Figure 12	
"Trends in the Occurrence of MTBE in Drinking Water Derived from Ground Water in 6 Northeast States, 1993-2006"	

Title:	"Percent of systems with concentrations of MTBE greater than human-health standards, by State and by year"
	
	
Description:	This is a graph of frequency of MTBE concentrations greater than human-health benchmarks for each State and by year for the period of record
	
	
	
Origin of data:	The data were obtained from the full data set on MTBE in drinking water:  frozen_data_set_for_both_original_and_new_reports.rdb
	
	
	
Manipulation of data set:	"All concentrations data for each PWSID were compared to human-health benchmarks.  Then, data were made uniqe by PWSID retained a flag of one or more exceedances for each PWSID, by year.  Then detection frequencies of exceedance were computed by year."
	
	
	
Other:	
	
