1. John Leahy, EPA Pesticide Re-evaluation Division
Risk Overview
Why Changes are Needed
John Leahy, EPA Pesticide Re-evaluation Division
This part of the presentation will include a general overview of the risks associated with fumigants and why new mitigation and new product labels are needed.
This soil fumigant REDs are the first comprehensive re-evaluation of methyl bromide, chloropicirin, metam sodium/potassium, and dazomet since they were first registered.
EPA looked at the fumigants together for review to ensure similar risk assessment tools and methods were used and that there was consistency with our management approaches

2. Fumigants Are Applied Many Ways to Control a Variety of Pests
Soil fumigant uses in the US that cover a wide range of crops, growing regions, weather conditions, and cultural practices.
The human health risk assessments covered potential exposure scenarios for this this broad range of use scenarios.
The risk assessments evaluated risks for handlers involved in the application process as well as bystanders who live and work near fumigated fields. 2 2

3. Focus On Acute Residential Bystander & Occupational Risks
Wind
Wind blows emissions from an application to a receptor of concern (e.g., house or school)
The primary route of exposure for soil fumigants is from inhalation although skin contact with fumigant vapor and liquid can also lead to adverse health effects.
Due the volatility of fumigants and their potential for offsite movement, the focus of the risk assessments and our risk management mitigation strategy that you will hear more about today is on acute inhalation risks to residential bystanders who live and work near treated fields.
Along with the residential exposures we also looked at risks to fumigant handlers and re-entry workers.
Other types of exposures also considered including:
Dietary (methyl bromide only)
Drinking water (methyl bromide only)
Environmental
Community based or ambient exposures in the population 3 3

4. Risk Assessment Process
Hazard Identification
Does the agent cause the
adverse effect?
Dose-Response Assessment
What is the relationship between
dose and incidence/severity of effects?
What exposures are currently
experienced or anticipated under
different conditions?
Exposure Assessment
This slide summarizes the risk assessment process, beginning with an analysis of the toxicology of a pesticide:
Is it toxic?
If so, what does it do and how much do you have to be exposed to cause the effect?
Then an exposure assessment considers whether exposures are expected and at what levels under different conditions based on all of the possible ways the chemical can be used.
The risk characterization tells a story about the chemical, the data used for the assessment and the severity of the risks.
It puts the hazard and exposure pieces together and estimates the likelihood of adverse effects.
What is the estimated incidence
likelihood of the adverse effect
in a given population?
Risk Characterization

5. Scientific Foundation
Recognized methods used
Public peer review processes under FACA rules
SAB on RfC inhalation risk methodology (1998)
SAP on exposure modeling (2004)
Multi-agency collaboration
USDA
DPR
FDACS
Based on multiple lines of evidence
Hazard data, Monitoring, Modeling, Incidents
Refined as a result of multiple public comment periods
For the fumigant risk assessments, EPA used standard, well recognized methods for both hazard and exposure analyses.
These were publically peer reviewed under processes established by the Federal Advisory Committee Act (FACA).
The EPA Science Advisory Board (SAB) review the inhalation risk assessment methodology in 1998.
And the FIFRA Scientific Advisory Panel (SAP) reviewed the exposure modeling approaches in 2004.
EPA also collaborated with scientists and researchers from USDA, the California Dept. of Pesticide Regulation (DPR), Florida, and others on the risk assessments and review of data.
The assessments are based on multiple lines of evidence that include hazard data, monitoring studies, modeling, and information from exposure incidents.
As mentioned in the regulatory overview, there were several comment periods on the risk assessments and at each phase the assessments were refined as new data and information were submitted to EPA.
As a result, EPA believes the risk assessments are highly refined and have a strong basis in science.

6. Fumigant Toxicity Comparison
Parameter
Chloropicrin
MITC
(Metam/Dazomet)
MeBr
Iodomethane
1,3-D
DMDS
Study used in risk assessment
Human Eye Irritation
1 hr/day
Human Odor & Eye
1-8 hr/day
Developmental Rabbit
6 hrs/day
1.Subchronic-Rat
2. Develop.-Rabbit
Acute -Rat
4 hrs
Special 24-hour inhalation study-rat
Endpoint
Eye irritation
response
Agenesis of gall bladder, ↑fused sternebrae, ↓fetal wt
Degeneration of olfactory epithelium, ↑ fetal losses
↓ body weights
Inflammation and degeneration of the nasal olfactory epithelium (levels II-VI); all minimal
Completeness of Database
Moderate-High
Low
Moderate
High
Symptoms reported from Incidents
Odor, eye, nasal irritation, difficulty breathing, pulmonary edema
Eye, throat & skin irritation, nausea, coughing
Headache, weakness, difficulty breathing, convulsions (soil uses)
No incidents
Eye, throat & skin irritation, cough
Limited incidents, odor issues, no other confirmed effects
This slide compares the toxicity of some of the main soil fumigants in use or proposed for use.
Some things to note:
Some fumigants are primarily irritants or cause effects at the point of entry (the nose) while others cause systemic effects– e.g., birth defects (endpoint row of table)
Generally severity of effects increases as concentration increases (last row of table)
Some fumigant assessments are based on human studies; others are based on animal (laboratory) studies.
Not all hazard databases are equal. Generally when there are missing studies or the effect is more severe, EPA is more conservative in regulating a pesticide.

7. Field Emissions (Flux) Monitoring
Emissions Are Described As Flux Values (µg/m2/sec)
Volatile Residues
Cross Section Of
Treated Field With
Known Surface Area
Fumigant field emissions are also called “flux”
This study describes a little about flux or emission monitoring studies.
These studies characterize the amount of fumigants off-gassing from a treated field by measuring residues in the air, or air concentration levels.
The diagram on the right shows an example of where air monitoring devices would be place in a field emissions study.

8. Actual Flux Monitoring Results
430’ & ND ppm
430’ - ND & ND ppm
288’ & 0.21 ppm
30’ – & ppm
MeBr Field 8 Results
19A; tarped raised bed in CA
200 lb/A; 98/2 MeBr/Pic
12 hr samples; LOD ppm
430’ &
ND ppm
30’ 0.24
& ppm
5’ &
1.0 ppm
405’ & 0.69 ppm
This slide shows actual results from a methyl bromide field monitoring study.
It was a 19 acre field treated with MeBr/pic 98:2, 200 pounds per acre.
Samples were collected in two 12-hour increments.
Concentrations were measured at different distances from the field and in different directions.
ND means “no detection”
Note that in some cases concentrations are higher farther from the field than near the field.
This can result from surface irregularities that cause air turbulence that can push gases above monitors near the field, but then are pushed closer to ground farther from the field.
Also note that the wind seems to have moved around during the 24 hour study period.
30’ – & 0.23 ppm
430’ &
0.74 ppm
408’ & ppm
430’ – & 0.65 ppm

9. Example Emissions Profiles0% 5%
10%
15%
20%
25%
30% 20 40 60 80
100
120
140
Mean Time Since Application (hours)
Flux Rate (% of Application)
This graph shows how the majority of emissions tend to come off treated fields within the first 48 hours after application. This is typical for most fumigants.
Time in hours is the horizontal axis; percent of total emissions is on the vertical axis.
Each line represents the emission profile for one of 3 different fields.
Note the green line has a small peak at about 110 hours; this probably correlates with when tarps were cut after the application on that field.
Monitoring studies give highly accurate measurements of real airborne concentrations of fumigants in and around fields following application at a specific location under the conditions where and when the study was conducted.

10. Modeling 5 Years of Weather Data Used
Sources Include*:
National Weather Service (NWS)
FAA’s Automated Surface Observing System (ASOS)
California Irrigation Management Information System (CIMIS)
Florida Automated Weather Network (FAWN)
EPA used one of the industry-developed models called “PERFUM” or Probabilistic Exposure and Risk Model for FUMigants.
This was peer reviewed by our Scientific Advisory Panel in 2004
PERFUM integrates a standard EPA dispersion model with actual weather data to predict air concentrations under a wide range of weather conditions.
EPA used 4 major sources of weather data (see slide).
EPA used data from 6 different locations where fumigants are commonly used: The southeast, California, the Midwest, and the Pacific Northwest.
EPA also used coastal and inland weather stations for CA and the SE.
*Data from 6 stations used for analyses including Ventura & Bakersfield CA; Bradenton & Tallahassee FL; Flint MI; Yakima WA

11. PERFUM Model Outputs
Solves for distance at target concentration which is defined by HEC/UF
Uses 5 years of weather data so each analysis would contain 1825 sets of outputs
Tallahassee & Bradenton weather used for southeast region
Weather Day 1
Treated Field
Weather Day 2
This slide shows an example of two “output days” from the PEFUM model but an entire analysis would have 5 years worth of these days.
The model “solves” for the distance from the field where our concentration of concern is expected and . . .
- compiles the information over the 5 years of permutations in order to evaluate different percentiles or probabilities of exposure at that level.
In this example, the weather on day 2 resulted in lower concentrations closer to the field than on day one, likely a result of windier conditions or less stable atmospheric conditions that would enhance dispersion of fumigant vapors in the air.

12. Incident Overview
Generally, low frequency of incidents relative to numbers of applications
Severe effects occur but low percentage of overall incident rate
Reports are consistent with risk assessments based on the nature of effects
Major incidents (those involving many people) typically occur because of equipment failure, applicator error, atmospheric conditions
Workers tend to have higher incident rates than bystanders
“Reconstructing” incidents to examine exact factors which lead to problem can be difficult especially for bystander exposure
In general there is low frequency of incidents relative to the volume of fumigant used throughout the US
Severe effects are reported but they represent low percentage of the overall incidents
Major incidents that involve large numbers of bystanders or workers generally occur because of equipment failure, applicator error, and weather conditions.
The available incident data for soil fumigants comes from a variety of sources including Poison Control Centers, our own Incident Data System, California, and NIOSH.
It is important to note that it is very difficult to reconstruct past incidents to see what factors or events led to a problem, especially when bystanders are involved.
For all of the soil fumigants, metam sodium has highest incident rate, but also the highest number of applications.
Additional key points about incidents
Although the frequency is low, when things go wrong large numbers of people can be affected
People offsite are much less likely to connect symptoms with pesticide vapors so there may be some under reporting
Lastly, in some incidents when people or first responders did NOT know what to do, they made things worse with the their actions (e.g., moving exposed people down wind from field)
States that do not have robust incident surveillance systems have few reported incidents; those that do, tend to have more incident reports. 12 12

13. Summary Peer reviewed methods
Extensive emissions & occupational monitoring data
Also focused on factors which impact emissions
Results indicate risk management required, incident rates are low and effects consistent with risk assessment
Key concern is near applications, buffers reduce those types of exposures
Much ongoing research to evaluate emission controls (e.g., low permeability tarps & soil adjuvants)
To summarize the risk assessments—
EPA used peer reviewed tools and assessment methods
EPA evaluated a large amount of data and used all relevant data in the risk assessments
We considered the affects of various factors on emission rates, which affects predicted exposures and risks around fumigated fields.
Based on multiple lines of evidence, the assessments show that as currently labeled risks to fumigant handlers and bystanders are of concern and measures to reduce those risks are needed to prevent adverse effects.
One of the key areas of concern is bystander exposures near treated fields. The risk assessments show that as distance from a fumigated field increases, risk to bystanders decreases. So buffers are an important way to reduce bystander risk.
Finally, there is a lot of research currently under way on emissions and factors that affect off-gassing. EPA is working with researchers and will keep abreast of new studies and tools that can refine risk assessments in the future.