Control, management, and treatment of metal emissions from motor vehicles

Metals comprise a complex group of elements with a broad range of toxicity, including effects on genes, nervous and immune systems, and the induction of cancer. Some metals (e.g., lead) are toxic at very low levels, whereas others (e.g., manganese) are essential to living systems at low concentrations, but may be toxic at higher concentrations. Metals may exist in several valence states that differ in toxicity and may be associated with organic matter and inorganic materials that can affect their toxicity. The presence of metals in the environment has received a great deal of attention in recent years. Their accumulation in the environment is of concern because of their persistence. Among metals, transition metals are particularly of concern because they are considered to be toxic.