Illinois Pesticide Review
January / February 2009
In This Issue
It may be you thought it was just government regulatory agencies that might check on you while you are making a pesticide application or handle a complaint of alleged drift. It turns out other people might be watching as well, and they take a very negative view on the use of pesticides. I am referring to the Pesticide Action Network North America (PANNA) and a recent fact sheet detailing pesticide drift in Florida.
The fact sheet reports on citizens who conducted sampling for drift near Chinese cabbage fields in Hastings, Florida. They claim to have found four types of pesticides in the air near a local school. The drift sampling was carried out using a device called the drift-catcher. The drift-catcher was developed by PANNA specifically to measure pesticide levels in the air and document areas where drift is a concern. PANNA makes the drift-catchers available to groups interested in changing laws and policies related to pesticide use. The drift-catcher is a device that sucks in air, drawing the air through resin-containing tubes. The resin traps airborne particles and can then be analyzed for the presence of pesticides.
The sampling near Hastings was conducted from October 1 to December 6, 2007, with 39 samples collected. Four different pesticides were found in the samples: endosulfan, diazinon, trifluralin, and chlorothalonil. Endosulfan and diazinon are restricted-use insecticides, trifluralin is a general use herbicide available to homeowners, and chlorothalonil is a fungicide. Eight samples taken over a period of 9 days the previous year detected only three pesticides: endosulfan, diazinon, and trifluralin.
In the 2007 samples, endosulfan was found in 87 percent of the samples, with an average concentration for the 39 samples of 248 ng/m3 (nanograms of pesticide per cubic meter of air) and a maximum concentration of 1,376 ng/m3. Diazon was present in only 23 percent of the samples and had an average concentration of of 42 ng/m3 and a maximum concentration of 575 ng/m3. Trifluralin was present in 92 percent of the samples, with an average concentration of 23 ng/m3 and a maximum concentration of 136 ng/m3. Chlorothalonil was present in 85 percent of the samples, with an average concentration of 107 ng/m3 and a maximum concentration of 555 ng/m3.
PANNA describes these levels of pesticide in the air as "potentially harmful." To assess the risk of harm, they use a level of concern that they derived "based on U.S. Environmental Protection Agency (EPA) data and methodologies developed by the EPA and California's Office of Environmental Health Hazard Assessment." For endosulfan, they give a level of concern for infants of 340 ng/m3 and a level of concern for 7-year-olds of 500 ng/m3. The infant level of concern for diazinon was listed as 145 ng/m3, with a 7-year-old level of concern of 220 ng/m3 and an adult level of concern of 335 ng/m3. The levels of concern for trifluralin and chlorothalonil were not given.
A review of the full technical report on the air monitoring, available at PANNA's Web site (http://www.panna.org/files/hastingsFLTech092308.pdf) offers more details on how these levels of concern were derived. In the technical report, these levels are referred to as 24-hour Reference Exposure Levels (RELs) and are based on U.S. EPA toxicology data. PANNA states that the REL represents "a level of concern for inhalation exposure analogous to U.S. EPA's Reference Dose for dietary exposure." The PANNA-derived REL is an air concentration measured in ng/m3, which they say is equivalent to a dose in milligrams of pesticide per kilogram of body weight. At levels below the REL, they state that "the risk of adverse effects is anticipated to be negligible." To calculate the RELs, PANNA started with the No Observable Adverse Effect Levels (NOAEL) determined by EPA from test-animal studies. NOAELs are measured in milligrams of chemical per kiliogram of body mass per day (mg/kg-day). The RELs for endosulfan, diazinon, and trifluralin were calculated using NOAELs from inhalation studies. The REL for chlorothalonil is based on a NOAEL from an oral study.
The NOEALs from the EPA are further reduced using uncertainty factors. A factor of 10 is used to account for the difference between test animals and humans. Another factor of 10 is used to allow for differences between individual humans in terms of their sensitivity to pesticides and their bodies' ability to remove the chemicals. For diazinon, the Lowest Observed Adverse Effect Level (LOAEL) from the inhalation study was used instead of a NOAEL because adverse effects were seen at all dose levels. Therefore, an additional uncertainty factor of 3 was used for diazinon. Another reduction factor of 10 was used for endosulfan to allow for children, because children can be more susceptible to some chemicals. Child uncertainty factors for trifluralin and chlorothalonil were set at one (no reduction) because the EPA does not have evidence to indicate that children are more susceptible to these chemicals than adults. For diazinon, a child uncertainty factor of 1 was used; but EPA has previously used both 1 and 10.
After dividing the NOEALs by the appropriate uncertainty factors, the modified number is referred to by PANNA as an "inhalation reference dose" (iRfD). Separate acute and subchronic iRfDs were calculated for adults and children, using the appropriate uncertainty factors. The iRfDs, measured in mg/kg-day, were converted to the RELs, measured in ng/m3, by using an equation that accounted for the average body weight and breathing rate of three populations: 70 kg adult males, 7-year old children, and 1-year old infants. An REL was calculated by multiplying the iRfD in mg/kg-day by the body weight in kg (technically the gram is a measurement of mass, not weight) by 106, the number of nanograms in a milligram. This was then divided by the breathing rate in m3/day. Finally, this was multiplied by 100 percent regardless of whether it was based on inhalation or oral data, as EPA methodology assumes absorption of a compound through inhalation is equivalent to absorption through digestion.
PANNA states that an REL calculated using this formula answers the question of what the concentration of the pesticide in the air would have to be "for a person to inhale, over the course of 24 hours, a dose equivalent to the iRfD." In other words, a person would need to remain in the same location as the REL concentration for a full 24 hours to inhale the iRfD, which is lower then the NOAEL measured by the EPA by at least a factor of 100. The technical report denotes that most of the 39 samples were collected at roughly 24-hour intervals, with some exceptions by which samples were collected after a sampling period of a few days and some times with no samples collected.
The opening paragraph of the fact sheet describes the pesticides as being "in the air near South Woods Elementary School." However, an examination of the map included in the fact sheet reveals the drift-catcher was located at the edge of the field in which the applications were made, only 65 feet from southern edge and western edge of the field, according to the full technical report. This location was about 1,500 feet from the school. In addition, there is a forested barrier about 600 feet deep between the drift-catcher and the school.
Trees and other vegetative barriers have been found to reduce drift dramatically by intercepting spray and reducing air flow. Various studies have shown a windbreak located at the edge of an application site can reduce drift between 70 and 90 percent within the first 10 feet downwind of the windbreak. A single row of trees downwind of the application site was found to decrease drift by 50 percent. Increasing the height of vegetation in a windbreak increases its effectiveness in reducing drift.
The technical report states that the location was chosen for the drift-catcher because its position relative to the field it is adjacent to is similar to the position of the school playground relative to a different Chinese cabbage field east of the school. No trees were present between the school and the Chinese cabbage field to the east of the school.
There is another Chinese cabbage field to the south of the school as well. If the goal of the project was to document the presence of spray drift at the school from the fields in closest proximity to the school, it would have been more prudent to locate the drift-catcher on the school grounds instead of 1,500 feet away. Why this was not done is not mentioned. An underlying assumption to the speculation that the pesticide levels at the drift-catcher and the school are similar is that the field to the east of the school received the same type of pesticide applications at the same rates and frequency.
The 600 feet of forest between the drift-catcher and the school could conceivably reduce most if not all of the pesticides present in the air at the location of the drift-catcher, which was located next to the application site, before they reached the school. In addition to the forest buffer, the wind also influenced the amount of drift present at the school. According to the technical report, the major wind direction near the study site is from the northeast to east-northeast during the day. This means the location of the drift-catcher is downwind of the Chinese cabbage field it is adjacent to. These wind directions would blow any pesticide drift present at the drift-catcher away from the school not toward it. However, this wind direction would blow any drift from the field to the east of the school directly toward the school. As previously mentioned, the schoolground itself would have been a much better location for the drift-catcher if the objective of the study was to quantify pesticide levels at the school.While the actual amount of pesticides present in the air at the school in Hastings and whether those levels represent a hazard are not certain, what is certain is that more and more people are paying attention to pesticide applications. With the use of pesticides under increasing scrutiny, it is imperative that everyone involved in pesticide applications does everything possible to make sure the applications are both effective and safe. (Scott Bretthauer)
Illinois Pesticide Misuse Case Summary for 2008
115 formal complaints received
73 agriculture cases
25 lawncare cases
17 other cases
60 cases closed (no misuse)
30 warning and advisory letters
17 administrative hearings
26 fines levied
• 6—$100 fine—Lawncare Act violation, as a result of the complaint
• 10—$500 fine—applicator-license violation, as a result of the complaint
• 4—$750 fine—misuse
• 6—$1,000 fine—Lawncare Act violations as a result of the complaint
Complaints involving aerial applicators (These complaints are included above.)
• All involved potential drift or application to nontarget site.
• 7 cases closed with no evidence of misuse
• 0 applicator license violations
• 1 administrative hearing—$750 fine due to drift
• 5 warning letters issuedPlease note, this list is not all-inclusive, as it does not represent data from pesticide-containment violations, dealer violations associated with restricted-use pesticides, or general-applicator license violations not associated with a complaint. (Source: A handout created by Scott Frank, Illinois Department of Agriculture Bureau of Environmental Programs, at the Interagency Committee on Pesticides meeting, December 11, 2008. Adapted by Phil Nixon.)
Will Delayed Spraying of Tank-Mixed Herbicides Reduce Weed Control?
Ever finished filling your spray tank with pesticides, adjuvants, and carrier, only to realize that a thunderstorm is about to hit your intended application's site? Do you go ahead and spray and risk the application being washed off? Or do you wait it out? Your chemicals, if allowed to sit in the tank for an extended period can settle out, degrade, or bind to the tank. Which is the lesser of the two evils?
In December, I attended the North Central Weed Science Society of America meetings, where I learned of some recent research focused on determining the length of time corn herbicides can remain in the spray tank prior to application in the field without impacting efficacy (control).
Studies were conducted at two locations in southwestern Ontario by Robert E. Nurse, research scientist with Agriculture and Agri-Food Canada, and Peter H. Sikkema, associate professor, University of Guelph. Between 2006 and 2008, ten field trials were conducted.
Preemergent treatments included (Canadian registered products noted in parentheses; similar U.S. products follow.)
—isoxaflutole + atrazine (Converge PRO), BALANCE + ATRAZINE
—dimethenamid + dicamba/atrazine (Frontier + Marksman), OUTLOOK + MARKSMAN
—s-metolachlor/atrazine + mesotrione (Lumax), LUMAX
—rimsulfuron + s-metolachlor + dicamba (Battalion)
Postemergent treatments included
—nicosulfuron/rimsulfuron (Ultim), STEADFAST
—dicamba/diflufenzopyr (Distinct), DISTINCT
—mesotrione + atrazine (Callisto), CALLISTO + ATRAZINE
—glyphosate (Roundup WM), ROUNDUP WEATHERMAX
—glufosinate (Liberty), LIBERTY, IGNITE
Their research abstract states that
Four preemergence and five post-emergence herbicides were mixed at their labeled rates and then applied in field corn following label specifications. Herbicides were either applied immediately, or after being left for 1, 3 or 7 days in the spray tank. The most common weed species in the trials were velvetleaf (Abutilon theophrasti), redroot pigweed (Amaranthus retroflexus), common ragweed (Ambrosia artemisiifolia), and common lambsquarters (Chenopodium album). Delaying herbicide application did not affect the efficacy of postemergence herbicides in this study. Similarly, control of redroot pigweed and common lambsquarters was not affected by a delay in the application of preemergence herbicides. However, control of velvetleaf was decreased when isoxaflutole + atrazine, dimethenamid + dicamba/atrazine, or rimsulfuron + s-metolachlor + dicamba applications were delayed by more than 1 day. Nonetheless, there were no decreases in yield for any treatment combinations.
The results of this study suggest that for most herbicides and weed species it is better to postpone application (even if it's a week later) rather than make applications under nonideal conditions. It is also better to delay an application, rather than to dispose of the mixture. If an application must be delayed, it is recommended that the tank mixture be agitated at least once per day for best results. The spray tank should also be stored so that it is protected from direct sunlight, which can further degrade chemicals. Be sure to monitor treated fields closely. Of course, it is best to wait for inclement weather to pass before mixing your chemicals.Dr. Nurse tells me that the data are being submitted for publication with the journal Crop Protection. To learn more details of the study, watch for its publication. (Michelle Wiesbrook. Credits: 2008 North Central Weed Science Society Proc. 63:131. How long can various herbicides remain in the spray tank prior to application in the field? Robert E. Nurse and Peter H. Sikkema, research scientist, Agriculture and Agri-Food Canada, Harrow, ON N0R 1G0, and associate professor, Ridgetown Campus, University of Guelph, Ridgetown, ON N0P 2C0.)
Washington State Officials Investigate Pesti-cide Exposure
On October 17, 2008, 22 people reportedly were exposed to metam sodium gases from a Washington potato field. Twelve of the victims were treated that evening at a hospital in Pasco, Washington. The victims' symptoms included coughing, congestion, headaches, nausea, and nose and throat irritation. All were released the same evening.
This incident is one of five metam sodium exposure incidents investigated by the state of Washington's health department since 2000. The incidents involve a total of 34 people, including two Pasco-area residents who reportedly were exposed to the gases in the fall after the October 17 incident. Included among the exposure victims on Octobe 17 was a law enforcement officer who responded to the incident. Five of 17 victims interviewed by the health department did not seek medical treatment. Among those treated were a 2-week-old infant, four young children, four teens, and three adults.
If an application violation occurred, the state could issue a civil penalty of up to $7,500 per violation, said a spokesman for the Washington State Department of Agriculture. The department would not release additional information, including the name of the farmer or applicator involved in the incident, pending completion of its investigation.
Washington state's health department and Washington State University installed gauges to measure metam sodium gas emissions in Franklin County. The gauges annually show peaks each October just before the Franklin County Irrigation District shuts off irrigators. It was quoted that "[a] lot of metam sodium is going on that week before irrigation cutoff." "People are racing to get it on."
While these types of exposure cases are rare—especially when considering the millions of pounds of metam sodium are applied to Washington's fields each year—they are fairly consistent when a temperature inversion is present during an application. The case on October 17 involved a pending irrigation cutoff and environmental conditions ideal for accumulation of metam gases and off-target drift: a temperature inversion that trapped the gases. Also, the existing corn stubble from the previous crop impeded the movement of the fumigant into the soil, leaving it to disperse into the atmosphere as a gas. Under inversion conditions metam sodium gases accumulate in the breathing zone, and if people are in the way, they are going to breathe it.
The exposure victims were downhill from the sprinkler application, in an ideal position to be exposed. Plus the temperatures rose into the mid-70s during the application, which helped keep gases volatile. (During warm weather, there is a better chance for the off-target movement of fumigants.) The health department investigators found evidence of off-target movement 3 days after the October 17 application in soil and foliar samples taken from around the houses and from surfaces investigators swabbed.
The incident could prove a stumbling block for an agricultural industry hoping to shrink buffers proposed in new labels for metam sodium and other fumigants. At the very least, according to Department of Health toxicologist Barb Morrissey, the case underscores how important it is for producers to use caution when applying soil fumigants. Another result of the incident, according to Sandy Halstead, an EPA farm specialist in Prosser, Washington., is it helps the agency understand what changes are needed to fumigant labels to prevent future exposures. In a presentation at the Hermiston Farm Fair on December 3, Halstead said changes proposed for metam sodium labels would have prevented the exposures. The families involved in the incident would have been in the buffer zone and would have been told to vacate the area for 48 hours.
Depending on how much fumigant is used, application technique, and other factors, buffers proposed for the new labels range from 25 feet to a half-mile, according to the EPA. EPA officials are expected to reduce buffer requirements in cases where fumigants are shank-applied or where they are applied under a drizzle boom. Grower groups and the pesticide industry have come out in opposition to the proposed restrictions, saying they will cost farmers millions of dollars annually on the West Coast alone in lost production and increased compliance expenses. Environmental activists, meanwhile, say the proposed restrictions don't go far enough to protect public health and the environment.The label changes are being implemented under the 1996 Food Quality Protection Act. Fumigants are some of the last pesticides reviewed under the act. Metam sodium and four other fumigants under review are widely used throughout the United States by fruit and vegetable producers. In addition to metam sodium, fumigants being reregistered include methyl bromide, metam potassium, dazomet, and chloropicrin. In 2005, Washington state growers applied more than 20 million pounds of metam, according to Washington State University figures. A 2007 WSU report noted recent housing expansions into traditional farming areas are contributing to more health complaints. (Adapted by Jim Schuster, PSEP, Plant Pathology, Department of Crop Sciences, University of Illinois; from a press release sent from Heather Hansen, executive director, Washington Friends of Farms & Forests, to Carol Ramsay, Extension pesticide education specialist, Washington State University.)
National Poison Prevention Week
Every 13 seconds, a U.S. poison control center receives a call about an unintentional poisoning. In observance of National Poison Prevention Week (March 15–21), EPA is reminding families how to take precautions and properly use and store household pesticides to avoid poisonings.
The American Association of Poison Control Centers data show that more than half of the 2 million poisoning incidents each year involve children younger than 6 years old. According to www.poisonprevention.org, more than 90% of these poisonings occur in the home. In addition, poison centers reported more than 70,000 calls made to poison centers with concerns about potential exposure to common household pesticides (potential exposures do not necessarily represent a poisoning).
EPA observes National Poison Prevention Week each year to increase awareness of the danger to children of unintentional poisonings from pesticides and household products, and to encourage parents and caregivers to lock up products that could potentially harm children.
Pesticides aren't the only dangerous chemicals in your home that kids may come into contact with. The EPA gives this list on its Web site:
—bath and kitchen disinfectants and sanitizers, including bleach
—household cleaning or maintenance products, such as drain cleaner, paints, or glues
—automotive products stored around the home, such as anti-freeze or windshield-washer fluid
—health- or beauty-care products, such as medicines, hair and nail products
—roach sprays and baits
—rat and other rodent poisons
—products used to kill mold or mildew
—flea and tick shampoos, powders, and dips for pets
—swimming pool chemicals
When not in use, these products should be kept in a locked cabinet away from small children. When in use, it is advised that the products not be unattended. Containers should be closed when possible. An unexpected guest at the door may pull you away for a few minutes and unfortunately, a few minutes; is all it takes for a child to find something excitedly forbidden to play with.
For poison prevention resources, check out http://www.epa.gov/pesticides/health/poisonprevention.htm.The national poison center hotline is
1-800-222-1222. Take the time to program this number into your phone's address book for fast retrieval when you need it. (Michelle Wiesbrook; adapted from an EPA newsroom release, March 15, 2007.)