Biodiesel reduces the health risks associated with the combustion of fossil fuels.
The high oxygen (11% by mass) and cetane levels (53-67) in biodiesel allow for a more complete combustion of the fuel and an overall reduction in emissions as a result.  Thorough testing of the fuel has been completed by the EPA (Environmental Protection Agency), in addition to countless other scientific bodies and researchers that universally agree on the positive attributes of biodiesel as an alternative fuel.  Since biodiesel is manufactured from animal or plant biomass, the carbon it releases has been accounted for by our ecosystem.  In other words the carbon has been cycled between animal/plant and the atmosphere for millions of years.  In contrast the combustion of petroleum diesel will release carbon that has been stored outside of the atmosphere, within the earth for millions of years, and therefore increases the level of green house gases (GHG) globally.

Carbon monoxide (CO)
An odorless, colorless and tasteless gas that is the product of the incomplete combustion of carbon-containing compounds from internal-combustion engines.  Exposure to the gas can increase toxicity in the central nervous system, the heart, and can have severe effects on the fetus of a pregnant woman.

Particulate matter (PM)
Fine particles of solid or liquid suspended in a gas.  The health effects from inhaling particulate matter can include asthma, lung cancer, cardiovascular problems and premature death.  In addition, built up plaque deposits in the arteries cause vascular inflammation and atherosclerosis; this can lead to an eventual heart attack or other cardiovascular problems.

Sulfates (SO4)
Microscopic particles resulting from fossil fuel and biomass combustion.  They are a direct contributor to acid in the atmosphere and form acid rain.

Unburned hydrocarbons (UHCs)
Hydrogen and carbon compounds emitted after petroleum is burned in an engine.  Byproducts such as soot from carbon as well as other compounds that latch on to the hydrogen/carbon compound can be emitted into the atmosphere, such as nitrogen or sulfate.

Polycyclic aromatic hydrocarbons (PAHs)
One of the most widespread organic pollutants and are suspected carcinogens (cancer causing agents) caused from the incomplete combustion of fossil fuels.  Seven different PAH compounds are considered probable human carcinogens.

Carbon dioxide (CO2)
Created from the combustion of fossil fuels or vegetable matter, among other chemical processes.  It is also one of the leading causes of global warming.

Nitrogen oxide (NOx)
Produced during combustion, they are believed to aggravate asthmatic conditions and are a component that assists in forming acid rain.

Nitrated polycyclic aromatic hydrocarbons (nPAH)
Formed during incomplete combustion in mainly diesel vehicles.  Also a carcinogenetic nPAH’s are harmful to humans over time and when exposure levels are high.