POLICY--The use of Fluorescent dyes in hydrologic studies May 16, 1966 WATER RESOURCES DIVISION MEMORANDUM NO. 66.90 To: District Chiefs and Staff Officials, Water Resources Division From: Acting Chief Hydrologist Subject: POLICY--The use of Fluorescent dyes in hydrologic studies As you know, many Federal agencies such as the Geological Survey and the Public Health Service, as well as many state and local agencies, universities, and private groups, have used fluorescent dyes extensively as tracers in various surface water, ground water, and oceanographic studies. All of these agencies naturally have been concerned by the possibility of harmful effects of the dyes on people or on aquatic plant and animal life. Although there have been a number of studies of the toxic effects of Rhodamine B and fluorescein, past attempts on the part of WRD officials to obtain an authoritative, definitive statement regarding the use of the dyes for water tracing purposes have not been fruitful. In early 1964 we did get an unofficial opinion by the U.S. Food and Drug Administration that there was little likelihood of toxic results from the low concentrations which we use. Recently, however, the Federal Water Pollution Control Administration raised the question of discontinuing the use of Rhodamine B, specifi- cally, because of its potential as a carcinogen (cancer-producing agent). A re-evaluaiton of existing literature on the subject by Public Health Service resulted in a policy statement which is attached. We concur in the policy stated by Public Health Service and have so indicated in the statement developed by us and attached hereto. Existing information indicates that use of dyes at low levels of concentration should not be harmful, thus our statement emphasizes the importance of careful determinations of expected dye concentrations and requires that the actual concentrations be carefully monitored and documented. Dyes have been used in both surface water and ground water investigations but the principal use has been in connections with studies of stream flow. Policies and criteria as discussed herein were developed specifically for surface water studies. Any planned use of dyes for ground-water studies should be discussed with and approved by this office prior to the time that firm plans are developed. Sufficient information should be presented to permit an evaluation of the degree of hazard involved to users of the ground-water supplies. Little, if any, change in current operational procedure for surface water studies will be necessary, because current procedure conforms with that outlined in the attached policy statement with the primary exception of documenting the need for exercising care when computing dosages and selecting injection sites. For protective as well as informational purposes public relations is an important aspect of tracer studies. For most time-of-travel measurements and for discharge measurements to the extent appropriate, the following three-point procedure is recommended. 1. If an agency, inter-agency commission, or other group is responsible for activities in a given stream, obtain that groups' endorsement of the study well in advance. 2. In advance, notify other Federal, state, county, and local health, fish and game, pollution control, and water-supply agencies having jurisdiction along or immediately below the study reach. Industrial water users also should be notified, if appropriate. 3. Provide news media with ample material for local release in advance of the study, to inform and warn the general public. E. L. Hendricks Attachments [Contact the Branch of Operational Support, Reston, for a copy of the attachment(s)]. WRD Distribution: A,B,S,FO,SL Key Words: Dye Tracer, Time of Travel, Fluorescent Dyes