In June 2000, representatives of the U.S. Congress announced that biodiesel had become the first and only alternative fuel to have successfully completed the Tier I and Tier II health effects testing requirements of the Clean Air Act Amendments of 1990.

The first tier of health effects testing was conducted by Southwest Research Institute and involved a detailed analysis of biodiesel emissions. Tier II was conducted by Lovelace Respiratory Research Institute, where a 90-day sub chronic inhalation study of biodiesel exhaust with specific health assessments was completed.

Results of the health effects testing concluded that biodiesel is non-toxic and biodegradable, posing no threat to human health. Also among the findings, comparing biodiesel emissions to petroleum diesel emissions:
• The exhaust emissions of particulate matter (recognized as a    contributing factor in respiratory disease) from biodiesel are 30 percent    lower.
• The exhaust emissions of aromatic compounds known as PAH and NPAH    compounds (suspected of causing cancer) are substantially reduced for    biodiesel.
• The exhaust emissions of carbon monoxide (a poisonous gas and a    contributing factor in the localized formation of smog and ozone) from    biodiesel are 50 percent lower.
• The exhaust emissions of sulfur oxides and sulfates (major components    of acid rain) from biodiesel are completely eliminated.
• The exhaust emissions of hydrocarbons (a contributing factor in the    localized formation of smog and ozone) are 95 percent lower.

¹National Biodiesel Board