Agricultural land, particularly sod farms and orchards, slated for residential development - may be contaminated with harmful chemicals. In one case, a housing development in New Jersey had much of its topsoil removed, after severe contamination was discovered. The homes were built on the site of a former orchard.
Full remediation is the only answer.
Regardless of whether a property is used for residential or commercial use, health risks should be mitigated to the greatest extent possible. Old landfills should be vented in order to prevent landfill gases from migrating underground and consentrating in nearby buildings. These gases can be extremely harmful to health. Those living nearby should have their indoor air tested. Too often, federal, state, and local officials do not keep records of old local landfills or contaminated sites.