## ~n~roe sct Pmmtiscn, 

### Pestlcldes, 

### and T* Sum



## Environmental Fate and Ecological Risk Assessment for the Registration of Iodomethane (Methyl Iodide)

### I. ENVIRONMENTAL RISK CONCLUSIONS
Iodomethane is a short-lived chemical in the lower atmosphere and unlikely to reach the upper atmosphereto depletethe ozonelayer. The estimated maximum concentration ofiodomethane in air appears unlikely to pose an acute risk to birds and mammals. Short-term inhalation exposures of iodomethane are unlikely to pose chronic risk tobirds and mammals. It also appears that no adverse effect on aquatic invertebratesorfish are likelybecause of lowpotential ofrunofftothe surfacewater bodies from the tarped post application sites of iodomethane. The environmental fate data, the residual contentsin soils, and Tier I and I1models estimated concentrationssuggestthat the adverse effect on ground water or surface water is highly unlikely due to iodomethane use. Iodomethaneis proposed for use as an alternative pre-plant hmigant for methyl bromide in fields to be planted to tomatoes, strawberries, peppers, select ornamentals, turf, and re-plants of trees and vines. Low aMinity for sorption into the soil (KO, 34.8

### LKg-')and highvapor pressure (405.9

### rnrnHg) of iodomethanesuggestthat volatilizationofiodomethane isthe majorroute of dissipation. Available data indicatethat there is 54 to 80% dissipationtothe air evenbefore the tarpaulin is removed. Once it volatilized, iodomethane degrades rapidly in the lower atmospherevia direct photolysis and lasts in the atmospherelessthan twelve days, as compared with two years for methyl bromide. Therefore, iodomethane is unlikely to reach upper atmosphere to impact ozone layer. The estimated ozone depletion potential (ODP) for iodomethane is 0.029 as compared to 0.65 for methyl bromide. However, global uncertainty on volatilizationrates, residence time in soil, photolytic degradation of iodomethane, and the removal of iodine radicals from troposphere means that the possibility of detrimental effects of iodomethane on ozone layer and a contribution to global warming can not be excluded.
The primary route of iodomethane exposure of nontarget terrestrialanimalswillbe inhalation.Direct flux of iodomethane in air was estimated using the Industrial Source Complex (ISC) dispersion model and monitoring data from iodomethane treated field. The estimated maximum concentration of iodomethane (0.987ppm) at 242 lbs a.i./acre appearsunlikely to pose an acute risk to birds and mammals (the maximum proposed applicationrate is 235 lbs a.i./acre).Iodomethaneis a short-lived chemical in the atmosphere. Therefore, there is low potential for chronicrisk tobirds and mammals. It also appears that no adverse effect on aquatic invertebrates or fish are likely because of low potential to runoff from the tarped post application sites ofiodomethanetothe surfacewater bodies. Based upon Tier I1 PRZM/EXAMS estimated environmental concentrations (EECs) for surface water, no Levels-of-Concern (LOCs) for aquatic invertebrates or fish are exceeded. EFED also believes that the Henry's Law Constant of 5.23~-03atm-m3/mole (highly soluble and volatile) of iodomethane suggest that chronic exposures to the aquatic invertebrates and fish are not likely to occur. EFED is uncertain regarding the effects of this hmigant toterrestrial and semi-aquatic plants aswell as aquatic plants. Tier I and Tier I1 plant data will enable EFED to complete the risk assessment of plants. However, based in part on a prior draft of a biological opinion from the United StatesFish and Wildlife Service (USFWS) for tarped uses of methyl bromide, the Field and External Affairs Division (FEAD) does not presentlyhave a concern for the proposed tarped uses ofiodomethane and Page 2 of 37endangered species, including endangered plants.
Based on environmental fate data, the residual contents in soils, and Tier I and I1 models estimated concentrations, 

### EFED does not expect iodomethane to adversely impact ground water or surface water. Tier I1PRZM/EXAMS for surfacewater and Tier I SCIGROW for ground water were used to estimate iodomethane concentrations. These concentrations are in nanograms per liter (ng/L), or parts per trillion. However, since this compound is very soluble in water, there is the possibility of leaching to ground water, if slicing or removal of the tarpaulin coincides with, or is followed soon by, a rain event. 

### EFED recommends adding cautionary languageto the label to prohibit the slicing or removal of the tarpaulin if it is raining or if rain is expected within 48 hours.

Page 3 of 37

### IT. INTRODUCTION Methyl bromide is used extensively on a global basis as a pesticide against nematodes, weeds, insects, fungi, bacteria, and rodents. However, methyl bromide has been identified as a significant ozone depleting substance, resulting in regulatory actions being taken by the U.S. Environmental Protection Agency and by the United Nations Environment Program (Montreal Protocol). Iodomethane is proposed for use as an alternative pre-plant Iixnigant for methyl bromide in fields to be planted to tomatoes, strawberries, peppers, select ornamentals, turf, and re-plants of trees and vines. It is formulated as a 98% active ingredient (a.i.) product (TM-42501) with 2% chloropicrin as a "warning odorant", and a 25% a.i. product (TM-42503) with 75% chloropicrin as an active ingredient. The mode of action ofmonohalomethanes (chloride, bromide, iodide substituted)is still not well understood. The iodide ion concentrationis insufficient to explain iodomethane toxicity. Toxicologic and metabolic similarities amongthe monohalomethanes suggest a common mechanism of toxic action, probably methylation and disturbance or inactivation of essential proteins.


### 111. INTEGRATED ENVIRONMENTAL RISK CHARACTERIZATION Iodomethane, an alternative fumigant to methyl bromide, is a short-lived chemical in the lower atmosphere and unlikely reach the upper atmosphereto deplete the ozone layer. The environmental fate data, the residual contents in soils, and Tier I- and I1 model- estimated concentrations suggest that the adverse effect on ground water or surface water is highly unlikely due to iodomethane use. The estimated maximum concentrationof iodomethane in air appearsunlikely to pose an acute risk tobirds and mammals. Short-terminhalationexposures ofiodomethane areunlikelyto pose chronic risk tobirds and mammals. It also appears that no adverse effect on aquatic invertebrates or fish are likelybecause oflow potential to runoff from the tarped post application sites ofiodomethane to the surface water bodies.
Thehighvapor pressureof405.9mmHg at 25°C andHenry's Law constant of5.23E-03atm-m3/mole and low affinity for sorption on soil (KO, 34.8 

### L Kg-') of iodomethane suggest that volatilization is the most important environmentalroute of dissipation. Field data fkom the applied iodomethane via broadcast shank injection in the bare-ground plot and followed simultaneously with a standard 1mil plastic tarpaulin over the treated plot suggest that 54 to 80 percent of iodomethane was dissipated to the atmosphere even before the tarpaulin is removed. Once volatilized into the atmosphere, it degrades rapidly due to direct photolysis and the estimated atmospheric residence time is less than 12 days. The estimated ODP iodomethane is less than 0.029, well below the level of Class 

### I ozone depleters. Under Title 

### VI, Section 602 of the Clean Air Act, the US Environmental Protection Agency classified any substancewith an ODP 0.20 or greater as a Class 

### I ozone depleting substance. However, global uncertainty on volatilizationrates, residence time in soil, photolytic degradation of iodomethane, and the removal of iodine radicals from troposphere means that the possibility of detrimental effects of iodomethane on ozone layer and a contribution to global warming can not be excluded.
Field dissipation data suggestthat applied iodomethanewas more confined tothe soil layers adjacent to the 30-cm depth of iodomehane placement than the soil layers below 60 cm depth. No residual Page 4 of 37iodomethane was detected at the end of the field study period (90 days) at either site. Even if any iodomethane exposure should occur in the surface water, Henry's Law constant of 5.23E-03atmm3/mole suggests rapid volatilization of iodomethane to atmosphere. Tier I1 PRZMIEXAMS for surface water and Tier I SCIGROW for ground water were used to estimate iodomethane concentrations. These concentrations are in nanograms per liter (ng/L), or parts per trillion. Based on environmental fate, the residual contents in soils, and Tier I and I1 models estimated concentrations, EFED does not expect iodomethane to adversely impact ground water or surface water.
Todomethane's use as a pre-plant fbmigant is not expected to pose a substantial direct risk to nontarget terrestrial or aquatic wildlife. It appears that the primary route of exposure of nontarget terrestrial organisms will be inhalation. Direct flux of iodomethane in air was estimated using the Industrial Source Complex (ISC) dispersion model and monitoring data from iodomethanetreated field. Estimated data indicatethat air concentrations ofup to 0.987 ppm (at 30cm above the tarped ground at 8 

### - 19hours post-application). Sincethe availableavian acuteinhalationLC50 is 395 pprn (over 400X this peak estimated residue), there does not appear to be a substantial risk of acute lethality to birds, even ifthey do fly above or land on the tarpaulin on the day of application. Birds off-site would be exposed to even lower residues and potential risk.
It appears that mammals are less acutely sensitivethanbirds toiodomethane (LC50 equivalentto 689 ppm). TheHED recommended endpoint for human health risk assessment is an inhalation maternal NOAEL of 10ppm in a developmental toxicity study, where rabbits were exposed for six hourslday for 23 days. The peak estimated short-termresidues above the tarp (0.987ppm) arebelow even this NOAEL from a 23-day study. Off-site or long-term residues and risk would be even lower.
EFED does not consider iodomethane to pose an acute or chronic risk to fish and aquatic invertebrates because oflow potentialto runofffiomthe tarpedpost application sitesofiodomethane to the surface water bodies. The low octanollwater partition coefficient (log 

### KO, I 1.69) indicates that iodomethane is not likelytobebioconcentratedintissues ofaquatic organisms. Thehighest acute aquatic EEC for the iodomethane ecological risk assessment is 0.942 ppb, for Florida peppers. Comparingthisvaluetothe acutetoxicity value (LC,,) for the most sensitivetest species 

### (D. magna, 570 ppb) produces a maximum risk quotient of 0.0017. This is well below the lowest acute aquatic Level-of-Concern (LOC) of 0.05 (endangered species). EFED also believes that the Henry's Law Constant of 5.23E-03atm-m3/mole (highly soluble and volatile)ofiodomethane suggestthat chronic exposuresto the aquatic invertebrates and fish are not likely to occur. 

### IV. ENVIRONMENTAL FATE ASSESSMENT 

### (A)Physicochemical Properties
Table 1presents the importantphysical and chemicalproperties ofiodomethane. The vapor pressure andHenry's Law constant arehigh, suggestingthatvolatilization isthe most importantenvironmental route of dissipation.Field volatilization studies 

### (MRID 45593710 and 45593822) suggest that the concentrations ofiodomethanein the fbmigated areas were significantly higherthan the atmospheric Page 5 of 37background level (0.12 pg m-3 or 0.02 ppbv) during the 10-day monitoring period. Cumulative volatilization losses 

### of iodomethane ranged from 54 to 94 percent within 10 days. The low octanol/water partition coefficient indicates that iodomethane is not likely tobe bioconcentrated in tissues 

### of aquatic organisms.

Table 1. Physico-chemicaland environmental fate properties of iodomethane.

Phvsical and Chemical Properties Chemical Name - Iodomethane CAS No.74-88-4 (Methyl Iodide, CH,I) Molecular weight 141.94g/Mol MRID 45593705 Water solubility 1420mg/L at 25OC MRID 45593705 Specific gravity 2.8 at 20°C Product Chemistry Vapor pressure 405.9 rnrn Hg at 25OC Product Chemistry Henry's law constant 5.23E-03 atm-m3/mole www.toxnet.nlm.nil.gov UV absorption Maximum (2.5 absorbance MRID 45593706 units) at ca. 200 nm, with a smallerpeak (0.25 au) at ca. 250 nm OctanoVWaterpartition coefficient 1.51 

## - 1.69 (1% KO,) Melting point International Occupational Safety and Health Information Centre International Occupational Safety and Health Information Centre Boiling point 42.4OC Product Chemistry Environmental Fate Pro~erties Hydrolysis Half-Life @ pH 4 @ 25oC pH 7 @ 250C pH 9 @ 250C Hydrolysis Half-Life @ pH 4 @ 500C pH 7 @ 500C pH 9 @ 500C MRID 45593705 105 days 94 days 108 days 3.4 days 2.5 days 2.6 day

Page 6 of 37Table 1. Phvsico-chemical and environmental fate ~ro~erties of iodomethane.

Aerobic Soil Metabolismt,, 2 hours (short half-life resulted MRTD 45593707 due to volatilizationof iodomethane) Anaerobic Soil MetabolismtIh, 38 hours (Sediment only) MRID 45593708 Aerobic Aquatic Metabolismt,, 39 hours (Water only) MRID 45593708 Anaerobic Aquatic Metabolismt,, 40 hours (Whole system) MRID 45593708 Direct photolysis (atmosphere) 11.5 days1 D. Wuebbles, University of Illinois (personal communication, 2002) Direct Aqueous Photolysis 13 days MRID 45593706 Soil Water Partition Coefficient 34.8L Kg-' (SD k16.8) MRID 45593709 

### (kc) (Mean of five soils) 'Atmospheric model-estimated lifetimebased on emissions globally distributed; lifetimewill vary with location of emissions Conversion Factors To convert concentrations in air (at 25 

### "C) fromppm to mg/m3: mg/m3= (ppm) 

### molecular weight ofthe compound)/(24.45). For methyl iodide: 1ppm = 5.81mg/m3. To convert concentrations in air from pg/m3 to mg/m3:mg/m3= (pg/m3) x (1mg/1,000 pg). 

### (B) Fate and Transportin soil and water
The environmental fate data for iodomethane are also presented in Table 1. The rapid dissipation of iodomethane in both the aerobic soil (MRID 45593707) and anaerobic aquatic 

### (MND 45593708) conditions isprimarily theresult ofvolatilization rather than microbialdegradation. However, carbon dioxide was detected in both studies. It gradually increased to 1.1 percent of the total applied radioactivity by the end of the aerobic soil study and to 2.5 percent of the total applied radioactivity by the end of the anaerobic aquatic study. This indicates that limited microbial degradation of iodomethanemayhave affected soilaerobicand anaerobic metabolisms.Iodomethanewashydrolyzed slowly (94 to 108days) in acidic, neutral, and alkaline conditions at ambient temperature yielding 16 to 18percent ofmethanol (MRID 45593705). Photolysis occursbothin gas and solution phases. The aqueous photolysis half-life for iodomethane in the irradiated solution was 13 days, based on the continuous irradiation used in the laboratory study (MRID 40593706). The major transformation products of aqueous photolysis were methanol and formaldehyde, which increased steadily to maximum concentrations of 18.7% and 36.5% respectively, after 15 days of irradiation. In batch equilibrium studies (MRID 45593709), iodomethane shows low absorption potential in five soils tested. The calculated Q,, 

### , values ranged from 15-59 

### L ~g-l suggest that it has a high mobility in soil. In the field dissipation study (MRID 4559371I), maximum iodomethane concentrations were 4.157 mg a.i./kg (1.3 days) in the 15-30 cm soil depth, 2.677mg a.i./kg(4 days) in the 30-45 cm soil Page 7 of 37depth, and 0.442 mg a.i./kg (4 days) in the 107-122 cm soil depth in California. Following the removal oftarpaulin,theplots were aeratedthroughchiselingtofacilitatethevolatilization ofresidual iodomethane. The concentration ofiodomethanebelow 122cm was negligible (0.011 a.i./kg)at day 8 post-treatment.At the Florida site, maximum iodomethane concentrationswere 10.785mg a.i./kg (0.3 days) in the 30-45 cm soil depth, 8.461mg a.i./kg(1 day) in the 45-61 cm soil depth, and 0.209 mg a.i./kg (14 days) in the 107-122 cm soil depth. Iodomethane was not detected at the end of the study period (90 days). Field dissipation data suggestthat applied iodomethanewas more confined to the layers adjacent to the 30 cm depth of iodomethaneplacement than soil layers below 60 cm. However, since this compound is soluble in water, there is the possibility of leaching through soil profile into ground water ifremoval or slicing ofthetarpaulin coincides with, or isfollowed soonby, a rain event. (C) 

### Fate and Transport in atmosphere
Twofieldvolatilization studies

### (MRID455937 10and45593822) were conductedusing iodomethane, whichwas appliedvia broadcast shank injectionin the bare-ground plot and followed simultaneously with a standard 1mil plastic tarpaulin overthe treated plot. Thevolatilization ofiodomethane

### (MRID 455937 10; methyl iodide; TM-425; technical; analytical purity 99.7%) was determined under field conditions on a sandy loam soil (41.6% sand content) in Watsonville, Californiaand on a loamy sand (sand content 88.0%) soil in Dover, Florida. The sampling intervals for the study were inadequate to accuratelyestablishthe half-life ofthetest substance (> 50% ofthetest material degradedbetween the initial sample at day 0 and the second sample on day 1).

Table 2. Time weighted average iodomethane (TM 425) residue at selected above ground heights in the center of the treated field in Manteca, California.

3-6 hours 6-8 hours 8-19 hours

NA = Not available

Page 8 of 37Another field volatility study was conducted in a bareground plot of low organic matter containing sandy soil (sand content 9 1.0% ) located in Manteca, California 

### (MRID 45 593822). This study includes more frequent sampling intervalsin the first 8 hours and the total mass ofiodomethane lost from the soil was 94% ofthe applied (554 lb or 25 1kg;) after 10 days. The greatest mass loss, 21%, occurred duringthe firstthreehours ofapplication, while a mass loss of4 1 %occurred within the first 24 hours, and a 62% mass loss occurred withinthe first 2 days following application.Rapid diffisions ofappliediodomethanethrough thetarpaulin suggest that the effectiveness ofthetarpaulinto contain the appliedhmigant may have been compromised. There was a slight increasein volatilization when the tarpaulinwas cut open at day 4, but the recorded concentrations ofiodornethanewere well below the concentration on the application day. Table 2 showsthe time-weighted average ofiodomethane level at the center of the treated plot at various heights from the ground surface. These monitoring data in conjunction with time-averaged profiles of wind speed and air temperature were used to calculatethe direct flux of iodomethaneusing 

### ISC dispersion model. Flux rate decreased from 48 1 yg/m2-sduring the 3-hours following application, to 276 yg/m2-sat 3-6 hours, 87 Clg/m2-s at 6-8 hours, and 48 pg/m2-secat 8-19 hours on the application day (Table 3). In the first 12 hours of day 1 (daytime), flux rate had increased to 115 yg/m2-sec,before decreasingto 17 CLg/rn2-sec at 12-24 hours (nighttime) of day 1. Results suggest that volatilization of iodomethane exhibited diurnal fluctuation, with daytime period flux rates greater than nighttime period flux rates.
Table 3 also presents the estimated iodomethaneair concentrations at two different heights from the ground surface at the center of the hmigated field in California. At a height of 30 cm, the estimated concentration ofiodomethanein airwas 921 ppbv (5345 yg/m3) in the first 3 hours after application, 607 ppbv at 3-6 hours, 987 ppbv at 8 to 19 hours, an average of 347 on day 1, and 12 ppbv on day 10.At a height of 80 cm, the concentration ofiodomethane in air was 453 ppbv in the first 3 hours after application, 266 ppbv at 3-6 hours, 182ppbv at 8 to 19hours, an average of 102ppbv on day 1, and 5 ppbv on day 10.

Table 3. Estimated direct flux and air concentrations of Iodomethane (TM 425) at selected above ground heights in the center of the treated field in Manteca, California.

Day 0,O-3 hours Day 0, 3-6 hours Day 0,6-8 hours Day 0,s-19 hours Day 1,O-12hours Day 1, 12 24 hours Day 2,O-12 hours Day 2, 12 24 hours 481 276 87 48 115 17 34 6 Page 9 of 37Table 3. Estimated direct flux and air concentrationsof Iodomethane (TM 425) at selected above ground heights in the center of the treated field in Manteca, California.

Day 3,O-12 hours Day 3, 12 24 hours Day 4,O-12 hours Day 4, 12 24 hours Day 10,O-12 hours Day 10, 12 24 hours 

### (D) Persistence
The distribution and lifetime of CH31in the atmosphere is a factor of the rate of emission and removal, and is important for determining the build-up of the chemical in the atmosphere. To determinethe atmospheric lifetime of CH31, estimates ofremoval 

### [UV absorption cross-section and reaction rate constant of hydroxl (OH)] were obtained from other studies (MRID 45593712). Assuming evenly distributed flux of CH31with latitude, Don Wuebbles and colleagues at the UniversityofIllinois obtained a model-calculated atmosphericlifetimefor iodomethaneof 11.5days. The derived atmospheric lifetime will depend on where emissions occur, with a shorter lifetime derived for emissions in the tropics and a longer lifetime for emissions at high latitudes @on Wuebbles, Personal 

### communication, 2002). Atkinson et al. (1997) reported that iodomethanewill degrade in atmosphere through direct photolysis process, with a lifetime of 2.8 to 5.5 days, but this is based on a crude approach to estimating the atmospheric lifetime for such a short-lived gas (Wuebbleset al., 200 1).Iodomethanewill be also photolyzed at slowerrates with the hydroxyl (OH) radical with roughly an atmospherichalf-life of about 117to 220 days, based on atmospheric average concentration of OH radicals (Brown et al., 1990 and Atkinson et al., 1997).Again, actual lifetime will depend on location of the emissions for such a short-lived gas. As a substance with a short atmospheric lifetime, iodomethane falls into the same category as npropyl bromide which has 

### an atmospheric lifetime of 19days. 

### 7he MontrealProtocolon Substances that Deplete the Ozone Layer to date has not called for the regulation or phase out of these substances. In turn, the EPA under its authorityunder the Clean Air Act has chosen to allow the production, import, and use of these substances. However, there is a disparity in the atmospheric lifetimes, and therefore ozone depletion potential, of these substancesdepending on where they are emitted. The impacts of short-lived substances emitted from the tropical latitudes, which happens to be the general location of developing countries, may actually prove to be consequential. In such an event, it is not clear that the Parties to the Montreal Protocol would require that a stricter set of rules apply to developing countriesthan to developed ones. Thus, even short-lived compounds that Page 10 of 37have minimal impact when emitted from the U. S., could be phased out due to policy considerations by the Parties. (E) 

### Monitoring Data (Air)
TheUnited StatesEnvironmental ProtectionAgency has compiled ambient air monitoring data from several urban and suburban locationsthroughout the United States ofAmerica and calculated a mean concentrationofiodomethanein ambient air of0.02ppbv during 1972-85.Theglobal measurements of iodomethane show that it is uniformly distributed over the ocean, with a range of 0.5-1.0 ppbv (Rasmussen et al., 1982). Brodzinsky and Singh (1982) have also compiled 561 ambient air data from severalurban and rural locationsthroughout the United States ofAmerica for a period of 1983 to 1985. They reported a maximum of 0.08 ppbv with the median concentration of 0.004 ppbv of iodomethane. 

### (F) Ozone Depletion Potential Methyl halide compounds (methyl bromide, methyl chloride, and methyl iodide) are very reactive agents when released into the atmosphere (Redeker et al., 2000). Ozone depletion can be caused by an increaseinthe concentrationofhalogen radicals (chlorine, bromine and iodine)inthe stratosphere. Photodissociation ofCH31 producesiodine radicalsthat canreachthe stratospherein two ways: CH31 can drift into the stratospherebefore photo- dissociation releases iodine radicals (Pathway A), or dissociation can occurin the troposphere and a fraction of the iodineradicals can be transportedinto the stratosphere (PathwayB).Because CH31 is short-lived in the atmosphere, pathway 

### B is likelyto be quite important because the iodine radicals will generally be released in the troposphere, rather than the stratosphere, where the ozone layer is located. Ifiodomethane andlor iodine transportedto the stratosphere, all iodinebecame availablefor freeradical chemistry and it has been calculated that at the altitudes between 15-20 

### krn the efficiency of iodine for ozone destruction is several folds greaterthan that ofchlorine (Solomanet al., 1994; up to 800 times more effective accordingto recent modelling studies ofWuebbles et al., 200 1.)
To simulate the distribution of 

### I,, the Atmospheric and Environmental Research's 2-dimensional chemicaltransport model 

### (AER 2-D CTM) was used 

### (MRID 45593712). The calculation assumes the soluble 

### I, species released (HI, HOI and ION02) are subject to removal by the processes of washout or dry deposition in the troposphere, while the bulk of I, in the stratosphereis in the form of I and 

### 10.Calculated standard washout rate, which has an average first-orderremoval lifetime of 2 to 10 days, and 

### a deposition velocity of 1 cmlsec. The empirical ODP can be defined by the following equation: ODPemp = ODP(trop) 

## + ODP(stratA) 

### + ODP(stratB) where ODP(trop) = ODP of in the troposphere due to 

### I, accumulation, ODP (stratA) = ODP in the stratospheredue to 

### I, that are delivered by pathway A, ODP(stratB) = ODP in the stratospheredue to I, that are delivered by pathway B.

Page 11 of 37All of these pathways need to be considered in deriving the Ozone Depletion Potential for a shortlived gas like iodomethane.
Reliable ODPvalues for CH31 are difficult to obtaindirectly frommodel calculations fortwo reasons: 1)the model calculations showthat the accumulation ofI, inthe troposphereleadsto ozonedepletion in the troposphere, but the model is not capable of resolving variabilities in the troposphere on a regional scale, making the predicted results unreliable. 2) The models have not been tested to determine if they can accurately predict transport of short-lived source gases and their degradation products from the troposphereto the stratosphere.Nonetheless, the recent studies ofWuebbles and colleagues at the University of Illinois (personal communication, 2002) give an ODP for CH31of 0.029 assuming evenly distributed emissionswith latitude. The ODP would be greater in the tropics and smaller than this at high latitudes. Only in the case of emissions in the tropics would there be an ODP approaching 0.1. Zhang et al. (1998) reported that the estimated ODP of iodomethane is less than 0.016, which is well below the 0.65 ODP for methyl bromide and the Class 1 listed ozone depleter compounds ofthe U.S. Environmental Protection Agency. Under Title 

### VI, Section 602 of the Clean Air Act, the US Environmental Protection Agency classified any substance with an ODP 0.2 or greater as Class 1 ozone depleting substance. However, this analysis would not have considered all ofthe pathways, and certainly did not consider that the ODP would be a fbnction of location of the emissions for such a short-lived gas (Wuebbles et al., 2001). (G) Global Warming Potential Radiative forcing is the ability of a gas to absorb infrared radiation (within the atmospheric spectral window of 750cm-1 and 1300 cm-1), changing the balance ofradiation absorbed or emitted by the atmosphere. 

### A gas that strongly absorbs radiation in the atmospheric window, reduces the direct transmission of radiation emitted by the earth to space, enhancing the greenhouse effect (MRID 45593712).
One measure ofthe effectivenessofa gasto act as a greenhouse gas is the change in radiative forcing at the tropopause. Using the 

### IR absorption cross-section derived from the absorption data from EPA7s Officeof Air Quality Planning and Standards 

### (Izttp://m.epa.ov/ttnl'emc/fiirirefcas.htmI), the AER 1-DRC model to calculatethe radiative forcing for CH31,assuming that the concentration ofCH31 in the stratosphere was zero. If the mixing ratio of CH31 decreasedto 5% ofits surfacevalue at the tropopause, the radiative forcing was 2.8

### x 10" Watt m-2 pbbv-' burden. Ifthe CH,I was wellmixed, the radiative forcing was 5.0 

### x 10" Watt m-2 per pbbv burden. For comparison purposes the radiative forcing for methane (CH,) and CH3Brwere 5.0 x 1 Watt m-2 pbbv-' and 1.0

### x 1 0-2 Watt m-2 pbbv-l, respectively. The radiative forcing results and a lifetime of 5.2 days were used to calculate the global warming potential (GWP) with different integration time horizons. In the case in which the mixing ratio of CH31 decreases to 5% of its surfacevalue at the tropopause (radiative forcing is 2.8 x 10" Watt m-2 pbbv-l), the GWP(20), GWP(100) and GWP(5OO) were calculated to be 0.06, 0.02, and 0.01, respectively. If CH31 is assumed to be well-mixed (radiative forcing is 5.0 x loq3 Watt m-2 pbbvql),
Page 12 of 37the GWP(20), GWP(100) and GWP(5OO) were calculated to be 0.11, 0.03, and 0.01, respectively. The calculated values indicatethat iodomethanemay have negligible impact ongreenhousewarming.


### V. WATER RESOURCE ASSESSMENT Rapid volatilization of iodomethane from water and soil surfaces is expected to be an important process dueto a Henry's Law constant of 5.26E-03 atm-m3/mole. Field studies suggestthat volatility yielded 54to 80percent ofappliediodomethaneevenbefore tarpaulinwasremoved.Field dissipation data suggestthat applied iodomethanewas more confined to the soil horizons adjacent to the 30-cm depth of iodomethane placement. In California, hrnigated field was chiseled to aerate the site and enhancedthe volatilizationofresidual iodomethane.Residual concentration of 1 0.011mg a.i./kgon the day 8 and no iodomethane after 15 days were detected below one meter depth. In Florida, low residual concentrations ofiodomethane of I 0.269 mg a.i./kgat day 7 and 10.034 mg a.i./kgat day 28 were detected below one meter depth of the soil profile, which were higher than the California site.No residual iodomethane was detected at the end of the study period (90 days) in either site. Sincethis compound isvery solublein water and has low adsorption into soil, it can potentially leach into shallow ground water and leaky aquifers, especially when removal or slicing of the ground tarpaulin coincides with, or is followed soon by, a rain event. Tier I1 PRZMEXAMS for surface water and Tier I SCIGROW for ground water were used to estimate iodomethane concentrations (Table 4 and 5). Note that these concentrationsarein nanograms per liter (ng/L), orpartsper trillion. Based on environmental fate, the residual contents in soils, and Tier I and I1 models estimated concentrations, EFED does not expect iodomethane to adversely impact ground water or surface water. (B) 

### Estimated Environment Concentration for Drinking Water Assessment
The estimated drinking water concentrations (EDWCs) in surface waters derived from Tier I1 PRZMEXAMS simulationemploying Florida pepper index reservoir scenario and in ground waters calculated from SCIGROW are noted in Table 4. Since iodomethane is a volatile compound, additional input parameters like 

### DAIR (vapor phase diffusion coefficient) and ENPY (enthalpy of vaporization)were activated duringthe PRZM-EXAMS simulation.The assessments werebased on maximum application rate of iodomethane for pepper in Florida. 

### A complete discussion of these models and the associated input parameters and output for each scenario is presented in Appendix 

### A. Thesevalues generallyrepresentupper-bound estimatesof the concentrationsthat might be found in surface water and groundwater due to the use of iodomethane on pepper in Florida.

Table 4. Tier I and I1 Estimated Drinking Water Concentrations of iodomethane

Page 13 of 37 Iodomethane 

### ngn= PPt 1965 6.7 60

### (B) Estimated Environment Concentration for Ecological 

### Risk Assessment
Estimated Environmental Concentrations(EECs)used todetermineacuteand chronic riskstoaquatic organisms were estimated using tomato and pepper scenarios and Tier I1 PRZMEXAMS models. Since iodomethane is a volatile compound, additional input parameters like DAIR (vapor phase diflbsion coefficient) andENPY (enthalpyofvaporization) were activated duringthePRZM-EXAMS simulation.

Table 5. Tier I1 Estimated Environmental Concentrations of iodomethane

California Tomato 

## 1 242 

## 1 1 

## / 383 

## 1 140 

## 1 29 

## 1 10

A complete discussion of these models and the associated input parameters and output for each scenario is presented in Appendix A. The maximum application rate (242 a.i. 1bsIA)forthese crops and the relevant environmental fate parameters for iodomethane were used in PRZMEXAMS screening models. The EECs to be used for ecological risk assessments are presented in Table 5.

Florida Pepper



### Monitoring Data (Surface water and Groundwater)
Iodomethanehas been detected in the surfacewater bodies. Naturally occurring iodomethanein sea water have been interpreted in terms ofphotochemicalproductionmechanisms orin-situ synthesizing by marine organisms. Recent studies (Schall et al., 1994 and Nightingale et al., 1995) have demonstrated that marine organisms like phytoplankton and macro algae are capable ofproducing iodomethane in marine environments. Moore and Zafirou (1994) reported that the mean concentration of 1.6ngll in the seawater samples from the eastern Pacific Ocean. At present time, iodomethane is not included in the Pesticides in Ground Water Database, National Water Quality AssessmentProgram (NAWQA) ofunited StatesGeological Survey

### (www.water.wr.usgs.gov),and it is also not included in the National Pesticide Survey. 242



### VI. ECOLOGICAL HAZARD DATA (A) Summary 1

Available data indicate iodomethane is moderately toxic to birds (bobwhite quail) on both an acute oral and inhalation basis. It is highly toxic on an acute basis to freshwater invertebrates (Daphnia magna) and moderately toxic on an acute basis to fish (rainbow trout). Below is a presentation ofthe EPA's current iodomethane ecological toxicity data base. 942

Page 14 of 37 224 43 15

### (B) Toxicity to Terrestrial Animals i. Birds, Acute and Subacute


### An acute oral toxicity study using the technical grade of the active ingredient (TGAI) is required to establishthe toxicity ofiodomethaneto birds. The avian oralLD,, is an acute, single-doselaboratory study designed to estimate the quantity of toxicant required to cause 50% mortality in a test population of birds. The preferred test species is either the mallard duck, a waterfowl, or northern bobwhite quail, an upland gamebird. TheTGAI is administeredby oral intubationto adultbirds, and the results are expressed asLD,, milligrams (mg) active ingredient (a.i.)per kilogram (kg). Toxicity category descriptions are the following:
If the LD,, is less than 10mg a.i./kg, then the test substance is ve7y highly toxic. If the LD,, is 10-to-50 mg a.i./kg, then the test substance is highly toxic. If the LD,, is 51-to-500 mg a.i./kg, then the test substance is moderately toxic. 

### If the LD,, is 501-to-2,000 mg a.i./kg, then the test substance is slightly toxic. If the LD,, is greater than 2,000 mg a.i./kg, then the test substance ispractically nontoxic.

northern bobwhite quail 99.7 57 moderately toxic 45593716fGallagher & Core (Colinus virginianus) Beavers12001 

### ' Core means study satisfies guideline. Supplemental means study is scientificallysound, but doesnot satisfy guideline. The guideline (71-la) is hlfilled (MRIDs 455937 16).

Two dietary studies using the TGAI are usually required to establish the toxicity of pesticides to birds. However, given the volatility of iodomethane and its proposed use as a soil hmigant under ground that is immediately tarped, these studies are not needed at present for risk assessment.
Because of the volatility of iodomethane, the registrant has submitted an avian inhalation study There is no established guideline (Subdivision 

### E, 1982) for this test type.

Table 8: Avian Acute Inhalation 

### - Technical

Northern Bobwhite Quail 99.7 395 moderately toxic 45593717/Kiplinger/2002 Supplemental (Colinus virginianus) (4-hr. exposure)
Core means study satisfies guideline. Supplemental means study is scientificallysound, but does not satisfy guideline.
Page 15 of 37

### While this study is considered scientifically sound, it is not a guideline study and thus is classified as Supplemental. Iodomethane is considered moderately toxic on an acute basis. (C) Toxicity to Freshwater Aquatic Animals 

### i. Freshwater Fish, Acute


### Two freshwater fish toxicity studiesusing the TGAI are usually required to establish the toxicity of pesticidesto fish. The preferred test species are rainbow trout (a coldwater fish) and bluegill sunfish (a warmwater fish). Results of one of these tests are listedbelow. Thetoxicity category descriptions for freshwater and estuarinelmarinefish and aquatic invertebrates, are defined below in parts per million (pprn). If the LC,, is less than 0. I pprn a. i.,then the test substance is very highly toxic. Ifthe LC,, is 0. I-to-I.0 pprn a. i.,then the test substance is highly toxic. Ifthe LC,, isgreater than I and up through 1Oppm a. i.,then the test substanceismoderately toxic. Ifthe LC,, isgreater than 10 and up through I00pprn a. i.,then the test substance isslightly toxic. If the LC,, isgreater than 100pprn a. i.,then the test substance is practically nontoxic.

RainbowTrout 99.7 1.331 (1.12-1.56) Moderately 45593714/Drottar,et. Core (Oncorhynchussp.)/static-renewal toxic a1.12002



### With an LC,, of 1.33ppm, iodomethane is categorized as moderately toxic to rainbow trout on an acutebasis. The guidelinefor rainbow trout (72-lc) is hlfilled (45593714). Abluegill sunfish study is required for risk assessment and labeling. (ii) Freshwater Invertebrates, Acute


### A freshwater aquaticinvertebratetoxicity test using the TGAI is required to establish the toxicity of iodomethaneto aquatic invertebrates. The preferredtest organismisDaphnzamagna,but earlyinstar arnphipods, stoneflies, mayflies, or midges may also be used.Results ofthistest aretabulatedbelow.

Table 10: Freshwater Invertebrate Acute Toxicitv 

## - Iodomethane Technical

Daphnid 99.7 0.571(0.43-0.79) highly toxic 45593713lDrottaret. Core (Daphnia magna)lstatic- NOEC= 0.073 a1.1200 1 renewal

- - - - Core (studysatisfies guideline). Supplemental (study is scientificallysound, but does not satisfy guideline). 

### With an EC,, of 0.57 ppm, iodomethane is categorized as highly toxic to freshwater aquatic invertebrates on an acute basis. The guideline (72-2a) is hlfilled (MRID 

### 450899 14). Page 16 of 37

### VII. AQUATIC EXPOSURE AND RISK ASSESSMENT
The highest acute aquatic exposure estimate (EEC) for iodomethane presented in Table 5 above is 0.942 ppb, for Florida peppers. Comparing this value to the acute toxicity value for the most sensitivetest species

### (D. magna, 570 ppb) produces a maximum risk quotient of 0.0017. This iswell below the lowest acute aquaticLevel-of-Concern (LOC) of0.05 (endangered species). Thus,EFED does not consider iodomethane 

### to pose an acute risk to aquatic invertebrates or fish. EFED also believes that the Henry's Law Constant of 5.23E-03atm-m3/molefor iodomethane suggest that chronic exposuresto the aquatic invertebratesand fish are not likely to occur. Although methanol and formaldehyde are major transformation products of aqueous photolysis of iodomethane, such transformationis expected to be minimal due to the primary route of dissipationto the air.


### VIII. TERRESTRIAL EXPOSURE AND RISK ASSESSMENT
It appears that the principal risk to terrestrialwildlife will be from the inhalation of air residues near the treated sites. Estimated air concentrations are the highest on the application day, despite the mandatory tarping oftreated sites. Estimated concentrationsrange up to 0.987 pprn at 30 cm above the tarp and up to 0.453 pprn at 80 cm above the tarp, based on submitted data. These values are estimated flux values based on cumulative charcoal tube residues collected following an application of 242 lb ailA (measured rate). This measured applicationrate is just above the proposed maximum label rate of 23 5 lb ailA.
The avian acuteinhalationLC,,, based on afour-hour exposure ofbobwhite quail, is 395ppm. Given that this is over 400X the peak estimated residues above, it does not appear that there is a substantial risk of acute lethalityto birds, even ifthey do fly above or land on the tarp on the day of application. The lowest test concentration was 344 ppm, where sublethal effects were seen, including ataxia, gasping, and rales. Given that a No Effect Level was not obtained, it is not possible to say with certainty that there would be no sublethal effects at the expected maximum exposure levels above. However, given that the lowest test level was approximately 350X greater than the expected maximum residues, it is quite possible that there would be no sublethal effects as well. Iodomethane is also a short-lived chemical (direct photolysis, 11 1.5days) in the atmosphere, therefore, there is low potential for chronic risk to birds and mammals.
Because ofdispersion and photolysis ofiodomethane,organismsoffthetreated sites (e.g.,birds, wild mammals) would likely be exposed to substantially lower residues and risk than those immediately above the tarp on the day of application. Mammals appear to be less acutely sensitive than birds to iodomethane.Thereported mammal acuteinhalationLC50is 4.0mgL(8112102HEDMemorandum; Appendix B), which is equivalentto 689 ppm. The HED recommended endpoint for human health risk assessment for all exposure time intervals is the inhalationmaternalNOAEL in a developmental toxicity study with femaleNew Zealand White rabbits, which is 10 pprn (8112102 HED Memorandum). This study included exposure of six hourslday on gestationdays 6through 28 (ibid.). It appears that 10pprn is above acutewild mammal exposure and thus substantial risk is not expected.
Page 17 of 37It is not expected that there would be any major use by wildlife of the soil under the tarp. However, some wildlife (e.g., amphibians)may possibly seek dark, warm, moist areas that such an area might provide. Any such use could possibly result in a lethal exposure, due to hrnigant concentrations. Guideline plant studies (seedgerminationlseedlingemergence,vegetativevigor, aquaticplant growth) are required to complete a risk assessment to plants. It is assumed, given the label reference to potential "...damagecaused by drift to other plants or crops", that iodomethane could be hazardous to plants off-site. However, based in part on a prior draR biological opinion fromUSFWS for tarped uses of methyl bromide, the Field and External Affairs Division (FEAD) does not presently have a concernfor the proposed tarpeduses ofiodomethaneand endangered species, including endangered plants (3120103 note fkom 

### A. Stavola, FEAD).

Page 18 of 37

### REFERENCES Atkinson, R., D.L.Baulch, R.A. Cox, R.F. Hampson Jr., J.A. Kerr, M.J.Rossi, and J. Troe, (1997) Evaluatedkinetic, photochemical and heterogeneous data for atmosphericchemistry. J.Phys. Chem. Ref. Data, 26 (3), 521 - 1011. Brodzinsky R. and H.B. Singh. 1982.Volatile organic chemicals in atmosphere: an assessment of available data. SRI Intr Contract 68-02-3452. Brown, A.C., Canosa-Mas, C.E., R.P. Wayne. 1990. A kinetic study of the reactions of OH with CH31and CF31.AtmosphericEnvironmental 24:361-367. Moore, R.M. and O.C.Zafirou. 1994.Photochemical production ofmethyl iodidein sea water. 

### J. of Geophy. Res. 99: 16415-16420. Nightingale, P.D., Malin, G., and P.S. Liss. 1995.Production of CHC13 and other low molecular weight halocarbons by some species of macroalgae. Limnology and Oceanography40:680-689. Rasmussen,R.A.Khalil, M.A.K.,Gunawardena,R, and S

### .D.Hoyt. 1982. Atmosphericmethyliodide. J. of Geophy. Res. 87: 3086-3090. Redeker, K.R., N.Y. Wang, J.C. Low, 

### A. Mcmillan, S.C. Tyler, R. J. Cicerone. 2000. Emissions of methyl halides and methane from rice paddies. Science 290: 966-979. Schall,C.,

### F.Laturnus, and K.G.Heumann. 1994. Biogenicvolatile organoiodineand organobromine compounds released from polar macroalgae. Chemosphere 28: 1315-1324. Soloman, 

### S., R.R. Garcia, and A.R. Ravishankara. 1994. On the role of iodine in ozone depletion. J. Geophy. Res. 99: 20491-20499. Wuebbles, 

### D. J., 

### K. 

### 0. Patten, M. T. Johnson, and R. Kotamarthi. 2001. New methodology for OzoneDepletion Potentials of short-lived compounds:n-Propyl Bromide as an example. J. Geophys. Res., 106, 14551-14571. Zhang, W., M.E.McGiffen (Jr.), J.

### 0.Becker, H.O. Ohr, J. J. Sims, and S.D. Campbell. 1998.Effect of soil physical factors on methyl iodide and methyl bromide. Pestic. Sci. 53:71-79.

Page 19 of 37

### Page 7 

### of 8

- - -- , Table Al. Status of Environmental fate and ecological effect data requirements for iodomethane

Date: May 08,2003 IODOMETHANE Case No: DATA REQUIREMENTS FOR THE Chemical No: 000011 ENVIRONMENTAL FATE AND EFFECTS DIVISION

Data Requirements

141-1 Honey Bee Acute Contact 141-2 Honey Bee Residue on Foliage 141-5 Field Test for Pollinators Composition1

TGAI

(TEP)

5158.290ENVIRONMENTAL FATE Degradation Studies-Lab: Use Pattern2

1,2,3
1,2,3
1,2,3

160-0Global warming and ozone depletion potential 161-1 Hydrolysis 161 -2 Photolysisin Water 161-3Photolysis on Soil Does EPA Have Data To Satisfy This Requirement? (Yes, No, Partially)
No

No

No

TGAI

TGAI TGAI TGAI Metabolism Studies-Lab: Bibliographic Citation

Not applicable
Not applicable
Not applicable

1,2,3
1,2,3 1,2,3 1,2,3

162-1 Aerobic Soil Metabolism 162-2 Anaerobic Soil Metabolism 162-3 Anaerobic Aquatic Metabolism 162-4Aerobic Aquatic Metabolism Study Classification

Not applicable

Not applicable
Not applicable

YES

YES Partially Not applicable

TGAI

TGAI

TGAI

TGAI Additional Data Required Under FIFRA 3(~)(2)(B)?

NO'

No

No

Mobility Studies: 45593712

45593705 45593706 Not Applicable

1,2,3
1,2,3
1,2,3
1, 2, 3

163-1 Mobility (unaged) 163-1 Mobility (aged) 163-2 Laboratory volatility 163-3Field volatility Special

Core Core Not Applicable

YES

YES

YES

YES

TGAI TGAI

TG AI No

No No No

Dissipation Studies-Field: 45593707

45593708

45590708

45590708

1,2,3 1,2,3 1,2,3 1,2,3

164-1 Terrestrialfield dissipation Core

Core

Core

Core

Partially

No Not applicable YES

TGAI No

No

No

No

Accumulation Studies: 45593709 Not applicable Not Applicable

45593710

1,2,3

165-1 Fish bioaccumulation Core Not applicable Not Applicable Core

YES

1,2,3 No No No No

Ground Water Monitoring Studies: 45593711

Not Applicable

166-1 Small scale prospective groundwater study. Core

Not Applicable

1,2,3 No

Not Applicable

No No

Not Applicable Not Applicable No1. Composition: TGAI=Technical grade of the active ingredient; PAIRA=Pureactive ingredient, radiolabeled; TEP=Typical end-use product Table Al. Status of Environmental fate and ecological effect data requirements for iodomethane
Date: May 08,2003 IODOMETHANE Case No: DATA REQUIREMENTS FOR THE Chemical No: 000011 ENVIRONMENTAL FATEAND EFFECTS DMSION

2. Use Patterns: l=Terrestrial/Food;2=TerrestriaVFeed; 3=Terrestrial Non-Food; 4=Aquatic Food; 5=AquaticNon-Food (Outdoor); 6=AquaticNonFood (Industrial); 7=AquaticNon-Food (Residential); I=GreenhouseFood; 9=GreenhouseNon-Food; lO=Forestry, 1l=Residential Outdoor; 12=IndoorFood; 13=IndoorNon-Food; 14=IndoorMedical; 15=IndoorResidential
3. This study is not required due to the high volatilityofiodomethane. Additional Data Required Under FIFRA 3(~)(2)(B)?

4. This study is required for risk assessment and labeling.

Data Requirements

5. At thistime, available aquaticEECs are less than 0.01 ofthe lowest acute aquatictoxicity value and it does not appearthat these studieswill be needed. However, they are resewed pending any fhture EEC calculation andlor further analysis of aquaticexposure potential, as well as submissionand review ofthe acutebluegill study. Bibliographic Citation

$158.440 SPRAY DRIFT

6. These studies are required since plants are amongthe target species and there are phytotoxicity warnings onthe proposed labeling. Study Classification Does EPA Have Data To Satisfy This Requirement? Wes, No, Partially) Composition1

NO

NO Use Pattern2

201-1 Droplet Size Spectrum
202-1 Drift Field Evaluation Not Applicable
Not Applicable Not Applicable

Not Applicable 1,2,3

1,2,3 NO

NOAPPENDIX A Modeling Inputs/Outputs for Ecological and Drinking Water Risk Assessment
The maximum application rate and relevant environmental fate parameters for iodomethane were used in the two screening models PRZMIEXAMS and SCIGROWfor iodomethane concentrations in surfacewater and groundwater,respectively. The outputs of the two screening models represent estimates of the concentrationsthat might be found in surface water and groundwaterdue to the use of iodomethane on selected crops. Estimation of surface water exposure concentrations for Ecological Risk Assessment
The maximum application rate and relevant environmental fate parameters for iodomethane were used in the PRZMIEXAMS Tier I1 model for EECs in the surface water. The output of the screening modelrepresent anupper-bound estimate ofthe concentrations ofiodomethane that might be found in surface water due to use of iodomethane on selected crops. The weather, agricultural practices, and iodomethane applications were simulated over 30 years so that the ten year excedence probability at the site could be estimated. The EECs generated in this analysis were estimated using PRZM 3.12 (Pesticide Root Zone Model ) for simulating runoff and erosion from the agricultural field and EXAMS 2.98.5 (Exposure Analysis Modeling System) for estimating environmental fate and transport in surfacewater. TableA-1 summarizesthe input values used in the selected crops and models run for PRZMIEXAMS.
Estimation of Surface Water Exposure Concentrations for Drinking Water Assessment PRZMIEXAMS modeling using the Index Reservoir 

### (IR) and the Percent Crop Area (PCA) adjustment was used to estimate concentrationsin surface water used as a source ofdrinkingwater. The index reservoir represents a watershed that is more vulnerable than most used as drinkingwater sources. It was developed from a real watershed in western Illinois. The index reservoir is used as a standard watershed that is combined with local soils, weather, and cropping practices to represent a vulnerable watershed for each crop that could support a drinking water supply. If a community derives its drinking water from a large river, the estimated exposure would likely be higher than the actual exposure. Conversely, a community that derives its drinking water from smaller bodies of waterwith minimal outflowwould likely get higher drinkingwater exposure than estimatedusing the index reservoir. Areas with a more humid climate that use a similar reservoir and golf coarse turf managementpractices would likely get more pesticides in their drinking water than predicted levels.
A single steady flow has been used to represent the flow through the reservoir. Discharge fromthe reservoir also removes chemical from it sothis assumption will underestimateremoval from the reservoir during wet periods and overestimatesremoval during dry periods. This assumption can both underestimate or overestimate the concentration in the reservoir depending upon the annual precipitation pattern at the site. The index reservoir scenario uses the characteristic of a single soil to represent all soils in the basin. Soils can vary substantially across even small areas, thus, this variation is not reflected in these simulations.
Page 20 of 37The index reservoir scenario does not consider tile drainage. Areas that are prone to substantial runoff are often tile drained. This may underestimate exposure, particularly on a chronic basis (the watershed on which the IR is based had no documented tile drainage). Additionally, EXAMS is unable to easily model spring and fall turnover which would result in complete mixing of a chemical through the water column duringthese events. Because ofthis inability, Shipman City Lakehas been simulatedwithout stratification. There is data to suggestthat ShipmanCityLake does stratify in the deepest parts of the lake at least in some years. This may result in both an over and underestimation ofthe concentration in drinking water depending upon the time ofthe year and the depththe drinkingwater intake is drawing fi-om.A full descriptionof the Index Reservoir isprovided in the 

### "Guidance for Use of the Index Reservoir inDrinking Water Exposure Assessment" from EFED upon request. Development a Percent CropArea (PCA), watershed-based adjustmentfactorforthepercent of land in production for a specific crop, for Cherrylstonefruits has not been performed. The SAP recommended against the use ofthe PCA for 'minor7crops because it believed that the scale of the watershed size used to develop the PCA (8-digit HUC) wastoo largeto capture each drinkingwater watershed and the resulting PCAs would likely be highly inaccurate and not conservative (for the purpose of PCA development, cherrylstone fruits can be considered a minor crop). In the absence of a crop specific PCA, a default PCA of 0.87is currentlybeing used.
Themaximum applicationrate andrelevant environmentalfateparametersfor cyprodinil were used in the PRZMEXAMS Tier 

### I1 model for EDWCs in the surface water. The output of the screening model represent an upper-bound estimateofthe concentrations ofcyprodinilthat might be found in surface water due to use of cyprodinil on Florida cabbage (Table A-6). The weather, agricultural practices, and cyprodinil applicationswere simulated over 30 years so that the ten year excedence probability at the site could be estimated. The EDWCs generated in this analysis were estimated using PRZM 3.12 (PesticideRoot Zone Model )for simulatingrunoffand erosionfi-om the agricultural field and EXAMS 2.98.5 (Exposure Analysis Modeling System) for estimating environmental fate and transport in surfacewater. TableA-1 summarizesthe input values used in the Florida cabbage and models run for PRZMIEXAMS.

Table A-1. PRZMIEXAMS Input Parameters for Iodomethane I I Parameters 

### ( Values & Units 

### ( Sources Molecular Weight 141.94 g Mole'' Registrant Data Vapor Pressure 25°C 405.9 mm Hg @ 250C Product Chemistry Water Solubility @ pH 7.0 and 25°C 1420 mgL @ 250C MRID 45593705 Henry's law constant 5.26E-03atm-m3/mole www.toxnet.nlm.nil.gov Air Diffusion Coefficient 5345 cm21day Calculated Enthalpy of vaporization 20 kcallmol PRZM Standard Hydrolysis Half-Life (pH 7) 94 days MRID 45593705 Aerobic Soil Metabolismt,, 0 .25dayst MRID 45593707$

Page 2 1 of 37Table A-1. PRZMIEXAMS In~ut Parameters for Iodomethane

Direct Aqueous Photolysis 13.0days MRID 45593706 Soil Water Partition Coefficient 34.8 L Kg-' (Mean KO,) MRID 45593709 CROP 

### MANAGEMENT Parameters

Florida Tomato Modeling scenario j Riviera Sand 

### - MLRA 1564,Florida

................................................................................................................................... Culture type (Weed and moisture control) 

### i Plastic Tarp

........................................................................ d ..........................................................................................

Anaerobic- Aquatic metabolism:for entire 5.0 days? MRID 45593708t sedimentJwater system Values & Units

Pesticide application frequency and rate 1 x 242.0 (lb a.i./A) Registrant Provided Sources

Application Date 37694 Registrant Provided ApplicationMethod Ground Injection Registrant Provided Spray Efficiency 100% EFED Spray Drift None Standard assumption

.................................................................................................................................................................

t = Input half-life was calculated from reported half-livesaccordingto Guidancefor selectinginput parameters in modeling for environmental fate and

transport ofpesticides.Version 11. December4,2001.



### Estimation of Ground Water Concentrations for Drinking Water Assessment
SCIGROWis a regression-basedmodel that provides a groundwater screening exposurevalue tobe used in determining the potential risk to human health from drinking water contaminated with the pesticide. Since the SCI-GROW concentrations are likely to be approached in only very small percentage ofdrinkingwater sources(i.e.highlyvulnerable aquifers), it is not appropriatetouse SCIGROW for national or regional exposure estimates.
SCIGROW estimates likely groundwater concentrations if the pesticide is used at the maximum allowable rate in areas where groundwater is exceptionally vulnerable to contamination. In most cases, a large majority of the use area will have groundwater that is lessvulnerable to contamination than the areasused to derive the SCIGROW estimate.

Table 2. SCIGROW Input Parametersfor Iodomethane
I I Parameters 

### ( Values & Units 

# I sources Aerobic Soil Metabolism t,,t 0.25days MRID 45593707% Soil Water Partition Coefficient 34.8L Kg-'

.................

(Mean K ) MRID 45593709

...................................................... ............ oc Pesticide application ratelyear 1 x 242.0 (lb a.i./A) Registrant Provided


### Page 22 

### of 37

### Attachments (1) PRZMIEXAMS Model 

### Output for Ecological Risk Assessment
Florida Pepper Chemical: Iodomethane PRZM environment: FLpeppersC.txt EXAMS environment: pond298.e~ Metfile: w12844.dvf ApplicationMethod: Ground Injection ApplicationRate: 1X 242 ai.lbs/A

Year Peak 1961 0.00035 1962 1.193-10 1963 6.733-14 1964 0.003237 1965 6.353-25 1966 3.953-19 1967 3.223-16 1968 0.1735 1969 0.000863 1970 4.053-11 1971 9.153-27 1972 1.833-18 1973 6.953-13 1974 41.98 1975 3.403-23 1976 4.323-40 1977 0 1978 0 1979 0 1980 9.223-22 1981 0.000995 1982 2.383-12 1983 0.9544 1984 7.083-09 1985 1.623-06 1986 1.843 1987 0.8319 1988 1.303-11 1989 1.233-19 1990 6.443-20

Sorted results Prob. Peak 0.03 41.98 0.06 1.843 0.10 0.9544 0.13 0.8319 0.16 0.1735 Water segment concentrations (ppb) 96 hr 21 Day 60 Day 90Day 0.00007 0.00001 0 0 2.923-11 5.653-12 1.983-12 1.323-12 1.713-14 3.383-15 1.183-15 7.893-16 0.000686 0.000131 4.593-05 3.063-05 5.883-25 3.333-25 1.403-25 9.393-26 1.323-19 2.673-20 9.333-21 6.223-21 1.023-16 2.053-17 7.173-18 4.783-18 0.04365 0.008431 0.002951 0.001967 0.000218 4.213-05 1.473-05 9.813-06 9.253-12 1.773-12 6.213-13 4.143-13 2.883-27 5.943-28 2.083-28 1.393-28 5.523-19 1113-19 3.893-20 2.593-20 1.663-13 3.253-14 1.143-14 7.593-15

8.59 1 .642 0.5747 0.3831 2.483-23 1.193-23 4.773-24 3.193-24 3.993-40 2.343-40 1.013-40 6.733-41 0 0 0 0 0 0 0 0 0 0 0 0 2,813-22 5.643-23 1.983-23 1.323-23 0.000232 4.463-05 1.563-05 1.043-05 4.933-13 9.463-14 3.313-14 2.213-14

0.2293 0.04415 0.01545 0.0103 1.853-09 3.793-10 1.333-10 8.853-11 3.513-07 6.713-08 2.353-08 1.573-08

0.4628 0.08907 0.03118 0.02078 0.1796 0.0344 0.01204 0.008026 2.913-12 5.573-13 1.953-13 1.303-13 3.693-20 7.423-21 2.603-21 1.733-21 1.873-20 3.763-21 1.323-21 8.783-22

96hr 21 Day 60Day 90Day 8.59 1.642 0.5747 0.3831 0.4628 0.08907 0.03118 0.02078 0.2293 0.04415 0.01545 0.0103 0.1796 0.0344 0.01204 0.008026 0.04365 0.008431 0.002951 0.001967 

### Page 23 

### of 37 Yearly 7.993-07 3.253-13 1.953-16 7.533-06 2.323-26 1.533-21 1.183-18 0.000484 2.423-06 1.023-13 3.443-29 6.383-21 1.873-15 0.09447 7.873-25 1.683-41 0 0 0 3.243-24 2.573-06 5.443-15 0.00254 2.183-11 3.863-09 0.005125 0.001979 3.203-14 4.27000e-22

2.163-22
Yearly 0.09447 0.005125 0.00254 0.001979 0.000484Inputs generaged by pe4.plAverage of yearly averages: .8-January-2003

California Tomato Chemical: Iodomethane PRZM environment: CAtomatoC.txt EXAMS environment: pond298.e~ Metfile: w93193.dvf Application Method: Ground Injection Application Rate: 1x242 a.i. lbs/A

Year 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 Water segment concentrations@pb) Peak 96 hr 21 Day 60 Day 90 Day Yearly 3.903-17 2.603-17 7.50E-18 2.643-18 1.763-18 4.343-19 1.673-16 7.633-17 1.813-17 6.333-18 4.223-18 1.043-18

0.7684 0.2743 0.05596 0.01959 0.01306 0.00322 1.583-18 1.343-18 8.733-19 4.453-19 3.053-19 7.533-20 3.233-31 3.043-31 2.123-31 1.08331 7.36332 1.823-32 0 0 0 0 0 0 0 0 0 0 0 0 0.0522 0.01742 0.003497 0.001224 0.000816 0.000201 4.513-20 3.913-20 2.583-20 1.313-20 9.003-21 2.233-21 1.24332 1.043-32 6.543-33 3.19333 2.173-33 5.373-34 0 0 0 0 0 0 0 0 0 0 0 0 Page 24 of 371973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 Sorted results Prob. 0.03 0.06 0.1 0.13 0.16 0.19 0.23 0.26 0.29 0.32 0.35 0.39 0.42 0.45 0.48 0.52 0.55 0.58 0.61 0.65 0.68 0.71 0.74 0.77 0.81 0.84 0.87 0.90 0.94 0.97 0.10 Peak 27.92 0.7684 0.3982 0.2422 0.0522 0.01037 0.000149 1.643-11 2.793-13 7.803-14 2.343-16 1.673-16 3.903-17 1.583-18 4.463-19 4.513-20 3.473-21 4.253-23 2.053-27 2.483-29 3.23331 1.24332 5.18335 9.053-39 1.403-42 0 0 0 0 0 0.3826 21 Day 1.632 0.05596 0.03016 0.01776 0.003497 0.000883 1.033-05 1.113-12 2.513-14 7.243-15 2.063-17 1.81E-17 7.503-18 8.733-19 4.063-20 2.583-20 2.353-21 3.823-24 1.193-27 1.443-29 2.12331 6.54333 2.713-35 5.143-39 1.403-42 0 0 0 0 0 0.02892 Page 60 Day 90 Day 0.5714 0.3809 0.01959 0.01306 0.01056 0.007037 0.006216 0.004144 0.001224 0.000816 0.000309 0.000206 3.613-06 2.413-06 3.883-13 2.593-13 8-783-15 5.853-15 2.533-15 1.693-15 7.213-18 4.813-18 6.333-18 4.223-18 2.643-18 1.763-18 4.453-19 3.053-19 1.423-20 9.473-21 1.313-20 9.003-21 1.173-21 7.973-22 1.343-24 8.913-25 5.923-28 4.033-28 7.213-30 4.923-30 1.083-31 7.363-32 3.193-33 2.173-33 1.31335 8.92336 2.60339 1.77339 0 0 0 0 0 0 0 0 0 0 0 0 0.010126 0.006748 Average ofyearly averages: 25 of 37 Yearly 0.09392 0.00322 0.001735 0.001022 0.000201 5.083-05 5.933-07 6.383-14 1.443-15 4.173-16 1.193-18 1.043-18 4.343-19 7.533-20 2.343-21 2.233-21 1.963-22 2.203-25 9.923-29 1.223-30 1.82332 5.373-34 2.203-36 4.373-40 0 0 0 0 0 0 0.001664 0.003338(11) 

### PRZMEXAMS Model Output for Drinking Water Assessment (Surface Water)
Florida Pepper Chemical: Iodomethane PRZM environment: FLpeppersC.txt EXAMS environment: ir298.exv Metfile: w12844.dvf Application method: Ground Injection Application Rate: 242 a.i. lbs/A Water segmentconcent~ Year Peak 96 hr 21 Day 1961 0.000839 0.000162 3.093-05 1962 2.863-10 6.513-11 1.263-11 1963 1.613-13 3.753-14 7.353-15 1964 0.00776 0.001522 0.000291 1965 9.263-25 8.533-25 4.863-25 1966 9.473-19 2.983-19 5.963-20 1967 7.713-16 2.313-16 4.603-17 1968 0.4159 0.09522 0.01828 1969 0.00207 0.000476 9.153-05 1970 9.713-11 2.043-11 3.913-12 1971 2.203-26 6.513-27 1.323-27 1972 4.383-18 1.253-18 2.493-19 1973 1.673-12 3.133-13 5.993-14 1974 101 19.11 3.646 1975 3.753-22 2.773-22 1.353-22 1976 1.073-38 9.763-39 5.753-39 1977 0 0 0 1978 0 0 0 1979 0 0 0 1980 2.213-21 6.353-22 1.263-22 1981 0.002387 0.000511 9.793-05 1982 5.703-12 1.103-12 2.113-13 1983 2.288 0.5027 0.09632 1984 1.693-08 4.133-09 8.303-10 1985 3.873-06 7.703-07 1.473-07 1986 4.418 1.014 0.1943 1987 1.995 0.4087 0.07813 1988 ( 3113-11 6.513-12 1.253-12 1989 2.963-19 8.383-20 1.673-20 1990 1.543-19 4.323-20 8.603-21 Sorted results Prob. Peak 96 hr 21 Day 0.03 101 19.11 3.646 0.06 4.418 1.014 0.1943 0.10 2.288 0.5027 0.09632 0.13 1.995 0.4087 0.07813 0.16 0.4159 0.09522 0.01828 0.19 0.00776 0.001522 0.000291 0.23 0.002387 0.000511 9.793-05 0.26 0.00207 0.000476 9.153-05 -ations @pb) 60 Day 1.083-05 4.393-12 2.573-15 0.000102 2.073-25 2.093-20 1.613-17 0.006398 3.203-05 1.373-12 I4.633-28 8.723-20 2.103-14

1.276 5.473-23 2.513-39 0 0 0 4.413-23 3.433-05 7.373-14 0.03371 2.913-10 5.153-08 0.06799 0.02735 4.373-13 5.843-21 3.013-21

60 Day 1.276 0.06799 0.03371 0.02735 0.006398 0.000102 3.433-05 3.203-05 90 Day 7.213-06 2.933-12 1.723-15 6.783-05 1.393-25 1.393-20 1.073-17 0.004265 2.133-05 9.113-13 3.093-28 5.813-20 1.403-14 0.8508 3.663-23 1.683-39 0 0 0 2.943-23 2.283-05 4.913-14 0.02248 1.943-10 3.433-08 0.04533 0.01823 2.913-13 3.893-21 2.013-21

90 Day 0.8508 0.04533 0.02248 0.01823 0.004265 6.783-05 2.283-05 2.133-05 Yearly 1.783-06 7.223-13 4.233-16 1.673-05 3.423-26 3.433-21 2.643-18 0.001049 5.263-06 2.253-13 7.633-29 1.433-20 3.453-15

0.2098 9.033-24 4.133-40 0 0 0 7.223-24 5.633-06 1.213-14 0.005542 4.763-11 8.473-09 0.01118 0.004495 7.163-14 9.603-22 4.953-22
Yearly 0.2098 0.01118 0.005542 0.004495 0.001049 1.673-05 5.633-06 5.263-06 Page 26 of 37Average ofyearly averages: Inputs generaged by pe4.pl- 8-January-2003

Estimated Drinking Water Concentration (EDWC)
Acute EEC = (1110 peak value)( percent crop area)

= ( 2259 ng/L)(0.87) =I965 ng/L
Non-cancer Chronic EEC =(I110 yearly value)@ercentarea area) (5.4 ng/L)(0.87) =4.70 ng/L Cancer chronic EEC = (Mean of annual value)@ercentcrop area) (7.7 ng/L)(0.87) = 6.7 ng/L



### Page 27 of 37

### (III) SCIGROW Model Output for Drinking Water Assessment (Ground Water)

RUN No. 1 FOR Iodomethane INPUT VALUES

APPL (#/Ac) APPL. URATE SOIL SOIL AEROBIC RATE NO. (#/Ac/YR) KOC METABOLISM (DAYS)
242.000 1 242.000 34.8 .25
GROUND-WATER SCREENING CONCENTRATIONS IN PPB

Page 28 of 37

### APPENDIX B

TXR NO. 0051037


### DATE: August 12,2002



### MEMORANDUM

SUBJECT: Iodomethane 

### - Report ofthe Hazard Identification Assessment Review Committee.


### FROM: John E.Whalan, Toxicologist Registration Action Branch 2 Health Effects Division (7509C)


### THROUGH: Jess Rowland, Co-Chair and Elizabeth Doyle, Co-Chair Hazard Identification Assessment Review Committee Health Effects Division (7509C)


### TO: Mary 

### L. Waller, PM 12 Registration Division (7505C)
PC Code: 000011
On July 30,2002, the Health EffectsDivision (HED)Hazard IdentificationAssessment Review Committee 

### (HIARC) reviewed the recommendations of the toxicology reviewer for iodomethane with regard to the toxicological endpoint selectionfor use as appropriate in occupational and bystander risk assessments. The potential for increased susceptibility of infants and children from exposure to iodomethane was not considered because there will be no residue on food. The conclusions drawn at this meeting are presented in this report.

Page 29 of 37

-- .=#. ~wA*.- .- - - -- - - - ---- -

### CommitteeMembers in Attendance
Members present were: William Burnam Pamela Hurley Elizabeth Mendez John Liccione Jess Rowland Jonathan Chen Brenda Tarplee Member(s) in absentia: Elizabeth Doyle David Nixon Ayaad Assaad Steve Knizner Sue Makris
Data evaluation prepared by:
John E. Whalan, RAB2


### Also in attendance were: Alan Levy, RAE32

Data Evaluation / Report Presentation

-- 

### John 

### E.Whalan Toxicologist

Page 30 

### of 37

- -- -- . - ----- -

### INTRODUCTION On July 30, 2002, the Health Effects Division (HED) Hazard IdentificationAssessment Review Committee (HIARC) reviewed the recommendations of the toxicology reviewer for iodomethanewith regard to the toxicological endpoint selectionfor use as appropriatein occupational and bystander risk assessments. The potential for increased susceptibility of infants and children from exposure to iodomethane was not considered because there will be no residue on food.
Iodomethane is a methyl bromide alternativethat does not affect stratospheric ozone. Arvesta Corporation (formerly TomenAgro) has requested the registration of iodomethane as a pre-plant soil hmigant for use on strawberries and tomatoes to control soil-borne diseases, nematodes, and weed seeds. It can be injected into fields with the same equipment used for methyl bromide. Iodomethane has a higher boiling point than methyl bromide (42.5"C v 3.6"C), and one-fourth the vapor pressure (398 mmHg v 1600 mmHg at 20°C).


### Names: Description: CAS #: 

### Molecular Weight: Melting Point: Boiling Point: Vapor Pressure: Specific Gravity: TLV-TWA Structure: Iodomethane, methyl iodide Deep yellow, translucent liquid 74-88-4 141.95g/Mol -66.5"C 42.5"C 398 mmHg 2.28 at 20°C (2001 O ACGIH) 2 ppm (12 mg/m3) 

# I-CH,

The toxic mode of action on target pests, laboratory animals, and humans is not known. Because there are no food residues in crops grown in treated soil, this is not a food use. Although there are no residential uses, homes and businesses adjacent to a treated field can be exposed to off-gassed iodomethane. Proposed 

### iodomethane:chloropicrin formulationsinclude 98:2, 50:50, and 25:75. Formulating with chloropicrin allows much less iodomethaneto be used.


### I. FOPA HAZARD CONSIDERATIONS
There are no FQPA considerations because iodomethane is a non-food use and there are no residential uses.

1. 

### Acute Reference Dose (am) 

### - Because there are no food uses, an acute 

### RfD was not established.
2. 

### Chronic Reference Dose (cRfD) 

### - Because there are no food uses, a chronic

### RfD was not established. Page 3 1 of 373. -sure: Short-Term (1-30 days) 

## - There are no residential uses and no potential for exposure to infants or children, so an oral dose and toxicity endpoint were not selected.
4. Incidental Oral Exposure: Intermediate-Term (1

# - 6 Months) 

### - There are no residential uses and no potential for exposureto infants or children, so an oral dose and toxicity endpoint were not selected.
5. Dermal Absorption 

### - Not applicable.
6. Dermal Exposure: Short-Term (1- 30 davs) Exposure 

### - The use pattern will not result in dermal exposure, so a dermal dose and toxicity endpoint were not selected.
7. Dermal Exposure: Intermediate-Term (1 

## - 6 Months) 

## - The use pattern will not result in dermal exposure, so a dermal dose and toxicity endpoint were not selected.
8. Dermal Exposure Long-Term (> 6 Months) 

### - The use pattern will not result in dermal exposure, so a dermal dose and toxicity endpoint were not selected.
9. Inhalation Exposure: All-Time Intervals and All Populations Study Selected: Inhalation Developmental Toxicity Study in Rabbits fj870.3700


### MRID No.: 4559381 1
Executive Summary: In a developmental toxicity study 

### (h4RID 455938 1 1), groups of 24 female New Zealand White rabbits were dynamically exposed to iodomethane vapor (Lothatch # 007403102; 99.6% a.i.)in whole-body inhalation chambers at analytical concentrations of 0, 2, 10, or 20 ppm (0, 0.012, 0.058, or 0.12mgL1day) six hours per day on gestation days (GDs) 6 through 28. All surviving does were sacrificed on GD 29, and their fetuses were removed by cesarean section and examined.
No mortalities occurred during the study. When compared to concurrent controls, no treatmentrelated changes were observed in body weights, body weight gains, food consumption, sex ratios, or maternal gross pathology.
At 20 ppm, an increased number of late resorptionsldoewere observed (1.6 treated vs. 0.1 controls), which resulted in increased post-implantation loss in these animals (2.0treated vs. 0.7 controls). In addition, decreased (p<=0.05) gravid uterine weights were noted (decreased 3 1%). This decrease was attributed to decreased numbers of live fetusesldoe (decreased 41%) and decreased fetal weights (decreased 20%). Increased incidences of hair loss and wet, clear matting around the nose were noted in the 20 ppm animals compared to controls. Although these findings are of equivocal toxicological importance, they are evidence of nasal irritation. The postimplantation loss, decreased number of live fetuses, and decreased fetal weights may have been a consequence of subjecting the does to repeated respiratory irritation.

Page 32 of 37The maternal LOAEL is 20 ppm (0.12 mg/l/day) based on post-implantation loss due to late resorptions, and a decreased number of live fetuses. The maternal NOAEL is 10ppm (0.058 mg/l/day).
The developmental toxicity LOAEL is 20 ppm (0.12 mgmday) based on decreased fetal weights 

### (120%). The developmental toxicity NOAEL is 10ppm (0.058 mg/l/day). DoseJEndpoint for Risk Assessment: The maternal NOAEL is 0.058 mg/l/day based on postimplantation loss due to late resorptions, and a decreased number of live fetuses at the LOAEL of 0.12 mg/l/day.
Comments about Studmndpoint: This endpoint should be used in risk assessments for all durations of human inhalation exposure. The following table demonstrates that the length of the inhalation toxicity study (from 1to 90 days) has little effect on toxicity. The maternal NOAEL in the rabbit developmental toxicity study is about half that ofthe other NOAELs, possibly due to an idiosyncratic effect in rabbits. Study NOAEL LOAEL Acute neurotoxicity 

### - rats 0.16mg/L 0.54 mg/L Developmental toxicity 

### - rats 0.12mg/L/day 0.35rngiLlday Developmental toxicity 

### - rabbits 0.058 mg/l/day 0.12 mg/l/day 13-week toxicity 

### - rats 0.12mg/l/day 0.41 mg/l/day
10. Margin
- of Ex~osure The target Margin ofExposure (MOEs) for inhalation occupational and bystander exposure risk assessments is 100.
11. Recommendation for Aggregate Exposure Risk Assessments
Not applicable because there are no residentialuses. 

### III. CLASSIFICATION OF CARCINOGENIC POTENTIAL
1. Combined Chronic 

### Toxicity/Carcinoeenicity Study in Rats 

### - This study is not required because iodomethaneis a non-food use.
2. Carcinogenicity Study in Mice 

## - This study is not required because iodomethane is a nonfood use.
3. Classification of Carcinogenic Potential 

### - Carcinogenicity is not a concern because iodomethane will not have a food use, and there is no likelihood of long-term human exposure.



### IV. MUTAGENICITY Page 33 of 37Negative responses were observed in an Ames Assay, an 

### in vitro mammalian cell mutation test in Chinese Hamster Ovary Cells, and in an 

### in vivo micronucleus assay in mice. The only positive finding was in an 

### in vitro chromosomal aberration test in Chinese Hamster Ovary in which there was induction of structural chromosome aberrations (clastogenesis). There was no induction of numerical aberrationsin CHO cells, however. The HIARC concluded that there is no concern for mutagenicity resulting from exposureto iodomethane.


### V. HAZARD CHARACTERIZATION Toxicity Data Base Overview: The toxicity data base for iodomethane is limited because it has no food uses. The inhalation route has been well characterized, however, because this is the major route of worker exposure. The studies that have been submitted and reviewed include an battery of acute studies, an inhalation acute neurotoxicity study in rats, a 13-weekinhalation toxicity study in rats, inhalation developmental toxicity studies in rats and rabbits, four mutagenicity studies, and a comparative oral v inhalation metabolism study in rats (not required by HED). These are all AcceptableIGuideline studies.
There is a potential for accidental dermal exposureto iodomethane in workers due to a spill. Dermal exposure is expected to cause a rapid and persistent dermal response, but no systemic toxicity. No dermal toxicity studies were requested because the dermal dose cannot be quantified (iodomethane evaporates quickly from the skin), and there is no expectation of systemic toxicity.
An inhalation 2-generation reproductivetoxicity study was submitted, but was not reviewed due to regulatory time constraints and the fact that it is not needed for non-food-use registration. No chronic or carcinogenicity studies are required because iodomethane has no food uses, and there is no likelihood of long-term human exposure. 

### Acute Toxicity: The Toxicity Categories for technical iodomethane are 

### I for eye irritation, 

### I1 for acute oral toxicity (in rats and mice) and skin irritation, I11 for acute dermal toxicity, and 

### IV for acute inhalation toxicity. It is corrosive to the eyes with adverse signs persisting at 21 days, and is a severe skin irritant with rapid onset and effectspersisting as much as 28 days.


### Pharmacokinetics and Cumulative Toxicity: A comparison of NOAELs and LOAELs demonstrates that the length of an inhalation toxicity study (from 1to 90 days) has little effect on toxicity. This illustrates that there is minimal cumulation of iodomethane in the body. Although the maternal NOAEL in the rabbit developmental toxicity study is about half that of the other NOAELs, this is likely due to an idiosyncratic effect in rabbits (hypersensitivityto an irritant).
Study NOAEL LOAEL Acute neurotoxicity 

### - rats 0.16 mg/L 0.54mg/L Developmental toxicity 

### - rats 0.12 mg/L/day 0.3 5 mfllday Developmental toxicity 

### - rabbits 0.05 8 mg/l/day 0.1 2 mg/l/day 13-weektoxicity 

### - rats 0.12mg/l/day 0.4 1mgL/day A comparative oral v inhalation metabolism study 

### (MRID 45641401) was performed in Sprague-Dawley rats using [14C]CH,I. Maximum blood concentrations were achieved within 4 hours (oral) and 0-2 hours Page 34 of 37(inhalation), and were proportional to dose/concentration. Initial t, was 5.1-7.2hours, and terminal t, was 116-136 hours.
Recovered radioactivity was primarily as CO, (39.40-60.81% dose) and in the urine (26.50-33.40% dose) in all treated groups, while feces accounted for <2% dose. Radioactivity remained in the carcasses (1 1.92-14.39% dose) of all treated animals 168 hours followingtreatment in the main test. Elimination t, were 17.8-22.3 hours for urine, 29.7-38.0hours for feces, and 5.8-6.8hours for CO, in all treatment groups. At 0-1 hour post-treatment in orally treated rats and 233 pprn inhalation exposed rats, relatively high levels of radioactivity were observed in the liver and GI tract. Radioactivity was relatively high in the kidney, lung, and nasal turbinates of the 25 pprn inhalation exposed rats and in the kidney, thyroid, and lung of the 233 pprn inhalation exposed rats. At 168 hours post-dose, radioactivity had declined in all tissues and was highest in the kidney, liver, and thyroid. Tissue concentrationsincreased (not proportionally) with dose. The major metabolites were expired CO,, and N-(methylthioacetyl) glycine and S-methyl glutathionewhich were excreted in the urine. Minor metabolites were methylthioacetic acid, methyl mercapturic acid, and S-methyl cysteine. Subchronic Toxicity: In a subchronic inhalation toxicity study (MRID 45593810), rats were dynamically exposed to iodomethane vapor for 6 hourslday, 5 dayslweek for 13 weeks at analytical concentrations of 0, 5, 21, or 70 pprn (0, 0.029, 0.12, or 0.41mg/l/day). There were no effects on mortality, ophthalmology, urinalysis, hematology, organ weights, or gross pathology. The NOAEL is 21 pprn (0.12 mg/l/day), and the LOAEL is 70 pprn (0.41mg/l/day) based on initial decreasesin body weights, body weight gains, and food consumption (males); and nasal degeneration. Respiratory irritation was observed at the interim (4 weeks) and terminal sacrifices. Microscopicfindings indicated minimal to mild 

### degenerationlregenerationofthe nasal tissues characterized by subacuteinflammation, respiratory epithelial metaplasia, degeneration, goblet cell hypertrophy, squamous cell hyperplasia, and minimal alveolar macrophages (females only). Developmental Toxicity: Female rats were dynamically exposed to iodomethane vapor in whole-body inhalation chambers at analytical concentrations of 0, 5, 20, or 60 pprn (0, 0.03, 0.12, or 0.35 mg/l/day) six hours per day on gestation days (GDs) 6 through 19 (MRID 45593812). No treatment-related changes were observed in clinical signs, the number of live and dead fetuses, resorptions, sex ratios, postimplantation losses, or maternal gross pathology. The maternal NOAEL is 20 pprn (0.12mg/l/day), and the maternal LOAEL is 60 pprn (0.35 mgWday) based on decreased body weight gain (1 19%; 15-6% absolutebody weight). Because no treatment-related developmental findingswere noted at any concentration tested, the developmentalNOAEL is 60 pprn (0.35 mgL1day).
Female New Zealand White rabbits were dynamically exposed to iodomethane vapor in whole-body inhalation chambers at analytical concentrations of 0, 2, 10, or 20 pprn (0, 0.012, 0.058, or 0.12 mg/l/day) six hours per day on gestation days (GDs) 6 through 28 (MRID 4559381 1). No treatmentrelated changes were observed in body weights, body weight gains, food consumption, sex ratios, or maternal gross pathology. The maternal NOAEL is 10 pprn (0.058 mgLIday), and the maternal LOAEL is 20 pprn (0.12mglL/day) based on post-implantation loss (2.0treated v 0.7 controls) due to late resorptions (1.6ltreated doe v 0.l/control doe), and a decreased number of live fetuses (1 41%). The post-implantation loss, decreased number of live fetuses, and decreased fetal weights may have been a consequence of subjectingthe does to repeated respiratory irritation. The developmentalNOAEL is 10
Page 35 of 37ppm (0.058 mg/l/day), and the developmental LOAEL is 20 ppm (0.12 mgL/day) based on decreased fetal weights ( 1 20%).


### Chronic ToxicitylCarcinogenicityand Mutagenicity: No chronic or carcinogenicity studies are required or have been submitted. Negative responses were observed in an Ames Assay (MRID 45593813), 

### an in vitro mammalian cell mutation test in Chinese Hamster Ovary Cells (MRID 45593815), and in an in vivo micronucleus assay in mice 

### (MRID 45593816). The only positive finding was in an in vitro chromosomal aberration test in Chinese Hamster Ovary 

### (MRID 45593814) in which there was induction of structural chromosome aberrations (clastogenesis), but no induction of numerical aberrations in CHO cells. The HIARC concluded that there is not a concern for mutagenicity resulting from exposure to iodomethane. 

### Neurotoxicity: In an acute neurotoxicity study (MRID 45593817), rats were dynamically exposed to iodomethane vapor in a single, six-hour, whole body inhalation exposure at analytical concentrations of 0, 27, 93, or 401 ppm (0,0.16, 0.54, or 2.3 mgL). The time of peak effect was estimated to be three hours post-exposure. The NOAEL is 27 ppm (0.16 ma). The LOAEL is 93 ppm (0.54 ma) based on FOB findings (clonic convulsions and decreased body temperature), and decreased motor activity 

### (175-78% in males, 8 1-84% in females). 

### Endocrinopathy: None of the animal studies provide any evidencethat iodomethanedisrupts endocrine receptors. 

### VI. DATA GAPS I

### REOUIREMENTS
There are no data gaps.


### VII. ACUTE TOXICITY Acut~

Acute Oral 

### - rat

Acute Oral 

### - mouse 

# 11 870.1200 

# 11 Acute Dermal 

# 1 870.1300 Acute Inhalation 

# 1 870.2400 

# 11 Primary Eye Irritation 

# 1 870.2500 

# 11 Primary Skin Irritation 

# 11 870.2600 

# 11 Dermal Sensitization Toxicity of Iodomethane

45593808 

# I Severe irritant 

# I I1

Page 36 of 37

------- -- 45593809 Negative -

### VIII. SUMMARY OF TOXICOLOGY ENDPOINT SELECTION Summary of Toxicology Endpoint Selection for Iodomethane

Maternal LOAEL = 0.12 mg/L/day based on post-implantation loss due to late resorptions,



### Page 37 

### of 37

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### ---

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