United States Environmental Protection Agency Washington, D.C. 20460
Nov. 17, 2004
The Honorable Colin L. Powell
U.S. Department of State
Washington, D.C. 20520
Dear Secretary Powell:
I am pleased to inform you that the U.S. Environmental Protection Agency has completed its consultation review of the potential human health and environmental effects concerning the U.S.-supported aerial coca and poppy eradication program in Colombia.
In your letter of September 27, 2004, you asked the Agency to provide you with written confirmation that the Department of State and EPA have consulted in preparing a certification required by the Consolidated Appropriations Act, 2004. Specifically, you asked EPA to confirm: (1) that the Department of State and EPA have consulted concerning the U.S.-supported aerial coca eradication program in Columbia; (2) that the herbicide mixture employed by the U.S.-supported program of aerial eradication of coca and opium poppy in Colombia is being used in accordance with EPA label requirements for comparable use in the United States and any additional controls recommended by the EPA for this program, as well as with the Colombian Environmental Management Plan for aerial fumigation; and (3) that this herbicide mixture, in the manner it is being used, does not pose unreasonable risks to or have adverse effects upon humans or the environment.
EPA conducted its assessments based on information provided to us by the Department of State's Bureau of International Narcotics and Law Enforcement Affairs. As you know, INL has consulted with EPA's Office of Pesticide Programs, and as part of this effort, EPA has previously provided reviews of the Department of State's eradication spray program activities in 2002 and 2003. EPA has compared coca and poppy eradication practices with the closest approximate use in the United States, reviewed potential human health concerns, and evaluated toxicity testing conducted on the spray mixture that INL has indicated is being applied in Colombia. In this consultation review, we have also reviewed progress of the Colombian government's efforts to evaluate the effects of the spray program on human health and the environment in areas where it has been used to eradicate illicit crops.
I have attached the consultation review document that we trust will assist you in preparing the certification that must be submitted to Congress. Please let me know if you have additional questions concerning our consultation review.
Michael O. Leavitt
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PESTICIDE PROGRAMS
DETAILS OF THE 2004 CONSULTATION FOR THE DEPARTMENT OF STATE
USE OF A HERBICIDE FOR COCA AND POPPY ERADICATION PROGRAM IN COLOMBIA
CONSULTATION REVIEW OF THE USE OF A HERBICIDE FOR COCA AND POPPY ERADICATION IN COLOMBIA, 2004
The Department of State (DoS) assists the Government of Colombia with training, contractor support, financial assistance, and technical and scientific advice for aerial pesticide spraying activities designed to eradicate the illicit crops coca and poppy in Colombia. The U.S. Environmental Protection Agency (EPA) has completed an assessment at the request of DoS, on whether the herbicide mixture, in the manner it is being used in Colombia for coca and poppy eradication, does not pose unreasonable risks or adverse effects to human health or the environment. The Agency has reviewed information provided to us by the DoS to confirm that the herbicide mixture is being used according to EPA label requirements for comparable use in the United States, any additional controls recommended by EPA for this program, and with the Colombian Environmental Management Plan for aerial fumigation.
EPA concludes from its assessment of the submitted and available information on the spray program and the herbicide glyphosate that there does not appear to be any evidence that glyphosate aerial spraying of coca or poppy has resulted in any adverse human health effects among the population where this spraying occurs in Colombia. There have been no substantive changes to the eradication program's method of aerial glyphosate application or the spray formulation. Although the measured toxicity and estimated exposure indicate that only nontarget terrestrial plants are likely to be adversely affected by the use on coca and poppy, important uncertainties should be considered. The Agency findings from 2002 and 2003 remain relevant to the current coca and poppy eradication activities in Colombia. The DoS and the Government of Colombia made modifications and enhancements to the spray program as EPA recommended in its prior assessments. This is an interim finding that may change as new information becomes available and followup is performed. Details of EPA findings are provided in the attached document.
The Department of State (DoS) assists the Government of Colombia with training, contractor support, financial assistance, and technical and scientific advice for an aerial pesticide spraying program designed to eradicate the illicit crops coca and poppy. The eradication program includes the use of a spray mixture of a glyphosate formulation, an adjuvant (Cosmo-Flux 411F), and water. The glyphosate tank mixture is applied aerially as a foliar application in certain provinces of Colombia. As required by the Consolidated Appropriations Act, 2004 (H.R.2673), DoS has consulted with the U.S. Environmental Protection Agency (EPA) to ensure that the herbicide mixture, in the manner it is being used, does not pose unreasonable risks or adverse effects to human health or the environment. As part of this effort, EPA has previously reviewed DoS eradication spray program activities in 2002 and 2003. This review updates and comments on the progress of the Colombian government to evaluate the effects of the glyphosate spray program on human health and the environment in areas where it has been used to eradicate illicit crops, as requested by DoS, in a letter dated September 27, 2004.
II. SUMMARY OF PREVIOUS ASSESSMENTS
In 2002, EPA reviewed the coca eradication program in Colombia and concluded that there was no evidence of significant human health or environmental risks from the spraying. EPA did recommend that DoS switch to a herbicide product with lower toxicity due to a potential hazard to the eyes of pesticide mixers/loaders. EPA also asked DoS to conduct field investigations of health complaints associated with coca eradication. The Agency further concluded that spray drift was likely to cause phytotoxicity downwind of sprayed coca fields. The Agency reached its conclusions from a thorough review and assessment of the available scientific studies on glyphosate and glyphosate-containing formulated products and their use in the United States and in conjunction with information on the spray program in Colombia. The final conclusion was that EPA could not verify the product formulation because the product was manufactured outside the United States and not registered by the EPA.
In 2003, DoS adopted EPA's recommendation and began using a lower-toxicity glyphosate product in its coca and poppy eradication programs, and implemented a program to investigate health complaints. Based on a comparison of the glyphosate use pattern in Colombia and approved use patterns of glyphosate products in the United States, EPA determined that application rates for both coca and poppy eradication in Colombia were within the parameters listed on U.S. labels. The Agency could not verify the quality of the product since it is formulated outside of the United States, but a review of toxicity testing on the spray mixture solution did not uncover any irregularities.
EPA concluded in 2003 that there were no risks of concern from dietary exposures or from exposures to mixer/loader/applicators or field workers, including bystanders. The concerns for mixer/loader eye irritation discussed in EPA's 2002 review were mitigated in 2003 by switching to a lower-toxicity glyphosate product registered by both EPA and the Government of Colombia.
The DoS and the Government of Colombia initiated two programs to investigate health complaints. Regarding potential environmental effects from the eradication programs, EPA concluded that the switch to a lower-toxicity product would present less risk of acute poisoning to wildlife, while potential phytotoxicity due to spray drift could still be a factor in both coca and poppy spraying. EPA recommended that DoS continue programs for investigating health complaints, and the Agency also asked DoS to develop a case definition for what would constitute a glyphosate-related adverse effects exposure, provide further documentation of its investigations and how they are conducted, and standardize data collection.
In February 2004, in response to a request from DoS, EPA reviewed the Environmental Management Plan for the Illicit Crop Eradication Program in Colombia (EMP). DoS asked EPA to assess whether use of the herbicide mixture in Colombia is in accordance with the EMP. The Plan described general descriptions of many activities related to the spray program including references to Colombian laws that were to be followed. EPA concluded that the Plan contained appropriate types of activities for a pesticide spray program. These activities include spray application requirements and restrictions, training and safety precautions for personnel who handle and apply the pesticide, handling of waste resulting from program operations, training public health workers to recognize and treat pesticide poisoning, handling of health and environmental complaints, environmental monitoring, and contingency plans for emergencies. EPA recognized that these types of activities were appropriate for pesticide spray programs and generally reflect similar activities that can be included on pesticide spray programs in the United States, depending on the specific pesticide, use conditions, known potential risks, and federal, state, or local laws.
EPA offered comments on two specific sections of the EMP. First, the Agency urged DoS to investigate methods for properly disposing of pesticide containers rather than reusing them. The second comment was regarding the statement in the EMP that there were no significant impacts to plants that surrounded the illicit crops being sprayed. EPA reiterated its position previously stated in the consultations - that glyphosate is highly toxic to many plants and that some level of adverse effects is likely to occur to some nontarget plants as a result of spray drift, as can be expected with herbicide applications. The Agency suggested an appropriate revision of the wording in the EMP.
III. ASSESSMENT OF THE AERIAL SPRAY PROGRAM IN 2004
In a letter dated September 27, 2004, to Michael O. Leavitt, Administrator of EPA, the Secretary of State formally asked EPA for a written response to confirm that the DoS and EPA have consulted concerning the U.S.-supported coca and poppy eradication program in Colombia. The Secretary asked EPA help certify that the herbicide mixture is being used in accordance with EPA label requirements for comparable use in the United States, any additional controls recommended by EPA for this program, and the Colombian Environmental Management Plan for aerial fumigation. The Secretary also asked EPA to confirm that the herbicide mixture, in the manner it is being used, does not pose unreasonable risks or adverse effects to humans or the environment.
EPA has reviewed the following reports, enclosed with the above letter, pertaining to human health and the environment:
A. REVIEW OF HUMAN HEALTH RISK
Evaluation of the Effects of Glyphosate on Human Health in Illicit Crop Eradication Program Influence Zones. Bogota, July 2003, National Health Institute.
This document provides the protocol for conducting a descriptive case study to determine if there are any human health risks associated with spraying glyphosate. The authors note that according to reports, glyphosate, along with paraquat and 2,4-D, are widely used herbicides on land where coca crops are grown. An estimated 61 percent of the use on the land is due to paraquat and about 19 percent of the use is due to glyphosate application by coca growers. Fungicides and insecticides also figure prominently in the cultivation of coca. Given this widespread use of pesticides and exposures to other chemicals, there may be some health effects that could be difficult to differentiate as to cause. The lack of technical knowledge by growers and surrounding farmers is an important barrier to distinguishing the effects of aerial spraying from those of other pesticides.
The study protocol identifies the specific areas to be studied based on the prevalence of spraying for eradication in those areas. Case definitions for suspected and probable cases are defined for individuals who seek health care based on symptoms and signs of poisoning. A questionnaire was developed that evaluates signs and symptoms, medical history, the person's exposure to pesticides and use of protective equipment, and types of pesticides used. Biological monitoring was developed to assess exposure to glyphosate, organochlorines, and cholinesterase-inhibiting insecticides. Procedures for collecting biological samples are clearly described. An integral part of the study was a training course on diagnosis of pesticide intoxication for health professionals residing in the area under study.
The protocol requires that "all subjects with a history of exposure to pesticides who have signs and symptoms compatible with acute intoxication will be reported to the National Public Health Control System (SIVIGILA) using the individual notification form." Duties for different individuals participating in collecting and monitoring the study progress are specified. An Epi-Info program will be used to capture the information collected and to perform analysis. Inclusion and exclusion criteria are specified to determine which individuals will be included in the final analysis.
Progress Report on the Illicit Crop Eradication Program Through Glyphosate Spraying (PECIG) Environmental Management Plan by the National Institute of Health.
The National Health Institute of Colombia acknowledged that there had been under-reporting and low coverage of pesticide poisonings in the past. Four territories where spraying is most active were targeted for training of health teams. A total of 284 environmental health professionals, technicians, and rural health providers received training in recognition and reporting of pesticide poisoning between September 2003 and January 2004. An active search for cases identified 39 possible cases of glyphosate intoxication from May to July 2004. Another four possible cases were reported to the health units. Samples have been taken to determine the presence of glyphosate, its metabolite, and other pesticides in urine. Telephone followup has been performed, and field investigations are being considered to identify additional cases that may be occurring after spraying. An additional seven training sessions are planned in the targeted areas.
Limitations in reporting and following up cases involving glyphosate are recognized and acknowledged in the report by the National Institute of Health. These include:
Survey to Evaluate the Effects of Glyphosate and Other Pesticides on Human Health in Pecig Influence Zones.
The survey form used to capture information in a standardized format includes sections for general data, patient's data, medical exam data, characterization of exposure, occupational history, social background, attitude towards the ICEPG, medical chart, and laboratory results. The questionnaire is fully responsive to the earlier recommendations by EPA to "standardized collection of data on patients and their symptoms."
A presentation entitled "Evaluation of the Effects of Glyphosate on Human Health in Areas of Influence of the Illicit Crop Eradication Program (PECIG)"
This presentation provides specific objectives for monitoring potential adverse effects of aerial glyphosate application. Cases may be reported by persons consulting the Institute of Health directly, by an active search for cases by the environmental health professionals and rural health providers, and by reporting from community leaders and municipal ombudsmen. The presentation provides specific case definitions for a suspect, probable, and confirmed case. It also advises on key procedures to follow to obtain biological specimens for determination of glyphosate and its metabolite in urine. This presentation is appropriately targeted to identifying health effects due to pesticides.
Toxicologist's report on the investigation of the case of the death of a person exposed to spraying using a glyphosate mixture. "Report on Issues Related to the Aerial Eradication of Illicit Coca in Colombia" by J. H. B. Tobon. M.D.. July 4.2003
This report describes the followup on a reported fatality associated with exposure to glyphosate application for coca eradication. Information collected from the initial clinical files reported intense headaches, vomiting, fever, and progressive deterioration of consciousness. The victim's spouse reported that the symptoms described started ten days after the coca field where he had been working was sprayed. When hospitalized this patient exhibited additional signs and symptoms of hypersecretion of saliva, contracted pupils, paleness, difficulty breathing, excessive pulmonary secretions, profound depression of consciousness, and no response to stimuli. Despite treatment, which included atropine for suspected organophosphate insecticide poisoning, the patient died two hours later. Another physician reported that the patient had renal failure and his symptoms were consistent with central nervous system infection or intoxication due to organophosphate or carbamate insecticide. Dr. Tobon concluded that the signs "greatly suggest intoxication of a cholinesterase-inhibitor chemical substance" and that "we are certain that the death cannot be attributed to exposure to glyphosate." The Agency agrees with these findings based on the known toxicity of glyphosate as compared to other pesticides.
Ministry of the Environment, Housing and Regional Development report on Ruling number 707 which includes a public health program (specification number 7)
Consistent with the reports above, the public health program was designed "to develop risk management measures for preventing, mitigating, correcting and offsetting effects on health which could be associated with aerial spraying of glyphosate in areas where PECIG operates." The report notes an initial budget for this activity of around 200 million pesos (about $80,000 in U.S. dollars). As reported above, 284 members of health teams in the four targeted provinces "have received training in diagnosing, managing, preventing and supervising poisoning caused by herbicides and in the research project execution methodology." The report submitted by the National Health Institute found only three suspicious cases that have been reported since September 2003. An international agreement is being put in place to permit analysis of samples, so that it can be established whether glyphosate or other pesticides are present at levels that might be harmful to public health.
Comments on the Reports on Human Health
The reports submitted by DoS make clear that an aggressive program to identify glyphosate poisoning has been implemented in the areas of Colombia where illicit crop eradication spraying programs are prevalent. A significant number of health care providers have received training and additional training is under way or planned. EPA had earlier recommended case definitions and standardized collection of data. The submitted test protocol meets those objectives. Trainees received specific information on being alert for digestive, dermal, ocular, and respiratory symptoms. This is a comprehensive and appropriate approach for detecting ill effects of glyphosate. The use of biological monitoring to further confirm exposure will help eliminate numerous cases of illness that are likely to occur coincidently to aerial spraying, but are not, in fact, caused by the exposure to glyphosate. Although there have been reports (about 43 in 2004), the majority were classified as possible or suspicious. There were no cases classified as probable or confirmed, though a confirmed case would require verification from laboratory samples which, apparently, have not yet been processed or may not be available yet.
Despite an aggressive search for cases, there does not appear to be any evidence that glyphosate aerial spraying has resulted in any adverse health effects among the population where this spraying takes place. This is an interim finding that may change as new information becomes available and follow-up is performed. Since efforts to obtain and gather such information are under way, one should be cautious and not over-interpret these preliminary findings.
EPA also offers the following suggestions for the data collection form:
EPA found the distinction between the suspect and probable case definitions somewhat difficult to follow. The Agency suggests measuring the length of time between last exposure and effects and giving greater weight to those effects that appear within 24 hours, when glyphosate effects would normally be expected.
The Agency provides these suggestions to assist the Colombian National Institute of Health in the efficient analysis of information that comes as a result of its investigations. The Colombian Ministry of Social Protection and the National Institute of Health are to be commended for their responsive and aggressive approach to assessing the public health concerns associated with the use of pesticides. The Colombian agencies' scientific protocol for identifying potential effects of glyphosate shows great care. Their approach is scientifically sound and responsive to previous comments provided by EPA.
B. REVIEW OF ECOLOGICAL RISK
In 2002, EPA prepared an ecological risk assessment of the coca eradication program in Colombia. EPA determined that spray drift was likely to cause phytotoxicity downwind of coca fields. The Agency was asked to consider the opium poppy eradication program in 2003. As with coca eradication, the use of glyphosate for opium poppy eradication is done aerially. Based on information provided by the DoS regarding poppy eradication, the total area sprayed is less than for coca eradication, individual poppy sites are smaller and located at higher elevations, and the rate of glyphosate application for poppy eradication is lower than that for coca. Application rates for both coca and poppy eradication in Colombia are within the parameters listed on labels of glyphosate products registered by EPA for use in the United States. Based on the results of the opium poppy eradication assessment, EPA concluded that the potential for spray drift phytotoxicity continues to be a factor for coca spraying. Spray drift and potential effects down wind of the target sites are common, universal factors in most if not all pesticide applications from aerial or ground applications for all uses. In the United States, EPA considered estimates of spray drift in its risk assessments of pesticide uses and registration decisions.
In addition to the documents submitted with the September 27, 2004, request, the DoS also indicated that there have been no substantive changes to the eradication program's method of aerial glyphosate application or the spray formulation. Based on a review of the submitted documents and current information indicating no changes to the program's application methods, the Agency findings from 2002 and 2003 remain relevant to the current coca and poppy eradication activities in Colombia. A review of the submitted information as it pertains to the results of previous ecological assessments is provided below.
Soil and Water Residue Analysis
Interagency Soil and Water Sampling Field Study Report: Glyohosate Persistence in and Effects on the Soil and Bodies of Water
Soil and Water Sampling Protocols and Excel Spreadsheets of the Soil and Water Residue Sampling Results
During November and December of 2003, a Government of Colombia interagency team collected and analyzed soil and water samples to determine the persistence of glyphosate and its principal metabolite - amino-methyl phosphonic acid (AMPA) - in Colombian soils and water following aerial application to illicit coca crops. A review of the methods used to analyze the soil and water samples indicates that they are typical analytical chemistry methods and recognized by EPA as acceptable to characterize glyphosate and AMPA in soil and water.
The results of the soil sampling showed no statistically significant differences between residual levels of glyphosate and AMP A in the pre- and post-spraying soils. It appears that similar levels of glyphosate and AMPA in pre- and post-spray soils may be the result of interception of the herbicide by the foliage. The toxic effect of glyphosate to post-emergent plants is a result of aerial application of glyphosate onto the foliage of nontarget species (i.e., plants other than coca, and poppy). Therefore, the soil data cannot be used to refine environmental exposure concentrations for plants. Glyphosate levels on the foliage are expected to be much higher than those in soil, and toxic effects are due to application of the herbicide directly to the postemergent foliage rather than to soil uptake. The fraction of glyphosate that reaches the soil is a result of precipitation that washes the herbicide from the plant leaves and stems into the soil, and/or attempts by growers to wash the plants after spraying to salvage their crops. In addition, it appears that detected concentrations of AMPA in the pre-spraying soil may be due to glyphosate usage by growers to control weeds and undesirable plants that compete with the coca crop.
Pre-spraying concentrations of glyphosate and AMPA in bodies of water contiguous to or near coca crop plants were negligible (i.e., less than detection limits) from the four sample sites. Maximum concentrations of glyphosate and AMPA in water following spraying activities were 397 ppb and 0.18 ppb, respectively. Comparison of the glyphosate monitoring data with modeled concentrations used in the EPA's ecological assessments for glyphosate applications in the U.S. shows that the modeled surface water concentration of 230 ppb is lower than the maximum detected concentration of 397 ppb. The Agency's modeled concentration is based on direct application of 3.75 lb acid eq./acre of glyphosate to a 1-acre, 6-foot deep pond, EPA's standard for modeling pesticide residues in water bodies. Although glyphosate was detected in water adjacent to coca crops at a higher concentration than predicted by the Agency's previous assessments, the maximum detected concentration of 397 ppb is well below acute and chronic effects levels (ppm) for fish, aquatic invertebrates, and aquatic plants, species used for estimating risks to species in the U.S. Therefore, similar to the results of previous Agency assessments, no risks are predicted for aquatic animals and plants, based on exposure to residual glyphosate or AMPA in water bodies contiguous to or near coca crops.
Maximum concentrations of glyphosate measured in surface water as part of the monitoring program were 397 ppb. According to data presented in the Interagency Soil and Water Sampling Field Study Report (Section 3.2), pre- and post-spray glyphosate surface water samples were collected from only four sites. At two of the four sites, post-spray glyphosate was not detected (detection limits were not provided). At the other two sites, post-spray glyphosate was detected at concentrations of 0.998 and 397 ppb. Therefore the results of the water sampling are highly variable and the limited number of samples allows for only-qualitative comparison and not a quantitative statistical analysis of the water monitoring data.
Using runoff simulations from Agency exposure models PRZM and EXAMS, the concentration that may result from direct application of 3.75 lb acid eq/acre of glyphosate to a 1-acre, 6-foot deep pond is 230 ppb, as noted above. The coca use application rate is 4.4 lb a.i./acre or 3.3 lb acid eq/acre; therefore, use of 3.75 lb acid eq/acre in modeling is a conservative estimate of exposure. It is possible that greater levels of exposure could occur from direct overspray of water bodies much smaller than a 1-acre, 6-foot deep pond, but such simulation is not a standard component of Agency risk assessments. The product label for glyphosate prohibits such direct overspray of water bodies, but it is possible that some water bodies too small or ephemeral to appear on maps could be sprayed directly in a project as large as the coca eradication program. U.S. EPA approved uses of certain glyphosate products do permit application to aquatic areas for vegetation control; for these uses EPA would expect glyphosate and AMPA residues in water.
Colombia Ministry Technical Opinion and Efficacy Testing
July 23, 2004, Technical Opinion from the Republic of Colombia Ministry of the Environment, Housing and Regional Development evaluating the program's compliance with management measures established in the Environmental Management Plan
Glyphosate (10.4 L/HA) and Three Adjuvants, for the Control of Illicit Coca Crops, Erythoxium spp.: Agronomic Efficacy Testing of Doses of Glyohosate in Illicit Crops, July 2004
A Technical Opinion was issued by Colombia's Ministry of the Environment, Housing and Regional Development on July 23, 2004. The purpose of the Technical Opinion was to evaluate the program's compliance with management measures established in the Environmental Management Plan (EMP). The EMP was created by the Ministry to prevent, mitigate, control, offset, and correct any possible negative environmental effects or impacts which might result from eradicating illicit crops. Based on the evaluation, the Ministry concluded that the entities responsible for executing the crop eradication program are currently complying with the measures established in the EMP. A summary of the compliance evaluations for the spray operation management program and environmental monitoring program is discussed below.
The Ministry's evaluation of the spray operation management program shows that technical parameters established in the EMP relating to flight altitude, maximum spray mix discharge, application rate, spray drift control measures, droplet size, temperature, and wind speed are being followed. Operations records indicate that spray missions are cancelled for unfavorable weather conditions that could affect application efficiency and/or adherence to meeting safety and environmental standards. A review of the spray systems fitted to aircraft shows that they operate normally, and routine maintenance and calibration of all spray systems are conducted.
Spraying efficacy verifications and collateral effect evaluations were completed in 2004. Coca plant death effectiveness figures of more than 85 percent were observed from spraying activities in different areas. Phytotoxicity to border plants from spray drift of the glyphosate spray mixture were observed on a random basis, and were described as temporary in nature and small in extent. This is expected and is from the mode of toxicity and degradation of glyphosate commonly demonstrated in the United States from glyphosate applications. Drift effects included partial defoliation of the canopy of high trees. No other collateral damage from spraying activities was observed at the selected sites. In spray areas that were subsequently abandoned, it was noted that vegetation, including grasses and herbaceous species, was beginning to grow again. In the case of plots that had been completely abandoned (i.e., with no evidence of human activity), advanced vegetative succession, including the presence of balsa wood and secondary forest, was observed.
The results of the glyphosate soil and water samples were discussed as part of the environmental management program evaluation. In addition, the evaluation included a discussion of a current study on the dynamics of vegetative succession based on existing satellite images of sprayed areas. Satellite images showed a spectral response of stubble grass and low stubble three months after spraying; at less than three years following spraying, secondary forest appeared, indicating significant signs of recovery in the vegetative structure.
Although the measured toxicity and estimated exposure indicate that only nontarget terrestrial plants are likely to be adversely affected by the use on coca and poppy, important uncertainties should be considered. One of these is the extrapolation of North American data to the conditions and wildlife found in Colombia. The toxicity of a pesticide to different classes of animals and plants can vary widely among species in an individual ecosystem. The Agency uses for its hazard and risk assessments of pesticides used in the United States, test North American species as surrogates for other North American species not tested, but has limited experience with tropical flora and fauna. Similarly, laboratory and field estimates of the environmental fate of pesticides, including potential surface-water contamination, are performed with North American soils, hydrology, and climate data. Identifying characteristics that define sensitive tropical ecosystems would most effectively reduce the uncertainty of extrapolating North American exposure and effects data.