California Regulatory Impacts on Adoption of MeBr Alternative Fumigants

Tom Trout, USDA-ARS Water Management Research Laboratory, Fresno, CA

From 1991 to 1999, methyl bromide use in California decreased from 18.5 to 15 million pounds, while use of alternative registered fumigants increased from 7.5 to over 24 million pounds. Telone (1,3-dichloropropene) was reintroduced for use in 1994 and about 3 million pounds was used in 1999, mainly on orchards and vineyards and at reduced rates on annual vegetables (carrot, tomato, and sweetpotato). Chloropicrin use has gradually increased in the last 2 years to about 4 million pounds because it is being used at higher ratios in methyl bromide mixtures as a means of extending the limited methyl bromide supplies. Very little chloropicrin is used as a stand-alone fumigant, although current research shows it has potential as a stand-alone fumigant for some crops. Over 70% of the chloropicrin use is on strawberries. Use of metam sodium, which generates the fumigant methyl isothiocyanate (MITC), has increased dramatically to over 17 million pounds and has now surpassed methyl bromide in use. It is primarily used on annual vegetable crops (carrot, tomato, potato, melons) as a less costly alternative to other fumigants.

These increasing use patterns appear to indicate that current regulations are not precluding use of these currently available alternatives. However, growers and applicators are quick to provide examples of how current or anticipated regulations will limit their use. This is especially true in California where use conditions in addition to those on the United States Environmental Protection Agency (EPA) label are often imposed. I will summarize the regulatory procedures in California and the impacts of these current and anticipated regulations on use of alternative fumigants.

California Fumigant Regulatory Process

California fumigant use regulations may vary from those in other states in three ways—the California label, State-issued permit conditions, and specific conditions imposed at the county level for individual applications. The California Department of Pesticide Regulation (DPR) may require data in addition to that required by EPA before it will register and allow use of a pesticide. For fumigants, this often includes efficacy data for the material under the proposed use and information on air emissions, transport, and fate. Fumigant registrants may work simultaneously with EPA and DPR so that their registration packages meet both needs. DPR's current intent is to adopt the national label without changes and to impose any further restrictions they feel are necessary in the form of Suggested Permit Conditions. These permit conditions may include restrictions on application rates, buffer zones around fumigated fields, worker conditions, environmental conditions, and total fumigant use in an area.

Suggested Permit Conditions are actually recommendations to county agricultural commissioners who are responsible for authorizing, regulating, and accounting for all fumigant applications. All pesticide applications in California are required to meet the intent of the California Environmental Quality Act (similar to the federal NEPA) through a notice and permit process with public scrutiny. Thus, all fumigant applications begin with a "Notice Of Intent" filed with the county agriculture commissioner's office. These notices include the field, crop, fumigant, and rate, and the issued Permit will note use conditions and restrictions specific to the fumigant and application. County agriculture commissioners (appointed by the county board of supervisors) must answer to both farmers and concerned citizens (neighbors and other residents concerned about the potential dangers of pesticides). They usually follow DPR issued Suggested Permit Conditions, but may also (and sometimes do) further restrict use. Although county restrictions are on individual applications, they may be printed up as county guidelines. County restrictions may be based as much on nuisance aspects (smell, irritation) and perception as on actual risk. County inspectors ensure that the permit conditions are met.

Regulatory Impacts on Use of Telone

Telone is the only one of the three currently registered fumigants to have completed the EPA re-registration process. It has also completed most of the State's risk characterization process. Telone is also the most restricted of the three currently. Current label restrictions include 300-foot buffers around occupied residences (100 feet for drip application and no buffer if not refumigated for 3 years), 35 gal/acre maximum application rates (except for nurseries), 5-day field reentry periods, use of full face respirators and chemical resistant hats, gloves, boots, and aprons for workers in the field, and moist soil requirements during application and a soil "seal" following application to reduce emissions.

Each of these restrictions can limit use in some situations. Three hundred foot buffers eliminate fumigation on about 7 acres of surrounding land; 100-foot buffers affect only about an acre. The worker personal protective equipment (PPE) requirements limit the ability to install plastic tarps in warm climates. Thirty-five gallons per acre may not be adequate for deep-rooted tree and vine crops. The soil moisture requirements in most years are difficult and/or expensive for California tree and vine growers to achieve.

California Suggested Permit Conditions imposed 300-foot buffers until this summer when they were reduced to 100 feet to match the new EPA drip-applied Telone (InLine and Telone EC) label. Applications are also restricted in the San Joaquin Valley in December and January when air inversions are common.

The primary restriction in current California Permit Conditions are township caps on Telone applications. Chronic exposure is a concern with Telone, and township caps are designed to limit air concentrations over extended time periods in an area. California township caps limit Telone applications to no more than 9,600 "adjusted" gallons of Telone (90,050 lb 1,3-D) in any 36 square mile (23,040 acre) township. Adjusted pounds are the actual pounds multiplied by an application factor of 1.0 for deep (>18 inch) shank applications and 1.9 for shallow (>12 inch) shank applications. Township caps limit applications to about 1 percent of the land for a typical strawberry or orchard/vineyard fumigation and 2 percent of the land for a typical vegetable fumigation.

As Telone use has increased, township caps have begun to limit applications. In 2000, cap limits were hit in four townships and were nearly hit in nine additional townships. As methyl bromide is phased out and Telone use increases, the caps will be more constraining. An analysis of the impacts of the township caps on potential use (Carpenter et al. 2001, Trout 2001) showed that only about two-thirds of the land presently fumigated with either Telone or methyl bromide would be able to use Telone.

The township cap impacts varied greatly by crop and region, because fumigated crops are concentrated in particular townships. By far the greatest impact is on strawberries. Eighty-five percent of California strawberries are grown in 23 townships and only about one-third of the strawberry land could be fumigated with Telone. Other crops affected by the township cap are crops grown in the same coastal townships as strawberries (flowers, nurseries, vegetables) and other crops grown in concentrated areas such as carrots and sweetpotatoes. Impact on trees and vines would be about 10 percent statewide because these fields are only replanted, and thus fumigated, every 7 to 40 years. Tomato has not traditionally used methyl bromide but is beginning to use Telone over wide areas. Because of the large number of acres involved, the caps will limit this use.

Dow AgroSciences is currently working with DPR to determine if township caps can be raised in some areas. However, because strawberry cropping is so concentrated, doubling the township caps will only raise the portion of the land currently fumigated with Telone or methyl bromide that can use the product from 67 percent to 80 percent, and will raise the portion of strawberries that can be fumigated from one-third to one-half.

Because the Telone label and permit conditions are restrictive, county agriculture commissioners seldom impose further use restrictions.

Dow AgroSciences was issued an EPA and DPR label for their drip-applied emulsified formulations of Telone (Inline and Telone EC) this summer. The current label restricts the crops (strawberries, vegetables, melons) and application methods (drip under plastic (HDPE) mulch). Applicators are not required to wear respirators during application if the delivery system is "closed". Drip application in California has an application factor for township cap calculations of 1.16. The formulation is not labeled for perennials or ornamentals.

Regulatory Impacts on Use of Chloropicrin

Current chloropicrin labels are not restrictive to use. There are no buffer or crop limitations, allowable rates are high, respirators are not required unless air concentrations exceed 0.1 ppm, and the reentry period is 2 days. Soil surfaces can be sealed with sprinkler irrigation, cultivation, or plastic tarp. One label (TriClor) includes field mixing with an emulsifier for drip application at up to 300 lb/acre. The TriClor label limits drip application irrigation amounts to 1.5 inches of water, which is inadequate for some applications.

Because chloropicrin use in the past has typically been in combination with methyl bromide, DPR has not issued Suggested Permit Conditions specifically for chloropicrin. However, in anticipation of increased use, some county agriculture commissioners have created local guidelines for chloropicrin permits. For example, Santa Cruz and Monterey counties limit application rates to 200 lb/acre (inadequate for most stand-alone uses), and requires 100-foot buffers for "sensitive sites" (occupied residences nearby). When DPR completes its risk assessment for chloropicrin, there will likely be additional use restrictions.

Regulatory Impacts on Use of Metam Sodium

Current metam sodium labels allow application by spray/incorporation, shank injection, drip, sprinkler, and flood irrigation at rates up to 75 gal/acre. The soil must be moist (between 50 percent and 80 percent of field capacity), and the surface can be sealed by tarps, sprinkler irrigation, or cultivation. Respirators are not required unless odors are strong. Reentry is 2 days.

The Suggested Permit Conditions for metam sodium restrict use near "sensitive sites" when rates exceed 15 gal/acre (most uses). Conditions include 500-foot buffers, hourly field monitoring for odors, and sprinkler systems in place if odors become strong. With sprinkler application, a "water cap must be applied immediately following application. The DPR issued guidelines point out that county agriculture commissioners may institute more restrictive conditions, which many do. For example, in Fresno County, the Notice of Intent to fumigate must be filed 96 hours in advance and must map all occupied structures within one-half mile of the site. If the site is in a sensitive or residential area, the buffer is one-half mile for all except shank applications. The Metam Sodium Task Force is currently working with the DPR to develop acceptable Permit Conditions, including buffers, that can be used uniformly by counties. Applications will likely include improved soil sealing and site monitoring.

Future Regulatory Impacts

Fumigants are going through re-registration at the Federal level and reevaluation in California. The state process involves a risk assessment of the compound and then steps to mitigate the risks. Mitigation can take the form of permit conditions or State regulations. California DPR issues a monthly Status Report for Fumigant Pesticides where information on the fumigant risk assessment/management process is summarized and updated.

Of the three registered alternatives, only Telone products have completed this re-registration process. Dow AgroSciences is now working with DPR to reassess the analysis that was used to establish the Telone township caps with the goal to increase the caps in some areas. A draft of the risk assessment document for metam sodium is under public review. Metam sodium has been placed on the restricted materials list. The risk assessment for chloropicrin has just begun. As was noted, some county agriculture commissioners are applying permit condition restrictions on these materials.

The State is carrying out ambient air monitoring of fumigants in areas of heavy use. Monitoring in the Watsonville area in 2000 indicated methyl bromide levels exceeded target seasonal (subchronic) exposure levels (1 ppb) in some areas. This nearly triggered emergency regulations on the use of methyl bromide and has resulted in a court-ordered temporary restraining order on methyl bromide applications in specific areas. This summer and fall, ambient air concentrations of methyl bromide, 1,3-D, chloropicrin, and MITC (generated from metam sodium) are being monitored in two regions.

California fumigant users point to methyl bromide regulation as an example of what could happen to other soil fumigants. Restrictions in California on methyl bromide use have increased dramatically in the last 5 years. A recent court decision requires DPR to issue use regulations instead of Suggested Permit Conditions. These regulations include a complex formula to calculate buffers depending on application method and rates. For example, for a 10-acre orchard fumigation, the buffer would be 840 feet if it were fumigated at one time. Multiple applications of portions of the field are often required to reduce buffers to acceptable levels. The new regulation also requires extensive prenotification of occupants of residences within 300 feet of the buffer, and limits in-field workers (drivers, copilots, tarp layers) to no more than 4 hours per day in the field. These restrictions have resulted in both legal and practical limitations where methyl bromide can be used and increased application costs.

Conclusions

Fumigant use regulations are more complex and restrictive in California than in other states. Telone township caps will severely restrict use in some areas. County applied buffers also limit uses. Although current restrictions on alternative fumigants are of concern to growers, of more concern is not knowing what future regulations will be. As long as the rules may change, it is precarious to invest time and money into adopting and adapting to alternative fumigants.

References

Carpenter, Janet, Lori Lynch, and Tom Trout. 2001. Township limits on 1,3-D will impact adjustment to methyl bromide phase-out. California Agriculture 55(3):12-18.

Trout, Tom. 2001. Impact of township caps on Telone use in California. The Pink Sheet, published by the California Strawberry Commission, 01(9), 4 pp.

Last Updated: January 17, 2002