibited by legislation in on-road automotive gasoline, however, several authorized uses of alkyl-lead still remain. Currently, the largest use of alkyl-lead occurs in aviation gasoline for general aviation (piston-engine) aircraft. In 1998, the aviation industry used approximately 295.3 million gallons of leaded gasoline, which is estimated to contain 1.39 million pounds of TEL. Other uses of alkyl-lead include automotive racing gasoline, and recreational marine fuel. These current uses, as well as trace amounts of lead in automotive gasoline, result in releases to the environment.

There are a number of regulations that pertain to alkylated lead compounds. Most recently, alkyl-lead compounds have been regulated under the 1990 Clean Air Act Amendments (CAAA). The CAAA specifically prohibits the use of leaded gasoline for on-road vehicles, misfueling vehicles built after 1990 (or vehicles designated solely for unleaded gasoline) with leaded gasoline, and the production of engines requiring leaded gasoline. The CAAA also contain requirements pertaining to the identification of sources of alkyl-lead and language specific to emissions of lead compounds resulting from the use of leaded gasoline.

In light of progress made to date in eliminating the use of alkyl-lead in automotive gasoline, there are two primary strategic directions for addressing the remaining alkyl-lead use and emissions in the United States:

  1. Pursue voluntary initiatives to reduce the use of alkyl-lead in aircraft gasoline, race cars, and non-road vehicles.
  2. Collect information and assess exposure in sensitive geographic areas for at-risk populations.

Table E1 summarizes options for key actions that could be undertaken by EPA to achieve further reductions toward the goal of virtual elimination.


Table E1. Options for Key Actions to Reduce Risks from Alkyl-lead

Focus

Action

  1. Pursue voluntary initiatives
  • Encourage a NASCAR voluntary phase-out partnership/program
  • Identify contacts in other racing (auto and non-auto) organizations to initiate similar programs/partnerships
  • Identify contacts in other organizations to initiate similar programs/partnerships
  • Work with Coordinating Research Council and FAA to promote alternative, unleaded fuels and the phase-out of leaded aviation gasoline

  1. Collect information on lead emissions, leaded gas use, and exposure
  • Refine CAA 112(c)(6) emission estimates
  • Investigate exposure to at-risk populations
  • Update inventory of leaded gasoline production and use
  • Determine the availability of leaded gasoline and the potential for misfueling

 

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