Historic, Archive Document Do not assume content reflects current scientific knowledge, policies, or practices. Reserve aTD427 A86A87 . 1992 United States Department of Agriculture A National Agricultural Library Surface Waters Atrazine in A Report of the Atrazine Task Group to the Working Group on Water Quality April 1992 Working Group on Water Quality Ad hoc Atrazine Task Groups MEMBERS POLICY WORK GROUP PROGRAM WORK GROUP D. Bucks, ARS J. Antognini, ARS G. Grubbs, EPA70W A. Having! EPA/OCWDW , J. Bushnell, ES C. Landers, SCS P. Patterson, SCS P. Ytsnowsky, ASCS Wood, APHIS Wood, APHIS J. J. C. Rumburg, CSRS W. Wheeler, CSRS/NAPIAP J. Roelofs, EPA/OPP B. Lowery, CSRS D. Rickert, USGS H. Jacoby, EPA/OPP T. Browning, ASCS H. Mattraw, USGS M. Rjbaudo, ERS A. Weinberg, EPA/OW WGWQ F. Swader, J. Bushnell, ES WGWQ J. Meek, J. Parochetti, CSRS WGWQ WGWQ L. Adams, F. Swader, ATRAZINE IN SURFACE WATERS USDA Working Group on WATER QUALITY Atrazine Task Group April 1992 INTRODUCTION In February 1989, the President’s Initiative on Water Quality proposed a vigorous national effort to protect groundwater and surface waters from contamination by agricultural chemicals and wastes, especially pesticides and nutrients. Named the lead agency in the Initiative, the USDA developed a Water Quality Program to "minimize the risk of contaminating groundwater and surface waters with agricultural chemicals." The Working Group on Water Quality (WGWQ) is an interdepartmental group established to carry out this program. It includes 12 USDA agencies, along with the U.S. Geological Survey (USGS); the U.S. Environmental Protection Agency (EPA); the National Oceanic and Atmospheric Administration (NOAA); the U.S. Army Corps of Engineers; the Fish and Wildlife Service; and the Tennessee Valley Authority (TVA). As another part of the President’s Initiative, the USGS monitored the Mississippi River and some of its tributaries to determine the presence, levels, and variability of selected pesticides in the water. They found that 1) increased concentrations of dissolved atrazine occur in the river system for 4 to 6 weeks following com planting; 2) the concentrations ofdissolved atrazine vary by as much as one order of magnitude above "background" levels; 3) increased levels are associated with rainfall; 4) individual elevations ("spikes") are relatively short-lived; and 5) levels occasionally exceed three parts per billion (ppb). It should be noted that "background levels," generally, are in the range of 0.5 ppb or less; that some observed spikes have exceeded 12 ppb; and that the fate of atrazine spikes has not been studied with regard to their dilution during movement in rivers. WGWQ The coordinated the Water Quality Initiative response to this documented presence of dissolved atrazine in surface water through an ad hoc task group of USDA, USGS, and EPA staff. The task group worked to develop a realistic assessment of the problem and an appropriate reaction -- a process that can serve as a model for coordinated interagency responses to similar future challenges. SCOPE OF RESPONSE WGWQ The response to the atrazine Findings is based on the EPA’s current established Maximum Contaminant Level (MCL) and the presence of atrazine spikes in the Mississippi River and some of its tributaries. It takes into consideration the implications of the seasonal variations of atrazine levels; the ability of public water suppliers to comply with the Safe Drinking Water Act; and the perceptions and concerns of the general public. The study area includes the States of Nebraska, Kansas, Missouri, Illinois, Iowa, and Indiana. 2 ISSUE This report addresses the issue of what more the cooperating agencies should do, under the President’s Initiative, to monitor the presence of atrazine and other agricultural chemicals; to reduce the loadings and concentrations of atrazine in surface waters, especially in the Com Belt; and to provide information to the public and to farmers. Is there a clear need for new programs or program changes to reduce seasonal increases in atrazine concentrations in surface waters? CURRENT SITUATION Atrazine use Atrazine was registered by Ciba-Geigy in 1958, and first marketed to U.S. farmers in 1959. It is applied as a pre-emergence and early post-emergence herbicide to control broadleaf and grassy weeds. Most of the atrazine (80 percent) is used for com production. In 1990, an estimated 33 million pounds of atrazine were used in the 6 states in the study area. The average rate of application on cropland was 1.13 pounds per acre Ob/A). Use rates varied from 0.5 lb/A for post-emergence applications, to about 1.75 lb/A for pre-emergence uses. The number of treated cropland acres has not changed, but the amount of atrazine applied has dropped by about 20 percent over the last 8 years. Lower application rates, the use of other herbicides in combination with atrazine, prescription weed control, more stringent state requirements, and increased grower awareness of the potential for water contamination are factors in this reduction. Some surveys project a dramatic shift toward post-emergence herbicides, suggesting that by 1996 they will account for 62 percent ofdealer-applied herbicides. The USDA Conservation Reserve Program has removed 8.8 million acres of highly erodible lands from active cropping in the geographic area ofconcern. This should contribute to reduced atrazine loadings; but we cannot estimate the magnitude of these reductions. A USDA study (1986) estimated that the loss of atrazine for com production would cause an annual economic loss of $780 million. There are a number of registered herbicides for use on com, but they do not control the same spectrum of weeds, nor are they as effective as atrazine. Regulatory Framework Two federal laws — the Federal Insecticide, Fungicide and Rodenticide Act (FEFRA) and the Safe Drinking Water Act (SDWA)- and their respective regulations are relevant to this matter. FIFRA established the EPA as the lead agency in regulating pesticides,and gave the EPA- approved label the force of law. Under the SDWA, the EPA’s National Primary Drinking Water Regulations define a public water system as "not in compliance" if the concentration of any contaminant at any sampling point is greater than the EPA-established MCL. 3 Under the SDWA, the EPA’s National Primary Drinking Water Regulations define a public water system as "not in compliance" if the concentration of any contaminant at any sampling point is greater than the EPA-established MCL. The MCL for atrazine was promulgated by EPA on January 30, 1991, and becomes effective on July 30, 1992. Public water suppliers are required to begin monitoring finished drinking water for atrazine beginning January 1993. One-third of suppliers must begin to sample in 1993, a second third in 1994, and the final third in 1995. However, EPA encourages public water suppliers using surface water in areas where atrazine is used to begin sampling early. All public water systems must meet compliance requirements by July 1996. The MCL for atrazine in drinking water is currently an annual average value of 3 parts per billion (ppb), based on a minimum of four quarterly samples. Though a single sample may exceed 3 ppb, a water system remains in compliance with federal regulations until the annual average concentration of atrazine exceeds 3 ppb. EPA considers the annual average to be an appropriate indicator of the long-term exposure and risk. With the minimal quarterly sampling regime, if a single quarterly sample exceeds 12 ppb — or if any two quarterly samples exceed 6 ppb in one year — the system will be out of compliance, even if the remaining samples contain no contamination. EPA has said that they cannot determine whether water suppliers in the USGS survey areas are likely to exceed MCL’s until the full year’s worth of samples are collected. Occurrence Data - The USGS analyzed surface water samples from 149 sites in 122 river basins in the midw-estem U.S. They were collected during a harvest phase (October and November, 1989); a pre-planting phase (March and April 1990); and a post-planting phase (May and June 1990). These data indicated that "large concentrations of herbicides were flushed from croplands and were transported through the surface-water system as pulses in response to late spring and early summer rainfall." Median concentrations of atrazine increased by one order of magnitude and then decreased to near pre-planting levels by harvest sampling. About 50 percent of the sampling sites had concentrations of dissolved atrazine in excess of 3 ppb. Such elevated levels of atrazine were associated with rainfall and subsequent runoffs. During the first runoff following atrazine application, 29 percent of the samples had atrazine concentrations greater than 12 ppb. -- In November, 1991, the USGS released monitoring data from the Mississippi River and some of its tributaries for the period of April, May, and June 1991. Concentrations of dissolved atrazine above 3 ppb were sustained for 4-6 weeks from about mid-May to mid- or late June in the lower Platte River in Nebraska, the lower White River in Indiana, the lower Illinois River in Illinois, and the lower Missouri River in Missouri. 4 About 80 percent ofthe detections above 3 ppb fell between 3.0 and 6.0 ppb. About 20 percent occurred at levels above 6.0 ppb. Detections in the upper Mississippi River (at Clinton, IA) were all below 3 ppb. The highest concentration occurred in the Platte River at Louisville, NE - — 10 ppb on June 7. Subsequent data from this site (through August 1991) included only two additional spikes of 3 ppb and 2.6 ppb. Since a full year of monitoring has not yet been concluded, annual average values cannot be determined. — The Missouri River Public Water Supplies Association monitored pesticide concentrations from May through July 1991 in the Platte River in Nebraska; the Kansas River in Kansas; and the Grand, Chariton, Osage, and Gasconade Rivers in Missouri. Average atrazine concentrations ranged from 0.7-3.2 ppb, and maximums ranged from 6.7-11.1 ppb. ~ Dr. David Baker (Heidelberg College, Tiffin, OH) conducted detailed and long-term studies of pesticide concentrations in the Maumee and Sandusky Rivers of Ohio. The rivers drain 6,313 and 1,251 square miles, respectively, of intensive row crop agriculture, and also serve as water sources for public water supplies. His data indicate that while monthly average atrazine concentrations during May, June, and July exceed 3 ppb, even the highest observed annual average concentrations were below 3 ppb. The relationships among the sampling sites and water treatment intakes were not specified for the foregoing data. The lack of such information raises questions about the validity of direct or implicit extrapolation of such data to water intake sites or to treated drinking water. Some lakes and reservoirs also exhibit fluctuations in atrazine concentrations. Since these levels MCL persist longer than they do in actively flowing rivers, violations of the appear to be more likely in drinking water from these sources than in drinking water from river supplies. The number of such sources has not been determined. UNCERTAINTIES Besides the uncertainties about the scope and the intensity of the atrazine problem and the MCL likelihood of violations, there are other important information needs. — While increased levels of dissolved atrazine, and discrete atrazine spikes can be expected in rivers following the planting season, available data do not allow confident predictions of the annual average concentrations in drinking water supplies. A legitimate quarterly test schedule could, conceivably, not include the 4-6 week period of peak atrazine concentrations. If it did include sampling during that period, the presence of a significant atrazine spike at the specific time and place of sampling would be a random, rainfall-related event.