“…Initial field studies (e.g., refs and ) measured 10 or fewer TPs, but that number has continued to increase with improved analytical methods. Liquid chromatography/tandem mass spectrometry analytical instruments now provide increased sensitivity and selectivity that allows for the determination of parents and their more polar TPs at environmentally relevant concentrations. − The U.S. Geological Survey (USGS), a pioneer in the measurement of pesticide TPs, evolved from measuring 8 TPs in surface water and groundwater in the 1990s to measuring 40 TPs in the 2000s. , More recently, target methods, including those of the USGS, have expanded to measure more than 100 TPs. ,,, Newer target and suspect-screening methods measure hundreds to more than a thousand TPs, , although their application in field studies has been limited to a relatively small number of samples. Despite these analytical advances, research regarding TP exposure and toxicological effects of TPs in stream communities continues to be the exception rather than the rule. ,, …”