55	125	0	55	0	5	0	0	0

60	145	0	70	0	5	0	0	0

65	170	0	85	0	5	0	0	0

70	200	5	110	0	5	0	0	0

75	230	5	130	5	25	0	0	0

80	260	10	150	5	40	0	0	0

85	305	30	180	5	65	0	0	0

90	350	70	220	25	90	5	5	0

95	430	150	280	80	125	5	5	0

97	470	210	320	125	150	35	5	0

99	555	330	390	215	200	90	5	5

99.9	725	510	500	355	265	190	20	5

99.99	760	680	555	485	305	265	60	45

UF=10

5	0	0	0	0	0	0	0	0

10	0	0	0	0	0	0	0	0

15	0	0	0	0	0	0	0	0

20	0	0	0	0	0	0	0	0

25	0	0	0	0	0	0	0	0

30	0	0	0	0	0	0	0	0

35	0	0	0	0	0	0	0	0

40	0	0	0	0	0	0	0	0

45	0	0	0	0	0	0	0	0

50	0	0	0	0	0	0	0	0

55	0	0	0	0	0	0	0	0

60	0	0	0	0	0	0	0	0

65	0	0	0	0	0	0	0	0

70	0	0	0	0	0	0	0	0

75	5	0	0	0	0	0	0	0

80	5	0	0	0	0	0	0	0

85	5	0	0	0	0	0	0	0

90	5	0	5	0	0	0	0	0

95	5	5	5	0	0	0	0	0

97	30	5	5	0	0	0	0	0

99	70	5	5	5	5	0	0	0

99.9	105	65	20	5	5	5	0	0

99.99	140	125	60	45	5	5	0	0

UF=3

5	0	0	0	0	0	0	0	0

10	0	0	0	0	0	0	0	0

15	0	0	0	0	0	0	0	0

20	0	0	0	0	0	0	0	0

25	0	0	0	0	0	0	0	0

30	0	0	0	0	0	0	0	0

35	0	0	0	0	0	0	0	0

40	0	0	0	0	0	0	0	0

45	0	0	0	0	0	0	0	0

50	0	0	0	0	0	0	0	0

55	0	0	0	0	0	0	0	0

60	0	0	0	0	0	0	0	0

65	0	0	0	0	0	0	0	0

70	0	0	0	0	0	0	0	0

75	0	0	0	0	0	0	0	0

80	0	0	0	0	0	0	0	0

85	0	0	0	0	0	0	0	0

90	0	0	0	0	0	0	0	0

95	0	0	0	0	0	0	0	0

97	0	0	0	0	0	0	0	0

99	0	0	0	0	0	0	0	0

99.9	0	0	0	0	0	0	0	0

99.99	0	0	0	0	0	0	0	0

The information that is included in Tables 9 and 10 can also be
graphically presented (as can the results of any of the completed PERFUM
analysis).  Figures 13 and 14 present the maximum buffer distances based
on uncertainty factors of 30 and 10, respectively, that were calculated
using the Ventura California weather data and the tarped flux profile.
In these graphs, buffer distance results are plotted versus the
percentile of exposure for 1, 10 and 40 acre fields at varying
application rates including the maximum, 75 percent and 50 percent rate
(i.e., 1 acre tables are not presented above for simplicity but the
information is included in the graphs for comparison).  Figures 15 and
16 are similar in nature except they present the whole field buffer
results instead of the maximum buffer results.  When reviewing the
results in Figures 13 through 16 note that the scale of the “y” axis
are similar for direct comparison.

Figure 13

Figure 14

Figure 15

Figure 16

For comparative purposes, similar graphs are presented below in Figures
16, 17, and 18 that are based on results for Ventura California weather
data but flux profiles for different application methods.  In Figure 17,
the flux profile is for raised bed applications (i.e., bedded tarped)
while Figure 18 presents hot gas application method results (i.e., also
known as drip application).  The hot gas method is the highest emitting
application method (i.e., it has the highest flux rates). As a result,
it is the one where buffer zones greater than 25 to 50 meters or so were
identified at a combined uncertainty factor of 3 (as opposed to 10 for
the others above) so these results are included as Figure 19.

Figure 17

Figure 18

Figure 19

Table 11 provides a comparison of results for selected percentiles of
exposure among flux profiles for a 40 acre field at varied application
rates and an uncertainty factor of 30.  The results essentially track
with the relative differences in emission ratios that are described
above in Table 5 with the tarped application method having the lowest
associated emission and lowest predicted PERFUM buffer results.
Conversely, the relative ranking of the hot gas and bedded tarped
application methods as having the highest and penultimate emission
ratios is also consistent with the PERFUM results provided below.  The
relative trends illustrated in Table 11 would be expected to be similar
regardless of the choice of meteorological data selected for the
analysis.  Figure 20 illustrates these trends for varied application
rates based on a combined uncertainty factor of 30.  Figure 21 provides
similar information but also provides results for a combined uncertainty
factor of 10 for comparative purposes.  As expected, the absolute values
are decreased with a lower uncertainty value so the effect appears to be
attenuated among flux types.

Table 11:   Comparison Of Results For Methyl Bromide PERFUM Buffer
Distributions Based On A 40 Acre Square Field, Ventura California
Weather Data, And All Flux Profiles At A UF=30

Percentiles	Max (430 lb/Acre)	75% (323 lb/Acre)	50% (215 lb/Acre)	25%
(108 lb/Acre)

	Max

Distance	Whole

Field	Max

Distance	Whole

Field	Max

Distance	Whole

Field	Max

Distance	Whole

Field

Flux Profile = Tarped Application Method

50	110	0	40	0	5	0	0	0

75	230	5	130	5	25	0	0	0

90	350	70	220	25	90	5	5	0

95	430	150	280	80	125	5	5	0

99	555	330	390	215	200	90	5	5

99.9	725	510	500	355	265	190	20	5

99.99	760	680	555	485	305	265	60	45

Flux Profile = Shallow Untarped Application Method

50	245	0	150	0	45	0	0	0

75	425	30	290	10	135	5	5	0

90	615	150	430	90	230	30	20	0

95	710	285	510	190	290	85	50	5

99	895	565	665	400	410	225	110	30

99.9	1185	835	855	610	520	365	150	105

99.99	1205	1130	880	810	575	500	185	170

Flux Profile = Hot Gas Application Method

50	505	25	360	10	200	5	35	0

75	705	135	510	95	305	50	85	5

90	985	315	725	235	450	135	150	25

95	1185	450	880	340	565	210	210	60

99	1440	790	1250	605	795	395	355	150

99.9	1440	1285	1440	970	1205	655	500	315

99.99	1440	1440	1440	1275	1330	845	545	455

Flux Profile = Deep Untarped Application Method

50	165	0	85	0	5	0	0	0

75	305	20	195	5	70	0	0	0

90	450	105	305	55	140	5	5	0

95	530	200	370	125	185	40	5	0

99	695	420	490	285	290	140	45	5

99.9	875	635	630	445	365	260	110	45

99.99	935	850	700	605	430	350	115	100

Flux Profile = Bedded Tarped Application Method (Note:  Effective
Maximum Broadcast Maximum Application Rate = 250 lb ai/Acre)

50	135	0	70	0	10	0	0	0

75	200	30	115	10	40	5	5	0

90	295	95	190	50	80	10	5	0

95	395	145	260	90	120	30	5	5

99	670	290	525	195	305	95	85	5

99.9	1225	590	925	440	555	285	210	85

99.99	1305	1005	955	730	565	480	230	205

Figure 20

Figure 21

In addition to the comparisons described above among flux types, a
comparison was also completed that evaluated differences concurrently
among meteorological data and flux profile (Table 12 & Figure 22).  The
relative difference based on flux profile is similar regardless of the
weather data used for the analysis.  For results based on the selection
of meteorological data, it appears that results for Bradenton Florida
have higher associated buffer distances than (in order) Ventura
California, Tallahassee Florida, Flint Michigan, and Bakersfield
California.  These results are consistent with the sensitivity analysis
completed by the model developer and presented at the 2004 FIFRA
Scientific Advisory Panel meeting
(http://www.epa.gov/oscpmont/sap/meetings/2004/index.htm).  The results
presented in Table 13 are based on a 40 acre field and an uncertainty
factor of 30 at the maximum application rate for each method.  It is
anticipated that the general trends observed in Table 12 and Figure 22
would also still apply regardless of the field size, uncertainty factor
basis, or application rate.

Table 12:   Comparison Of Results For Methyl Bromide PERFUM Buffer
Distributions Based On A 40 Acre Square Field, All Weather Data, And All
Flux Profiles At A UF=30 And Maximum Application Rate

%tiles	Ventura California	Tallahassee Florida	Flint Michigan	Bakersfield
California	Bradenton Florida

	Max

Distance	Whole

Field	Max

Distance	Whole

Field	Max

Distance	Whole

Field	Max

Distance	Whole

Field	Max

Distance	Whole

Field

Flux Profile = Tarped Application Method

50	110	0	60	0	50	0	95	0	155	0

75	230	5	130	5	115	5	145	15	290	15

90	350	70	225	50	190	40	200	65	420	105

95	430	150	290	95	240	85	235	105	510	185

99	555	330	435	215	385	185	315	190	695	350

99.9	725	510	620	415	515	360	390	295	905	575

99.99	760	680	630	585	580	500	395	375	935	790

Flux Profile = Shallow Untarped Application Method

50	245	0	150	0	130	0	195	5	305	0

75	425	30	265	25	240	25	280	65	500	50

90	615	150	410	110	350	105	365	145	695	185

95	710	285	515	185	425	170	410	205	855	305

99	895	565	770	375	650	330	540	330	1130	555

99.9	1185	835	1050	690	905	605	640	495	1405	925

99.99	1205	1130	1065	995	960	860	705	625	1440	1340

Flux Profile = Hot Gas Application Method

50	505	25	485	20	370	5	455	65	670	35

75	705	135	705	135	495	120	605	195	950	175

90	985	315	970	315	695	265	800	335	1320	380

95	1185	450	1170	460	850	365	935	435	1435	530

99	1440	790	1440	820	1365	625	1285	665	1440	940

99.9	1440	1285	1440	1395	1440	1110	1440	1040	1440	1435

99.99	1440	1440	1440	1440	1440	1440	1440	1435	1440	1440

Flux Profile = Deep Untarped Application Method

50	165	0	105	0	90	0	135	5	220	0

75	305	20	195	10	170	10	200	40	375	35

90	450	105	310	80	255	70	265	100	530	145

95	530	200	390	140	315	120	305	145	645	235

99	695	420	605	290	490	245	400	245	865	435

99.9	875	635	810	540	680	455	500	375	1160	725

99.99	935	850	830	745	725	625	530	475	1255	995

Flux Profile = Bedded Tarped Application Method (Note:  Effective
Maximum Broadcast Maximum Application Rate = 250 lb ai/Acre)

50	135	0	135	0	100	0	85	5	170	5

75	200	30	205	35	150	25	125	35	235	50

90	295	95	280	100	205	75	175	70	315	125

95	395	145	350	150	265	115	210	100	385	175

99	670	290	500	270	415	200	320	165	475	285

99.9	1225	590	605	455	1025	380	440	285	665	440

99.99	1305	1005	650	580	1440	1245	485	440	715	600

Figure 22

In addition to the comparative analyses presented above, other factors
were evaluated relative to their possible impacts on PERFUM-based buffer
zone predictions.  These included evaluating the effect of field size
and shape on results as well as discerning if there are significant
seasonal differences in results since many fumigant use patterns are
seasonal in nature.  Figure 23 illustrates differences associated with
increasing field sizes and the results indicate that, as expected,
buffer distances increase relative to field size.  Similar trends are
observed regardless of the application rate or whether or not the
results are based on maximum or whole field buffer results.

Figure 23

Figure 24 illustrates differences based on field shape.  In this
analysis, results for a square 5 acre field and rectangular fields
(i.e., based on a 2:1 aspect ratio) oriented alternatively on
perpendicular sides were calculated.  Results were essentially similar
for all types but the “long” field orientation always provided lower
buffer estimates.  The results of this analysis may also be sensitive to
different weather conditions, site topography, and field aspect ratio
but these factors were not evaluated in more detail because their
relevance is likely more significant to specific use sites than to the
development of generally applicable buffer estimates using PERFUM.

Figure 24

The seasonal impacts of changing weather patterns have been evaluated in
every PERFUM analysis.  Table 13 below provides an example of the
outputs that are available.  In this type of analysis PERFUM compiles
distributions based on only the specific month’s worth of
meteorological data from the 5 years used for the analysis so each of
the distributions is based on 5 months instead of 5 years worth of data.
 [Note:  For comparative purposes, the corresponding 5 year distribution
for Table 13 is included in Table 9 above for whole fields, maximum
application rate with an uncertainty factor of 30 (i.e., 95th %tile = 35
m; 99th %tile = 115 m; etc.).]  It appears in this case that longer
buffer distances are predicted in the cooler winter months which may be
due to an overall trend toward a more stable atmosphere in those months
due to less convective heating and atmospheric turbulence than in the
spring and summer months.

Table 13:  Methyl Bromide PERFUM Monthly Whole Field Buffer
Distributions For A 10 Acre Square Field Based On Ventura California
Weather And Tarped Flux Profile At The Maximum Application Rate And With
An Uncertainty Factor = 30

Percentile Of

Exposure	PERFUM Monthly Buffer Distributions

	JAN	FEB	MAR	APR	MAY	JUN	JUL	AUG	SEP	OCT	NOV	DEC

5	0	0	0	0	0	0	0	0	0	0	0	0

10	0	0	0	0	0	0	0	0	0	0	0	0

15	0	0	0	0	0	0	0	0	0	0	0	0

20	0	0	0	0	0	0	0	0	0	0	0	0

25	0	0	0	0	0	0	0	0	0	0	0	0

30	0	0	0	0	0	0	0	0	0	0	0	0

35	0	0	0	0	0	0	0	0	0	0	0	0

40	0	0	0	0	0	0	0	0	0	0	0	0

45	0	0	0	0	0	0	0	0	0	0	0	0

50	0	0	0	0	0	0	0	0	0	0	0	0

55	0	0	0	0	0	0	0	0	0	0	0	0

60	0	0	0	0	0	0	0	0	0	0	0	0

65	0	0	0	0	0	0	0	0	0	0	0	0

70	0	0	0	0	0	0	0	0	0	0	0	0

75	0	0	0	0	0	0	0	0	0	0	0	0

80	5	5	5	0	0	0	0	0	0	0	5	5

85	5	5	5	5	5	5	5	5	5	5	5	5

90	25	25	20	5	5	5	5	5	5	5	5	10

95	75	65	55	40	25	15	5	15	20	40	50	40

97	110	95	85	60	45	35	30	40	45	70	75	80

99	170	145	130	105	85	70	65	75	95	125	135	130

99.9	265	240	195	175	140	155	120	120	145	175	240	195

99.99	330	290	235	200	170	185	185	160	185	200	260	275

As indicated above, monitoring data in the previous phase 3 risk
assessment for methyl bromide (D316326, 6/13/05) were identified and
summarized.  None of this information or analysis has changed since the
previous assessment.  Table 14 below provides a summary of these data
and presents margins of exposure (i.e., MOEs) calculated based on them
(i.e., MOEs > 30 are not of concern).  Note a trend for maximum
concentration estimates is not observed.  For consideration, this can be
due to many factors such as building characteristics, absorption rates
of treated materials, differences in aeration, and prevailing weather
conditions.

  SEQ CHAPTER \h \r 1

Table 14:  Risks From Methyl Bromide Exposure Based On Maximum 24 Hour
TWA Concentrations Based On Pre-Plant Agricultural Field Volatility Data

Distance From Treated Field

(feet) & No. Samples	Max. 24 Hour [TWA] (ppm)	Acute MOE

26 to 34 ft

(N = 206)	1.4	7

35 to 79 ft

(N = 80)	0.59	17

80 to 115 ft

(N = 27)	0.470	21

> 115 ft

(N = 90)	1.5	7

The results indicate that the potential risks which have been calculated
for methyl bromide emissions from treated fields are of concern as
calculated acute MOEs are less than 30 for all distances from the field
where data are available.  It should be noted that within each distance
category described in Table 14 that there are a number of samples.  If
MOEs were calculated for many of these they would be greater than 30 and
thus, would not be of concern.  This would not be unexpected.  If one
were to review PERFUM outputs for various analyses it would also
indicate that for many circumstances predicted buffer distances would be
small (e.g., <10 meters or so) at lower percentiles of exposure.  In
summary, monitoring data support the types of results that have been
calculated using the PERFUM model.  Additionally, the limitations
associated with the use of monitoring data can be illustrated based on
the summarized data where there are different numbers of samples in each
distance category and the distance categories themselves were defined
based on the data and not conversely which would be more appropriate.
If so desired, the previous risk assessment and its associated
appendices that contain all of the monitoring data information can be
found at   HYPERLINK "http://www.Regulations.gov"  www.Regulations.gov
under docket OPP-2005-0123 (i.e., key various elements include:
OPP-2005-0123-007 – bibliography; OPP-2005-0123-008 – field
monitoring data).  [Note:  ISCST3 results are not summarized in this
document since PERFUM uses ISCST3 as its core processor and PERFUM-based
results provide more realistic estimates of risk based on actual
meteorological data.]

In conclusion, it is clear that many different factors can impact the
air concentrations (and hence, risks) in proximity to agricultural
fields that have been treated with methyl bromide; these include many of
the factors which have been investigated in this analysis.  It is also
important to acknowledge this issue so that stakeholders understand that
the results of this analysis can be interpreted in many ways depending
upon the factors which are considered.  Many conclusions can be drawn,
but the key ones include: (1) at the edge of the treated fields that
NOAEL HECs (i.e., UF=1) generally are not exceeded given proper use of
methyl bromide but conversely the distance predicted for higher
uncertainty factors (i.e., UF=30) are hundreds of meters for many
scenarios; (2) the methods used to evaluate methyl bromide exposure in
this assessment generally agree and they are based on techniques that
have been routinely used for regulatory purposes, they have also
undergone a significant level of review; (3) the sensitivity of results
to changes in key factors such as flux and meteorological conditions is
generally within a factor of 4 or 5 for those which have been evaluated;
(4) PERFUM is an empirically based approach so the generation of
additional flux and meteorological data would allow a broader analysis
that could be applied more specifically to other regions of the country
and application parameters; and (5) the identification of a result, per
se, for any sort of regulatory action (e.g., a percentile of exposure or
maximum/whole field) would depend upon careful consideration of the
variability and uncertainty as well as any particular merits of the
inputs associated with each.

<IP_ADDRESS>.b:  Bystander Exposures And Risks From Greenhouse Use tc \l5
"<IP_ADDRESS>.b:  Bystander Exposures And Risks From Greenhouse Use

The "greenhouse" industry sector is extremely varied because of the
breadth of the facilities that are used across the country and because
of the nature of the products that are produced.  As a result, some
clarification is required in order to interpret the results presented
below.  Certainly, in common "greenhouse" operations, many types of
containerized ornamental plants and vegetable starter sets are produced
in either closed structures that will be referred to as "greenhouses" or
in other related nursery operations such as small fields, or in what are
commonly known as "shade" houses (i.e., essentially fields with an
overhead sunblock of some sort typically a semi-transluscent black shade
cloth).  In the latter type of operation, cultural practices related to
methyl bromide use are essentially identical to the pre-plant field uses
described above in Section <IP_ADDRESS>.a except they typically occur on a
smaller scale (e.g., 1 acre applications or less).  As a result, for
risk estimates related to these types of use patterns, please refer to
the results presented above for pre-plant soil uses and smaller sized
fields.

For the actual greenhouse operations considered in this assessment, a
maximum application rate of  4 lb ai/1000 ft3 was used based on the
Meth-O-Gas label (EPA Reg. No. 5785-41) for rhizomes, seeds, roots,
bulbs, corms and tubers.  A process has been defined, based on the
PERFUM model described above, for characterizing the off-site
dissipation of methyl bromide that has been released either
intentionally during aeration after treatment is complete or that leaked
from a structure during treatment.  Aeration can be accomplished using
several techniques that employ different devices and/or locations
relative to the treated structure.  In summary, aeration is
predominantly accomplished using either portable industrial fans that
are typically rated to move air volumes up to 5000 CFM (i.e., cubic feet
per minute) or much larger static ventilation systems that can move much
larger quantities of air.

Based on the observations above pertaining to "greenhouse" uses, it
follows that the methods used to quantify potential risk estimates in
the recently completed commodity assessment (i.e., that addressed the
food uses) for methyl bromide are applicable to this industry.  In both
cases, a structure is treated and the methyl bromide is held in
accordance to a "CxT" (i.e., concentration by time) table in order to
achieve the desired level of efficacy; then the material is typically
actively aerated from the treated structure using various methods.  This
type of operation would occur regardless of whether or not food
commodities were in the structure.  The only elements which may differ
would be the amount retained because of the absorptive capacity of the
materials in the structure being treated.  Food use or not, insufficient
information is available to quantify this phenomenon for more than a
handful of situations so it is believed that the analysis and methods
developed and used for the commodity assessment are directly applicable
to the greenhouse use pattern.  Identification of the applicable results
will depend on how individual fumigation events occur.  In the risk
management strategy for addressing food use patterns the Agency decision
was to allow for flexibility among users depending upon the aeration
method used which is also anticipated for this use pattern.  These
methods and applicable results are presented in detail in the following
documents:

Methyl Bromide:  Phase 5 Health Effects Division (HED) Human Health Risk
Assessment For Commodity Uses, PC Code: 053201, DP Barcode D304623,
Authors:  J. Dawson and E. Mendez, Issued:  3/10/06.

Methyl Bromide:  Addendum To Phase 5 Health Effects Division (HED) Human
Health Risk Assessment For Commodity Uses, PC Code 053201, DP Barcode
D304619 Authors:  J. Dawson E. Mendez, T. Goodlow, M. Metzger, Issued:
7/12/06

A coding error in the calculation algorithms of the PERFUM model was
identified that pertained to the minimum stack aeration scenario.  The
results summarized below are based on the corrected version of PERFUM.
It should also be noted that there have been comments pertaining to the
method used to evaluate the PPQ aeration method (i.e., placing an
exhaust fan and vent in the middle of a parking lot attached to the
treated structure by a flexible large hose).  In essence, the issue
pertained to accounting for the orientation of the output orifice and
two options were considered (i.e., referred to as the "vertical stack"
or "horizontal stack").  It was determined that the "horizontal stack"
approach is the most appropriate, consequently, results based on this
method are presented below.  Additionally, comments were made pertaining
to the averaging times used as the basis for both the time-weighted
average air concentrations and the HEC for structural types of uses.
Based on these comments, the values for exposure and the HEC have been
matched for risk calculation purposes (i.e., both are based on 6 hours).
 Active aeration or leakage during treatment are thought to occur over
short periods so exposure estimates are based on 1 hour emissions
followed by 5 hours of zero emissions in order to reflect anticipated
actual occurences and to reflect an appropriate time basis calculating
risks.  At times, greenhouse and nursery operators also tarp quantities
of potting soil and treat it with methyl bromide.  It is believed that
the no stack scenario (akin to no active aeration) is the most
representative for determining risks reflective of this use pattern.  In
addition, there are times when orchard and tree replanting activities
occur in order to replace whole blocks or individual trees that may have
died due to disease or other factors.  These should not be considered a
greenhouse operation.  If whole blocks of trees are being replaced,
cultural practices related to methyl bromide use are essentially
identical to the pre-plant field uses described above in Section
<IP_ADDRESS>.a except they typically occur on a smaller scale (e.g., 1 acre
applications or less).  If single (or a few) trees are being replaced, a
handheld injector is typically used.  No emissions data are available
for this pattern, however, it is believed that this technique presents
minimal risks for bystander populations because of the low amount used.

Table 15 presents a summary of some the results of the PERFUM analyses
that were completed to assess events during treatment (from leakage)
associated with the greenhouse uses of methyl bromide.  The commodity
assessment documents D304623 and D304619 detail the PERFUM iterations
that were completed which could apply to greenhouse treatments.  The
scenarios presented in Table 15 have been selected for illustrative
purposes because they represent many typical greenhouse settings and
they also represent the maximum application rate, uncertainty factor of
30, and typical to high end emissions during treatment (i.e., 1 and 10
percent leakage of the nominal application concentration).  Additional
PERFUM output files which can be provided for review of other situations
if so desired.

Table 15: PERFUM Methyl Bromide Buffer Distances (meters) During
Greenhouse Treatment Based On UF30, 4 hour Exposure Duration,

4 lb/1000 cubic feet Application Rate, Varied Structure Size & Varied
Percent Mass Released

Aeration Type	Percentile	1,000 Cubic Feet	10,000 Cubic Feet	50,000 Cubic
Feet	100,000 Cubic Feet

10% Mass Release	1% Mass Release	10% Mass Release	1% Mass Release	10%
Mass Release	1% Mass Release	10% Mass Release	1% Mass Release

Maximum Buffer Distances

No Stack	95	0	0	10	0	110	0	200	0

	99	0	0	20	0	125	0	225	0

	99.9	0	0	25	0	130	0	230	0

Whole Field Buffer Distances

No Stack	95	0	0	0	0	0	0	10	0

	99	0	0	0	0	40	0	75	0

	99.9	0	0	10	0	105	0	190	0

Table 16 presents a summary of some the results of the PERFUM analyses
that were completed to assess aeration events associated with the
greenhouse uses of methyl bromide.  The commodity assessment documents
D304623 and D304619 detail the thousands of PERFUM iterations that were
completed which could apply in some regard to the greenhouse industry,
depending upon the size and configuration of the facility.  The
scenarios presented in Table 16 have been selected for illustrative
purposes because they represent many typical greenhouse settings and
they also represent the maximum application rate, uncertainty factor of
30, and typical to high end emissions after a treatment (i.e., 75 and 95
percent of the nominal application concentration).  Additional PERFUM
output files which can be provided for review of other situations if so
desired.

Table 16: PERFUM Methyl Bromide Buffer Distances (meters) For All
Greenhouse Aeration Processes Considered Based On UF30, 4 hour Exposure
Duration, 4 lb/1000 cubic feet Application Rate, Varied Structure Size &
Varied Percent Mass Released

Aeration Type	Percentile	1,000 Cubic Feet	10,000 Cubic Feet	50,000 Cubic
Feet	100,000 Cubic Feet

95% Mass Release	75% Mass Release	95% Mass Release	75% Mass Release	95%
Mass Release	75% Mass Release	95% Mass Release	75% Mass Release

Maximum Buffer Distances

Minimum Stack

1  xch/min	95	0	0	0	0	0	0	0	0

	99	0	0	0	0	0	0	0	0

	99.9	0	0	0	0	0	0	0	0

No Stack	95	30	20	205	175	545	470	835	725

	99	35	25	225	195	600	520	930	805

	99.9	40	30	235	200	625	535	975	830

Portable Stack

1 xch/min.	95	0	0	0	0	0	0	0	0

	99	0	0	0	0	0	0	0	0

	99.9	0	0	0	0	0	0	0	0

PPQ

1 xch/min.	95	5	0	20	15	0	0	105	0

	99	10	10	30	25	70	60	140	105

	99.9	15	10	70	60	160	140	170	170

Whole Field  Buffer Distances

Minimum Stack

1  xch/min	95	0	0	0	0	0	0	0	0

	99	0	0	0	0	0	0	0	0

	99.9	0	0	0	0	0	0	0	0

No Stack	95	0	0	10	5	25	25	30	25

	99	0	0	70	60	195	170	290	255

	99.9	30	20	195	165	520	450	810	700

Portable Stack

1 xch/min.	95	0	0	0	0	0	0	0	0

	99	0	0	0	0	0	0	0	0

	99.9	0	0	0	0	0	0	0	0

PPQ

1 xch/min.	95	0	0	10	5	15	10	25	0

	99	0	0	20	15	50	45	80	0

	99.9	5	5	30	25	70	60	105	20

As indicated above, monitoring data have been integral in the
development of this risk assessment.  In the previous phase 3 risk
assessment for methyl bromide (D316326, 6/13/05), all of the monitoring
data that were evaluated were identified and summarized.  None of this
information or analysis has changed since the previous assessment.
Table 17 below provides a summary of these data and presents margins of
exposure (i.e., MOEs) calculated based on them (i.e., MOEs > 30 are not
of concern).  Note that in some cases, air concentrations increase as
the number of days after application increase.  This appears incongruous
but could be due to a number of factors including monitoring was
completed at different facilities which could impact results, the
absorptive properties of the facilities and treated material could
retain methyl bromide until days after treatment, and wind patterns
could have shifted to a particular sample collection location.

  SEQ CHAPTER \h \r 1

Table 17:  Risks From Methyl Bromide Exposure Based On Maximum 24 Hour
TWA Concentrations Using Greenhouse Volatility Data

Distance Downwind From Treated Greenhouse

	Days After Application	Maximum 24 Hour [TWA]

(ppm)	Acute MOE

50 feet	0	0.287	35

	1	0.292	34

	2	0.295	34

	3	1.870	5

150 feet	0	0.150	67

	1	0.127	79

	2	0.112	89

	3	0.820	12

The results indicate that the potential risks which have been calculated
for methyl bromide emissions from treated greenhouses can be of concern
as calculated acute MOEs in two cases out of  8 are less than 30.  If
one were to review PERFUM outputs for various analyses it would also
indicate that for many circumstances predicted buffer distances would be
small (e.g., <10 meters or so) at lower percentiles of exposure or
depending  upon the aeration method.  In summary, monitoring data
support the types of results that have been calculated using the PERFUM
model.   If so desired, the previous risk assessment and its associated
appendices that contain all of the monitoring data information can be
found at   HYPERLINK "http://www.Regulations.gov"  www.Regulations.gov
under docket OPP-2005-0123 (i.e., key various elements include:
OPP-2005-0123-007 – bibliography; OPP-2005-0123-009 – greenhouse
monitoring data).

<IP_ADDRESS>.c: Bystander Exposures And Risks From Residential Use tc \l5
"<IP_ADDRESS>.e: Bystander Exposures And Risks From Residential Use

The residential sector represents a small percentage of the overall use
of methyl bromide.  The maximum application rate used for this
assessment is 3 lb ai/1000 ft3 based on the Brom-O-Gas label for
residential uses (EPA Reg. No. 5785-55 or -08).  A process has been
defined based on the PERFUM model described above for characterizing the
off-site dissipation of methyl bromide that has been released either
intentionally during aeration after treatment is complete or that leaked
from a structure during treatment.  Aeration can be accomplished using
several techniques that employ different devices and/or locations
relative to the treated structure.  In summary, aeration is
predominantly accomplished using portable industrial fans that are
typically rated to move air volumes up to 5000 CFM (i.e., cubic feet per
minute).  [Note:  As described with the greenhouse use above, the
analysis for residential treatments is based on the previous commodity
assessment and the related changes.  For more information refer to the
above.]  In this evaluation, home volumes range from 10,000 to 50,000
cubic feet for small to large single family houses while a 100,000 cubic
foot volume is intended to represent a multi-dwelling unit.

Table 18 presents a summary of some the results of the PERFUM analyses
that were completed to assess events during treatment (from leakage)
associated with the residential uses of methyl bromide.  The commodity
assessment documents D304623 and D304619 detail the PERFUM iterations
that were completed which could apply to residential treatments.  The
scenarios presented in Table 18 have been selected for illustrative
purposes because they represent many typical residential settings and
they also represent the maximum application rate, uncertainty factor of
30, and typical to high end emissions during treatment (i.e., 1 and 10
percent leakage of the nominal application concentration).  Additional
PERFUM output files which can be provided for review of other situations
if so desired.

Table 18: PERFUM Methyl Bromide Buffer Distances (meters) During
Residential Treatment Based On UF30, 4 hour Exposure Duration,

3 lb/1000 cubic feet Application Rate, Varied Structure Size & Varied
Percent Mass Released

Aeration Type	Percentile	10,000 Cubic Feet	25,000 Cubic Feet	50,000
Cubic Feet	100,000 Cubic Feet

10% Mass Release	1% Mass Release	10% Mass Release	1% Mass Release	10%
Mass Release	1% Mass Release	10% Mass Release	1% Mass Release

Maximum Buffer Distances

No Stack	95	0	0	30	0	80	0	165	0

	99	0	0	40	0	90	0	180	0

	99.9	0	0	45	0	95	0	190	0

Whole Field Buffer Distances

No Stack	95	0	0	0	0	0	0	5	0

	99	0	0	0	0	25	0	60	0

	99.9	0	0	30	0	70	0	155	0

Table 19 presents a summary of some the results of the PERFUM analyses
that were completed to assess aeration events associated with the
residential uses of methyl bromide.  The commodity assessment documents
D304623 and D304619 detail the thousands of PERFUM iterations that were
completed which could apply in some regard to the residential uses
depending upon the size of the structure being treated and the type of
aeration used.  The scenarios presented in Table 19 have been selected
for illustrative purposes because they represent many typical
residential settings (i.e., small to large, multi-unit structures) and
they also represent the maximum application rate, uncertainty factor of
30, and typical to high end emissions after a treatment (i.e., 75 and 95
percent of the nominal application concentration).  Additional PERFUM
output files which can be provided for review of other situations if so
desired.

Table 19: PERFUM Methyl Bromide Buffer Distances (meters) For All
Residential Aeration Processes Considered Based On UF30, 4 hour Exposure
Duration, 3 lb/1000 cubic feet Application Rate, Varied Structure Size &
Varied Percent Mass Released

Aeration Type	Percentile	10,000 Cubic Feet	25,000 Cubic Feet	50,000
Cubic Feet	100,000 Cubic Feet

95% Mass Release	75% Mass Release	95% Mass Release	75% Mass Release	95%
Mass Release	75% Mass Release	95% Mass Release	75% Mass Release

Maximum Buffer Distances

Minimum Stack

1  xch/min	95	0	0	0	0	0	0	0	0

	99	0	0	0	0	0	0	0	0

	99.9	0	0	0	0	0	0	0	0

No Stack	95	170	145	295	255	455	395	705	605

	99	185	160	330	280	505	435	780	675

	99.9	195	165	340	290	520	450	810	695

Portable Stack

1 xch/min.	95	0	0	0	0	0	0	0	0

	99	0	0	0	0	0	0	0	0

	99.9	0	0	0	0	0	0	0	0

PPQ

1 xch/min.	95	20	15	40	35	60	50	90	75

	99	30	25	50	45	75	65	115	100

	99.9	40	30	65	55	90	80	140	120

Whole Field  Buffer Distances

Minimum Stack

1  xch/min	95	0	0	0	0	0	0	0	0

	99	0	0	0	0	0	0	0	0

	99.9	0	0	0	0	0	0	0	0

No Stack	95	5	5	15	15	25	20	25	25

	99	60	50	110	95	170	145	245	215

	99.9	160	135	285	245	440	375	680	580

Portable Stack

1 xch/min.	95	0	0	0	0	0	0	0	0

	99	0	0	0	0	0	0	0	0

	99.9	0	0	0	0	0	0	0	0

PPQ

1 xch/min.	95	5	0	10	5	10	5	15	10

	99	15	10	30	25	45	35	65	60

	99.9	20	15	40	35	60	50	90	75

As indicated above, monitoring data have been integral in the
development of this risk assessment.  In the previous phase 3 risk
assessment for methyl bromide (D316326, 6/13/05), all of the monitoring
data that were evaluated were identified and summarized.  None of this
information or analysis has changed since the previous assessment.
Table 20 below provides a summary of these data and presents margins of
exposure (i.e., MOEs) calculated based on them (i.e., MOEs > 30 are not
of concern).

Table 20:  Risks From Methyl Bromide Exposure Based On Maximum 24 Hour
TWA Concentrations Using Residential Fumigation Volatility Data

N	Number Monitors

Not Detected	Timing and Distance from Structure	Maximum 24 Hour [TWA]
(ppm)	Acute MOE

56	11	During Fumigation

10 ft	1.5	7

56	2	During Aeration

10 ft	0.611	16

35	0	During Aeration

50 to 100 ft

(Inside Neighboring Houses)

	0.077	130

The results indicate that the potential risks which have been calculated
for methyl bromide emissions from treated residences can be of concern
as calculated acute MOEs in two cases are less than 30.  If one were to
review PERFUM outputs for various analyses it would also indicate that
for many circumstances predicted buffer distances would be small (e.g.,
<10 meters or so) at lower percentiles of exposure or depending  upon
the aeration method.  In summary, monitoring data support the types of
results that have been calculated using the PERFUM model in some
circumstances.  Additionally, the limitations associated with the use of
monitoring data are also explicit based on the nature of the data.  If
so desired, the previous risk assessment and its associated appendices
that contain all of the monitoring data information can be found at
HYPERLINK "http://www.Regulations.gov"  www.Regulations.gov  under
docket OPP-2005-0123 (i.e., key various elements include:
OPP-2005-0123-007 – bibliography; OPP-2005-0123-012 – residential
monitoring data).

5.1.2 	Ambient Bystander Exposure From Regional Sources tc \l3 "6.1.2
Ambient Bystander Exposure From Multiple Regional Sources

Ambient levels of methyl bromide are generally not attributable to
specific application events, rather contributions may occur from
multiple sources within a region.  For example, it is likely that
individuals could potentially be exposed to methyl bromide if they live
in proximity to or otherwise frequent areas where significant uses occur
such as a neighborhood located around several strawberry fields in
California during the season of use.

Exposures from ambient air were estimated from monitoring data collected
solely in California to represent conditions at a regional and
state-wide level.  The California Air Resources Board (hereafter
referred to as CARB) generated most of the data considered in this
analysis.  CARB is a widely recognized institution for these types of
programs and it is part of the California Environmental Protection
Agency.  CARB conducts air monitoring studies for various types of
chemicals throughout California.  The studies conducted by CARB can
generally be categorized as one of two types including: (1) targeted
monitoring typically completed upon request to provide information
related to specialized issues such as fumigant exposures in areas of
high use during the season of use and (2) routine monitoring for select
pollutants via established networks in order to better quantify
exposures in the general population (i.e., CARB Toxic Air Contaminant
monitoring program or TAC).  Additional data were considered that were
generated by the Alliance of the Methyl Bromide Industry (AMBI).  Review
of the AMBI data identified quality control issues in some sample
collection procedures and for this reason they are presented only for
comparative purposes.

For ease and clarity, the Agency has opted by convention to describe the
available ambient bystander data used in this assessment as follows:

(1) “CARB Data”:  includes targeted monitoring data generated by
both CARB and AMBI focused on areas of high methyl bromide use in the
season of use  (AMBI is for comparative purposes only); and

(2) “TAC Data”:  includes data from CARB’s Toxic Air Contaminant
Network for Methyl Bromide that quantifies background levels in
non-agricultural, urban environments.

The results associated with the CARB data are presented in Section
<IP_ADDRESS> below while the results associated with the TAC data are
presented in Section <IP_ADDRESS>.

<IP_ADDRESS>	Exposures From Regionally Targeted Ambient Air Monitoring tc \l4
"<IP_ADDRESS>	Exposures From Regionally Targeted Non-Point Source Ambient Air
Monitoring

In 2000 and 2001, CDPR requested that CARB conduct a series of studies
to quantify ambient levels of methyl bromide
(http://www.cdpr.ca.gov/docs/empm/pubs/tac/requests.htm).  [Note:  An
additional study, which is not included below, was completed by CARB in
Ventura California in 2005.  This study is being repeated since it
appeared not to quantify peak emission times based on the initiation
date.]  The CDPR also requested that the Alliance of the Methyl Bromide
Industry (AMBI) conduct monitoring studies.  Because most of
California’s pesticide applications normally occur in agricultural
areas and are seasonal in nature, CARB conducts the monitoring studies
to collect data during the worst-case situation - in the areas of high
use during the season of peak use - instead of collecting samples
throughout the State. This "worst-case" information can then be used to
determine the ambient exposures of those people living near places where
pesticides are used.

For the targeted ambient air analysis, HED evaluated different durations
of exposure including single day acute exposures, short- and
intermediate-term exposures, and chronic exposures (Table 21).  Since
samples were collected 3 to 4 times per week from each station, and the
contribution of specific

applications could not be determined, the statistics were calculated by
station and not on a regional basis (e.g., county).  Risks from acute
exposures were calculated using the maximum 24 hour TWA values measured
at each station and comparing them to the acute 24 hour HEC.

Risks from short- and intermediate-term exposures (i.e., same HEC and
uncertainty factors apply to both durations) were calculated using the
mean of 8 weekly means calculated by DPR for samples taken over the
course of the use season and comparing them to the short- and
intermediate-term HEC.  This approach was taken in order to
statistically weigh equally each week’s contribution to the overall
seasonal mean because of differing numbers of samples in some weeks.
Concentrations over the course of a season monitored in these studies
did not vary extensively so calculation of average concentrations for
shorter durations (e.g., 4 weeks) or even the use of an overall mean of
all samples would not expected to be significantly different than
estimates used in this assessment.  This supposition is supported
physically because these studies spanned high use seasons in high use
areas and use would not be expected to dramatically change at these
locations during use seasons.  It should be noted that the statistical
summaries of the available data were completed by DPR and that the
Agency reviewed and concurred with this approach.  There are many
possible ways to calculate exposure estimates given the available data
for completing a short- and intermediate-term assessment.  For example,
a TWA over an entire season could be calculated or weekly TWAs could be
calculated and then averaged over a season. The Agency agrees with the
CDPR use of the mean of 8 weekly means because it does not weigh results
for the number of samples collected in a week (i.e., most weeks had 4
samples but some had 3) and it does not require a data filling procedure
for the days missing each week (i.e., usually Wed., Sat., and Sun with
most applications early in the weekend because of near school issues).

Chronic exposure estimates were also calculated using the targeted
ambient data.  These calculations should be considered relatively
uncertain estimates of exposure because of a lack of monitoring studies
specifically designed for this purpose and the manner in which seasonal
estimates were extrapolated.  Specifically, short- and intermediate-term
estimates were amortized to reflect a potential for exposure of 180 days
out of each calendar year in order to calculate chronic estimates of
exposure.  This was determined based on the approximate use patterns for
methyl bromide over a year in high use areas.  This approach does
introduce the potential for significant uncertainty into the estimates,
however, the Agency views the potential for chronic exposures in high
use regions as significant and has addressed this scenario in order to
be health protective.  Because there are many uncertainties associated
with the approach used in this assessment it is difficult to determine
how these estimates either over- or under-predict actual chronic
exposures for those living in high use areas.  There are several factors
that should be considered:

Monitoring was specifically targeted toward areas of high use, this
limits the  populations for which these types chronic exposure estimates
could be applied (i.e., for those living in such regions);

More refined amortization approaches on a regional basis could be
possible with use data, especially in California, but in most regions
such data are not available; and

Targeted monitoring was conducted during selected seasons of high use,
but because the data are limited, the impacts of changing conditions
(e.g., from different pest pressures, use patterns, or extended seasons)
cannot be quantified, especially for different regions of the country
with different climates, which could lead to potentially missing higher
end exposures under some conditions.

Acute exposures (24 hour TWAs) for all of the monitoring stations
considered (i.e., 30 stations), do not exceed the Agency's level of
concern (i.e., all calculated MOEs > 30).  Results were similar for the
8 week TWA exposures (short- and intermediate-term exposures) in that
risks calculated based on results from none of the monitoring stations
exceed the level of concern.  For both durations of exposure, risks were
orders of magnitude less than the level of concern (i.e., MOEs >30 in
many cases, some by 2 or 3 orders of magnitude).  These results should
be considered in conjunction with the fact that these studies were
deemed to be worst-case situations as described by CDPR above.  Risk
estimated from chronic exposure based on extrapolating seasonal CARB
data were also calculated because monitoring data specifically meant to
establish chronic exposure levels in high use areas were not available.
Based on this approach, in some cases, chronic risks exceeded the level
of concern (i.e., MOEs < 100 for 13 of 46 stations/years); however, it
is believed that these results do not pose an imminent health concern to
the general public due to the nature of the calculations as described
above.  CDPR also reached similar conclusions that risks resulting from
exposure to ambient air were of minimal concern.

Table 21: Results of 2000 Through 2002 California Ambient Monitoring In
High Use Areas During Season Of Use

CA.

County	Data Source	Site	Dates &

Mon.

Days (N)	Maximum 24 Hr. TWAs (ppb)	Acute MOE!	8 Week TWA  (mean of
means) (ppb)	Short and Intermediate-Term MOE2	Amortized 180 days (ppb)
Calculated Chronic MOE3

Kern	CARB	ARB	7/10-9/1, 2000 (25)	0.996	10040	0.189	5291	0.09	966

	6/30-8/31, 2001	0.31	32258	0.12	8333	0.06	1521

SHA	7/10-9/1, 2000 (26)	3.52	2841	0.792	1263	0.39	230

CRS	7/10-9/1, 2000 (24)	14.2	704	2.16	463	1.07	84

	6/30-8/31, 2001	33.50	299	2.49	402	1.23	73

MVS	7/10-9/1, 2000 (26)	0.487	20534	0.092	10870	0.05	1984

	6/30-8/31, 2001	0.23	43478	0.08	12500	0.04	2281

VSD	7/10-9/1, 2000 (26)	0.247	40486	0.099	10101	0.05	1843

	6/30-8/31, 2001	0.23	43478	0.08	12500	0.04	2281

MET	7/10-9/1, 2000 (26)	0.224	44643	0.084	11905	0.04	2173

	6/30-8/31, 2001	0.25	40000	0.07	14286	0.03	2607

ARV	6/30-8/31, 2001	0.22	45455	0.07	14286	0.03	2607

Ventura	AMBI

(CDPR Stats Used)	SHA	8/15-10/10, 2001	2.94	3401	0.50	2000	0.25	365

	7/10-8/31, 2002 (31)	5.77	1733	0.58	1724	0.29	315

ABD	8/15-10/10, 2001	0.44	22727	0.18	5556	0.09	1014

	7/10-8/31, 2002 (30)	3.44	2907	0.76	1316	0.37	240

UWC	8/15-10/10, 2001	4.35	2299	0.82	1220	0.40	223

	7/10-8/31, 2002 (26)	13.17	759	2.22	450	1.09	82

PVW	8/15-10/10, 2001	3.17	3155	0.56	1786	0.28	326

	7/10-8/31, 2002 (32)	9.51	1052	1.62	617	0.80	113

Santa Barbara	AMBI

(CDPR Stats Used)	PLN	8/23-10/9, 2001	2.69	3717	0.93	1075	0.46	196

EDW	8/23-10/9, 2001	11.15	897	1.32	758	0.65	138

AGC	8/23-10/9, 2001	1.16	8621	0.28	3571	0.14	652

BLO	8/23-10/9, 2001	4.55	2198	0.73	1370	0.36	250

SLO	8/23-10/9, 2001	1.12	8929	__	__	__	__

Monterey	CARB	SAL	9/11-11/3, 2000 (31)	7.91	1264	1.29	775	0.64	141

	9/8-11/7, 2001	9.25	1081	1.38	725	0.68	132

OAS	9/11-11/3, 2000 (31)	1.84	5435	0.387	2584	0.19	472

CHU	9/11-11/3, 2000 (31)	2.41	4149	0.644	1553	0.32	283

	9/8-11/7, 2001	1.84	5435	0.56	1786	0.28	326

LJE	9/11-11/3, 2000 (30)	24.0	417	3.79	264	1.87	48

	9/8-11/7, 2001	14.49	690	2.82	355	1.39	65

	AMBI

(CDPR Stats Used)	BBC	9/4-10/26, 2002 (32)	6.28	1592	2.08	481	1.03	88

MAQ	9/4-10/26, 2002 (32)	4.53	2208	1.12	893	0.55	163

Santa Cruz	CARB	PMS	9/11-11/3, 2000 (31)	30.8	325	7.68	130	3.79	24

	9/8-11/7, 2001	21.08	474	2.99	334	1.47	61

SES	9/11-11/3, 2000 (31)	16.4	610	2.60	385	1.28	70

	9/8-11/7, 2001	5.31	1883	1.22	820	0.60	150

MES	9/8-11/7, 2001	36.64	273	5.51	181	2.72	33

SCF	9/8-11/7, 2001	0.74	13514	Not Sampled	__	__	__

	AMBI

(CDPR Stats Used)	WAT	9/4-10/26, 2002 (30)	16.38	611	3.79	264	1.87	48

FRM	9/4-10/26, 2002 (31)	14.00	714	2.62	382	1.29	70

CPW	9/4-10/26, 2002 (30)	11.12	899	2.06	485	1.02	89

SCF	9/4-10/26, 2002 (7)	0.69	14493	NA	--	--	--

Background site sampled only during 2 nonconsecutive weeks

1.  	Acute MOE based on maximum 24 hr. TWA.

2.  	Short term  and intermediate term MOE are based on 8 wk. TWA (i.e.,
mean of weekly means).

3. 	Chronic MOE based on short-/intermediate-term exposures amortized
for 180 days exposure per year.

<IP_ADDRESS>	Exposures From Urban Background Ambient Air Monitoring tc \l4
"<IP_ADDRESS>	Exposures From Regionally Targeted Non-Point Source Ambient Air
Monitoring

In 2002, CARB added methyl bromide to its list of contaminants for which
it routinely screens in its TAC program (see
http://www.cdpr.ca.gov/docs/empm/pubs/tac/monitoring.htm).  The location
of these monitoring stations, however, shifted from a potential
“worst-case”, in-season use situation as described in section
<IP_ADDRESS> above to the following:

“The ARB has a network of stations that routinely monitor California's
air for a variety of pollutants such as ozone, particulate matter,
metals, and other toxic air contaminants. In 2002, ARB began monitoring
for two pesticides, Methyl Bromide and 1,3-dichloropropene, every 12
days at approximately 20 stations in primarily urban areas throughout
the State.”

The following should also be considered (see
http://www.arb.ca.gov/aqd/toxics/toxuses.html):

“The toxics sampling network was designed to produce a statewide
annual average to support the determination of a statewide risk
assessment. Where fewer than 12 continuous months of data are present,
we believe that it is seldom appropriate to calculate an annual average.
Most of the toxic substances show some seasonal variation, and some
substances differ by as much as two orders of magnitude between the high
and low periods of the year. If a month's data are missing, the
calculated average could be radically different from the real average,
the average that would have been calculated had the missing month's data
been available.”

TAC monitoring sites are located throughout California in urban
environments that include urban areas such as Long Beach, Burbank, Los
Angeles, Fremont, Fresno, San Francisco and San Jose.  The statistical
summaries of the 2002/2003 CARB monitoring data are provided in Table
22.  They were taken directly from
http://www.arb.ca.gov/adam/toxics/statepages/mbrstate.html.
Additionally, state-wide summaries from 2004 and 2005 are included in
Table 22.  [Note:  Station-specific results for 2004 and 2005 are also
available but do not differ significantly from the earlier years (i.e.,
they do not alter the interpretation of the risks associated with urban
background levels of methyl bromide).  As such, they have not been
included in Table 22 for brevity.]

Maximum values at each station were compared to acute HECs to estimate
acute MOEs.  Short- and intermediate-term risks were estimated by
comparing means to the short- and intermediate-term HECs.  Means were
selected for this analysis because they appear in most cases to be
heavily influenced by the typical 6 to 8 week use season based on the
relative contributions of a relatively small number of samples and that
medians for most stations were reported as the level of detection.
Medians from each location were used to calculate chronic MOEs.  True
chronic exposures (continuous exposures >6 months) in and around most of
the monitored sites probably do not occur because the limit of detection
(½ LOD or 0.015 ppb) has been reported as the median for approximately
75 percent of the stations for each year where there are data.  These
monitoring data indicate that exposure patterns track with seasonal use;
therefore, shorter duration exposures are more prevalent which reflects
the seasonal use of most methyl bromide in California.

No exposure levels reported by through the TAC program exceed the level
of concern for any duration of exposure including acute (all MOEs >30),
short-, intermediate-term (all MOEs >30), or chronic (all MOEs > 100)
exposures in an urban environment.

Table 22:  Results of 2002 Through 2005 California Ambient Monitoring
For Methyl Bromide In Urban Areas

Site

Year

N

Results of Annual Methyl Bromide Monitoring (ppb)

Maximum

Acute MOE!

Mean

Short and Intermediate-Term MOE2

Median

Chronic MOE3

Statewide

2002

440

0.91

10989

0.042

23810

0.015

607

2003

503

0.90

11111

0.040

25000

0.015

607

	2004	503	1.1	9090	0.036	27778	0.015	607

	2005	510	0.69	14493	0.036	27778	0.015	607

Azusa

2002

27

0.14

71429

0.041

24390

0.03

303

2003

28

0.16

62500

0.036

27778

0.015

607

Burbank

2002

30

0.14

71429

0.031

32258

0.015

607

2003

26

0.10

100000

NR

--

0.015

607

Calexico

2002

29

0.11

90909

0.020

50000

0.015

607

2003

30

0.33

30303

0.036

27778

0.015

607

Chula Vista

2002

29

0.06

166667

0.021

47619

0.015

607

2003

28

0.05

200000

NR

--

0.015

607

El Cajon

2002

28

0.06

166667

0.020

50000

0.015

607

2003

30

0.05

200000

0.021

47619

0.015

607

Los Angeles

2002

21

0.14

71429

NR

--

0.03

303

2003

29

0.10

100000

0.032

31250

0.015

607

Long Beach

2002

25

0.11

90909

0.035

28571

0.015

607

2003

27

0.13

76923

0.035

28571

0.04

228

Riverside

2002

25

0.13

76923

NR

--

0.015

607

2003

30

0.10

100000

0.028

35714

0.015

607

Simi Valley

2002

26

0.91

10989

0.101

9901

0.05

182

2003

31

0.90

11111

0.120

8333

0.015

607

Bakersfield

2002

29

0.22

45455

0.058

17241

0.04

228

2003

29

0.88

11364

0.080

12500

0.04

228

Chico

2002

29

0.14

71429

0.026

38462

0.015

607

2003

31

0.15

66667

0.022

45455

0.015

607

Fremont

2002

27

0.05

200000

0.018

55556

0.015

607

2003

30

0.11

90909

0.019

52632

0.015

607

Fresno

2002

30

0.19

52632

0.049

20408

0.015

607

2003

31

0.19

52632

0.055

18182

0.05

182

Roseville

2002

29

0.11

90909

0.021

47619

0.015

607

2003

31

0.03

333333

0.016

62500

0.015

607

San Francisco

2002

15

0.08

125000

NR

--

0.015

607

2003

31

0.015

666667

0.015

66667

0.015

607

San Jose - 4th Street

2002

8

0.09

111111

NR

--

NR

--

San Jose - Jackson St.

2002

6

0.05

200000

NR

--

NR

--

2003

31

0.23

43478

0.031

32258

0.015

607

Stockton

2002

27

0.90

11111

0.144

6944

0.05

182

2003

30

0.48

20833

0.088

11364

0.04

228

Mexicali - Mexico

2002

19

0.10

100000

NR

--

0.015

607

2003

17

0.07

142857

NR

--

0.015

607

Rosarito - Mexico

2002

25

0.05

200000

NR

--

0.015

607

2003

30

0.14

71429

0.027

37037

0.015

607

1.  	Acute MOEs based on maximum concentrations.

2.  	Short term and intermediate term MOE are based on the mean
concentrations.

3.  	Chronic MOEs are based on the median concentration.

5.2	Bystander Risk Characterization tc \l2 "6.2	Bystander Risk
Characterization

It is believed that the data and methodologies used in the development
of this assessment represent the state-of-the-science relating to
pesticides that can be characterized as fumigants.  However, it is clear
that there is an ongoing evolution relating to the types of data that
could be used to complete such assessments in the future.  Essentially,
all data that were currently available were used herein but those data
clearly have limitations related to overall quality, as well as temporal
and spatial limitations.  It is also clear that the PERFUM modeling
framework provides significant amounts of information appropriate for
risk managers to consider but that there are other systems that could be
considered as robust for the same types of analyses.  As indicated
above, submissions based on other viable modeling frameworks would be
considered for risk management purposes.

Some of the limitations and considerations that have been identified
that should be considered in the interpretation of these results
include:

All of the data used for this analysis have been generated in
California; however, methyl bromide is used in many regions of the
country.  In fact it is possible that most methyl bromide use occurs in
the Southeast but no emissions data are available for specifically
modeling emissions from that region or any other region where methyl
bromide is used.  As a direct result of a lack of additional data, the
results presented herein are based solely on California data and
agricultural practices.  Factors such as soil type, solar radiation
levels, or farming practices themselves may impact the overall amounts
of methyl bromide emitted and the rate at which it is emitted over time,
thus buffer outputs predicted using PERFUM could be impacted but it is
not possible to quantify this sensitivity at this point.  PERFUM is not
a first-principles model (i.e., it cannot predict results for
incremental changes in soil conditions parameters such as soil
temperature or percent moisture).  Instead, PERFUM is an empirical model
that is calibrated to specific emissions profiles that then serve as the
basis for predicted results.  This is a very common modeling approach
when first-principles models are not available.  Additionally, the flux
profiles that were used as the basis for the PERFUM results in this
assessment were defined based on what is known as the back-calculation
method as opposed to direct reading or aerodynamic flux approaches.  At
this point, the Agency treats results based on all of these methods
similarly as there is no information in the applicable literature to
suggest that any are inherently biased to over- or under-prediction of
flux.  Flux inputs for the greenhouse and residential uses are based on
the same approaches as D304623.

Data quality associated with the calculation inputs also needs to be
considered.  For most of the data, it is believed that they are of
reasonable quality for risk assessment purposes.  A significant number
of studies were generated by CARB and CDPR.  Because of the rigorous
quality control and quality assurance protocols employed by these
Agencies, the resulting data are generally believed to be of high
quality.  Additionally, the industry group AMBI also generated a
significant amount of data.  Some technical issues have been identified
with those data (i.e., problems with completeness and flow controller
issues in some data) but they have been included for comparative
purposes.  AMBI-based results are generally similar to those observed
based on the other data which indicates no major impacts based on data
quality.

The premise of the PERFUM-predicted buffer zones is based on a
developmental effect which by definition, implies that a pregnant woman
is at a location where the time-weighted average concentration of methyl
bromide can be of concern.  There are several probabilities related to
an exposure event which must be met for such developmental effects to
occur.  These include:

An exposed individual must be female and at a critical phase of the
pregnancy for the effect to occur;

An exposed individual has to be in proximity to a methyl bromide
application/aeration event for a sufficient duration for the effect to
occur - there are 3 key factors to consider for this element including:

that the types of applications considered in this assessment are either
seasonal or infrequent which limits the number of possible adverse
exposure events,

time-activity data indicate that many parts of the population move from
site to site on a daily basis (e.g., to go to work and back) which
limits the overall number of possible adverse exposures events, and

time-activity data indicate that most individuals spend a majority of
their daily time indoors and for intermittent exposure sources such as
this it is known that being indoors typically reduces exposures to
contaminants relative to outdoor air but the PERFUM results do not
account for this exposure reduction factor.

A multi-faceted approach was used to evaluate risks using monitoring
data, incidents, and the distributional model, PERFUM.  Monitoring data
have temporal and spatial limitations as has been discussed above.
Incident data are informative but their use for characterization
purposes is also limited because the exact conditions that lead to
specific incident events are difficult, if not impossible, to quantify
thus making any reconstruction of their circumstances limited unless
blatantly obvious such as a railcar accident.  However, for methyl
bromide, most incidents in the general population are believed to be
associated with a significant equipment failure, atmospheric inversion,
or misuse of some sort, intentional or not.  Because the endpoint of
concern associated with methyl bromide is developmental in nature, it is
highly likely that individuals in the general population would not
associate such health issues with a previous exposure to methyl bromide.
 For this reason, it is possible that methyl bromide incidents in the
general population could be under-reported.  Effects that would be
likely to be experienced in the general population after a methyl
bromide incident would be irritant effects from its companion chemical,
chloropicrin, for many applications.  Symptoms experienced such as
shortness of breath or chest tightness are not readily attributable to
methyl bromide exposure.

PERFUM modeling results (or any distributional model for that matter)
can provide risk managers with much needed information about the range
of risks expected in the general population.  At this time, policy
development is ongoing with regard to defining how appropriate
selections of PERFUM outputs can be defined for risk management purposes

It is believed that PERFUM provides the most refined estimates of risk
because it can consider actual weather data and also integrate flux
distributions in order to develop distributional estimates of buffer
distances and concentrations at various distances from a source.  PERFUM
uses ISCST3 as its core processor which is an existing Gaussian plume
technology that has been utilized for air permitting by the Agency for
many years (see Technology Transfer Network Support Center for
Regulatory Air Models at http://www.epa.gov/scram001/tt22.htm#isc).
Several issues need to be considered related to the modeling analysis
which was completed herein.  These include:

It has been assumed that there is a linear relationship between
application rate and flux, but this assumption has not been validated
with emissions data conducted in similar conditions but at different
application rates.  The California Department of Pesticide Regulation
has used this assumption in previous fumigant assessments.

The treatment of calm periods (wind speeds below 1 m/s) in PERFUM/ISCST3
is also an uncertainty.  PERFUM runs the ISCST3 model in the
“regulatory default option” (the default setting for ISCST3), which
includes the use of the calms processing routine as is described in
Agency guidance.  The calms processing routine for wind speeds below 1
m/s essentially ignores any hourly sequence in the calculations that
meets this criteria.  This approach can possibly skew results for
shorter averaging times because an analysis period that contained
several calm hours would be dominated by any period where there was a
windspeed above 1m/s.  This is a common approach in Gaussian plume
modeling.  PUFF-based models such as CALPUFF have meander algorithms
that can account for calm conditions by accounting for static or near
static plume conditions and representing such events in the results.
Whether or not buffer estimates are enhanced or under-reported as a
result of this phenomenon depends upon the nature of the weather data
used for the calculations.  Preliminary analysis related to this issue
do not indicate significant differences when hourly calculation steps
are used especially when 24 hour time weighted average exposures are
calculated.  If less than hourly steps (e.g., minute by minute
calculations such as in CALPUFF v6) are used, the effect is attenuated
because the relative percentage of calm periods in the available weather
data seems to be diminished.

The PERFUM analyses completed for this assessment are based on the
assumption that an application has an equal probability of occurring
each day out of the 5 years of weather data.  This method does not take
into account the seasonal use patterns of fumigants in different regions
of the country.  Table 14 above provides an example of monthly
distributional results which could be examined if so desired for every
PERFUM output.  The result for each month is based on 5 months worth of
weather data instead of 5 years when all months are considered.  It
should also be noted that the selection of the sources of weather data
for this assessment, as mentioned above, represent a range of mean
windspeed values as described in the SAP document for PERFUM.  The
locations of the Florida and California stations were intentionally
selected based on this range and their coastal and inland locations.

Different field sizes and aspect ratios were considered in this
assessment (most fields were square in shape for this analysis).  As
field size increases so do predicted buffer zones which is similar to
what is noted based on increases in application rates.  Field aspects
were also examined and the orientation did impact results although it is
difficult to ascertain any general prediction based on this analysis
since field orientations relative to prevailing wind directions will
vary from site to site or region to region.

The use of a maximum 40 acre field in the risk assessment may possibly
understate potential exposure received by bystanders near treated fields
that are larger.

PERFUM was recently modified to also produce distributions of
concentrations at various receptor ring distances from the edge of a
treated field or source.  This capability was added near the completion
timeframe of this assessment.  As appropriate, this capability will be
utilized in the development of risk management decisions.

Several factors also need to be considered in the interpretation of the
results associated with the assessment of exposures from ambient air.
It is clear from the characterization of the data provided by CARB that
some data represent highly targeted monitoring in a region during the
season of use and others represent urban background levels.  Because of
this, the results should be considered representative for the state of
California for those types of situations.  However, California has a
number of restrictions and systems in place where the overall goal is to
reduce environmental emissions from fumigant use.  Consequently, it is
difficult to quantify how the results presented above may apply to other
regions of the country that do not have these types of programs in
place.

6.0	Occupational Exposure tc \l1 "9.0	Occupational Exposure

In this assessment, a number of chemical-specific monitoring studies
were available to evaluate the exposures of applicators as well as those
otherwise involved in that process (e.g., co-pilots, shovelmen, or
greenhouse workers).  Likewise monitoring data were also available to
assess the possible exposures that could occur after application events
such as for tarp cutters and tarp removers.  [Note:  Tarp cutter and
tarp remover data were generated in a period 4 to 6 days (or greater)
after an application and most data represent exposures from fields
covered with high barrier films.]  The monitoring data were not adjusted
based on application rates because these data represent cultural
practices that are allowable under current methyl bromide labels even
though for many situations they could represent conservative estimates
of exposure.  This is because they were collected at higher application
rates than is currently typical.  Another consideration is the equipment
that was used because most of the data were generated in the 1980s and
early 1990s.  Since that time, California DPR has restricted methyl
bromide uses to types of equipment intended to minimize exposures.
However, this evolution is not evident in all other areas of the country
so the data, even though they were generated years ago for the most part
in California, can still be considered to be representative of many
methyl bromide domestic uses.

Overall, data indicate that worker exposure levels exceed the level of
concern for all scenarios considered when no respiratory protection is
used.  The use of either air purifying respirators (APRs) or self
contained breathing apparatus (SCBA) was also considered with varied
results.  The use of an APR reduces exposure levels by a factor of 10
and the use of SCBA reduces exposure levels by a factor of 10,000.
[Note: There are commercially available APR cartridges that have been
evaluated and recommended for reducing exposure levels, see the
technical bulletin 146 for cartridge 60928 at www.3M.com for more
information.  Protection factors are derived based on individuals who
have been trained, fit tested, and medically cleared for respirator use
but are generally applied for risk assessment purposes.]  Respirators
would be the most practical personal protective equipment choice for
reducing exposures for most workers.  The use of engineering controls is
also considered a viable option for reducing exposures.  However, much
of the field monitoring data used for this analysis already reflect the
use of varied levels engineering controls such as tarps, tractor cabs,
deep injection, or other devices including fans in proximity to drivers,
Nobel plows, or various compaction methods.

When APRs were evaluated with maximum exposure levels in order to assess
acute exposures, for most activities, exposures were not reduced
sufficiently to address risk concerns.  When APRs were evaluated with
mean exposure levels in order to assess short-/intermediate-term
exposures, the results were varied with all greenhouse scenarios
resulting in risks still exceeding the level of concern but risks from
most field uses not being of concern.  The use of SCBA is not normally
deemed to be a viable option for agricultural workers or for uses in
greenhouses due to the difficulty in handling and maintaining these
devices as well as the cost to implement them as an exposure reduction
tool.  However, in certain situations such as residential treatments, it
is believed that SCBA may represent a viable option for reducing
exposures for a limited number of workers.  Risks from exposures during
residential treatments were not of concern if SCBA is used.

Modeling has also been used to predict air concentrations at the edge of
a treated field to determine if air concentrations have diminished to
levels that are not of concern (e.g., use of concentration outputs from
PERFUM at varied ring distances from field perimeter).  This
information, coupled with available monitoring data can be useful for
defining how long the conduct of various post-application tasks or entry
into previously treated areas should be restricted.  Current
requirements for entry of post-application workers into previously
treated fields are dictated by the Worker Protection Standard as
described in PR 93-7.  For methyl bromide, such workers are excluded for
48 hours after treatment.  PERFUM outputs representing air
concentrations 5 meters from the treated field edge support the current
48 hour requirement for soil uses if tarps are not disturbed.  However,
tarp cutter and remover activities require APR use.  Greenhouse and
residential uses require active aeration to achieve levels that are not
of concern (e.g., current labels specify a 5 ppm target concentration).
Generally, this approach seems appropriate but the 5ppm target may be
altered based on risk management considerations.

The occupational tasks commonly associated with the use of methyl
bromide along with the corresponding risks are described below for each
use sector considered.  [Note:  Risks from chronic exposures have not
been calculated because methyl bromide use is highly seasonal.  Methyl
bromide is not expected to be used every working day for more than 6
months, for commercial applicators or large scale growers based on
available information.  Additionally, in smaller scale production,
applications are thought to be infrequent because growers would often
times just treat their own facilities.]  Sections 6.1 through 6.3
provide risk estimates for each use pattern considered in this
assessment while Section 6.4 describes the issues that should be
considered when interpreting these results.

6.1	Pre-plant Agricultural Field Fumigations tc \l2 "9.1	Pre-plant
Agricultural Field Fumigations

Several tasks were identified that are associated with the application
of methyl bromide to agricultural fields.  The data for each scenario
varied but essentially all available data for each was considered in
this assessment.  It should also be noted that for tarp cutters and tarp
removers, these activities were monitored mainly between 4 and 6 days
after application and in most cases the tarps were referred to as high
barrier materials. The tasks considered in this assessment include:

a) First Tractor Driver,

b) Co-pilot

c) Second Tractor Driver

d) Shovelman

e) Irrigation Worker

f) Tarp Cutter

g) Tarp Remover

Table 23 indicates that if no respiratory protection is considered,
risks exceed the level of concern for all scenarios and durations except
for the second tractor drivers where risks were acceptable even without
respiratory protection.  As a result, the impact of the use of an APR
(PF 10) with the recommended cartridge was evaluated to determine how
their use would impact worker risks.  Acute risks for all other
application scenarios with the APR still exceed HED’s level of concern
(with MOE <30).  Risks were not of concern for all tarp removal
operations if an APR is used (i.e., MOEs are 63 and 231).  Short- and
intermediate-term risks without respiratory protection were of concern
except for second tractor drivers as with the acute duration.  However,
short- and intermediate-term risks with the APR are not of concern for
the majority of tasks  (i.e., MOEs >30) except for tractor drivers and
co-pilots where the MOEs are 18 and 11, respectively.  [Note:  Table 23
has been modified from the Phase 3 assessment based on comments
submitted by the Methyl Bromide Industry Panel (MBIP) pertaining to the
specific data used for this analysis.  Essentially, many of the comments
are correct and the Agency has adjusted the values in Table 23
accordingly.  The MBIP comments are available in the methyl bromide
docket at the following:    HYPERLINK "http://www.Regulations.gov"
www.Regulations.gov  under docket number EPA-HQ-OPP-2005-0123-0127.]

As indicated above, restricting entry into previously treated fields can
be evaluated using a modeling approach or based on the tarp removal
monitoring data.  It appears that a the emission profile (based on
preliminary PERFUM outputs) indicates that concentrations will decrease
to levels that are not of concern, even at high percentiles of exposure
3 days after treatment.  This indicates that the current 48 hour
restriction is adequately protective.  However, if operations occur
which disturbs the tarp of a treated field it is likely that air
concentrations will be at levels of concern and that respirator use
would be required to reduce them to levels not of concern.

Table 23: Methyl Bromide Worker Exposure Associated With Pre-Plant
Agricultural Field Fumigation

Scenario	N	Acute Risk Summary	Short/Intermediate-term Risk Summary

Maximum Monitored [mebr]

(ppm)	Acute MOE With No Respiratory Protection	Maximum Monitored [mebr]
With Air Purifying Respirator (PF10)

(ppm)	Acute MOE With Air Purifying Respirator (PF10)	Average Monitored
[mebr]

(ppm)	Short-term MOE With No Respiratory Protection	Maximum Monitored
[mebr] With Air Purifying Respirator (PF10)

(ppm)	Short-term MOE With Air Purifying Respirator (PF10)

1st Tractor Driver	82	38.1	<1	3.81	8	2.5	2	0.25	18

Co Pilot	92	47.4	<1	4.74	6	4.1	1	0.41	11

2nd Tractor Driver	3	0.02	1500.0	0.002	15000	0.015	293	0.0015	2933

Shovelman 	67	12.4	2	1.24	24	0.95	5	0.095	46

Irrigation	20	20.4	2	2.04	15	1.2	4	0.12	37

Tarp Cutter	7	4.8	6	0.48	63	0.67	7	0.067	66

Tarp Remover	22	1.3	23	0.13	231	0.48	9	0.048	92

Total number of monitoring events used for this analysis = 293

MOE = Margin of Exposure, Level of concern is MOE<30

Acute MOE = (30 ppm HEC/maximum [mebr])

Short/Intermediate-term MOE = (4.4 ppm HEC/mean [mebr])

6.2	Greenhouse Fumigations tc \l2 "9.2	Greenhouse Fumigations

Several tasks were identified that are associated with the application
of methyl bromide in greenhouse operations.  The data for each scenario
varied but essentially all available data for each was considered in
this assessment.  The tasks considered in this assessment include:

a) Greenhouse Applicators

b) Venters

c)  Greenhouse Workers

Table 24 indicates for greenhouse applicators and workers, risks were of
concern for all scenarios and durations considered even when respiratory
protection such as an PF10 APR is used (i.e., all MOEs <30).  Risks for
greenhouse venters were of concern if no respirator is used but are not
of concern if an APR is used regardless of the duration of exposure
considered.

Determining when entry into previously treated greenhouse structures is
not of concern is important in the greenhouse industry because of the
many hand labor-based practices that are required to produce plant
materials in these settings (e.g., transplanting).  Currently,
greenhouse uses require active aeration to achieve levels that are not
of concern (e.g., current labels specify a 5 ppm target concentration).
Generally, this approach seems appropriate but the 5ppm target may be
altered based on risk management considerations.  No further
quantitative assessment has been completed for these scenarios because
results will be specific to the structures which are treated.

Table 24: Methyl Bromide Worker Exposure Associated With Greenhouse
Fumigation

Scenario	N	Acute Risk Summary	Short/Intermediate-term Risk Summary

Maximum Monitored [mebr]

(ppm)	Acute MOE With No Respiratory Protection	Maximum Monitored [mebr]
With Air Purifying Respirator (PF10)

(ppm)	Acute MOE With Air Purifying Respirator (PF10)	Average Monitored
[mebr]

(ppm)	Short-term MOE With No Respiratory Protection	Maximum Monitored
[mebr] With Air Purifying Respirator (PF10)

(ppm)	Short-term MOE With Air Purifying Respirator (PF10)

Greenhouse Applicators 	11	2000	<1	200	<1	330	<1	33	<1

Greenhouse Venters	13	5.8	5	0.58	52	0.92	5	0.092	48

Greenhouse Workers	17	200	<1	20	2	25	<1	2.5	2

Total number of monitoring events used for this analysis = 41

MOE = Margin of Exposure, Level of concern is MOE<30

Acute MOE = (30 ppm HEC/maximum [mebr])

Short/Intermediate-term MOE = (4.4 ppm HEC/mean [mebr])

6.3	Residential Fumigation tc \l2 "9.5	Residential Fumigation

Several tasks were identified that are associated with the application
of methyl bromide in residential operations (e.g., house preparation,
application and aeration activities).  The data for each scenario varied
but essentially all available data for each was considered in this
assessment.  However, the data were limited so the the tasks considered
in this assessment include:

Outside Worker

Inside Worker

Table 25 indicates for all scenarios and durations considered, risks
without respiratory protection exceed the level of concern for all
durations of exposure (i.e., all MOEs <30).  As a result, HED evaluated
how the use of a SCBA (PF 10,000) would impact worker risks since it is
believed that these represent a possible risk mitigation measure for
workers involved in residential fumigations.  SCBA use reduces risks to
levels where they are not of concern for all durations of exposure
(i.e., MOE>30).

Determining when entry into previously treated residential structures is
not of concern is important not to displace residents for extended
periods of time.  Currently, residential uses require active aeration to
achieve levels that are not of concern (e.g., current labels specify a 5
ppm target concentration).  Generally, this approach seems appropriate
but the 5ppm target may be altered based on risk management
considerations.  No further quantitative assessment has been completed
for these scenarios because results will be specific to the structures
which are treated.

Table 25: Methyl Bromide Worker Exposure Associated With Residential
Fumigation

Scenario	N	Acute Risk Summary	Short/Intermediate-term Risk Summary

Maximum Monitored [mebr]

(ppm)	Acute MOE With No Respiratory Protection	Maximum Monitored [mebr]
With SCBA (PF10000)

(ppm)	Acute MOE With SCBA (PF10000)	Average Monitored [mebr]

(ppm)	Short-term MOE With No Respiratory Protection	Maximum Monitored
[mebr] With SCBA (PF10000)

(ppm)	Short-term MOE With SCBA (PF10000)

Outside Worker	12	57	<1	0.0057	5263	22	<1	0.0022	2000

Inside Worker 	4	982	<1	0.098	306	357	<1	0.036	122

Total number of monitoring events used for this analysis = 16

MOE = Margin of Exposure, Level of concern is MOE<30

Acute MOE = (30 ppm HEC/maximum [mebr])

Short/Intermediate-term MOE = (4.4 ppm HEC/mean [mebr])

6.4	Occupational Risk Characterization tc \l2 "9.5	Residential
Fumigation

There are several issues that should be considered when interpreting the
results of this risk assessment.  Compared to most occupational
assessments, the data used to complete this assessment are plentiful in
that 293 chemical-specific monitoring events were considered in this
analysis.  Most data were generated by either CDPR or investigators with
significant experience monitoring for methyl bromide using standard
capture methods.

However, it should be considered that much of the data used in this
assessment are 10 years old or older and may not necessarily reflect
absolute state-of-the-art cultural practices in many areas of the
country.  For example, modern application controller systems, which are
becoming more widespread, are highly sophisticated programmable devices
that control applications in real-time by accounting for micro-changes
in application conditions such as changing line pressures or tractor
speeds.  It is possible that these systems could reduce exposure levels
but their impact is not reflected in the data upon which this assessment
is based.  Other examples of practices that may not be captured include
state-of-the-art shank designs that are intended to reduce emissions or
other emission reduction approaches such as high barrier films or
compaction methods.

In some cases, varied engineering controls were used by those being
monitored so they are inherent in the resulting exposure levels.
Examples of such devices include fans located near the tractor driver to
dilute potential methyl bromide exposures.  Varying shank depths or soil
sealing methods could also reduce exposures but again the impacts of a
single factor are difficult to ascertain based on the available data.
Rather than to attempt to further delineate the data based on these
factors, the data were grouped as presented above recognizing that each
task category presented above probably represents a range of exposures
that could occur for that task based on varied available equipment.
Alternatively, if an attempt was made to quantitatively assess each
possible scenario the numbers of monitoring events for each category
would sometimes be very low (i.e., in some cases, 1 or 2 events) which
minimizes the ability to compare results among scenarios.  In summary,
the data used for this assessment should be considered acceptable for
risk assessment purposes and that, if anything, current agricultural
practices and systems would likely lead to lower exposure estimates than
those presented above.  This is likely because the intent of the
evolving cultural practices over recent years has been to provide for
more efficient and accurate application events in a manner that still
achieves efficacy and to also reduce overall emissions and exposures.

The results of the occupational risk assessment should also be
considered in the context of the available incident data.  In many
cases, occupational incidents involve skin sensitization or even
chemical burns which are consistent with the toxicity profile for methyl
bromide (i.e., it is a Category 1 acute dermal and eye irritant – see
Appendix A).  For this reason, loose fitting clothing is stipulated on
methyl bromide labels so as not to trap residues close to the skin.
Irritation effects are also often noted as described above which are
difficult to differentiate from cholorpicrin exposure which is often
companion applied with methyl bromide.  As indicated above the
bystanders, it is also not surprising that other types of incidents are
not observed more frequently because some of the symptoms that could be
expected from exposure to methyl bromide may not be readily attributable
to those exposures.

[Note:  If so desired, the previous risk assessment (D316326, 7/13/05)
and its associated appendices that contain all of the monitoring data
information can be found at   HYPERLINK "http://www.Regulations.gov"
www.Regulations.gov  under docket OPP-2005-0123.]

7.0	Data Needs and Label Requirements tc \l1 "10.0	Data Needs and Label
Requirements

7.1	Toxicology tc \l2 "10.1	Toxicology

There are no additional data requirements at this time.

7.2	Residue Chemistry tc \l2 "10.1	Toxicology

Please refer to the Phase 5 risk assessment for the food uses of methyl
bromide (D304623).

7.3	Occupational and Residential Exposure tc \l2 "10.3	Occupational and
Residential Exposure

The assessment of occupational and residential risks associated with the
use of methyl bromide is complex.  There was a significant amount of
data available but additional data are still required in order to ensure
that exposures related to current cultural practices can be addressed in
future assessments.  Additionally, emissions data are required in order
to quantify the impact of using technologies intended to improve
efficacy and/or reduce emissions in order to develop model estimates
reflective of those technologies (e.g., impacts of high barrier films on
emissions).

The types of data, guideline citations, and examples of the scenarios
which need to be addressed are presented below.  It should also be noted
that the general data requirements for fumigants are being evaluated.
Factors such as application technologies, regions of use, possible
emission reduction technologies, and timing of applications will be used
to define factors such as the numbers of emissions studies which may be
required for specific use patterns, the meteorological data requirements
for modeling purposes, methods for flux calculations, and possible
criteria for ambient monitoring.  Other factors may include specific
guidance for sampling methods, numbers of samples and frequency of
sampling.  Until this effort is complete, final determination of the
types of studies to address each scenario below should be made in
consultation with the Agency.

OPPTS Guideline 835.8100 - Field volatility from soil

Volatility Studies To Determine Flux For Modeling Purposes In Major Use
Regions Of Country For Significant Application Methods (e.g., Florida or
Washington for tarped raised beds or drip irrigation)

OPPTS Guideline 875.1300 - Inhalation exposure for applicators
(outdoors)

Pre-Plant Field - (e.g., rig drivers & tenders, tarpers, tarp removers)

OPPTS Guideline 875.1400 - Inhalation exposure for applicators (indoors)

Greenhouse - (e.g., Fumigators, Media Handlers, Aerators)

Residential - (e.g., Fumigators, Tarpers, Aerators)

OPPTS Guideline 875.2500 - Inhalation exposure for postapplication
workers

Pre-Plant Field - (e.g., planters)

Greenhouse - (e.g., forklift drivers, plant maintenance workers)

Requirements For Special Studies

Meteorological data for probabilistic modeling purposes

Product Use Information By Major Use Region, Frequency, Application
Parameters (e.g., rate, acres treated, data, application equipment and
emission control technologies used)

Indoor air concentrations from residences that are in proximity of
treated areas

Ambient monitoring in high regions of use in the season of use.

 Since no effects were reported at 11 ppm during the first 5 weeks (24
exposures), exposure concentration of methyl bromide was increased from
11 ppm to 158 ppm for 6 additional days.

  Due to the limited severity of the effect, HED considered that a 3X UF
would be sufficient to extrapolate from the LOAEL to the NOAEL.

	Majewski, MS, Glotfelty, DE, Seiber, JN. 1989. A comparison of the
aerodynamic and the theoretical-profile-shape methods for measuring
pesticide evaporation from soil. Atmospheric Environment, 23:929-938

Majewski, MS, Glotfelty, DE, Kyaw Tha Paw U, Seiber, JN. 1990. A field
comparison of several methods for measuring pesticide evaporation rates
from soil. Environmental Science and Technology, 24:1490-1497.

Parmele, LH, Lemon, ER, Taylor, AW. 1972. Micrometerological measurement
of pesticide vapor flux from bare soil and corn under field conditions.
Water Air Soil Pollut. 1:433-451

 PAGE  v

 PAGE  70

Figure 7: Flux Rate Estimation, Area Under the Curve

Inputs -

Varied flux

& weather data

Air

Dispersion

Model (ISC, AERMOD,

CALPUFF)

Outputs -

Distributions of

buffer zones or air concentrations

“Whole Field”

“Maximum Distance”