1

Reducing Volatile Organic Compound Emissions from Pesticides: 

Analysis of Alternatives for Field Fumigation Methods 

Summary 

California’s ozone State Implementation Plan (SIP) for the federal Clean Air Act contains a 

pesticide element that requires the Department of Pesticide Regulation (DPR) to develop and 

maintain an emission inventory to track volatile organic compound (VOC) emissions from 

pesticides, and to reduce pesticide VOC emissions by 20 percent from the 1990 base year in 

four ozone nonattainment areas (NAA), and by 12 percent in a fifth NAA. To compile the 

emission inventory, DPR multiples the fraction of a pesticide product estimated to be VOCs 

by the amount of that product applied. The calculation is adjusted for fumigants to account 

for how emissions vary depending on fumigation method, based on monitoring data. The 

reduction goals have been met in all NAAs for the last two years of the inventory. 

Between January 2008 and May 2011, DPR adopted a series of regulations to reduce VOC 

emissions from fumigant pesticides. One part of the regulations reduces VOC emissions by 

requiring low-emission fumigation methods in certain NAAs. The regulations include the 

following types of fumigation method restrictions based on monitoring data: fumigant 

introduction method, tarping, pre-fumigation soil moisture, post-fumigation water treatments, 

and application rate limits. DPR developed the restrictions based on an analysis of possible 

low-emission method alternatives that included VOC reduction effectiveness, technical 

feasibility and availability, compliance and enforceability, pest management effectiveness, 

effect on other health or environmental concerns, and cost. In general, the regulations for 

low-emission fumigation methods require tarping, post-fumigation water treatments, or 

application through drip irrigation systems. Based on field monitoring data, DPR estimated 

that the emissions from low-emission fumigation methods were 9-48 percent of the amount 

applied, and high-emission fumigation methods were 64-100 percent of the amount applied, 

except for methyl iodide. The emission inventory indicated that some growers adopted lowemission fumigation methods prior to the regulations. The remaining growers who changed 

fumigation methods to comply with the regulations reduced fumigant VOC emissions by 

approximately one-third. The estimated reduction cost was $17,000 to $70,000 per ton of 

VOCs, based on 2007 prices. 

DPR is taking additional steps to reduce VOC emissions. The VOC regulations also include a 

fumigant emission limit for the Ventura NAA at least until 2012. This system is also a 

backstop measure in the event low-emission fumigation methods are insufficient to achieve 

the SIP goals for the other NAAs. DPR is working with pesticide registrants to reformulate 

certain pesticide products that contain high amounts of solvents. DPR and others are 

conducting research to further reduce VOC emissions from pesticides, such as additional 

changes to fumigation methods, soil amendments that degrade fumigants, and growing crops 

without fumigants. Other measures that would reduce VOC emissions are infeasible at this 

time for several reasons, such as incompatibility with fumigant properties, ineffective pest 

control, lack of equipment or other resources, adverse health or environmental effects, or lack 

of legal authority. The infeasible measures include prohibiting use of fumigants, requiring the 

Deleted: April 2009, 

Deleted: and grower allowance system 
2

lowest emitting fumigation method, requiring integrated pest management or use of certain 

pesticides, or reducing crop oils.

Introduction 

DPR has broad authority to regulate sales and use of pesticides under various federal and 

state laws. DPR regulates pesticide sales through its registration process. Similar to the U.S. 

Environmental Protection Agency’s (EPA’s) process, pesticide manufacturers and 

formulators (registrants) must submit and DPR must evaluate studies on toxicity, 

environmental effects, chemistry, and other pesticide characteristics. DPR registers a 

pesticide product (approves for sale) if the studies are acceptable and use is not anticipated to 

result in unacceptable risk to human health or the environment. Once registered, DPR can 

request additional studies and actions by registrants using the reevaluation process specified 

in state law. Application or use of pesticides is regulated at several levels. All pesticide 

products must have a U.S. EPA-approved label that describes the maximum application rate, 

methods of application, crops that can be treated, safety precautions, and other requirements. 

Labels are enforceable documents, and making pesticide applications contrary to label 

directions is a violation of both state and federal law. DPR also develops and implements 

state regulations that can be more restrictive than the label. Under state law, county 

agricultural commissioners can also impose additional use requirements through the 

permitting process required for certain pesticides (restricted materials), based on an 

evaluation of local conditions. Growers and applicators are required to follow the most 

stringent use requirements, whether specified by labels, state regulations, or county permit 

conditions. County agricultural commissioners are responsible for enforcing all pesticide use 

requirements, under DPR oversight. 

DPR has used its authority to regulate VOC emissions from pesticides. VOCs and nitrogen 

oxides react with sunlight in the atmosphere to create ground-level ozone, which is harmful 

to human health and vegetation when present at high enough concentrations. Under the 

federal Clean Air Act, California must meet national standards for airborne pollutants, 

including ozone, and must specify how it will achieve these goals in a federally approved 

SIP. California’s SIP contains a pesticide element that requires DPR to develop and maintain 

an emission inventory to track pesticide VOC emissions, and to reduce emissions by 20 

percent from the 1990 base year in four ozone nonattainment areas (NAA), and by 12 percent 

in a fifth NAA. These five NAAs are defined as areas that do not meet the National Ambient 

Air Quality Standards for ozone as designated in the Clean Air Act. The SIP specifies that 

DPR is responsible for tracking and reducing pesticide VOC emissions from agricultural use 

and commercial structural use (applications by structural pest control businesses), while the 

Air Resources Board (ARB) is responsible for VOC emissions from the home use of 

pesticides as part of their consumer products program. 

To DPR’s knowledge, no other state has measures to reduce VOC emissions from pesticides, 

and if one did they would likely be different from DPR’s measures due to California’s unique 

pesticide use permit program. DPR’s VOC program is a hybrid air pollution and pesticide 

regulatory program. Hence, it has some commonalities with other air pollution and pesticide 

programs, but differs in several respects. Pesticides are considered area sources of air 
3

pollution, as opposed to mobile sources (e.g., motor vehicles), or stationary sources (e.g., oil 

wells). Additionally, pesticides are intentionally introduced into the environment to control 

harmful pests, as opposed to waste discharges (e.g., smokestacks). Most pesticide regulatory 

programs focus on potential toxic effects from the active ingredients in pesticide products. In 

contrast, DPR’s VOC program does not consider toxic effects, but does consider both active 

and inert ingredients in pesticide products, and generally classifies the products as fumigants 

or nonfumigants. Fumigant pesticide products usually contain approximately 100 percent 

active ingredients (some contain a small percentage of a warning agent), and the active 

ingredients are gases under normal environmental conditions. Nonfumigant pesticide 

products are liquids or solids containing both active and inert ingredients, and many such 

products include VOC solvents as inert ingredients, particularly products formulated as 

emulsifiable concentrates. 

In April 2009, DPR adopted amendments to the pesticide SIP element for the San Joaquin 

Valley NAA. These amendments included a commitment to implement restrictions on 

agricultural fumigation methods and VOC emissions of nonfumigant pesticides. In addition, 

DPR proposed to commit to manage pesticide VOC emissions, to ensure that they do not 

exceed 18.1 tons/day in the San Joaquin Valley area. The 18.1 tons/day limit is equivalent to 

a 12 percent reduction from the 1990 base year, and “freezes” DPR’s emissions estimation 

methodology and pesticide emissions for 1990. The following web page contains the 

complete pesticide SIP and supporting documents: 

http://www.cdpr.ca.gov/docs/emon/vocs/vocproj/voc_state_imp_plan.htm 

Between January 2008 and May 2011, DPR adopted a series of regulations to reduce VOC 

emissions from fumigant pesticides. Title 3 of the California Code of Regulations (3 CCR), 

section 6452.2, includes specific emission target levels (VOC regulation benchmarks) for 

each of the five NAAs, equivalent to the SIP obligation of a 12 percent or 20 percent 

reduction. The regulations reduce VOC emissions by requiring low-emission fumigation 

methods in certain NAAs. If, in spite of these application method requirements, pesticide 

VOC emissions exceed specified trigger levels, DPR is required to ensure that the benchmark 

is achieved by establishing a fumigant limit. The fumigant limit is determined by subtracting 

the estimated nonfumigant emissions from the regulatory benchmark, basing the 

nonfumigant emissions estimate on VOC emission inventory data from previous years. The 

following web page contains all of the fumigant VOC regulations and supporting documents: 

http://www.cdpr.ca.gov/docs/emon/vocs/vocproj/reg_actions.htm 

In October 2009, ARB submitted DPR’s SIP amendments and three sets of fumigant VOC 

regulations to U.S. EPA. In July 2011, ARB submitted two additional sets of DPR fumigant 

VOC regulations to U.S. EPA. To assist U.S. EPA with its review, this document contains 

more detailed information than previously submitted on DPR’s evaluation of fumigation 

methods, and information on other potential pesticide VOC reduction measures. 

Additionally, this document includes more recent emission inventory data. 

Background Information on Fumigants 

Deleted: April 2009, 

Deleted: (NOTE: DPR adopted another 

set of fumigant VOC regulations in April 

2011, but these regulations have not been 

submitted to U.S. EPA yet.)
4

Fumigants are most commonly used to treat soil in agricultural fields prior to planting, but 

harvested commodities and other sites can also be fumigated. These other types of 

fumigations are not agricultural or structural uses, so they are not included in DPR’s VOC 

program, and are not included in the fumigant regulations. The nonagricultural uses of 

fumigants are very low compared to the agricultural uses. 

Field fumigants include products containing one or more of the following active ingredients: 

• 1,3-dichloropropene 

• Chloropicrin 

• Methyl bromide 

• Methyl iodide (first registered in California in December 2010)

• Sodium tetrathiocarbonate (because it generates carbon disulfide as a pesticidal agent) 

• Active ingredients that generate methyl isothiocyanate (MITC) as the pesticidal agent 

(dazomet, metam-potassium, and metam-sodium). 

Fumigants differ in several important aspects from other pesticides. As gases, fumigants are 

much more volatile than other pesticides. Since they disperse so readily and target large 

volumes of soil, fumigants are usually applied at rates of several hundred pounds of active 

ingredient per acre, while most other pesticides are applied at rates of a few pounds or ounces 

per acre. Fumigants are applied to fallow fields, prior to planting, while most other pesticides 

are applied to growing crops. Fumigants are applied once per year at most to any individual 

field, and only once for the lifetime of an orchard or vineyard. Many other pesticides are 

applied multiple times during the year. Most fumigant products contain only active 

ingredients, and no inert ingredients. Most other pesticide products contain a mixture of 

active and inert ingredients. Most pesticides target specific pests, such as a particular type of 

insect or weed. Fumigants can control a wide variety of pests in the soil, including most 

weeds, nematodes, insects, and diseases. However, due to the cost of the product and controls 

to reduce health effects, fumigant application rates are normally minimized to control only 

certain targeted pests. For example, MITC fumigants are primarily used to control weeds and 

chloropicrin primarily mitigates diseases. Because of the variable effectiveness, and to 

prevent pest resistance to a single pesticide, prohibiting all but the lowest emitting fumigant 

is infeasible. 

Field fumigant application methods are different from other pesticides. Most fumigation 

methods either use special tractors to inject fumigant below the soil surface, or apply 

fumigant with water through an irrigation system (chemigation). Due to the specialized 

equipment required, pest control businesses rather than growers conduct most of the 

fumigations. Fumigant applications cost more than most other pesticides, so fumigants are 

economically feasible only for high-value crops. Crops that commonly use fumigants prior to 

planting include almonds, carrots, flowers, grapes, nursery crops, raspberries, strawberries, 

sweet potatoes, tomatoes, and walnuts. The California regions with highest fumigant use are 

the Central Coast region between Ventura and Santa Cruz, and the San Joaquin Valley. 

While fumigations occur throughout the year, peak use is during the summer and fall for 

most crops and regions. 

Formatted: Bullets and Numbering

Deleted: (NOTE: In December 2010, 

DPR registered products containing 

methyl iodide for the first time and is 

working on a regulation to include this 

pesticide as a fumigant VOC.) ¶

¶
5

Like most other pesticides, fumigants are considered toxic chemicals. Since they are also 

volatile and applied at large rates, the risk from toxic exposure to fumigants is higher than 

most other pesticides. Due to this risk, U.S. EPA and DPR have implemented regulatory 

requirements to control exposures to both workers and the public. Fumigant label revisions in 

2010 include “good agricultural practices” requiring specific soil preparation and soil 

moisture levels, equipment calibration and equipment safeguards, and other restrictions. In 

the early 1990s, DPR and county agricultural commissioners began implementing a series of 

regulatory requirements for application methods, use limits, buffer zones, and worker 

protections. The label and other regulatory requirements to address exposures complement 

the VOC regulations. When possible, DPR developed measures to reduce fumigant VOC 

emissions as well as reduce toxic exposures. All of the field fumigants are restricted 

materials, requiring additional scrutiny and possible permit conditions by county agricultural 

commissioners. Based on inspections of applications by county agricultural commissioners, 

compliance with the regulatory requirements is higher for fumigants than most other 

pesticides. Summary statistics of pesticide inspections are available by county and year at the 

following website: http://www.cdpr.ca.gov/docs/county/statistics/index.cfm. 

U.S. EPA plans to implement additional label changes for field fumigants in 2011. These 

changes will include buffer zones to protect bystanders. The buffer zone distances depend in 

part on emission estimates for various fumigation practices. U.S. EPA’s estimates of 

emissions, particularly “buffer zone credits” assigned to various fumigation practices are 

based largely on modeling using CHAIN2D that was modified by the Chloropicrin 

Manufacturers Task Force. DPR did not use U.S. EPA’s emission estimates for several 

reasons: 1) U.S. EPA published its emissions estimates after the fumigant VOC regulations 

went into effect. 2) U.S. EPA and DPR rely on peak emissions over one day or less to 

determine the size of buffer zones. VOC estimates are based on total emissions over several 

days or weeks. 3) DPR decided not to use the modified CHAIN2D model for the reasons 

specified below. In brief, the modeling system is not validated. Major features of the model 

such as drip irrigation or the dynamic boundary layer were not tested. The testing that was 

done utilized an unsupported ‘shank trace’ feature to arbitrarily make model results fit more 

closely to measured results. A hydraulic parameter estimation scheme gives incorrect 

estimates. The general approach, which uses average texture class hydraulic parameters, may 

give incorrect results. DPR relied on field monitoring data for its emission estimates and 

reductions associated with various application practices. As discussed in the section on 

fumigation method options, some of DPR’s emission reduction estimates based on 

monitoring data differ from U.S. EPA’s buffer zone credits based on CHAIN2D modeling. 

Also discussed in a later section is DPR’s attempt to develop its own model to estimate 

fumigant emissions. The following document describes U.S. EPA’s emission estimates for 

buffer zone purposes: http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2007-

0350-0173. 

The following document describes DPR’s review of U.S. EPA’s estimates: 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2007-0350-0285.1. 

Measured in pounds, fumigants represent approximately 20 percent of all agricultural 

pesticides used in California. However, use of fumigants has changed dramatically since the 

early 1990s (Figure 3), and will likely continue to change for several reasons. Under the 
6

Montreal Protocol and Clean Air Act, U.S. EPA began phasing out production and 

importation of methyl bromide in the late 1990s due to stratospheric ozone depletion effects. 

In 1990, DPR directed the county agricultural commissioners to rescind all permits for 1,3-

dichloropropene due to exposure concerns. These actions caused MITC pesticides and 

chloropicrin use to increase. Use of 1,3-dichloropropene subsequently increased since its 

reintroduction in the mid-1990s, with revised regulatory requirements. However, recent 

decreased production of 1,3-dichloropropene due to the recession has led to decreased use of 

that fumigant in the last two years. DPR first registered methyl iodide in December 2010, and 

its introduction could change use patterns even more. These actions, as well as other 

regulatory requirements, have led to increased cost for all fumigants. 

Pesticide VOC Emission Inventory 

DPR prepares an annual estimate of VOC emissions from agricultural and commercial 

structural pesticide applications. There is an emission inventory for each year since 1990, the 

base year. Pesticide applications in five NAAs are included: Sacramento Metro, San Joaquin 

Valley, South Coast, Southeast Desert, and Ventura (Figure 1). Only agricultural and 

commercial structural pesticide applications are included. ARB tracks emissions from 

pesticides in consumer products. DPR uses data on VOC content and pesticide use to 

estimate emissions from reported agricultural and commercial structural applications in each 

NAA. The inventory focuses on May 1 through October 31, the peak ozone season in 

California. 

To estimate the VOC contribution of individual agricultural and structural use pesticides, 

DPR multiples the fraction of a pesticide product estimated to be VOCs (its “emission 

potential”) by the amount of that product applied. 

Estimated VOC emissions = (Emission potential of the product) X (Pounds of pesticide 

product applied)

Pesticide use reports provide the amount of product used. California requires full reporting of 

all agricultural pesticide use and the use of pesticides by pest control businesses. The reports 

document the product applied, the amount applied, date applied, location (within a one 

square mile section), crop treated, number of acres treated, and other information. 

DPR has several methods to determine the emission potential. The preferred way is through 

laboratory analysis, using a standardized method approved by DPR (thermogravimetric 

analysis). When it is not available, DPR uses other approaches to decide emission potentials. 

• Using the VOC emission potential already measured in TGA analysis of an identical 

or nearly identical pesticide product. 

• Using the confidential statement of formula on file with DPR to find out the 

percentage of water and other inorganic chemicals in the product. This is subtracted 

and the remainder is assumed to produce emissions that must be included in the 

inventory. 

Deleted: The registration of methyl 

iodide 
7

• Assigning an estimated value based on an evaluation of a product’s unique chemistry 

and composition. DPR takes this approach for high-use products with well-known 

chemical properties. 

• Assigning a default emission potential at a representative level, based on measured 

data that reflect the behavior of similarly formulated products. 

Because DPR has monitoring data, the calculation is adjusted for fumigants to account for 

how emissions vary depending on fumigation method (Application Method Adjustment 

Factor, AMAF, or emission rating). AMAFs have been determined from field study data and 

are active ingredient and application method specific (Table 1). Since the AMAFs are based 

on field measured data for specific application methods and fumigants, they yield more 

refined estimates of fumigant VOC emissions than the previous unadjusted emission 

estimates. 

 Estimated fumigant VOC emissions = lbs of product used x EP x AMAF 

Nonfumigant product emissions are not currently adjusted for application method or other 

field factors due to a lack of data to support such adjustments. 

Usually there are several different types of application methods used for a particular 

fumigant in any particular NAA. Each method of use (e.g. drip, sprinkler, shank, tarp, etc.) 

represents a fraction of the total number of methods used and is referred to as the method use 

fraction. The sum of all method use fractions for any particular (NAA/fumigant) combination 

is one. Use practices change over time so that different method use fractions are used for the 

base year (1990) as opposed to more recent inventory years. For 1990, 2005, 2006, and 2007, 

method use fractions were determined in a number of different ways. For 1,3-

dichloropropene the method use fractions are determined from use data collected by the 

registrant in support of DPR’s township application caps; for metam sodium and metam 

potassium grower/applicator surveys were conducted to determine types of applications for 

different crops and areas. Methyl bromide and chloropicrin method use fractions are based on 

expert opinion and regulatory history. Finally, method use fractions for dazomet and sodium 

tetrathiocarbonate equal one because the AMAFs for each of these two fumigants are 

constant, independent of application method. See Attachment 1a (DPR memorandum from 

Barry, Spurlock and Segawa to Sanders, dated September 29, 2007) for a detailed discussion 

of how method use fractions and AMAFs were determined. 

The 2008 fumigant VOC regulations included a change to pesticide use reports (3 CCR 

sections 6624 and 6626) that requires recording the specific application method for each 

fumigation within NAAs. The method use fractions for 2008 and later years are calculated 

using the fumigation method documented in pesticide use reports rather than the surrogate 

data described above. Some pesticide use reports for 2008 and later years are missing the 

identification of the application method. In these cases, DPR assumed that the application 

method with the highest AMAF allowed by the regulations for that fumigant was used. See 

the following web page for more details on the methodology to calculate pesticide VOC 

emissions: http://www.cdpr.ca.gov/docs/emon/vocs/vocproj/voc_method_est.htm 
8

The 2008 fumigant VOC regulations (3 CCR section 6452.4) require DPR to publish its 

emission inventory annually. The annual reports are available at: 

http://www.cdpr.ca.gov/docs/emon/vocs/vocproj/voc_data_analysis.htm. The most recent 

data is for 2009, and Figure 2 shows the pesticide VOC emissions relative to the SIP goals 

for 2009 and earlier years. The 2009 pesticide VOC emissions for all five NAAs complied 

with the SIP goals, ranging from 33 to 89 percent less than emissions in the 1990 base year. 

Relative to 2008, pesticide VOC emissions in 2009 ranged from a 4 percent increase to a 47 

percent decrease, depending on the NAA. 

• Adjusted emissions in 2009 in the Sacramento Metro continue to decline and fell to 

below 1 tons/day. Nonfumigants represented 87 percent of the total, and the total 

remaining well below the SIP goal. 

• Emissions in the South Coast NAA also decreased slightly over 2008 values and 

remain well below the SIP goal. Three quarters of the total adjusted VOC emissions 

came from nonfumigants. 

• In 2009, fumigants accounted for less than half of VOC emissions in the Southeast 

Desert, down slightly from 2008. Total VOC emissions in 2009 decreased by almost 

50 percent from 2008 and continue to meet the SIP goal. 

• 2009 VOC emissions in the Ventura NAA increased by 0.072 tons/day from the 

previous year but continue to meet the regulatory goal for 2010, 2011 and 2012. 

Seventy five percent of emissions come from fumigants. 

• In the San Joaquin Valley NAA, nonfumigants accounted for approximately three 

quarters of the total VOC emissions in 2009. In this NAA, VOC emissions decreased 

from 2008 to 2009 by about 7 percent, and continue to be below the SIP goal. 

As calculated for the emission inventory, fumigant emissions depend on the fumigant, 

fumigation method, and amount applied (application rate in pounds per acre and number of 

acres treated). Table 2 compares fumigant use and emissions prior to and after the 2008 

fumigant regulations (2006-2007 compared to 2008-2009, annual average for May-October). 

May-October fumigant VOC emissions declined 48-81 percent where the regulations 

required low-emission fumigation methods, depending on NAA. Some growers adopted lowemission fumigation methods prior to the regulations. The remaining growers who changed 

to low-emission fumigation methods to comply with the regulations accounted for a 31-32 

percent decrease, and less use accounted for 17-49 percent decrease, depending on NAA. The 

fumigant emission limit for Ventura likely contributed to the decrease in use for that NAA. 

Table 3 shows that the decrease in use was primarily due to less acreage fumigated in all 

NAAs after the fumigant VOC regulations were effective in 2008. Between 2006-2007 and 

2008-2009, the May-October fumigated acreage decreased by 17 percent (49,242 acres to 

40,862 acres) in the San Joaquin Valley NAA, by 33 percent in the Southeast Desert NAA 

(3,456 acres to 2,332 acres), and by 24 percent in the Ventura NAA (15,497 acres to 11,833 

acres). The percentage decrease in fumigated acreage for the entire year was less than the 

May-October period, indicating that shifting fumigation dates outside May-October caused 

part of the decrease in VOC emissions. 

Evaluation of Field Fumigation Method Options 
9

The key provision in the fumigant VOC regulations that achieves emission reductions is the 

requirement for “low-emission” fumigation methods in the San Joaquin Valley, Southeast 

Desert, and Ventura NAAs during May-October. The designation of low-emission 

fumigation methods is based on the AMAF and maximum allowed application rate. Field 

monitoring has demonstrated that fumigant emissions vary with several factors, but primarily 

with fumigant, fumigation method, and application rate. Several methods have been used to 

estimate fumigant emissions, including laboratory experiments, field measurements on small 

plots (less than one acre), field measurements of large plots (one acre or more), as well as 

computer modeling. DPR has relied on field measurements of large plots for emission 

estimates because they are most similar to commercial fumigations. Research continues on 

the other methods, but comparisons so far indicate that the other methods do not always 

agree with field measurements of large plots. 

Most of the low-emission methods specified by the regulations were based on field studies 

conducted by registrants, agricultural commodity groups, the University of California, and 

the U.S. Department of Agriculture (USDA). They developed the fumigation methods and 

measured the emissions. DPR and ARB have also monitored several fumigations to confirm 

the emissions. The studies DPR relied upon for its emission estimates are listed in 

Attachments 1a and 1b for each fumigant. (Attachment 1a was peer reviewed as part of the 

rulemaking process.) Appendix 4 to Attachment 1a lists other studies on fumigant emissions, 

but not used by DPR and the reasons for excluding the data. Attachment 1a describes the 

studies available at the time the fumigant VOC regulations were first developed in 2007. 

Attachment 1b describes the studies that DPR has evaluated since then. Additional studies 

which DPR has not yet evaluated are discussed in the Current Research on Fumigant VOC 

Emission Reduction section. 

The fumigant VOC regulations exempt certain small, specialized fumigations, such as 

individual tree-hole replant applications less than one acre. These fumigations have 

negligible emissions due to very low use. These applications are infrequent and small 

compared to other fumigations. Including these applications would have greatly complicated 

the regulations, with negligible reduction in VOC emissions. 

DPR’s regulations for field fumigation methods are described in 3 CCR sections 6446.1 for 

methyl iodide; 6447.3 for methyl bromide; 6448.1 for 1,3-dichloropropene; 6449.1 for 

chloropicrin; 6450.1 for metam-sodium and metam-potassium; 6450.2 for dazomet; and 

6451.1 for sodium tetrathiocarbonate and include the following types of fumigation method 

restrictions based on the monitoring data: 

• Fumigant introduction method 

• Tarping 

• Pre-fumigation soil moisture 

• Post-fumigation water treatments 

• Application rate 

DPR considered, but did not include the following types of fumigation method restrictions in 

the regulations: 

• Temperature and other weather conditions 

Deleted: This document 

Deleted: Additional 

Deleted: have been conducted 

Deleted: These studies 
10

• Soil characteristics 

• Soil amendments 

• Soil preparation, equipment preparation, general procedures 

DPR considered the following factors in developing the fumigation method requirements: 

• VOC reduction effectiveness 

• Technical feasibility and availability 

• Compliance and enforceability 

• Pest management effectiveness 

• Effect on other health or environmental concerns 

• Cost 

As summarized in Table 4 and described below, DPR has designated several fumigation 

methods as low-emission. Based on monitoring data, the emissions from low-emission 

fumigation methods were 9-48 percent of the amount applied, and high-emission fumigation 

methods were 64-100 percent of the amount applied, with the exception of methyl iodide

(Table 1). Requiring the lowest emission fumigation method is infeasible for several reasons: 

1) a single method is not physically possible for all fumigants; 2) a single method is not 

effective in reducing VOC emissions for all fumigants; 3) a single method is not effective 

against all target pests for all crops; and 4) the equipment and other resources are not always 

available or very costly. 

Evaluation of Fumigation Methods – Introduction Methods 

There are two main methods to introduce fumigant into the soil: chemigation or tractor. 

Fumigant introduction methods vary by fumigant and crop. Some methods are feasible for 

some fumigants and crops, but not others. In general, drip chemigation methods have lower 

emissions than tractor methods (Table 1 and Attachment 1a). However, methyl bromide’s 

volatility is too high and its water solubility is too low to be retained in water, so chemigation 

is not technically feasible for that fumigant. Drip irrigation systems are costly to install and 

maintain. In general, they are economically feasible for fields where drip systems will be 

used for irrigation, not just a fumigant delivery system, and where the drip system can be 

installed prior to planting and used for fumigation. Additionally, drip chemigation is usually 

only effective for crops where the target pest is at shallow depths (1 foot or less). 

Strawberries and raspberries are the most common crops where these conditions occur and 

fumigations use drip chemigation. Based on the monitoring data, all of the drip chemigation 

methods are designated as low-emission. 

MITC-generating pesticides and sodium tetrathiocarbonate are unusual because they can be 

applied using other chemigation methods, such as sprinkler or flood. The parent compounds 

metam-sodium, metam-potassium, and sodium tetrathiocarbonate are non-volatile salts, so 

they are easily applied through irrigation systems. Moreover, it takes several minutes to 

several hours for the parent compound to convert to MITC or carbon disulfide. This delay 

allows MITC and carbon disulfide pesticides to be applied through irrigation systems and 

still minimize emissions. In many cases, non-drip chemigation fumigations are less costly 

and have greater pest management effectiveness than drip applications. Other irrigation 

Deleted: (NOTE: In April 2011, DPR 

adopted revisions to the fumigant VOC 

regulations that include additional lowemission fumigation methods. These 

regulations have not been submitted to 

U.S. EPA yet.)
11

equipment is less costly than drip, and applications are usually more uniform. Many 

irrigation systems are portable and can be moved between fields. Like drip chemigation, 

other chemigation methods are suitable only for crops where the target pest is located at 

shallow depths. MITC sprinkler chemigations are most common for carrots and potatoes in 

the San Joaquin Valley and Southeast Desert NAAs. As discussed below, sprinkler 

fumigations with one post-fumigation water treatment is designated a high-emission method. 

Sprinkler fumigations with two or more post-fumigation water treatments are designated 

low-emission methods. Sodium tetrathiocarbonate and other chemigation methods are not 

commonly used. 

With the exception of sodium tetrathiocarbonate, all fumigants can be applied by a tractor. In 

most cases, fumigants applied with a tractor are injected beneath the soil surface through 

shanks attached to the back of the tractor. Some available data seems to support the theory 

that emissions may vary with depth. However, DPR’s analysis of methyl bromide 

applications and other fumigant data show that emissions vary significantly depending upon 

whether application occurs to a flat field (broadcast) or to a field that has been bedded 

(Attachment 2 – DPR memorandum from Barry to Sanders, dated December 2, 1999). In 

general, emissions are lower with flat fields. Fumigants are normally injected at 6-24 inches 

beneath the soil surface. The depth of crop roots and location of the target pest determines 

the depth of injection. Fumigants are usually injected at 6-12 inches for crops with shallow 

roots, such as strawberries and vegetables. Fumigants are usually injected at 18-24 inches for 

crops with deep roots, such as nut orchards and grapes. Injection depth cannot be increased to 

decrease emissions without losing pest management effectiveness. Also, increasing depth 

does not always decrease emissions. The available data for methyl bromide indicates that 

depth has no significant effect on emissions, at least within a 10-24 inch depth (Attachment 

2). This is likely due to the type of shank and tractor implements, and high soil moisture. 

Injection at greater depths requires wider shanks. The channel in the soil created by the 

shanks (shank trace) can be a pathway to the surface, so the wider the channel the higher the 

emissions. High soil moisture may increase this effect due to greater soil adhesiveness. 

Special shanks (e.g., Nobel plow) are often used for shallow injection to reduce this 

channeling effect. Nobel plows consist of a horizontal wing attached to the vertical shank, 

with fumigant released along the wings and away from the channel created by the shank. 

Nobel plows are usually not feasible for greater depths because the resistance is too high for 

tractors pull them through the soil. Applicators have developed other tractor implements 

(e.g., compaction rollers) to disrupt or close the channel created by the shanks. Broadcast 

fumigations are common for all crops and areas, particularly for nut orchards and grapes. 

Based on the monitoring data, deep injection is designated a low-emission method for 1,3-

dichloropropene and some chloropicrin methods. Deep injection is designated a highemission method for methyl bromide, unless accompanied with some other mitigation 

measure (e.g., tarping). MITC pesticides are usually not injected at deep depths because the 

primary target pests are weeds at shallow soil depths. 

Tractor fumigations to bedded fields usually have higher emissions than flat fields (broadcast 

fumigations). Bedded fumigations usually cost less than broadcast fumigations because the 

fumigation and bed forming occurs in a single tractor operation, and they use less fumigant. 

For broadcast fumigations, the fumigation and bed forming require separate tractor 
12

operations. The higher emissions with bedded fumigations are partially offset by lower 

application rates. The entire field is treated for a broadcast fumigation. In contrast, only the 

beds are treated for a bedded fumigation; the furrows are untreated. Therefore, the effective 

(or broadcast-equivalent) application rate is lower for a bedded field. Bedded shank 

fumigations are common for carrots and sweet potatoes in the San Joaquin Valley. Most 

bedded shank fumigation methods are designated as high-emission, unless accompanied with 

some other mitigation measure (e.g., tarping). 

There are a few tractor fumigation methods for MITC pesticides that do not involve injection 

beneath the soil surface. These include rotary tiller, power mulcher, and soil capping 

methods. These methods involve spraying a water solution of metam-sodium or metampotassium on the surface of the soil, and then incorporating into the soil or placing untreated 

soil on top. The available data indicates than these methods have comparable or lower 

emissions than other methods (Attachment 1a). These methods are most commonly used for 

tomatoes in the San Joaquin Valley. Based on the available monitoring data, most of the 

methods are designated as low-emission. The fourth set of regulations effective in April 2011 

added a drench method for MITC pesticides. For this method, a tractor is used to spray a 

dilute solution of a MITC pesticide on the top of the soil, at very low application rates. This 

method is used for specialty crops, such as cilantro, and has also been designated as lowemission (Attachment 1b, Ratto Brothers decision). The tractor fumigation methods for 

dazomet are unique. This MITC pesticide is granular material, applied to the soil surface, 

then incorporated and watered-in. The label requires multiple water treatments. This 

pesticide has low use for all crops. Based on the monitoring data all dazomet application 

methods are designated low-emission. 

As shown in Table 5, for fumigations that used a high-emission method, the estimated 

increased cost of using a low-emission method ranged $10-$2510 per acre in 2007, 

depending on fumigant and fumigation method. 

Other factors sometimes influence which fumigation method is used. Water supply is 

sometimes a factor in the feasibility of chemigation methods. For fields that rely on surface 

water, irrigation canals may not have water at the time fumigations occur prior to planting. 

Equipment availability may also be a factor. For any one commodity, fumigations are often 

seasonal in nature, with most fumigations occurring in a few weeks. There may be an 

insufficient number of rigs to complete all fumigations using tractors. Equipment shortages 

can be exacerbated by weather conditions. The soil must have the appropriate moisture for 

fumigation. Fumigations cannot occur during or immediately after storms. Additionally, 

tractors cannot enter fields that are too wet. Tractor fumigations often cannot be done in high 

winds due to tarpaulin considerations. If weather prevents fumigations for an extended period 

of time, the preferred fumigation method may not be available, so several different 

fumigation methods may be necessary. 

Evaluation of Fumigation Methods – Tarping 

Tarping reduces emissions for most fumigants and fumigation methods. Tarping is feasible 

for all tractor shank injection methods and drip chemigation. Tarping is physically 
13

impossible for most other methods, such as rotary tiller, sprinkler, and flood. The most 

common tarpaulin is high density polyethylene, generally 1.0-1.5 mil thick, and is sometimes 

referred to as the standard tarpaulin. Monitoring data indicates that the standard tarpaulin is 

effective in reducing emissions of chloropicrin and methyl bromide, but not 1,3-

dichloropropene (Attachment 1a). It is rare for MITC fumigations to use a tarp because of the 

relatively high cost of tarping compared to the cost of the fumigant, and field monitoring data 

is not available. Tarpaulin costs vary and have been increasing over the last several years. In 

general, tarped fumigations cost at least twice as much as untarped fumigations. The 

tarpaulins for fumigation are used once, and disposed, creating additional landfill waste. 

Tarpaulin fumigations for bedded fields are more efficient than flat field fumigations because 

less is used and the tarpaulins usually remain in place for the entire growing season, acting as 

a mulch. Tarpaulins for flat fields are discarded immediately after fumigation. As discussed 

in the section on research, newer tarpaulins such as “virtually impermeable film” or “totally 

impermeable film” may have somewhat misleading names, but are more effective in 

reducing emissions than standard tarpaulins. While emission data is available for some low 

permeability tarpaulins and fumigants, data to address exposure concerns is not available for 

most fumigants, so these tarpaulins are not widely used and prohibited for methyl bromide. 

For the upcoming label changes, U.S. EPA plans to assign a buffer zone credit of 10-60 

percent, depending on fumigant and type of low permeability tarpaulin. The estimated 

increased cost of changing from a high-emission untarped fumigation method to a lowemission standard tarpaulin fumigation method was $400 per acre in 2007 (Table 5).

For methyl iodide, California product labels require “highly retentive tarps” (virtually 

impermeable films or totally impermeable films approved by DPR and the registrant) for 

almost all fumigations. The highly retentive tarps are primarily required to control exposures, 

not reduce VOCs. To ensure that the buffer zones provide adequate protection, DPR assumes

that total methyl iodide emissions are 100 percent with highly retentive tarps, as an interim 

assumption. Field studies on methyl iodide applications with highly retentive tarps measured 

total emissions of approximately 30 percent of the amount applied, but DPR concluded that 

these studies likely underestimated the emissions (Attachment 1b, memo to John Sanders 

dated April 29, 2010). The registrant conducted another field emissions study to replace the 

earlier ones, and submitted a report to DPR in May 2011. DPR has not yet evaluated this 

report. Since it’s likely that actual methyl iodide emissions are less than 100 percent with 

highly retentive tarps and it is applied at relatively low application rates (maximum label rate 

of 100 pounds per acre), DPR has designated these methods as low-emission. 

Evaluation of Fumigation Methods – Pre-Fumigation Soil Moisture 

In general, higher soil moisture reduces emissions, particularly when the moisture is higher 

near the soil surface (Attachment 1a, sections on 1,3-dichloropropene and chloropicrin). 

However, higher soil moisture also reduces efficacy of the fumigant, by retarding dispersal. 

Compliance and enforcement of any soil moisture requirements are also problematic because 

there are no methods to easily and accurately measure soil moisture in the field. The U.S. 

EPA evaluated this issue in detail, and included a soil moisture requirement of 50-75 percent 

of field capacity as one of the revisions to fumigant labels in December 2010. This 

requirement is more stringent and supersedes DPR’s regulations for soil moisture of 25-50 
14

percent of field capacity. DPR’s regulations were based on the soil moisture levels in the 

field monitoring studies used to establish the AMAFs. Both the fumigant labels and DPR’s 

regulations specify the USDA’s “feel” method for determining moisture. (NOTE: The fourth 

set of regulations includes revisions that correct errors in the first set of regulations for the 

method of determining soil moisture.

Evaluation of Fumigation Methods – Post-Fumigation Water Treatments 

Applying water after the introduction of fumigant (post-fumigation water treatment) is 

effective in reducing emissions of most fumigants (Table 1 and Attachment 1a, sections on 

chloropicrin and metam). Field monitoring of water treatments has not been conducted for 

methyl bromide, but it is likely ineffective due to methyl bromide’s higher volatility. The 

amount of water required and frequency of application reflects the practices used for the 

monitoring studies. Post-fumigation water treatments are not always feasible. As discussed 

above, surface water may not be available prior to planting. Also, the irrigation system must 

cover the entire treated area. In the case of broadcast fumigations, this can only be done with 

overhead sprinklers, and not all growers have access to overhead sprinkler equipment. Postfumigation water treatments are most effective for untarped applications. Water treatments 

are likely the least effective for broadcast fumigations where the entire field is tarped, and 

this type of fumigation has not been monitored. Another disadvantage for water treatments is 

the potential for water contamination. If too much water is applied, there is a potential for 

contamination of surface or ground water. The amount of water specified by the regulations 

is the amount and frequency used in the monitoring studies, and DPR’s evaluation concluded 

that surface runoff or percolation to ground water will not occur. (NOTE: The fourth set of 

regulations includes revisions that correct errors in the first set of regulations for the water 

treatment requirements.) Post-fumigation water treatments are most common for MITC 

sprinkler fumigations of carrot and potato fields in the San Joaquin Valley and Southeast 

Desert NAAs. Fumigations that use at least two or three post-fumigation water treatments are 

designated as low-emission. The estimated increased irrigation cost of the post-fumigation 

water treatments was $10 per acre in 2007, assuming the irrigation system is already in place. 

If the irrigation system must be rented the estimated increased cost was $240 per acre in 2007 

(Table 5). 

To encourage the voluntary reduction of emissions, water treatments are one of three 

pesticide VOC measures for which the USDA – Natural Resources Conservation Service’s 

Environmental Quality Incentives Program (EQIP) provides matching funds to growers in 

California. 

Evaluation of Fumigation Methods – Application Rates 

DPR assumes that application rates and emission rates are proportional, if the application rate 

increases by 2x the emission rate increases by 2x. The regulations specify the maximum 

allowed application rate for each fumigant, when less than the rate specified on labels. The 

maximum application rates were based on several factors primarily related to exposure 

mitigation. 1) The rates do not exceed those used for the monitoring studies. 2) The rates 

resulted in buffer zone requirements (distances and field separation) that can be complied 
15

with and enforced. 3) The rates resulted in worker protections (e.g., respirators and work 

hour limits) that can be complied with and enforced. 4) The registrants supported the rates, 

indicating that they result in effective pest control. As discussed above, the effective 

application rate for bedded fumigations is less than broadcast fumigations because the 

furrows are untreated. Similarly, some growers will make “strip” fumigations, particularly 

for nut orchards or grapes. A strip fumigation is an application to a flat field, but every 

second or third tractor pass is left untreated. Trees and vines are planted only in the treated 

strips. Strip fumigations are less effective than normal broadcast applications, so are only 

feasible where the pest population is relatively low. The fourth set of regulations effective in 

April 2011 includes several fumigation methods for MITC pesticides that have been 

designated as low-emission in part due to low application rates. This includes several night 

fumigation methods, and the drench method (Attachment 1b, Responsible Farmers Coalition 

decision, Grimmway Farms decision, and Ratto Brothers decision). DPR designated some of 

these methods as low-emission because the regulations include a provision for approval if the 

emission rate (AMAF multiplied by the application rate) is no greater than the current lowemission methods. 

Evaluation of Fumigation Methods – Temperature and Other Weather Conditions 

The soil and/or air temperature may influence emissions. Higher temperatures may have 

higher emissions. However, the analyses so far have not demonstrated a significant 

relationship between temperature and emissions (Attachment 3 – DPR memorandum from 

Barry to Segawa, dated January, 29, 2010, page 6). Temperature may influence emissions, 

but the effect is too small to detect due to the field-to-field variability and the effect of 

fumigation method. Since the monitoring did not show an effect, the regulations do not 

include any requirements based on temperature. 

With the exception of rainfall, most other weather conditions have minimal effect on 

emissions. However, sprinkler and tarped fumigations have label language that includes wind 

speed restrictions for these types of fumigations, so there are no requirements in DPR’s 

regulations. 

Growers and applicators can only control the fumigant introduction, so any weather 

restrictions beyond the application period are problematic. Monitoring data indicates that 

emissions continue for several days or weeks after fumigant introduction, but no weather 

restrictions after fumigant introduction are possible. 

Evaluation of Fumigation Methods – Soil Characteristics 

The soil type and soil organic content may influence emissions. Soils consisting of finer 

particles (clay) are hypothesized to have lower emissions than coarser soils (sand). Soil with 

higher organic content may have lower emissions. DPR is attempting to estimate the effect of 

soil characteristics using the HYDRUS computer model, as discussed in Current Research on 

Fumigant VOC Emission Reduction section. However, it’s likely that the effect, if any, will 

be minor due to similar soil types for fumigations in California (Attachment 4 – DPR 

memorandum from Johnson and Spurlock to Segawa, dated January 23, 2009). Moreover, 

Deleted: No current application rates 

are designated as low-emission. 

However, a new fumigation method 

could be designated as low-emission in 

part due to a low application rate, since 
16

soil type can vary within a field, so determining compliance with any requirements may be 

problematic. For the upcoming label changes, U.S. EPA plans to assign a buffer zone credit 

of 10 percent for soils with greater than 27 percent clay content, and up to 30 percent 

depending on soil organic content. 

Evaluation of Fumigation Methods – Soil Amendments 

It’s possible that fertilizers or other soil amendments affect emissions. Several studies have 

measured emissions comparing fumigated fields with and without a thiosulfate amendment. 

Most of this data was not available at the time the fumigant VOC regulations were 

developed, and DPR is still reviewing the studies. For the upcoming label changes, U.S. EPA 

plans to assign a buffer zone credit of 15 percent when thiosulfate is applied with certain 

fumigants. 

Evaluation of Fumigation Methods – Soil Preparation, Equipment Preparation, and 

General Procedures 

Fields with large soil clods, debris, or crop residue can exacerbate the channeling effect of 

tractor shanks. Labels address proper preparation of fields, so DPR’s regulations do not 

include any requirements for soil preparation. Similarly, the labels include requirements for 

proper equipment calibration and maintenance, as well as prevention of leaks and spills. 

Evaluation of Fumigation Methods – Conclusions 

Requiring the lowest emission fumigation method is infeasible for several reasons: 1) A 

single method is not physically possible for all fumigants. For example, methyl bromide is 

too volatile to apply using chemigation systems, and tractor fumigations are not allowed by 

the label for sodium tetrathiocarbonate. 2) A single method is not effective in reducing VOC 

emissions for all fumigants. For example, tractor injection at deeper depths reduces emissions 

for 1,3-dichloropropene, but not methyl bromide. 3) A single method is not effective against 

all target pests for all crops. For example, chemigation methods are effective against weeds 

and other pests at shallow depths, but usually ineffective against pests at deeper depths. 4) 

The equipment and other resources are not always available or very costly, particularly 

availability of surface water and delays due to weather. 

It is also infeasible to designate the lowest emission fumigation method for individual 

combinations of fumigant, crop, pest, and region. This would greatly complicate and 

lengthen the regulations. There are approximately 50 fumigants/fumigant products, 25-60 

crops for each fumigant, 4 groups of pests, and at least 3 regions, creating several thousand 

combinations. Many products contain more than one fumigant, particularly methyl bromide, 

chloropicrin, and 1,3-dichloropropene. The fumigation method would need to be specified by 

product for these fumigants. New fumigant products or changes to labels that add crops or 

pests would require corresponding changes to the regulations. Additionally, specifying a 

single fumigation method for each of the combinations would not account for the availability 

of equipment and other resources. 
17

Cost of Low-Emission Fumigation Methods 

ARB’s Agency-wide Economic Analysis Unit estimated the direct cost of the fumigant VOC 

regulations. ARB used the information compiled by DPR in Tables 5a and 5b for the costs 

associated with the fumigation methods. DPR estimated that the total increased fumigation 

cost to growers and applicators to comply with the low-emission method requirements was 

$10 million to $40 million for all NAAs combined in 2007, depending on which lowemission fumigation methods growers and applicators selected. Table 2 shows that VOC 

emissions reduction attributed to the low-emission fumigation methods was 3.11 tons/day for 

all NAAs combined, or 573 tons of total VOCs during May-October. Therefore, the 

estimated VOC reduction cost was $17,000 to $70,000 per ton, based on prices in 2007. The 

cost has likely increased since 2007. Secondary economic impacts of the regulations were not 

considered. Secondary impacts such as loss of jobs to farm laborers, the increase in bank loan 

risk, or loss of income to processors and suppliers, while important to the community, do not 

expressly impact the grower’s profitability and were not included in the economic impact 

analysis. Direct impacts, such as land value losses to growers, were not considered, as 

estimating the impact on real estate is uncertain and highly subject to local influences. 

Other Reduction Options for Pesticide VOC Emissions 

The VOC regulations include a fumigant emission limit for Ventura until at least 2012 (3 

CCR sections 6452.2 and 6452.3). The regulations also include a trigger for the same system 

for the other NAAs in the event the reductions from low-emission fumigation methods are 

insufficient to achieve the SIP goals. Under this system, DPR establishes a NAA-wide 

fumigant emission limit each year by subtracting the estimated nonfumigant emissions from 

the SIP goal. County agricultural commissioners have three options to enforce the fumigant 

limit: by issuing a fumigant emission allowance to each grower who plans to fumigate for 

the upcoming May-October period; by tracking emissions and denying any permit that would 

cause the fumigant limit to be treated; or by conditioning permits to further restrict the 

fumigation methods that can be used. Agricultural commissioners may implement one or any 

combination of these three options. Under the fumigant allowance option, growers in an 

NAA where a fumigant limit is in effect must request an allowance from the commissioner. 

Allowance requests must include crop and acres. DPR or the commissioner estimates worstcase emissions by assuming the highest emitting fumigant and method by crop, for all of the 

requested acreage. The allowances are reduced proportionally to bring total fumigant VOC 

emissions below the limit for the NAA. Commissioners issue the allowances as a condition 

of the restricted materials permits. Each grower must manage his/her fumigations by 

selecting the appropriate combination of fumigants, fumigation methods, application rates, 

and number of acres fumigated so the allowance is not exceeded. As restricted materials, 

growers or applicators must submit a Notice of Intent to the county agricultural 

commissioner for each fumigation. Commissioners check each Notice of Intent to confirm 

that it complies with the allowance prior to fumigation. For the Ventura NAA, Table 3 shows 

that the May-October fumigated acreage decreased by 24 percent in the Ventura NAA 

between 2006-7 and 2008-9 (15,497 acres to 11,833 acres). At least part of this decrease is 

likely due to the fumigant limit and allowances. ( 

Deleted: 2008 

Deleted: and grower allowance system 

Deleted: All of the allowances 

combined are equal to the fumigant limit. 

Near the beginning of each year, g

Deleted: the name of the product, the 

application rate, 

Deleted: ,

Deleted: , fumigation method, and 

projected month of application. 

Commissioners forward emission 

requests to DPR. If the total amount of 

fumigant use requested by growers is 

above the NAA’s emission limit, DPR 

imposes 

Deleted: proportionate reductions 

Deleted: then 

Deleted: determined by DPR 

Deleted: NOTE: In April 2011, DPR 

adopted revisions to the fumigant VOC 

regulations that provide other alternatives 

in addition to allowances for county 

agricultural commissioners to enforce a 

fumigant limit. These revisions have not 

been submitted to U.S. EPA yet.)
18

Prior to implementation of the fumigant regulations in 2008, fumigants contributed 80 

percent of more of the pesticide VOC emissions in the Southeast Desert and Ventura 

nonattainment areas and more than 40 percent of the emissions in the San Joaquin Valley. 

DPR implemented regulations for fumigants because their reduction was the only way to 

ensure the SIP goals were achieved in the Southeast Desert and Ventura NAAs. These 

reductions were also effective for the San Joaquin Valley. However, DPR is working on 

other measures to further reduce VOC emissions, particularly for the San Joaquin Valley. 

In 1993, U.S. EPA published an alternative control technology document that addresses the 

control of VOC emissions from the application of agricultural pesticides 

(http://www.epa.gov/ttn/naaqs/ozone/ctg_act/199303_voc_epa453_r-92-

011_ag_pesticides.pdf). To DPR’s knowledge, no other state has measures to reduce 

pesticide VOC emissions, so there are no other evaluations to rely on. The following is 

DPR’s evaluation of the seven techniques the document identified as technically viable for 

reducing pesticide VOC emissions: 

• Reformulating organic solvent containing pesticide formulations (e.g., emulsifiable 

concentrates) 

• Reducing fumigant usage 

• Using alternative application methods 

• Applying microencapsulation techniques 

• Using integrated pest management 

• Using alternative active ingredients 

• Reducing the use of crop oils 

Other Reduction Options – Reformulating Organic Solvent Containing Pesticide 

Formulations 

In 2005, DPR initiated a reevaluation (regulatory process to request actions by pesticide 

registrants) for several hundred nonfumigant products. The reevaluation required registrants 

to submit plans for reformulating the inert ingredients in the products to reduce VOC 

emissions. DPR stopped work on this reevaluation and shifted its strategy to reducing 

emissions with the fumigant regulations. DPR restarted work on nonfumigants in 2010 and 

revised the reevaluation to limit reformulation efforts to the products with the highest 

pesticide VOC contribution in the San Joaquin Valley NAA (Figure 4): 

• Abamectin products (e.g., Agri-Mek) 

• Chlorpyrifos products (e.g., Lorsban) 

• Dimethoate products (e.g., Cygon) 

• Gibberellins products (e.g., Gibgro) 

• Oxyfluorfen products (e.g., Goal) 

• Permethrin products 

• Trifluralin products (e.g., Treflan) 

See the following web page for more detailed information on the reevaluation for VOC 

emissions from nonfumigant pesticides: 

http://www.cdpr.ca.gov/docs/emon/vocs/vocproj/req_reformulation_lid.htm 
19

Several registrants began reformulation efforts at the start of the reevaluation, most notably 

for chlorpyrifos. Products containing chlorpyrifos are the highest or second highest pesticide 

VOC contributor in the San Joaquin Valley, depending on year (Figure 4). VOC emissions 

from the inert ingredients in chlorpyrifos products declined 40 percent between 2008 and 

2009 in the San Joaquin Valley. This decline was due to a 25 percent decrease in use, and a 

15 percent decrease due to a change in products (Figure 5). DPR registered Lorsban 

Advanced in July 2008, and its emission potential is 18.45 percent. In contrast, Lorsban 4E, 

Lorsban 4E-HF, and similar emulisfiable concentrate products have emission potentials of 

approximately 50 percent. Many growers and applicators switched from the high-VOC 

chlorpyrifos products to Lorsban Advanced in 2009. Lorsban Advanced was the highest use 

chlorpyrifos product in the San Joaquin Valley during 2009 (Table 6). 

There are several activities to encourage the voluntary use of low-VOC products. Purchase of 

low-VOC products is one of three pesticide VOC measures for which EQIP provides 

matching funds to growers in California. Under a U.S. EPA grant, DPR prepared a 

conservation management practices guide for pesticide VOCs and developed a companion 

website for growers and applicators that calculates and compares the VOC emissions for 

pesticide applications. 

In conclusion, this measure is feasible because several registrants have implemented this 

measure, and DPR is evaluating possible additional regulatory actions for non-fumigant 

pesticides to require reformulation for certain pesticides. However, it may be infeasible to 

reformulate some products due to decreased pest control, increased toxicity of the inert 

ingredients, high cost, or other factors. 

Other Reduction Options – Reducing Fumigant Usage 

The fumigant regulations include a fumigant limit and allowance system in the Ventura NAA 

at least until 2012, and as a backstop measure in the event low-emission fumigation methods 

are insufficient to achieve the SIP goals for the other NAAs. This measure is feasible as a 

backstop. It requires a reduction in fumigated acreage, and planting of less profitable crops, 

or no crops. Additionally it requires a new administrative program for DPR, county 

agricultural commissioners, and the regulated community. Low-emission fumigation 

methods are more compatible and less costly with the current regulatory program. 

Other Reduction Options – Using Alternative Application Methods 

The alternative control technology document describes this option as “improved-efficiency 

application equipment.” To encourage the voluntary reduction of emissions, purchase of 

precision pest control application equipment or “smart sprayers” is one of three pesticide 

VOC measures for which EQIP provides matching funds to growers in California. Priority is 

given to application equipment that uses photo identification or sonar-type technologies. 

These technologies are primarily used for orchard sprayers, where a sensor controls the 

amount of spray, and turns off the spray in between trees. This results in less pesticide being 

applied. This measure is not feasible as a regulatory control because the equipment is costly 

and the VOC emissions due to pesticides applied with orchard sprayers are relatively low. 
20

Although not described in the alternative control technology document, the fumigant 

regulations rely primarily on low-emission fumigation methods to achieve reductions. 

Other Reduction Options – Applying Microencapsulation Techniques 

This measure consists of reformulating emulsifiable concentrates into microcapsules to 

reduce the amount of solvent in the product. DPR has grouped this measure with the 

reformulation option. 

Other Reduction Options – Using Integrated Pest Management 

The alternative control technology document describes integrated pest management as an 

“ecologically based pest management program that combines biological and nonbiological 

control techniques to suppress weeds, insects, and diseases. This option has been defined as 

a pest population management system that utilizes all suitable techniques in a compatible 

manner to reduce pest populations and maintain them at levels below those causing 

economic injury.” DPR regulates the use of pesticides, and lacks legal authority to require 

integrated pest management, which includes non-pesticidal practices. However, DPR has 

programs that encourage the adoption integrated pest management, not only to address 

VOCs, but also to reduce health and environmental risks. These programs include DPR’s 

IPM Innovator awards to honor California organizations that emphasize pest prevention, 

favor least-toxic pest control, and share their successful strategies with others. DPR has also 

funded grants and alliances that form a step-wise progression from applied research and 

demonstration projects to regional or statewide implementation of multi-disciplinary 

reduced-risk pest management practices. Reducing VOC emissions is one of the criteria DPR 

uses to judge applications for pest management grants. 

Organic crop production or growing crops with no fumigants is possible in some situations, 

but is infeasible for all crop production. For some annual crops such as strawberries, 

conventional crops are normally grown every year or every other year on the same field, 

made possible by soil fumigation. In contrast an organic crop must be rotated with other 

commodities and are grown on the same field once every several years. There is insufficient 

land in California with climate and water to support a conversion to 100 percent organic 

production. Growing perennial crops (orchards, vineyards) can be very risky without 

fumigants. These crops are subject to infestation by nematodes and nematode-borne 

pathogens in preplant/replant situations. In organic vineyards and orchards where soil 

fumigants are not allowed, the only options are nematode-resistant rootstocks and prolonged 

fallow periods. While nematode-resistant rootstocks are available for both crops, they are not 

always a good match for a particular soil type or local climate. The recommended fallow 

period for grapes is ten years, and this will only serve to delay the appearance of nematoderelated symptoms. Nonfumigant pesticides are not effective against these soil pests after the 

crop is planted. Use of fumigants for some nursery crops is essential. Many fields are planted 

with seedlings grown in nurseries. To prevent catastrophic failure in multiple production 

fields, federal and state laws require many nursery crops to be certified as pest-free prior to 

sales of seedlings. Fumigants are often the only alternative to obtain the certification. 
21

In conclusion, this measure is not feasible because integrated pest management and organic 

production are not always technically feasible, and DPR lacks legal authority to implement 

this as a requirement. 

Other Reduction Options – Using Alternative Active Ingredients 

This option is not feasible because DPR lacks legal authority to require certain pesticides to 

be used. While DPR can regulate or prohibit sales or use of certain pesticides based on 

unacceptable risks, DPR cannot require growers and applicators to apply specific pesticides 

in place of the regulated ones. 

Other Reduction Options – Reducing the Use of Crop Oils 

Crop oils have insecticidal uses, and are among the highest used pesticides in California. 

(Petroleum oil was ranked second and mineral oil was ranked third in pounds applied during 

2009.) However, DPR disagrees that reducing crop oils is a good option to reduce VOC 

emissions. Based on thermogravimetric analysis data and DPR’s evaluation of 26 oil 

products, the emission potentials for oil products are low, with a median value of 1.53 

percent. Even accounting for the high use, none of the oils are among the top 10 pesticide 

VOC contributors in any of the NAAs, so any reductions would have minimal impact on 

emissions. Moreover, DPR and others encourage the use of oils because they have lower 

health and environmental risk in comparison to most other active ingredients in insecticide 

products, particularly organophosphates. In conclusion, this measure is not feasible because 

the VOC emission reductions associated with this measure are minimal, and will likely cause 

an increase in use of pesticides with greater health or environmental impact. See the 

following for DPR’s VOC evaluation of oil products: 

http://www.cdpr.ca.gov/docs/emon/pubs/ehapreps/analysis_memos/2079_segawa.pdf 

Other issues 

Current Research on Fumigant VOC Emission Reduction 

Another reevaluation is in progress to obtain additional data for current fumigation methods 

because DPR relied on surrogate data for some fumigation methods. This reevaluation 

requested that registrants provide monitoring data to confirm the accuracy of the surrogate 

data. The registrants included CHAIN2D computer modeling of emissions as part of their 

response. While the registrant modeling was rejected, DPR started its own efforts to develop 

a computer model to estimate fumigant emissions. Under contract to DPR, the model 

developer has completed modifications of HYDRUS to account for the effect of tarps, bed 

shape, and other fumigation parameters. Comparisons of the HYDRUS model to field 

monitoring data have shown good agreement in some cases, and disagreement in other cases. 

To assist with validating the model, DPR plans a special field study to gather data that are 

used for the model inputs, but were lacking in earlier studies. If validated, the model will be 

used to determine the parameters that affect emissions and guide efforts to reduce emissions. 
22

Numerous researchers are working on methods to reduce fumigant emissions. Much of this 

work is sponsored by USDA as part of two area-wide programs on methyl bromide 

alternatives. The Pacific Area-Wide program includes several multi-year projects in 

California to develop, demonstrate, and implement fumigant reduction measures. It’s likely 

this research will lead to additional low-emission fumigation methods. DPR is currently 

evaluating data for low permeability tarpaulins from this program. Field monitoring data 

indicates that low permeability tarpaulins can reduce peak fumigant emissions by as much as 

90 percent. However, the data also indicates that relatively high emissions occur at the 

normal tarp removal time, and the normal tarp removal process may cause unacceptable 

exposure to workers. Current research is focusing on the appropriate time period and process 

to remove low permeability tarpaulins. It may be possible to achieve even greater reductions 

by using low permeability tarpaulins in combination with lower application rates and still 

effectively manage pests. The Pacific Area-Wide program developed a special a global 

positioning system (GPS) for tractors that reduces the amount of fumigant needed by 50 

percent or more. Intended for orchard and vineyard applications, tractors equipped with this 

system apply fumigant only at the spot where a tree or vine will be planted. Researchers are 

working with a major fumigant pest control business to modify the GPS system for 

commercial use. Research also continues on soil amendments, soil compaction techniques, 

and other fumigant emission reduction measures. The Pacific Area-Wide program is also 

conducting research on nonpesticidal alternatives to fumigants. This includes growing 

strawberries in soilless substrate, anaerobic soil disinfestation, steam disinfestation, 

biocontrol agents, and resistant rootstocks. All research of the Pacific Area-Wide program, as 

well as the Southeast Area-Wide program, and other fumigant research are presented at an 

annual conference. Information about the research is available at the following conference 

website: http://www.mbao.org/ 

In January 2011, U.S. EPA summarized its evaluation of the available fumigant emissions 

studies (Attachment 5 – U.S. EPA memorandum from Dawson, Smith, and Shelat to Leahy, 

dated January 11, 2011). DPR did not use all of studies used by U.S. EPA because: 1) some 

studies were not available when the regulations were developed in 2007 and are still under 

review by DPR; 2) some studies were conducted outside the state and do not reflect 

emissions under California conditions; 3) some studies measured emissions using methods 

unacceptable to DPR; or 4) some studies were insufficient to address all DPR exposure 

concerns. It’s likely that DPR will use the recent studies to revise the regulations and add 

new low-emission fumigation methods once the reviews are completed and other issues are 

addressed. 

Time Period of Emission Inventory and Regulations 

DPR’s emission inventory and fumigant regulations are based on the peak ozone season of 

May 1 through October 31 because they implement the pesticide element of the 1-hour ozone 

SIP. That SIP is based on seasonal inventories. Under that SIP, as approved by U.S. EPA, 

VOC reductions are, and always have been, measured over the 6-month ozone season. 

Likewise the VOC reduction goals of the pesticide element of that SIP apply, and always 

have been applied to that time period. The VOC reduction measures of the 1-hour ozone SIP 

are seasonal so that the reductions needed during the peak ozone season are required. 

Deleted: 2) some studies available after 

2007 led to fumigant VOC regulation 

changes that have not yet been submitted 

to U.S. EPA; 3

Deleted: 4

Deleted: 5
23

Moreover, requiring low-emission fumigation methods year-round could increase fumigant 

emissions during the peak ozone season. Fumigants are applied prior to planting, and are not 

applied to prevent immediate crop damage. Therefore, the time window for application is 

more flexible than most other pesticides. Under the current regulations, growers and 

applicators have shifted some fumigations outside the May-October period to avoid the 

additional restrictions. It’s likely that these fumigations will shift back to the May-October 

period if low-emission methods are required year-round. This will result in lower emissions 

outside the May-October period, but greater emissions during the May-October period, 

defeating the overall goals of the regulations. 

Conclusions 

DPR has implemented or is working to implement all feasible measures to reduce VOC 

emissions from pesticides. DPR has adopted regulations requiring low-emission fumigation 

methods in certain NAAs, usually consisting of tarping, post-fumigation water treatments, or 

application through drip irrigation systems. The VOC regulations also include a fumigant 

emission limit for the Ventura NAA at least until 2012. This system is also a backstop 

measure in the event low-emission fumigation methods are insufficient to achieve the SIP 

goals for the other NAAs. DPR is working with pesticide registrants to reformulate certain 

pesticide products that contain high amounts of solvents. DPR and others are conducting 

research to further reduce VOC emissions from pesticides. Other measures that would reduce 

VOC emissions are infeasible at this time. 

Deleted: and grower allowance system 
24

Table 1. Application Method Adjustment Factor (AMAF) and pesticide use report Field 

Fumigation Method (FFM) code for each fumigation method. 

Regulation 

Section Field Fumigation Method FFM Code AMAF (%) 

6447.3. Methyl Bromide Fumigation Methods (with or without chloropicrin) 1100 series 

6447.3(a)(1) Nontarpaulin/Shallow/Bed 1101 100* 

6447.3(a)(2) Nontarpaulin/Deep/Broadcast 1102 74* 

6447.3(a)(3) Tarpaulin/Shallow/Broadcast – Nobel Plow 1103 48 

 Tarpaulin/Shallow/Broadcast – Nobel Plow – Strip 1104 74* 

 Tarpaulin/Shallow/Broadcast – Closing shoes and compaction roller 1105 100* 

6447.3(a)(4) Tarpaulin/Shallow/Bed 1106 100* 

6447.3(a)(5) Tarpaulin/Deep/Broadcast 1107 48 

 Tarpaulin/Deep/Broadcast – Strip 1108 74* 

6447.3(a)(6) Drip System - Hot Gas 1109 100* 

 Other label method** 1190 --- 

 

6448.1. 1,3-Dichloropropene Fumigation Methods (with or without chloropicrin) 1200 series 

6448.1(c)(1) Nontarpaulin/Shallow/Broadcast or Bed 1201 65* 

6448.1(c)(2) Tarpaulin/Shallow/Broadcast 1202 65* 

 Tarpaulin/Shallow/Bed 1203 65* 

6448.1(c)(3) Nontarpaulin/Shallow/Broadcast /Three Water Treatments 1204 44 

6448.1(c)(4) Tarpaulin/Shallow/Bed/Three Water Treatment 1205 44 

6448.1(c)(5) Nontarpaulin/Deep/Broadcast or Bed 1206 26 

6448.1(c)(6) Tarpaulin/Deep/Broadcast 1207 26 

 Tarpaulin/Deep/Bed 1208 26 

6448.1(c)(7) Chemigation (Drip System)/Tarpaulin 1209 19 

 Other label method** 1290 --- 

 

6449.1 Chloropicrin-Fumigation Methods 1100-1300 

series 

6447.3(a)(1) Nontarpaulin/Shallow/Bed 1101 64* 

6447.3(a)(2) Nontarpaulin/Deep/Broadcast 1102 64* 

6447.3(a)(3) Tarpaulin/Shallow/Broadcast – Nobel Plow 1103 44 

 Tarpaulin/Shallow/Broadcast – Nobel Plow – Strip 1104 64* 

 Tarpaulin/Shallow/Broadcast – Closing shoes and compaction roller 1105 64* 

6447.3(a)(4) Tarpaulin/Shallow/Bed 1106 64* 

6447.3(a)(5) Tarpaulin/Deep/Broadcast 1107 44 

 Tarpaulin/Deep/Broadcast – Strip 1108 64* 

6447.3(a)(6) Drip System - Hot Gas 1109 100* 

 

6448.1(c)(1) Nontarpaulin/Shallow/Broadcast or Bed 1201 64* 

6448.1(c)(2) Tarpaulin/Shallow/Broadcast 1202 44 

 Tarpaulin/Shallow/Bed 1203 64* 

6448.1(c)(3) Nontarpaulin/Shallow/Broadcast /Three Water Treatments 1204 43 

6448.1(c)(4) Tarpaulin/Shallow/Bed/Three Water Treatment 1205 43 

6448.1(c)(5) Nontarpaulin/Deep/Broadcast or Bed 1206 64* 

6448.1(c)(6) Tarpaulin/Deep/Broadcast 1207 44 

 Tarpaulin/Deep/Bed 1208 44 

6448.1(c)(7) Chemigation (Drip System)/Tarpaulin 1209 12 

 

 Other label method** 1390 --- 

 
25

Regulation 

Section Field Fumigation Method FFM Code 

AMAF 

(%) 

6450.1. Metam-Sodium and Metam-Potassium Fumigation Methods 1400 series 

6450.1(d)(1) Sprinkler/Broadcast or Bed/One Water Treatment 1401 77* 

6450.1(d)(2) Sprinkler/Broadcast or Bed/Two Water Treatments 1402 28 

6450.1(d)(3) Sprinkler/Broadcast or Bed/Three Water Treatments 1403 21 

6450.1(d)(4) Nontarpaulin/Shallow/Broadcast or Bed/One Water Treatment 1404 77* 

6450.1(d)(5) Nontarpaulin/Shallow/Broadcast or Bed /Two Water Treatments 1405 28 

6450.1(d)(6) Nontarpaulin/Shallow/Broadcast or Bed/Three Water Treatments 1406 21 

6450.1(d)(7) Chemigation (Drip System) Tarpaulin 1407 9 

 Chemigation (Drip System) Nontarpaulin 1408 9 

6450.1(d)(8) Rotary Tiller 1409 14 

 Power Mulcher 1410 14 

 Soil Capping 1411 14 

6450.1(d)(9) Flood 1412 77* 

6452 Day Drench 1413 100

6452 Night 1A.M. Start/Sprinkler/Broadcast or Bed/Two Water Treatments 1452 77*

6452 Night Nontarpaulin/Shallow/Broadcast or Bed/Two Water Treatments 1455 28

6452 Night 4A.M. Start/sprinkler/Broadcast or Bed/Two Water Treatments 1472 35

 Other label method** 1490 --- 

 

6450.2. Dazomet Fumigation Methods 1500 series 

 Soil incorporation 1501 17 

Surface application – water incorporation 1502 17 

 Other label method** 1590 --- 

 

6451.1 Sodium Tetrathiocarbonate Fumigation Methods 1600 series 

 Chemigation (Drip) 1601 10 

 Chemigation (mini-sprinkler) 1602 10 

Chemigation (flood, basin) 1603 10 

 Chemigation (furrow, border) 1604 10 

Chemigation (foggers, jets, misters, other) 1605 10 

 Other label method** 1690 --- 

6446.1 Methyl Iodide Fumigation Methods 1700 Series

Day Tarpaulin/Shallow/Broadcast 1701 100

Day Tarpaulin/Shallow/Bed 1702 100

Day Tarpaulin/Deep/Broadcast 1703 100

Day Chemigation (Drip)/Tarpaulin 1704 100

Day Auger-Probe 1705 100

* Method prohibited within the San Joaquin Valley, Southeast Desert, and Ventura 

nonattainment areas during May 1 – October 31. 

**For use only outside of the May 1 – October 31 time period; or areas outside of the 

nonattainment areas; or for exempted applications (such as described in Sections 6447, 6448, 

6449, 6450, and 6451)

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26

Table 2. Comparison of fumigant emissions and use prior to and after implementation of 

fumigant VOC regulations (2006-2007 vs. 2008-2009 May-October annual average). 

Fumigant VOC Emissions and Use San Joaquin 

Valley NAA 

Southeast 

Desert NAA 

Ventura 

NAA 

2006-7 Fumigant Emissions (tons/day) 6.47 0.49 3.06 

2008-9 Fumigant Emissions (tons/day) 3.35 0.092 1.30 

 

2006-7 Fumigant Use (tons/day) 14.39 0.92 8.89 

2008-9 Fumigant Use (tons/day) 11.93 0.47 6.53 

 

2006-7 vs. 2008-9 Relative Difference (percent) 

 Decrease in VOC emissions 48 81 57* 

 Decrease in Amount Applied 17 49 26* 

 Decrease Due to Low-Emission Methods** 31 32 31 

 

2006-7 vs. 2008-9 Mass Difference (tons/day) 

 Decrease in VOC emissions 3.12 0.40 1.75* 

 Decrease Due to Low-Emission Methods** 2.01 0.16 0.95 

* Some of the decrease in use for Ventura was due to the fumigant limit and allowances 

required by the regulations. 

** Some of the decrease may be due to changes in the procedure for determining the 

frequency each fumigation method is used. 
27

Table 3. Comparison of fumigant use prior to and after implementation of fumigant VOC 

regulations (2006-2007 vs. 2008-2009 annual average). Data is for all fumigants combined. 

Fumigant Use San Joaquin 

Valley NAA 

Southeast 

Desert NAA 

Ventura 

NAA 

Amount of Fumigant Used 

May-Oct 2006-7 7,005,537 lbs 490,624 lbs 3,283,589 lbs 

Jan-Dec 2006-7 16,225,657 lbs 1,029,983 lbs 3,538,332 lbs 

May-Oct as fraction of 2006-7 43% 48% 93% 

 

May-Oct 2008-9 5,805,199 lbs 317,963 lbs 2,453,000 lbs 

Jan-Dec 2008-9 15,710,197 lbs 950,877 lbs 3,018,515 lbs 

May-Oct as fraction of 2008-9 37% 33% 81% 

Size of Area Fumigated

May-Oct 2006-7 49,242 ac 3,456 ac 15,497 ac 

Jan-Dec 2006-7 146,872 ac 6,906 ac 16,766 ac 

May-Oct as fraction of 2006-7 34% 50% 92% 

 

May-Oct 2008-9 40,862 ac 2,332 ac 11,833 ac 

Jan-Dec 2008-9 139,861 ac 6,403 ac 14,967 ac 

May-Oct as fraction of 2008-9 29% 36% 79% 

Average Application Rate

May-Oct 2006-7 175 lbs/ac 199 lbs/ac 216 lbs/ac 

Jan-Apr & Nov-Dec 2006-7 164 lbs/ac 190 lbs/ac 241 lbs/ac 

 

May-Oct 2008-9 167 lbs/ac 205 lbs/ac 291 lbs/ac 

Jan-Apr & Nov-Dec 2008-9 167 lbs/ac 189 lbs/ac 199 lbs/ac 
28

Table 4. Summary of the evaluation of possible fumigation method restrictions. 

Possible Restriction 1,3-Dichloropropene Chloropicrin Methyl Bromide Methyl Iodide MITC Sodium Tetrathiocarbon

Introduction - Drip Low-emission Low-emission Not allowed by labels Low-emission Low-emission Low-emission Introduction - Other Chemigation Not allowed by labels Not allowed by labels Not allowed by labels Not allowed by labels

Several methods allowed, additional requirements for low-emission 

Several methods allowed, all lowemission 

Introduction - Tractor Shank 

Several methods allowed, deep shank is low-emission 

Several methods allowed, additional requirements for low-emission 

Several methods allowed, additional requirements for lowemission 

Several methods allowed, additional requirements for low-emission

Several methods allowed, additional requirements for low-emission 

Not allowed by la

Tarping Ineffective Low-emission method Low-emission method Highly retentive tarp low-emission Not tested Incompatible wit

chemigation 

Soil Moisture Regs superseded by labels Regs superseded by labels Regs superseded by labels Label requirement Regs superseded by labels Regs superseded 

label 

Water Treatments 3 or more for low- emission 3 or more for low- emission Not tested Not tested 2 or more for low- emission Label requiremenApplication Rate Max based on highest rate tested Max based on highest rate tested Max based on highest rate tested Max based on highest rate tested Max based on highest rate tested Max based on hig

rate tested 

Weather Restrictions Insufficient data Insufficient data Little or no effect on emissions Insufficient data Insufficient data Insufficient data Soil Characteristics Insufficient data Insufficient data Little or no effect on emissions Insufficient data Insufficient data Insufficient data Soil Amendments Variable results, possible odor Variable results, possible odor Variable results, possible odor Not tested Not tested Not tested Soil and Equipment Prep Label requirements Label requirements Label requirements Label requirements Label requirements Label requiremen
29 

Table 5a. Standard fumigation costs in 2007. 

Fumigant $/lb. Active 

Ingredient Per acre costs** 

Methyl Bromide $3.50 $2100 (350 lbs/ac, broadcast shank injection, tarped 

Chloropicrin $3.00 $1400 (200lb/ac, broadcast shank injection, tarped) 

1,3-D tractor $1.40 $550 (35 gal/ac, broadcast shank injection, untarped) 

1,3-D drip $2.40 $640 (25 gal/ac, drip application) 

Metam Sodium $1.00 $400 (75 gal/ac, shank injection, water seal) 

*Tom Trout, USDA-ARS, Fumigant use trends in California; Response to MeBr PhaseOut. 

Annual International Research Conference on Methyl Bromide Alternatives and Emissions 

Reductions, 2006. 

**Includes both fumigant and application costs 

Table 5b. Costs of conversion to low-emission fumigation methods in 2007. 

Fumigant application 

method Fumigant Increased $/ac* 

Acres (average 

2003-2005)* 

Estimated total cost 

of conversion 

SJV = 124,750 $63,622,500 

SE Desert = 4,280 $2,182,800 

Convert to drip application 

from shank injection (drip 

system already in place)* 

1,3-dichloropropene 

Chloropicrin 

Metam 

$5101

Ventura = 6,408 $3,268,080 

SJV= 124,750 $313,122,500 

SE Desert = 4,280 $10,742,800 

Convert to drip application 

from shank injection 

(including installation of 

drip system)** 

1,3-dichloropropene 

Chloropicrin 

Metam 

$25102

Ventura = 6,408 $16,084,080 

SJV= 124,750 $1,247,500 

SE Desert = 4,280 $42,800 

Post-application water 

treatments (sprinkler system 

already in place)** 

1,3-dichloropropene 

Chloropicrin 

Metam 

$103

Ventura = 6,408 $64,080 

SJV= 124,750 $29,940,000 

SE Desert = 4,280 $1,027,200 

Post-application water 

treatments (including rental 

of sprinkler system** 

1,3-dichloropropene 

Chloropicrin 

Metam 

$2404

Ventura = 6,408 $1,537,920 

SJV= 16,898 $6,759,200 

SE Desert = 30 $12,000 Tarping – methyl bromide 

Trees & Vines Only ** Methyl Bromide $4005

Ventura = 32 $12,800 

* Increased costs per acre: Tom Trout, USDA-ARS, Fumigant use trends in California; 

Response to MeBr PhaseOut. Annual International Research Conference on Methyl Bromide 

Alternatives and Emissions Reductions, 2006. 

** Increased cost per acre estimates provided by Husein Ajwa, Ext Specialist, UC Davis 

Dept. of Plant Sciences, Salinas, CA +1 831 755 2823. 

 

1

 Materials and installation costs: tarp + drip tape = $500, water = $10 for 3 x 1⁄4 inch applications within two 

days after fumigation 

2

 Materials and installation costs: tarp + drip tape $500, water = $10, Install drip system $2000 

3

 Water: $10/ac in. for 3 x 1⁄4 inch applications within two days after fumigation 

4

 Sprinkler rental = $200 and setup = $40; (purchase sprinklers about $2000/ac). 

5

 Tarp and application = $400 
30 

Table 6. Use of major chlorpyrifos products and liquid low-VOC alternatives in the San 

Joaquin Valley NAA. 

Product Use May-Oct (lbs) Product Emission 

Potential (%) 2008 2009 

Nufos 4E 52.30 176,922 190,975 

Lorsban 4E 50.00 500,314 188,032 

Govern 4E 50.00 185,234 141,313 

Lorsban 4E-HF 48.68 423,639 116,953 

 

Lorsban Advanced 18.45 2,323 386,662 

Lock-On 20.90 305,620 176,505 
31 

Figure 1. Nonattainment areas included in the pesticide element of the ozone state 

implementation plan. 

CALIFORNIA CALIFORNIA

Sacramento 

Metro

San Joaquin 

Valley

Southeast 

Desert

South Coast

Ventura

* Sacramento Metro NAA 

- all of Sacramento and Yolo counties, and parts of 

El Dorado, Placer, Solano and Sutter counties.

* San Joaquin Valley NAA 

- all of San Joaquin, Stanislaus, Merced, Madera, 

Fresno, Kings, and Tulare counties, 

and the valley portion of Kern County.

* South Coast NAA 

- all of Orange County, and part of Los Angeles,

Riverside and San Bernardino counties.

* Southeast Desert NAA 

- the desert portions of Riverside (Coachella Valley), 

Los Angeles (Lancaster/Palmdale), 

and San Bernardino (Barstow) counties. 

* Ventura NAA - all of Ventura County.

®

FEDERAL NON-ATTAINMENT AREAS 

AFFECTED BY CALIFORNIA REGULATIONS

TO REDUCE EMISSIONS 

FROM

FUMIGANT PESTICIDES

January 2008
32 

Figure 2. Pesticide VOC emission inventory for 1990-2009. The emissions using fumigant 

Application Method Adjustment Factors cannot be calculated for 1991-2004 due to lack of 

data on the frequency each fumigation method was used (method use fractions). 

NAA 1 Sacramento Metropolitan

Year

1990

1995

2000

2005

2010

2015

Emission Rate (tpd)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

NAA 2 San Joaquin Valley 

Year

1990

1995

2000

2005

2010

2015

Emission Rate (tpd)

0

5

10

15

20

25

NAA 3 Southeast Desert 

Year

1990

1995

2000

2005

2010

2015

Emission Rate (tpd)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

NAA 4 Ventura

Year

1990

1995

2000

2005

2010

2015

Emission Rate (tpd)

0

1

2

3

4

5

NAA 5 South Coast

Year

1990

1995

2000

2005

2010

2015

Emission Rate (tpd)

0

2

4

6

8

10

12

• Adjusted Emissions 

(1990, 2004, 2005, 2006, 2007, 

2008 & 2009)

SIP Goals

 
33 

Figure 3. Statewide use of field fumigants. 

0

5,000,000

10,000,00015,000,00020,000,000

1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

Statewide Use (lbs)

1,3-D Chloropicrin Methyl Bromide MITC pesticides Sodium Tetrathiocarbonate
34 

Figure 4. VOC emissions from pesticide products used in the San Joaquin Valley during 

May-October 2009, by active ingredient. Emissions from glyphosate products are likely 

overestimated due to the lack thermogravimetric analysis data for one high-use product and 

the assignment of a high default emission potential. 

1,3-D

9%

Glyphosate

8%

Glufosinate

3%

Methyl bromide

2% Dimethoate

4%

Abamectin

5%

Gibberellins

5%

Oxyfluorfen

5%

Metam

11%

Acrolein

2%

Fenpyroximate

2%

Trifluralin

2%

All other pesticides

32% Chlorpyrifos

10%
35 

Figure 5. Chlorpyrifos use and product VOC emissions in the San Joaquin Valley during 

May-October. 

0

250,000

500,000

750,000

1,000,000

Active ingredient VOC emissions

Amount (lbs)

2008 2009