Health Effects of Emissions of Internal Combustion Engines: Success Story Joining Science, Technological Developments and Policy

ROGER MCCLELLAN, Independent Advisor, Toxicology and Risk Analysis

     Abstract Number: 449
     Working Group: History of Aerosol Science

Abstract
Spark ignition and compression ignition engines, the latter commonly referred to as Diesel engines, were invented in the late 1800s and quickly became a cornerstone of the industrial revolution. Typically, both are fueled by hydrocarbon fuels. The combustion process yields energy and a mixture of combustion products including carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), carbon particles and hydrocarbons. These engines soon found wide application leading to advances in engine and fuel technology. An early concern for the gasoline engines was emission of carbon monoxide and for Diesel engines “black smoke”. Later concern developed for “smog” produced by photochemical enhanced reactions between oxides of NOx and hydrocarbon compounds. Exhaust control systems were soon developed that required removal of Pb from to avoid poisoning catalysts in the exhaust system. The controls markedly reduced the CO, NOx and hydrocarbon emissions from gasoline spark ignition engines. In 1955 it was shown that organic extracts of exhaust painted on mouse skin caused cancer. In 1977, it was shown that Diesel exhaust particles contained an array of complex hydrocarbons that were mutagenic. In the 1980s it was shown that chronic inhalation exposure to high concentrations of Diesel exhaust caused lung cancer in rats. Early epidemiological studies yielded equivocal results for cancer induction. The International Agency for Research on Cancer (IARC) in 1988 categorized gasoline engine exhaust as “possibly carcinogenic to humans” and Diesel exhaust as “probably carcinogenic to humans”. Further action was taken to remove the “bad actors” from Diesel exhaust. In 2012 IARC elevated its classification of exposure to Diesel to “carcinogenic to humans” without distinguishing between emissions from traditional and new technology engines. Nonetheless, this is a remarkable success story of using science to inform both technological advances and regulatory policy. Recently, Societal concerns have shifted to “climate change” which is driven by concern for “greenhouse” gas emissions, including carbon dioxide, from internal combustion engines. This presentation will conclude with speculation as to options for the path forward.