Isoprene - similar to 1,3-butadiene. It causes skin, eye and mucous membrane irritation. It is used in rubber.
Lead - lead damages the nerves in the brain, as well as the kidneys and the human reproductive system. Lead intake can also cause stomach problems and anemia. It is a known carcinogen and is particularly toxin to children. Lead is used in paint and metal alloys.
Methyl Ethyl Ketone (MEK) - depresses the human nervous system, irritates the eyes, nose and throat. MEK is used in solvents.
Nickel - a known carcinogen, nickel also causes bronchial asthma and upper respiratory irritation.
Nitric Oxide - this is a major contributor to smog and acid rain. It is made by gasoline combustion. Scientists say it is linked to a higher risk of developing Alzheimer's disease, Parkinson's disease, Huntington's disease and asthma.