Pesticide contamination of Nassau County's public supply wells is not a major problem. Of the 105 pesticides and metabolites that were analyzed in 2001, 6 were detected in Nassau County public supply wells. Only 1 well exhibited a pesticide detection that exceeded a pesticide Maximum Contaminant Level (MCL) [Ethylene dibromide (EDB)]. This well has a history of EDB detections and, since 1998, utilizes granular activated carbon (GAC) filtration.

In 2001, samplings of the source water by Nassau County Department of Health (NCDH) revealed pesticide detections in 8 of 66 (12%) public supply wells tested. TCPA (tetrachloroterephthalic acid), a Dacthal metabolite, was the most frequently detected pesticide compound during the 2001 phase of the study.

Pesticide or pesticide degradation products were present in 5 of the 7 golf course irrigation wells tested. No detections exceeded a pesticide-related drinking water standard. The fungicide Metalaxyl was the most commonly detected compound, being found in 3 of the shallow irrigation wells tested.

Sampling in 2001 revealed perchlorate detections in 9 of the 60 (15%) public supply wells sampled in Nassau County. There were no perchlorate detections in the 7 shallow irrigation wells tested.

There were no detections of the metals arsenic and cadmium in any public supply well or golf course irrigation well tested. These metals were used in pesticide formulations in the past and their detection can be attributed to pesticide leaching.

Many of the samples collected for this monitoring program were collected in areas of known or suspected pesticide contamination (i.e., high-risk areas). The results, therefore, are representative only of the specific locales tested and should not be considered necessarily representative of ground water quality in other areas of Nassau County.