Pesticides in Drinking Water: Project-based Learning within the Introductory Chemistry Curriculum.

Public concern has been expressed regarding low-level contamination of public drinking water with "xenoestrogens", which are manmade compounds that act like the growth stimulant, estrogen. A new introductory chemistry module is described, which has as its central theme the measurement of trace levels of these xenoestrogens in the form of pesticides in the Town of Amherst's public drinking water. After a basic introduction to sample handling and measurement of pH, temperature, and conductivity, the students travel in small groups to several sites to collect water and perform preliminary characterization of their samples. In subsequent weeks, they learn to perform various analytical techniques such as solid-phase extraction, GC-MS, ELISA, and absorption spectroscopy to measure the levels of the pesticides DDT, DDD, DDE, methoxychlor, and endosulfan, all of which are potent estrogen mimics. In addition to individual lab reports, students are asked to combine their results and analyze the data set to determine the mean concentration and the statistical significance. Finally, they use molecular modeling to explore the three-dimensional structure of three pesticide families and compare these structures to the steroid hormones whose actions they are purported to mimic.