The DuPage County Health Department (DCHD) began a sampling program in 2005 to test private wells in the county for potential chemical threats. After testing was completed for roughly one thousand wells, two areas of contamination emerged. In one part of the county, there was a small area of contamination with methyl tertiary butyl ether (MTBE). The concentrations discovered were not a health hazard, however. DCHD informed the well owners of the presence of the contaminant and gave advice about how to reduce exposure. In Wayne Township, the well testing revealed vinyl chloride and cis-1,2 dichloroethene in a number of private wells in unincorporated areas.