New diesel engines will be required to use catalytic converters and soot traps beginning in 2007 and fully complying by 2010. Diesel trucks and buses have not. But land may also be polluted having serious consequences for the environment and human beings v Disposing toxins in soil is a mixed blessing. Soils can contain some toxins over a longer period of time than air or water, allowing for a slower release. Some toxins can be broken down by biological processes in the soil.
Soils can also filter some contaminants before they reach groundwater.
Concentrations can increase over time making them more lethal than if they were dispersed into air or water and diluted. Lead is one example. Although lead in air has been reduced dramatically, it still remains in large quantities in the nation s soils. Should, like water and air, be treated as an essential resource. Regulates only existing or future facilities, not historical sites.