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July 04, 2020

This page last modified:
March 21, 2001

Endosulfan No Longer Threatens Florida Bay

by Christine Rapozo

University of Florida/Monroe County Cooperative Extension

Florida Bay Education Project

A couple of years ago a fish kill one of the canals emptying into Florida Bay and at an adjacent fish farm raised concern about pesticide use in Dade County. One pesticide, endosulfan, stood out as a potential culprit because it was used extensively by tomato farmers and it was potentially highly toxic to marine animals.

However, the recent Florida Bay Conference indicated that the Miami-Dade farmers may be off the Florida Bay hook when it comes to pesticides. Florida Bay scientists recently concluded a five year survey on agricultural pesticide runoff effects in the Bay's surface water, sediments and food web. Special attention was paid to endosulfan, but the survey included other insecticides, herbicides, and fungicides as well. Although one hundred percent (100%) of the sites had traceable levels of endosulfan, none were over the EPA water quality standards. The lead scientist on this project, Dr. Geoff Scott, is now researching whether various combinations of the low levels of pesticides found within the ecosystem may have an additive effect on marine life.

In Florida Bay and adjacent inland habitats, Scott measured samples to the parts per trillion. That means measuring zero to 0.000000000000 (12 decimal places), therefore, if pesticides were present in the samples, he was going to find them. Thinking of all these zero's as if they were in dollars and cents; the EPA allows $8.50 worth of endosulfan in marine waters. Florida Bay had values of $0.32 to $2.33. Whereas, EPA standards in freshwater, allow $5.60. Canals ranged from $1.66 to $3.86. EPA standards for endosulfan in marine waters is 0.0085 parts per thousand. In the Bay, values of endosulfan ranged from 0.000329 to 0.002333 parts per thousand. In freshwater canals adjacent to farmlands values were 0.001657 to 0.0038614 parts per thousand with EPA freshwater standards of 0.0056 parts per thousand. So, what this showed is that yes, pesticides being used on Dade agricultural lands are entering the canal systems and runoff is entering Florida Bay, but the concentrations are legally safe.

In the sub-tropical environment the use of pesticides, like endosulfan, are needed by vegetable farmers to control a variety of crop eating insects such as aphids, beetles, and whiteflies. Researchers at the University of Florida Tropical Research and Education Center in Homestead continue to test more environmentally friendly chemicals to replace the use of toxic pesticides. In fact, they recommend a product called Admire which is considerably more effective and does not have the objectionable properties of endosulfan. However, Admire is considerably more expensive and is not authorized for all vegetable crops.

Most farmers in the Miami-Dade agricultural area utilize what is termed recommended management practices (RMP's). Some of these RMP's include integrated pest management (IPM); hiring a crop consultant to determine which spray, if needed, is best. Thus, reducing the use of pesticides and rotating the chemicals they apply so that the pests don't become immune. The RMP's also include timing the application of pesticides so that they are not washed off the crop with rainwater, as well as utilizing water irrigation management (not over watering) to name a few.

Endosulfan was of primary concern in Scott's project because it has been attributed to coastal fish kills in the U.S., as well as, identified in causing deformities and decreased reproduction within animals. Endosulfan can mimic hormones naturally produced by the endocrine system (thyroid, pituitary, intestines, ovaries and testicles). It is also stored in the fatty tissues and can be transferred up the food web. In relation to humans, it has the potential to play havoc in our bodies by either blocking messages or sending the wrong signal to disrupt growth, reproduction and digestion. Research funded by the EPA has so far shown that it only temporarily impacts adults, but may have permanent effects on children, infants and the unborn fetus in humans. This summer, the National Academy of Science is releasing a report summarizing current knowledge of endocrine disrupters.

If you are interested in learning more about this topic or other Florida Bay related research please contact our Florida Bay Education Office at 853-3592. Additional information on a variety of topics is available from the University of Florida/Monroe County Cooperative Extension Service, 5100 College Road, Stock Island or call at 292-4501; fax: 292-4415; email: or visit our web site Our services are free and available to all without regard to race, color, sex, or national origin.

The Florida Bay Education Project is an archived site. For more information go to NOAA's South Florida Ecosystem Education Project at