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January 2002, Issue No. 189

A monthly report on environmental and pesticide related issues

In This Issue

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Necessity is the Mother of Invention

EPA Unveils Preliminary Cumulative Risk Assessment on Organophosphorus Pesticides

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Dr. Allan S. Felsot, Environmental Toxicologist, WSU

"The problem is that science has not kept pace with policy in this area." So suggested an EPA regulator regarding the fact that water quality standards for industrial effluents may be set below plausible analytical detection limits (9). I was reminded of this statement as I pored over the EPA’s hot-off-the-presses Preliminary Cumulative Risk Assessment [CRA] of the Organophosphorus Pesticides (15). None of the toxicology and risk assessment books lining my shelves discusses how to cumulate exposure and risk from multiple chemicals. But the pace of science was not taken into consideration when policy created a hole that science had to fill. With passage of the Food Quality Protection Act (FQPA) in 1996, Congress mandated EPA to reassess all pesticide residue tolerances mindful of their safety for infants and children. Congress explicitly defined safety as "a reasonable certainty of no harm" that could only be determined if EPA considered the cumulative effects from residues with a common mechanism of action and the aggregated exposure from all sources (dietary, drinking water, and residential).

EPA moved swiftly in applying existing scientific methodology to determine hazards of the registered organophosphorus (OP) insecticides to infants and children, but new ground had to be broken if exposure was going to be aggregated and cumulated across dietary and non-occupational pathways. Aggregation of exposure seemed quite straightforward and logical. Simultaneously cumulating exposure to multiple OP pesticide residues was more problematic. No one had done it before.

Faced with the daunting task of inventing scientific methods to meet the new policy demands, EPA worked diligently to carry out Congress’ mandate. Some would say they worked too slowly. In 1999, EPA was sued by the Natural Resources Defense Council (NRDC), who alleged that EPA was not considering cumulative risk and therefore was not meeting the deadlines of the FQPA. During March 2001, the lawsuit was finally settled through a U.S. District Court’s issuance of a consent decree. EPA agreed to do what Congress mandated, which it had been doing all along, albeit not quickly enough for everyone. The plaintiffs must have walked away smiling as they pocketed the $40,000 that the Court awarded them for their troubles.

The Evolution of Cumulative Risk Assessment

In its infinite wisdom about toxicological matters, Congress was following the recommendations of the National Research Council (NRC) 1993 report, Pesticides in the Diets of Infants and Children (4) when they passed FQPA. But attempts to cumulate exposure to multiple OP insecticides predated the NRC’s report. The lawyers at the NRDC had commissioned the 1989 report, Intolerable Risk, the progenitor of all the hype about Alar (5). Buried and unnoticed within that report was a seminal section on OP insecticides. That section claimed that children were overexposed to OP insecticide residues because they tended to eat an extraordinary amount of fresh fruits, vegetables, and juices in comparison to adults.

Intolerable Risk was fundamentally flawed in its analysis (not to mention overshadowed by the brouhaha over Alar), but the ideas for how to cumulate exposure to multiple OP residues seemed to have influenced the NRC. NRC, however, moved cumulative exposure assessment two steps forward by considering the probability of eating more than one OP residue at a time and by also considering the possibility of exposure from drinking water.

Just prior to the release of NRC’s report, Environmental Working Group (EWG) emerged as the new protector of the food supply from pesticide residues. The group made a name for themselves with exposés showing the co-occurrence of multiple pesticide residues in foods that children ate (18). After passage of the FQPA, EWG bested all other advocacy groups with its 1998 publication of Overexposed: Organophosphorus Pesticides in Children’s Food (19). Hailed as groundbreaking by EWG’s fans and friends, the report was essentially a rip-off of what the NRC had already done. But there was a big difference. Whereas the NRC was trying to show how a cumulative exposure assessment should ideally be done, EWG used their analysis to make claims such as one bite of an apple could lead to OP insecticide exposure above safe levels. The scientific community concluded that the EWG report, like the NRDC’s earlier attempt, was flawed (1, 20).

To Cumulate or Not to Cumulate: That Is the Question

The FQPA explicitly states that exposure to pesticide residues with a common mechanism of toxicity must be cumulated. The common mechanism of toxicity, known by toxicologists as the mode of action, pertains to two or more pesticide chemicals or other substances that cause a common toxic effect(s) by the same, or essentially the same, sequence of major biochemical events (12). Thus, how a pesticide causes toxicity on the cellular level through interaction with biochemical targets like enzymes or receptors must be known before deciding that chemicals have common modes of action. All OP insecticides inhibit acetylcholinesterase enzyme, the proper functioning of which is necessary for modulation of nerve signal transmission in the central (brain and spinal cord) and peripheral (nerve-muscle interface) nervous system. If you think this seems like sufficient similarity to pronounce this group of pesticides as having a common mode of action, you would be in good company. An independent panel of seventeen scientists determined that, indeed, all OPs have a common mode of action (3).

Many of the other classes of pesticides, especially among the herbicides and fungicides, cause adverse effects only at comparatively high doses by nonspecific mechanisms that result in systemic toxicity after prolonged exposure. Thus, it is unlikely they can be concluded to have common mechanisms of toxicity. Nevertheless, EPA has already set its sights on several common-mechanism groups, including carbamate insecticides (e.g., carbaryl, aldicarb, methomyl) and triazine herbicides (atrazine, simazine).

How to Cumulate

Prior to the December 2001 release of its preliminary CRA for OP pesticides, EPA issued for comment a guidance document that laid out the fundamental processes for conducting a CRA (13). This document included a cumulative dietary exposure assessment of three "anonymous" OP insecticides to illustrate CRA principles. By November 2000, EPA released a CRA case study of twenty-four OP pesticides, each identified anonymously by letter codes (14). After consideration of feedback from the public, including advocacy groups like Consumers Union, and its own Scientific Advisory Panel (SAP), EPA released a revised guidance document (16).

Assuming that a determination of a common mechanism of toxicity already has been made for a group of pesticides, a CRA is developed by following four general steps:

  • Determine realistic exposure scenarios leading to co-occurrence of pesticide residues.
  • Combine residues from multiple pesticides into a single dose for each exposure scenario.
  • Determine magnitude of exposure.
  • Compare magnitude of exposure to a predetermined benchmark of toxicity (risk characterization).

Aggregate Exposure Assessment IllustrationIn addition to requiring that multiple pesticides with common toxicity mechanisms be cumulated from any one pathway of exposure, CRA also requires aggregation of all non-occupational (i.e., residential) exposures with dietary and drinking water exposure. Indeed, EPA recommends that prior to a CRA, single chemicals go through an aggregate risk assessment. EPA recently also released its revised guidelines for conducting aggregate exposure and risk assessment (17).

Based on years of monitoring food residues and observing U.S. marketing practices, EPA assumes the food supply contains a constant incidence of pesticide residues throughout the year. Residues in drinking water and at residences, however, are likely to be seasonal. Indeed, as illustrated in Figure 1, a distribution of possible exposures exists for each day of the year, and all must be summed on a daily basis to yield a total exposure per day. Although OP insecticides may have both agricultural and urban uses, the likelihood of co-occurring residues (and thus exposure) is far less than 100%. Undoubtedly it would be highly precautionary to assume a constant exposure every day from every source, but EPA is rightly moving to greater reality in risk assessment.


Realistic Exposure Scenarios

Dietary Exposure

The source of residue data for the dietary exposure scenario mostly came from the U.S. Department of Agriculture (USDA) Pesticide Data Program (PDP) studies conducted during 1994-2000 (7). These data are supplemented for meats using residue figures from the Food and Drug Administration (FDA) Total Diet Study program (8). For foods that are processed or are a combination of several commodities (e.g., pizza is wheat, tomatoes, and cheese), processing and translation factors are used to adjust the residues to reflect the foods as eaten.

The potentially exposed population is taken from the USDA’s CSFII (Continuing Survey of Food Intake by Individuals) database for the years 1994-1998. The database contains individual consumption records for over 20,000 people recorded on a two-day period. The database also contains records for over 5000 children under the age of nine years old. On the basis of the CSFII, EPA divided exposed populations into the following age groups: 1-2, 3-5, 20-49, and >50 years old.

A realistic CRA must account for the likelihood that any one food will have more than one OP residue. For example, apples and apple juice are consumed in proportionally large amounts by kids, and they also contribute significantly to dietary OP insecticide exposure compared to other foods. The USDA PDP database shows that over 36% of apple samples and 28% of apple juice samples had two or more pesticide residues of some kind. However, only 22% of apples and 2% of juice samples had two or more OP residues (Figures 2 and 3). Thus, the likelihood of a child being exposed to apple products containing two or more pesticides with a common mode of action on any one day is quite small and even further diminished by the fact that 56% and 79% of apple and apple juice samples, respectively, contained no detectable OPs (Figures 2 and 3).

Apple Residues Graph Juice Residues Graph

Drinking Water Exposure

Much less data are available about residues in water than in food. When EPA assesses risk for single chemicals, it often uses computer simulations of pesticide behavior in soil and water to estimate high-end residues in drinking water. However, concentrations are often unrealistically high when compared to actual monitoring data in the USGS National Water Quality Assessment Program (2). When cumulating, this kind of error can multiply, resulting in a gross overestimation of exposure.

The objective of CRA is to examine exposure to two or more OP residues within a restricted period of time. Unfortunately, existing water monitoring data does not sufficiently account for daily fluctuations in residues nor does it necessarily include all OPs used in an area over multiple years. Because data for a CRA is needed on a daily time step, EPA uses computer simulations to estimate the residue concentrations. The pesticide behavior model PRZM (Pesticide Root Zone Model) is used to estimate runoff to surface water and leaching to groundwater. The simulation model EXAMS (Exposure Analysis Modeling System) is used to predict behavior of residues in surface water.

To improve the accuracy of modeling, EPA has refined its analyses to consider regional trends in pesticide usage based on the twelve Farm Resource Regions defined by the USDA. These regions depict common geographical specializations in farm commodities. The pesticide behavior simulation models can account for everything from application and cropping practices to weather to physicochemical properties of the pesticide. EPA considers typical application rates (available from the USDA National Agricultural Statistics Service) and percent of crop acres treated rather than maximum use rates and assumptions that all registered crops are treated.

The exposure scenario chooses the most vulnerable surface and ground water resource in each of the twelve regions and uses its water as the drinking water source. For example, the Pacific Northwest is called Region 12, and its most vulnerable area for surface water contamination is the Willamette Valley. Thus, that location became the de facto water resource for the entire region. PRZM-EXAMS then models each OP pesticide crop combination for input residues. Residues in water are estimated on a daily basis but they are compared to residues from actual monitoring data to ensure a realistic exposure scenario.

Residential Exposure

Residential exposure has been another black hole in exposure assessment. Very little monitoring takes place in realistic residential settings. EPA has developed standard operating procedures for conducting residential exposure assessments (10) and applies these principles to CRA. As with water, EPA considered regional patterns in pesticide use based on the twelve Farm Resource Regions. In the absence of direct monitoring data, EPA estimates exposure from homeowner application and exposure to "bystanders" who may come in contact with a treated area either inside or outside of the home.

One source of information for residential exposure is a compendium of occupational exposure scenarios known as the Pesticide Handler Exposure Database (PHED). This database provides information about unit exposures to pesticides for each pound or gallon applied (expressed as milligrams of pesticide per pound or gallon). Another source of information is the Exposure Factors Handbook (11). The handbook is a database with distributions for a myriad of different parameters needed to calculate exposure given an estimated residue in the residential environment. For example, the handbook provides for each age group percentile breathing rates, body weights, and surface areas of body parts. If a person is playing outside on a lawn, the handbook gives information about the time likely to be spent in an activity for different ages.

Ideally, residential estimation procedures should also account for very unique exposure scenarios such as living in a community with area-wide mosquito control, spending time on golf courses, or having a pet on which flea control products are used. These practices would occur regionally as well as seasonally depending on the incidence of the pests. For the preliminary CRA, however, EPA did not consider exposure from flea control, but the agency indicated that a preliminary study of exposures from the use of pet flea collars was comparatively negligible.

How to Combine Residues

Each exposure scenario will have an associated database of pesticide residues. Because individual OPs have different potencies (i.e., toxicities), they cannot be simply added together. For example, methamidophos (Monitor) has an acute oral LD50 of 13 mg/kg, but malathion’s LD50 is 5700 mg/kg. (LD50 refers to the median lethal dose to 50% of test animals, extrapolated to account for human size.) If each of these two pesticides left an equal residue of 1 ppm on food, it would present a different likelihood of hazard. Thus, EPA had to develop a method to normalize the magnitude of each OP residue to the same potency scale.

EPA solved this problem by mathematically constructing a dose-response curve for brain acetylcholinesterase inhibition in female rats following at least twenty-one days of oral dosing with increasing amounts of each OP (expressed as mg/kg). All of this information was available in the manufacturers’ data packages submitted to EPA for consideration of registration. The data were fit to an exponential model that allowed estimation of a benchmark dose causing no more than a 10% difference in acetylcholinesterase activity from the non-dosed group of rats. This dose, called the BMD10, represents the Point of Departure (PoD) on the dose response curve because the change in response (i.e., acetylcholinesterase inhibition) can be definitely tied to an exposure dose. Effects may occur below the PoDs but have not been directly measured and their magnitude has a higher degree of uncertainty.

After deriving the BMD10 doses, the next step was to express the potency for acetylcholinesterase inhibition by each of the OPs relative to one of the OPs known as the index chemical. Methamidophos was chosen as the index chemical because of the completeness of its toxicity database. Division of the BMD10 for the index chemical by the BMD10 for any one of the OPs yielded a ratio called the Relative Potency Factor (RPF, formerly known as a Toxic Equivalency Factor). For example, the BMD10 for azinphos-methyl (AZM) is 0.90 mg/kg/day, and the BMD10 for methamidophos (METH) is 0.08. Thus, the RPF associated with AZM is 0.08/0.90 or 0.09 (Table 1).


The benchmark dose 10% (BMD10) and relative potency factors (RPF) for OP insecticides registered for use on apples.
LD50 (mg/kg)
BMD10 (mg/kg)
Residue (mg/kg)
Index Equivalent Residue (mg/kg)

To change all residues into methamidophos equivalent residues (i.e., index equivalent residues), the residue concentration for each OP in a matrix (e.g., food, water, home lawn) was multiplied by the RPF. Using the example above, each AZM residue value in the USDA PDP database would be multiplied by 0.09, effectively changing the residues into methamidophos equivalents but now having a magnitude nearly one-tenth of the actual AZM concentration (Table 1). The RPFs in relation to the LD50s and the corresponding transformation is illustrated in Table 1 for the tolerances of five compounds registered on apples.

Dose-response curves for dermal and inhalation exposures that are relevant for assessing residential exposure are not as well developed as those for oral exposures. Thus, the EPA examined the dose-response database to yield a concentration equivalent level (CEL), defined as the lowest dose giving a maximum of 15% inhibition of brain acetylcholinesterase relative to the control (non-dosed) animals. The RPFs for residues subject to inhalational or dermal exposure were calculated similarly as for the oral BMD10s, again using methamidophos as the index chemical.

Magnitude of Exposure

Once all of the residues regardless of exposure pathway were changed to equivalents of the index chemical, then all co-occurring equivalents were summed together to yield one equivalent residue. An example of the basic calculation is shown in Table 1 for five OP insecticides that have tolerances on apples. All chemicals as methamidophos equivalents are added together when they co-occur to yield the cumulative index equivalent residue.

EPA calculated the exposure from any pathway by multiplying the cumulative index equivalent residue by the amount of food eaten (weight of food and volume of water consumed) or the degree of residential contact (e.g., surface area of lawn or carpet contacted or volume of inhaled air). The calculations are actually probabilistic because they use the entire distribution of residue and consumption or contact data. EPA uses a proprietary exposure model called DEEM (Dietary Exposure Evaluation Model) to reflect the probability of eating food containing one or more pesticide residues. The calculations start with the first person in the CSFII database and multiply the amount of each food consumed by a randomly selected cumulative index equivalent residue associated with the specific food item. For each consumption record, the process of randomly selecting an index equivalent residue and multiplying is repeated many times to obtain a distribution of index equivalent exposures.

Although food residues and thus exposures are comparatively homogeneous from day to day, drinking water and residential exposures can vary widely depending on time of year and weather. Thus, cumulative index exposures are determined on a daily time step. Furthermore, by grouping likely drinking water and residential exposures according to the twelve Farm Resource Regions, peak seasonal use of products could be easily accommodated based on regional weather, cropping, and pest occurrence patterns. EPA was able to eliminate unlikely combinations of OPs from the calculations, thereby conserving computer resources. To handle the daily computations, EPA adopted the proprietary model CALENDEX to integrate all exposure scenarios across time.

Risk Characterization: Exposure vs. Benchmark Dose

All of the exposure information was assembled and organized by percentiles of exposure for each pathway (see Table 2 for an example of dietary exposure). For example, the 50th percentile represents a cumulative OP exposure that is 50% greater (or lower) than the rest of the exposures in the population. For acute dietary risk assessments of single chemicals, EPA had been examining exposure at the 99.9th percentile. At this percentile, only 0.1% of the population had exposures greater than the calculated value.


Estimated percentile of per capita days falling below the calculated exposure (mg/kg/day) of two population subgroups and the associated margin of exposure (MOE) (15). The MOE was based on the BMD10 oral dose.
1-2 year old
20-49 year old


Bear in mind that a computer simulation generates all of the exposure data by randomly and repeatedly selecting individual pesticide residues and consumption values from a large database. Thus, the exposures are theoretical for a population rather than an individual and are prone to greater error as the percentile increases. The only way to check whether exposure at the higher percentiles is real is to conduct actual studies with humans. Such a reality check was conducted for chlorpyrifos individually in an aggregate risk assessment of chlorpyrifos users (6). Modeled exposures at the 99th percentile predicted well the results observed in a study that biomonitored approximately 1000 individuals for urinary metabolites of chlorpyrifos.

For the risk characterization of individual chemicals, EPA has been comparing the estimated dietary and drinking water exposures with the Reference Dose (RfD). The RfD benchmark is derived by applying a safety factor of 100 to the acute or chronic oral No Observable Adverse Effect Level (NOAEL). If children are determined to be extraordinarily sensitive to a pesticide, an extra threefold to tenfold safety factor is applied to reduce the RfD to the Population Adjusted Dose (PAD). For dietary exposure, EPA would characterize risk as acceptable (i.e., a reasonable certainty of no harm) if exposure was less than 100% of the RfD or the PAD.

EPA characterizes risks for individual chemicals in the residential setting by examining the ratio between the dermal or inhalational NOAEL and the estimated exposure. The ratio is called the margin of exposure (MOE) and EPA expresses no concern when its magnitude is 100 or greater (300 or 1000 where children’s sensitivity is an issue.)

Figure 4For the preliminary CRA, EPA calculated MOEs on a daily basis for food, drinking water, and residential cumulative exposures in each of the twelve Farming Resource Regions. Instead of using the oral NOAEL as a basis of comparison, EPA used the methamidophos PoD (i.e., the BMD10s) specific to each route of exposure. They also calculated the aggregate cumulative exposure for the entire U.S. population. The latter information was presented as a three-dimensional graph for the percentile of each day’s exposure and the corresponding MOE (Figure 4).

Pertinently, EPA chose not to comment on the significance of the magnitude of the MOEs nor on the appropriate percentile of exposure at which to calculate the MOE. It seems that CRA is just too new of a tool and characterizations made for individual chemicals may not be properly applicable to cumulative assessments based on a common mode of toxicity. For example, EPA has made no decision as to whether extra FQPA safety factors should be considered in determining the significance of the MOE because the toxicological basis for grouping chemicals by a common mechanism may be entirely different than the basis for determining that children are extraordinarily sensitive.

Despite EPA’s lack of comment about what the CRA means in terms of OP insecticide risk, they did describe the pathways of exposure that contributed most to the calculated MOEs. First, drinking water contributed very little to the cumulative exposure. Drinking water exposures were at least tenfold lower than exposures from food. Naturally, if a specific food contributed disproportionately to residues because of a high incidence of occurrence of a single OP (for example, azinphos-methyl on apples), then food exposure would tend to give a low MOE when all residues are cumulated. In general, however, adults had MOEs greater than 100 at the 99.9th percentile, but the children’s MOE was about 50 (Table 2, above).

Most useful was the conclusion that residential exposure, not drinking water or food, accounted for the lion’s share of exposure and thus tended to significantly push up the MOEs. Inhalation of the OP insecticide DDVP (Vapona) from hanging home-use anti-pest strips was responsible for the greatest residential exposures along with indoor crack and crevice treatments. Among children, the age-characteristic behavior of putting the hands in the mouth was the overwhelming factor driving the magnitude of exposure.

Stay Tuned for Details on the Storm

Frankly, I found the preliminary CRA to be a well crafted, state-of-the-art invention that has made a giant leap in science policy. To me, it seemed that EPA bent over backwards to make the exposure scenarios as realistic as possible. OPs like chlorpyrifos and diazinon with canceled or soon-to-be withdrawn residential uses were not considered in the CRA, forestalling an unrealistic assessment of exposure. The United States was broken into regions that more accurately portrayed cropping and use practices. EPA replaced reliance on assumptions about residues and consumption (or contact) with actual distributions of these parameters. If any pesticide registrant wants even more realism, then I would advise them to put their money where their mouth is. More monitoring and carefully designed experiments, especially with regard to drinking water residues and residential exposures, should help lower the exposure outcomes and thus raise the MOEs even further.

I especially appreciated that EPA refrained from specific conclusions about the meaning of the daily MOEs and from choosing any specific percentile of exposure to examine. In my opinion, they used the preliminary CRA for the best good, namely, deciding what is contributing to the greatest exposure. Such information can be used to craft better risk mitigation strategies.

But I see storm clouds rising. Based on comments submitted after EPA’s pilot case study of the twenty-four anonymous OPs (14), I predict the environmental advocacy groups will be all over EPA like fleas on a dog. For the same reasons that I liked EPA’s approach to interpreting the CRA, the EAGs will scold EPA for its noncommittal and refusal to incorporate extra safety factors, which they will perceive as lack of action on OPs altogether.

But that’s the beauty of democracy, isn’t it? Everyone has a say. So, if you want to throw in your two cents, I encourage you to download the preliminary CRA and then submit your comments to EPA by March 8, 2002.

Editors Note: For information about submitting comments, contact EPA staff member Karen Angulo (703-308-8004 or

Dr. Allan S. Felsot is a frequent contributor to Agrichemical and Environmental News and a member of its editorial board. He can be reached at or (509) 372-7365.


1. Barraj, L. M., B. Petersen, and J. R. Tomerlin. 1998. Report on cumulative dietary risk assessment of organophosphorus insecticides is flawed. Reg. Toxicol. Pharmacol. 28:67-68.
2. Larson, S. J., R. J. Gilliom, and P. D. Capel. 1999. Pesticides in streams of the United States—Initial Results from the National Water Quality Assessment Program. US Geological Survey Water-Investigations Report 98-4222 (downloaded December 2000 from
3. Mileson, B. E., J. E. Chambers, W. L. Chen, W. Detttbarn, M. Ehrich, A. t. Eldefrawi, D. W. Gaylor, K. Hamernik, E. Hodgson, A. G. Karczmar, S. Padilla, C. N. Pope, R. J. Richardson, D. R. Saunders, L. P. Sheets, L. G. Sulatos, and K. B. Wallace. 1998. Common mechanism of toxicity: a case study of organophosphorus pesticides. Toxicological Sciences 41(1):8-20.
4. National Research Council (NRC). 1993. Pesticides in the Diets of Infants and Children, 133 pp. Natl. Acad. Press, Washington, DC.
5. Natural Resources Defense Council (NRDC), 1989. Intolerable Risk: Pesticides in our Children’s Food. New York, 1989.
6. Shurdut, B. A., L. Barraj, and M. Francis. 1998. Aggregate exposures under the Food Quality Protection Act: an approach using chlorpyrifos. Regulatory Toxicology & Pharmacology 28(165-177).
7. U.S. Department of Agriculture Pesticide Data Program Annual Summaries (1994-2000).
8. U.S. Food and Drug Administration. Center for Food Safety and Agpplied Nutrition: "Pesticides, Metals, Chemical Contamiants & Natural Toxins."
9. U.S. Environmental Protection Agency. 1994. Draft of National Guidance for the Permitting, Monitoring, and Enforcement of Water Quality-Based Effluent Limitations Set Below Analytical Detection/Quantitation Levels. March, 22, 1994. Washington, DC.
10. U.S. Environmental Protection Agency. 1997a. Standard Operating Procedures (SOPs) for Residential Exposure Assessments;" draft document. December 19, 1997. Office of Pesticide Programs, Office of Prevention, Pesticides, and Toxic Substances, U.S. EPA. Washington, D.C.
11. U.S. Environmental Protection Agency. 1997b. Exposure Factors Handbook. Volume 1, General Factors; Volume 3, Activity Factors. Office of Research and Development, National Center for Environmental Assessment. U.S. EPA, Washington, D. C.
12. U.S. Environmental Protection Agency (1999a), Guidance for Identifying Pesticide Chemicals and Other Substances That Have A Common Mechanism of Toxicity, Fed. Reg. 64:5796-5799.
13. U.S. Environmental Protection Agency. 2000a. Proposed Guidance on Cumulative Risk Assessment of Pesticide Chemicals that Have a Common Mechanism of Toxicity. Public Comment Draft. Office of Pesticide Programs, Office of Prevention, Pesticides, and Toxic Substances. U.S. EPA, Washington, D.C.
14. U.S. Environmental Protection Agency. 2000b. Cumulative Risk: a Case Study of the Estimation of Risk from 24 Organophosphate Pesticides. Released November 9, 2000. Office of Pesticide Programs, Health Effects Division (7509C). U.S. EPA, Washington, D.C.
15. U.S. Environmental Protection Agency. 2001a. Preliminary Cumulative Risk Assessment of the Organophosphorus Pesticides. Released December 3, 2001. Office of Pesticide Programs, U.S. EPA. Washington, D.C. Downloaded report and appendices December 5, 2001 via
16. U.S. Environmental Protection Agency. 2001b. Guidance on Cumulative Risk Assessment of Pesticide Chemicals that Have a Common Mechanism of Toxicity. Office of Pesticide programs, Office of Prevention, Pesticides, and Toxic Substances, U.S. EPA. Washington, D. C.
17. U.S. Environmental Protection Agency. 2001c. General Principles for Performing Aggregate Exposure and Risk Assessments. Final. December 2, 2001. Office of Pesticide Programs, Office of Prevention, Pesticides, and Toxic Substances. U.S. EPA, Washington, D. C.
18. Wiles, R., K. Davies, and S. Elderkin. 1995. A Shopper's Guide to Pesticide in Produce. Environmental Working Group, Washington, D.C. 46 pp.
19. Wiles, R., K. Davies, C. Campbell. Overexposed. Organophosphate Insecticides in Children’s Food. Environmental Working Group (EWG) (1998). 48 pp. Washington, DC.
20. Wilkinson, C. F. et al. 2000. Assessing the risks of exposures to multiple chemicals with a common mechanism of toxicity: how to cumulate? Regulatory Toxicology and Pharmacology 31:30-43.

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PNN Gets Good Grades from Subscribers

Results of the 2001 Survey


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Jane M. Thomas, Pesticide Notification Network Coordinator, WSU

After a nearly four year wait, Pesticide Notification Network (PNN) subscribers were once again given the opportunity to let us know their thoughts on the services provided by the PNN. For those not "in the know" the PNN is an information network funded by the Washington State Commission on Pesticide Registration and operated by Washington State University’s Pesticide Information Center. (For a complete description of the PNN, please visit Internet URL .) The survey questions sought subscribers’ input in three areas: PNN service in general, information provided on the PNN Web page, and ideas for future PNN enhancements.

Nearly half of those surveyed responded (47%, the same excellent response rate we received for the 1997 survey) and the survey results were positive overall. Sixty-nine percent of respondents indicated that PNN notifications were either always or often useful.

A Bit of Background

The purpose of the PNN is to inform Washington State pesticide users of registration and label changes for products of interest to agriculture. Information is distributed by e-mail, fax, and U.S. mail to representatives of various commodity groups and commissions and to WSU research and extension staff, with the idea that these primary contacts in turn disseminate the information to affected growers. Over time, we have also developed a PNN web page ( where this information is also posted.

Subscriber Feedback

What do subscribers do with the information they receive from the PNN? In the survey, 32% of the respondents stated that they formally distributed PNN information via newsletters, Web pages, e-mail, and presentations. Forty-seven percent of the respondents indicated that they informally distributed PNN information in discussions with colleagues. Therefore, nearly four out of five of the respondents (79%) are passing along information received from the PNN. With the PNN information being distributed to this degree, the system seems to be working even better than originally intended.

When asked if the PNN was redundant of other sources of information, an overwhelming 85% of respondents replied that the PNN was not redundant. Of those for whom the PNN was one of several similar information sources, 75% graded the PNN as more convenient to use than other sources.

As in the 1997 survey, PNN users were asked to rate the timeliness, level of detail, and volume of PNN notifications that they receive. The responses in 2001 compare very well with responses received in 1997 and continue to indicate that subscribers are happy with the timeliness, detail, and number of PNN notifications. Ninety-six percent of those who responded to the survey indicated that the number of PNN notifications they received was manageable, while only four percent found the number to be excessive.

Over the past couple of years an effort has been made to include relevant Web addresses in PNN notifications. Thirty-six percent of survey respondents found these useful (either "always" or "often"), with another 39% stating that the addresses were sometimes useful. This compares to 25% of respondents indicating that they rarely find the URLs useful or that they never used them. This response (75% favorable) indicates that there is sufficient interest in the Web addresses to continue devoting staff time to this practice.

As was done in the 1997 survey, PNN subscribers were asked to place a value, from a high of five to a low of one, on the types of content covered by the PNN notifications they receive. New product and label change notifications again topped the list of notification types most valued by PNN subscribers, but all types of notifications rated an average of higher than three.

PNN Web Page

This survey offered the first opportunity to obtain formal data on PNN subscribers’ use of the PNN Web page. This relatively new service was initiated as a "value-added" product for the convenience of PNN subscribers and others in agriculture who would benefit from the information disseminated via the notification network. We found that, while 38% of subscribers do not access the PNN Web page, the other 62% do access it, at least occasionally. An impressive 14% access it weekly.

Those users who do access the Web page rated the various types of information posted quite high: all items averaged between three and four-point-five in importance on a scale of one to five.

These results seem to indicate that the information posted on the PNN Web page is valuable, but that the site may be underutilized. Curiously, the high number of "never use" responses (38%) seemed to contradict the response to another question. When asked how useful the electronic copies of the Section 18 and 24c (SLN) were to users, over half of the total survey (63% and 68% for 18s and 24cs, respectively) stated they find labels "very useful." These labels are only accessible via the PNN Web page.

Searchable PNN?

Finally, a series of questions in the 2001 PNN survey attempted to ascertain the utility of a searchable database of PNN notifications. Such a database would allow people to search for notifications that have been sent out using multiple search criteria. For example, a user would be able to call up and review all the notifications that were sent covering newly issued SLNs pertaining to grass seed crops or review all the notifications that have been sent in 2001 regarding fungicides. Seventy-eight percent of respondents indicated that a searchable PNN database would be either very or somewhat useful.


All in all, the survey results for the PNN were very positive. Subscribers gave the PNN high marks for overall usefulness, timeliness, and quality and quantity of information. Anyone interested in comparing the results of the 2001 survey with those from 1997 can view the 1997 results in the May 1998 issue of the Agrichemical and Environmental News on the Internet at

Jane M. Thomas is the Pesticide Notification Network (PNN) Coordinator at Washington State University’s Pesticide Information Center. She can be reached at (509) 372-7493 or .

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Imidacloprid Boosts TSSM Egg Production

PDF button for TSSM article

Click here for PDF version of this document (recommended for printing). Should you not have Adobe Acrobat Reader (required to read PDF files), this free program is available for download at

Dr. David G. James, Entomologist, and Tanya S. Price, Research Technician, WSU

In the July 2001 issue of Agrichemical and Environmental News (AENews No. 183), we reported the possibility of imidacloprid acting as a "fertility drug" for twospotted spider mite (TSSM). We now present a full report on this research, which was conducted during the last twelve months at Washington State University’s Irrigated Agriculture Research and Extension Center (WSU-IAREC) in Prosser.

Background to Our Study

Imidacloprid, the first chloronicotinyl or neonicotinoid insecticide, was introduced in the early 1990s and is now widely used throughout the world for management of many pests on a host of diverse crops (see Allan Felsot’s analysis of this insecticide as a candidate for reduced-risk status in the October 2001 issue of AENews, No. 186). This versatile, broad-spectrum, systemic compound exhibits activity against sucking insects (e.g. aphids, whiteflies, leafhoppers) and several species of beetles, flies, and moths, but is not toxic to plant-feeding mites (3, 4).

Imidacloprid has a mixed reputation regarding its safety to natural enemies of pests. It has low toxicity to spiders, some predatory beetles, and some predatory bugs (5, 6, 8, 13). However, other studies showed it to be highly toxic to other species within most of these same insect families (1, 9, 16, 19, 20). Similarly, some predatory mite species are tolerant of imidacloprid while others are susceptible (8, 9, 12, 16).

Recently, increased egg production and population development was reported for the Australian predatory mite, Amblyseius victoriensis at sublethal doses of imidacloprid (8). The phenomenon of reproductive stimulation of pests (or beneficials) by sublethal doses of insecticides is known as hormoligosis (15). Examples include residues of azinphosmethyl increasing the fecundity of green peach aphids (14), citrus thrips producing more eggs on leaves containing residues of dicofol and malathion (17), and TSSM increasing egg production when exposed to carbaryl or DDT (2).

TSSM is the most important mite pest of horticultural and field crops worldwide and is exposed to imidacloprid in many crop systems, particularly those that have aphids or whiteflies as principal pests. One example is hop production in Washington where hop aphid (HA) and TSSM are the major pests. Imidacloprid is routinely used to control HA in late spring and is harmful to most predators of TSSM (9), contributing to mite outbreaks during summer (11). The usual severity of these outbreaks led us to consider the possibility of hormoligosis as an additional factor stimulating mite population development.

Study Methodology

We examined the effect of imidacloprid on TSSM egg production in the laboratory by exposing young adult TSSM to sprays of imidacloprid using a Potter Precision Spray Tower. We employed both formulations of imidacloprid (Admire 2 Flowable and Provado1.6 Flowable) and also sprayed a control group with a water-only treatment. After spraying, we placed mites individually on discs cut from bean leaves then placed the leaf discs on wet cotton wool in plastic boxes. We also placed another group of mites that had not been sprayed on leaf discs cut from a bean plant that was watered with Admire (i.e., systemically exposed). All imidacloprid formulations were used at their recommended rate for HA control in hop yards. Mites were stored at 82°F under constant illumination and ten discs were used per treatment in each of three experiments. We examined the leaf discs daily, recording the number of eggs present and removing the eggs until the mites died. Data were analyzed by Student’s t tests or analyses of variance with means separated by Fisher’s least significant difference (LSD) procedures (P < 0.05).

Egg Production Increased

Both foliar and systemic applications of imidacloprid resulted in significantly greater TSSM egg production than the water-only control treatment (Table 1). Increased egg production occurred immediately after exposure and lasted for about fifteen days in sprayed mites. In mites on the systemically-treated plants, the increase in egg production did not become apparent until the sixth day and lasted until the eighteenth day (Figure 1).

Mite longevity was not significantly different between those in the foliar spray and water-treatment groups, but females on the systemically-treated were significantly longer-lived (Table 1).


Effect of spray and systemically applied imidacloprid (0.013% a i. Admire™ 2 Flowable, 0.011% a.i. Provado™ 1.6 Flowable) on daily and lifetime egg production and longevity in twospotted spider mite compared to water only treatments.
Mean (±SE) Egg Production
Mean (±SE) Longevity (d)
Admire™ (spray)
8.4 (0.4)a
204.9 (7.7)a
24.9 (1.0)a
Admire™ (systemic)
7.6 (0.2)a
205.5 (5.1)a
26.9 (0.5)a
Provado™ (spray)
8.6 (0.4)a
198.1 (9.3)a
23.4 (1.1)b
7.1 (0.2)b
167.5 (6.6)b
24.0 (1.1)b
Means followed by different letters are significantly different (P < 0.05, LSD, Anova).


Implications for Hops

This study indicates that spray and systemic application of imidacloprid at rates used in Washington hop yards significantly increase the fecundity of TSSM. Female spider mites exposed to imidacloprid produced thirty to seventy more eggs during their lifetime (one to one and a half more eggs per day) than those not exposed to the insecticide. This represents an increase in fecundity of twenty to fifty percent, which clearly indicates a potential to dramatically increase the rate of population development in TSSM. The massive outbreaks of TSSM frequently seen on hops in Washington may be a consequence of imidacloprid stimulation of mite reproduction combined with suppression of natural enemies (9).

Greater Impact with Systemics?

The use of imidacloprid in hops systemically applied via drip irrigation systems is currently advocated in Washington because of presumed reduced risks to beneficial arthropods. However, the results from this study indicate that stimulation of mite fecundity is not lessened by this application method. In fact, systemic application may potentially have a greater impact because of imidacloprid’s stability in the soil (4), demonstrated multi-year carryover in hop plants (21), and consequent season-long exposure to feeding mites. In contrast, residues from foliar-applied imidacloprid degrade within a few days (18). Given these facts, we also looked briefly at whether application of imidacloprid to TSSM eggs followed by those eggs’ development on the treated leaves resulted in increased fecundity in resulting females. We saw no effect, supporting the idea that the residues of this insecticide are short-lived.

Fertile Ground for Future Research

A number of questions remain in the wake of this study.

  • Is the fecundity response dose-dependent? The effect of different rates of this insecticide should be studied.
  • Would other neonicotinoids have the same fecundity-stimulating effect? Imidicloprid is only one representative from this expanding class of insecticides.
  • Does imidacloprid affect all mite species (pest and beneficial) in this manner? The range of mite species present in numerous affected crop systems should also be considered.

The imidacloprid-enhanced reproductive potential of A. victoriensis in Australian stone fruit orchards (8) may be counterbalanced to some extent by increased reproduction of TSSM, the target mite pest in that crop system. The major predatory mite species (Galendromus occidentalis, Neoseiulus fallacis) important in hop mite management in Washington are both eliminated by foliar applications of imidacloprid at the recommended rate (9). However, one quarter of the rate is still effective against HA and does allow some survival of both predator species (7). Field evidence suggests that this rate may stimulate population development of G. occidentalis (10). If confirmed, this would open the possibility of using a reduced rate of imidacloprid to counterbalance the stimulatory effect on TSSM by stimulating its predator.

The stimulation of fecundity in TSSM by imidacloprid has great significance and importance to many crop protection and integrated pest management (IPM) programs throughout the world. The range of complex interactions between imidacloprid and mites, both pest and beneficial, requires further study, but useful application is imminent.

Dr. David James and Tanya Price are with WSU’s IAREC facility in Prosser. Dr. James can be reached at or (509) 786-9280.


We wish to thank Jennifer Coyle for assistance with the early experiments. This research was partially funded by the Washington Hop Commission and Hop Research Council.


1. Delbeke, F., P. Vercruysse, L. Tirry, P. De Clercq and D. Degheele. 1997. Toxicity of diflubenzuron, pyriproxyfen, imidacloprid and diafenthurion to the predatory bug, Orius laevigatus (Heteroptera: Anthocoridae). Entomophaga 42: 349-358.
2. Dittrich, V., P. Streibert and P. A. Bathe. 1974. An old case reopened: Mite stimulation by insecticide residues. Environ. Entomol. 3: 534-540.
3. Elbert, A., H. Overbeck, K. Iwaya and S. Tsuboi. 1990. Imidacloprid, a novel systemic nitromethylene analogue insecticide for crop protection. Proc. Brighton Crop Prot. Conf. Pests and Diseases 1: 21-28.
4. Elbert, A., B. Becker, J. Hartwig and C. Erdelen. 1991. Imidacloprid – a new systemic insecticide. Pflanzenschutz Nachrichten Bayer 44:113-116.
5. Elzen G. W. 2001. Lethal and sublethal effects of insecticide residues on Orius insidiosus (Hemiptera: Anthocoridae) and Geocoris punctipes (Hemiptera: Lygaeidae). J. Econ. Entomol. 94: 55-59.
6. Hough-Goldstein, J. and J. Whalen. 1993. Inundative release of predatory stink bugs for control of Colorado potato beetle. Biol. Cont. 3: 343-347.
7. James, D. G. Unpublished data.
8. James, D. G. 1997. Imidacloprid increases egg production in Amblyseius victoriensis (Acari: Phytoseiidae). Exp. Appl. Acarol. 21: 75-82.
9. James, D. G. and J. Coyle. 2001. Which pesticides are safe to beneficial insects and mites? Agric. and Env. News 178: 12-14. (
10. James, D. G. and T. Price. Unpublished data.
11. James, D. G., T. Price, L. C. Wright, J. Coyle and J. Perez. 2001. Mite abundance and phenology on commercial and escaped hops in Washington State, USA. Internat. J. Acarol. 27: 151-156.
12. James, D. G. and B. Vogele. 2001. The effect of imidacloprid on survival of some beneficial arthropods. Plant Prot. Quart. 16: 58-62.
13. Kunkel, B. A., D. W. Held and D. A. Potter. 1999. Impact of halofenozide, imidacloprid and bendiocarb on beneficial invertebrates and predatory activity in turfgrass. J. Econ. Entomol. 92: 922-930.
14. Lowery, D. T. and M. K. Sears. 1986. Stimulation of reproduction of the green peach aphid (Homoptera: Aphididae) by azinphosmethyl applied to potatoes. J. Econ. Entomol. 79: 1530-1533.
15. Luckey, T. D. 1968. Insecticide hormoligosis. J. Econ. Entomol. 61: 7-12.
16. Mizell, R. F. and Sconyers, M. C. 1992. Toxicity of imidacloprid to selected arthropod predators in the laboratory. Fla. Entomol. 75: 277-280.
17. Morse, J. G. and N. Zareh. 1991. Pesticide-induced hormoligosis of citrus thrips (Thysanoptera: thripidae) fecundity. J. Econ. Entomol. 84: 1169-1174.
18. Scholz, K. and K. Fritz 1998. Photolysis of imidacloprid (NTN 33893) on leaf surfaces of tomato plants. Abst. 9th Int. Cong. Pesticide Chem., London, UK.
19. Sclar, D. C., D. Gerace and W. S. Cranshaw. 1998. Observations of population increases and injury by spider mites (Acari: Tetranychidae) on ornamental plants treated with imidacloprid. J. Econ. Entomol. 91: 250-255.
20. Stark, J. D., P.C. Jeppson and D. F. Mayer. 1995. Limitations to use of topical toxicity data for prediction of pesticide side-effects in the field. J. Econ. Entomol. 88: 1081-1088.
21. Wright, L. C. and W. W. Cone. 1999. Carryover of imidacloprid and disulfoton in subsurface drip-irrigated hop. J. Agric. Urban Entomol. 16: 59-64.

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Pesticide Applicator Training

Washington State University (WSU) provides pre-license and recertification training for pesticide applicators. Pre-license training provides information useful in taking the licensing exam. Recertification (continuing education) is one of two methods to maintain licensing. (The other is retesting every five years.)

Course registration (including study materials) is $35 per day if postmarked 14 days prior to the first day of the program you will be attending. Otherwise, registration is $50 per day. These fees do not include Washington State Department of Agriculture (WSDA) licence fees. For WSDA testing sites, schedule, or other testing information, call 1-877-301-4555.

For more detailed information about WSU's pesticide applicator training, call the Pesticide Education Program at (509) 335-2830 or visit the Web site at

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PNN Update

The Pesticide Notification Network (PNN) is operated by WSU's Pesticide Information Center for the Washington State Commission on Pesticide Registration. The system is designed to distribute pesticide registration and label change information to groups representing Washington's pesticide users. PNN notifications are now available on our web page. To review those sent out in the month two months prior to this issue's date, either access the PNN page via the Pesticide Information Center On-Line (PICOL) Main Page on URL or directly via URL We hope that this new electronic format will be useful. Please let us know what you think by submitting comments via e-mail to Jane Thomas at

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Announcements & Upcoming Conferences

Pesticide Applicator's Drift Conference

Designed to provide Pacific Northwest pesticide applicators with the most current information concerning drift and related issues, this conference is being held at the Coeur d'Alene Resort in beautiful northern Idaho. Topics include drift management, public perception, label language, urban issues, buffer zones, and residential exposure. Sessions are appropriate for agricultural applicators, turf and ornamental urban applicators, right-of-way applicators, pesticide dealers, pesticide consultants, fieldmen, producers, and regulators. Registration fee is $40 in advance or $50 at the door, and attendees can obtain recertification credits for Washington, Idaho, Oregon, or Montana. This event is sponsored by the US EPA Region 10, the Idaho State Department of Agriculture, Washington State University, and the University of Idaho.

For further information, contact the Idaho Department of Agriculture at (208) 335-2830 or
Brochure available on-line.

February 5 & 6, 2002
Coeur d'Alene, Idaho

Environmental Stewardship Recognized

Dent award photoEnvironmental Stewardship awards were presented on November 15, 2001 at the Washington Pest Consultant Association (WaPCA) annual meeting in Yakima, Washington. The awards, co-sponsored by WaPCA and Northwest Ag Plastics, Inc. (NWAP), are presented to individuals, companies or organizations who demonstrate ongoing commitment to recycling plastic pesticide containers and/or promoting the recycling program. NWAP operates container recycling activities in Washington, Oregon and Idaho. WaPCA supports and promotes the program in Washington through its member organization.

Northwest pesticide container recycling is supported by the American Container Recycling Council (ACRC), an association of industry manufacturers, with offices in Washington, D.C. ACRC supports a nation wide program with strict guidelines that have to be followed for container decontamination, granulation, storage and remanufacture of end use products. End use manufacturers must be inspected and sign agreements that only specified products will be made out of the plastic. Current approved end use products are drain tile, sea pilings, truck decking, speed bumps, fence posts, hazardous waste drums, pallets and energy recovery.

Maahs award photo2001 proved to be the best year ever for the nine year old effort in Washington State, recycling over 320,000 pounds of plastic pesticide containers. This year’s recipients of the award were Tom Dent, owner/operator of Tom Dent Aviation in Moses Lake, Washington; Gene Maahs, owner/operator of Ag Northwest in Hermiston, Oregon; Ron Turner, crop advisor with Quincy Farm Chemicals in Quincy, Washington; and Carol Ramsay, Pesticide Education Specialist with Washington State University in Pullman, Washington.

Turner award photoTom Dent has been instrumental in promoting recycling in the Moses Lake area. Not only does he do a superb job of decontaminating his own containers and preparing them for recycling, he has also allowed others who wish to recycle their containers to bring them to his site on the collection day. He makes a special effort to call around the area to dealers, commercial applicators and growers to remind them of the collection dates. He had the most pounds of containers collected at one site in 2000. In addition, he provides extra labor to help feed the recycling equipment when it comes to his facility and has assisted with transporting the granulated plastic to the storage site in the Yakima area. Tom also has contributed articles on the recycling program to the nationally distributed Ag Pilot magazine and the Columbia Basin Business Journal newspaper.

Gene Maahs with Ag Northwest has been a pioneer with his recycling efforts in Northeast Oregon. Gene operates in Washington as well, serving some of the largest farming operations in the northwest. Gene has participated in storing his containers at central locations throughout the area, allowing the recycling equipment to service them periodically as they make their routine trips through the area. This makes recycling efficient. Gene has done an excellent job with participating in and promoting the recycling program.

Ramsay award photoRon Turner, with Quincy Farm Chemicals was one of the initial organizers of the recycling program which began in the early 1990s through the Columbia Basin Fieldmen’s Association, now known as the Columbia Basin Crop Consultants Association. Ron has continued his diligent efforts through the years. His most recent contribution was organizing the establishment of a 20 foot enclosed storage unit at one of his large customer’s farming operations near Quincy that serves as a collection site for their farm and others. Ron's efforts have shown what stewardship is all about.

Carol Ramsay is a tireless individual who promotes the recycling program through her pesticide education activities at Washington State University. Carol organizes several pesticide training seminars throughout the state every year. Her program is the core element of pesticide education activities throughout Washington State. She also serves on national committees and has been very involved with the National Pesticide Stewardship Alliance (NPSA). Carol has been instrumental in delivering the recycling message throughout the state. The program could not have grown as it has without her assistance.

The editorial staff at AENews congratulates these deserving award recipients and thanks WaPCA and NWAP for sponsoring the awards and continuing their efforts toward the promotion of environmental stewardship.

For more information about WaPCA, NWAP, or the recycling program, call NWAP at (509) 965-6809, see their Web site at, or see the WSU Pesticide Environmental Stewardship page at

Call for Presentations and Posters

Fourth Biennial

Agriculture and Water Quality in the Pacific Northwest

November 19-20, 2002 are the dates for the fourth Agriculture and Water Quality Conference. This conference is held every other year and will be held this year at the Yakima Convention Center. The conference mission is to provide a forum for agricultural interests, government, and environmentalists to come together in one place to discuss issues relevant to agriculture and water quality in a non-confrontational forum with the intent to help each other see and understand other points of view so we can work together for new solutions that benefit all.

The steering committee for the 2002 conference is now seeking presentations, posters, and exhibits. The 1996 and 1998 conferences held in Yakima were attended by over 400 people and the 2000 conference held in Eugene was attended by about 300 people representing a wide range of interests. Roughly 60 presentations will be made over the two-day period in a range of concurrent sessions.

The audience will be from the farming community, public and private agricultural service sector, university staff, government regulatory agencies, and environmental organizations. Main interests will include applied solutions, cooperative arrangements, and past, current and future approaches to agricultural water quality issues.

The steering committee is currently seeking presentations that provide the audience with a thoughtful, reasoned and informative point of view. Presentations should focus on applied solutions or introduce a topic and provide alternatives for addressing the issues surrounding the topic. We encouragepresenters to discuss what doesn't work, as well as what does and why. Additionally, cooperative efforts resulting in unique solutions are encouraged. Presenters should discuss a range of issues involved with their
topic including perspectives on legal issues; economic impacts; environmental effects; land use concerns; and property rights. Presentations of scientific studies need to provide the larger societal contexts being addressed and how the results might address these issues. (Otherwise, presentations of a purely scientific nature are best presented as posters at this conference.)

Presentations and posters may fall under the following general topic areas:

  • Interactions between the Clean Water Act, Endangered Species Act and pesticide registration laws
  • Irrigation water management and scheduling
  • Yakima / Columbia Plateau focus topics
  • AFO and CAFO solutions
  • Ground water quality and surface water interaction
  • Compliance and implementation: voluntary vs. regulatory and legal /liability issues
  • Nutrient, sediment and pesticide management
  • Stream restoration: habitat, buffers, wetlands and fish passage
  • Implementation of TMDLs, HCPs, BMPs, tillage and cropping practices, and rangeland management
  • Monitoring: water quality, ag practices, consequences, uses and considerations
  • Water quantity: minimum flows, metering and water sharing
  • Biotechnology in agriculture
  • Air quality related to water quality
  • Overview of emerging ag & WQ issues

Presentations of up to 30 minutes are desired. These will be grouped into three concurrent sessions of 90 minutes with presentations representing a range of view points on a topic. Additionally, there will be several panel discussion groups formed around certain topics. The steering committee may choose the topics and members of the panel for these groups.

Presentation proposals are due January 25, 2002.

For more information, see the conference Web page at or contact the committee at

Pesticide Medicine Course Scheduled for March

The Northwest Center for Occupational Health and Safety and the Pacific Northwest Agricultural Safety and Health (PNASH) are pleased to present "Pesticide Medicine," March 8, 2002, in Seattle. This course is geared towards physicians, industrial hygienists, nurses, toxicologists, laboratory and management representatives, attorneys, health professionals, educators, and safety and environmental health professionals. Professional credit is available. The registration fee is $165.00 before2/15/02 and $195.00 thereafter. A student rate of $95.00 is available for qualified attendees.

Local and national experts on pesticide use, pesticide exposure, and pesticide health effects will cover topics relevant for practicing clinicians and other professionals who interact with people with pesticide exposure. A guest from the University of California at Davis will share his valuable expertise on measuring pesticide exposure.

For more information about this course, call (206) 543-1069 or view

Timber Symposium Feb. 25-27

"Small Diameter Timber:
Resource Management, Manufacturing and Markets"

February 25-27, 2002
West Coast Grand Hotel at the Park
Spokane, Washington.

Nearly 50 speakers from 13 states and
Canada will present results of completed and ongoing activities related to
management and utilization of small diameter trees. There will also be
poster presentations and vendor exhibits.
Details and registration information can be found at


The National Pesticide Telecommunications Network (NPTN) has changed its name to the National Pesticide Information Center (NPIC). The 800-telephone number remains the same (800-858-7378), and NPIC will provide the same type and quality of service as was provided in the past under its previous name.

To be assured of the fullest access to NPIC information, please update your bookmarks and any links you may have to "old" NPTN pages to the current NPIC pages.

Please visit the new Web site at

Research and Extension Regional
Water Quality Conference 2002

Sponsored by USDA CSREES, this conference is an excellent opportunity for research, extension, and agency personnel to exchange information on water quality issues of importance in our region. The main objective of the conference is to present current science and scientific advances as well as their application for technology transfer and outreach.

February 20-21
Red Lion, Vancouver, WA

Organizers are Washington State University (Washington Water Research Center, WSU Cooperative Extension); University of Idaho (Idaho Water Resources Research Institute, UI Cooperative Extension); Oregon State University (Oregon Center for Water and Environmental Sustainability, OSU Extension Service), University of Alaska (Alaska Water and Environmental Research Center, Alaska Cooperative Extension); and Environmental Protection Agency Region 10.

For further information, go to

Washington Crop Profiles Available On-Line

In response to a 1998 request by the US Department of Agriculture's Office of Pest Management Policy (USDA/OPMP), each state is producing documents called "Commodity and Pest Management Profiles," or "crop profiles" for short. A list of crop profiles by state is available through a national Web site maintained by North Carolina State University. Washington State's crop profiles are also available in an easy-to-read, printable PDF format.

for the Washington State Pest Management Practices page maintained by the Pesticide Information Center at Washington State University. A definition of crop profiles is provided on this page, as well as links to each of the twenty crop profiles currently completed for Washington.


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Open Forum: In an attempt to promote free and open discussion of issues, The Agrichemical and Environmental News encourages letters and articles with differing views. To discuss submission of an article, please contact Dr. Allan Felsot at (509) 372-7365 or; Dr. Catherine Daniels at (509) 372-7495 or; Dr. Doug Walsh at (509) 786-2226 or; Dr. Vincent Hebert at (509) 372-7393 or; or AENews editor Sally O'Neal Coates at (509) 372-7378 or

Comments and questions: Technical Assistance: Copyright © Washington State University / Disclaimer Electronic Publishing and Appropriate Use Policy University Information: 509/335-3564