Department of Pesticide Regulation
Environmental Monitoring and Pest Management Branch
830 K Street
Sacramento, California 95814-3510
Environmental Hazards Assessment Program Study #176
MONITORING PESTICIDE AIR CONCENTRATIONS IN LOMPOC,
STAGE ONE
August 18, 1998
 

I. INTRODUCTION

The California Department of Pesticide Regulation (DPR) formed the Lompoc Interagency Work Group (LIWG) to help investigate the City of Lompoc's concerns about pesticide use and community health. The LIWG is composed of scientific staff from federal, state, and county agencies, as well as community representatives. The LIWG formed several subgroups to develop recommendations for a pesticide air monitoring strategy, as well as address potential exposure from other environmental agents. The exposure subgroup developed a work plan that recommended comprehensive air monitoring near agricultural areas during the growing season to determine if applied pesticides migrate by air to adjacent residential areas. The exposure subgroup prioritized 46 pesticides based on toxicity, use, and volatility. The exposure subgroup recommended monitoring for the top half of this list in a two-stage program with the first stage of monitoring to occur this summer, and the second stage to occur next summer. The monitoring recommendation was designed to measure maximum daily pesticide concentrations in air that could be compared to human health endpoints. The LIWG accepted the exposure subgroup's recommendations and forwarded them to DPR in April 1998.

Working with key members of the LIWG, DPR developed the following protocol to implement the LIWG's recommended first stage of pesticide air monitoring. DPR, the Air Resources Board (ARB), the Santa Barbara County Department of Agriculture, and several contractors will conduct this project jointly, as described below. In addition, DPR and the U.S. Environmental Protection Agency will begin work for stage two.
 

II. OBJECTIVES

The overall monitoring study (stages one and two combined) contains two primary objectives:

DPR plans to begin addressing the objectives in stage one, but none will be completed until stage two. Stage one monitoring will be limited in scope because time constraints only allow for a selected number of pesticides to be sampled and analyzed. Under a U.S. Environmental Protection Agency grant, DPR will contract to develop sampling and analytical methods for stage two.
 

III. PERSONNEL

DPR will conduct this study under the management of Doug Okumura, Chief, Environmental Monitoring and Pest Management Branch. Key personnel includes:

Questions from the media should be directed to Veda Federighi at (916) 445-3974, or email vfedergihi@cdpr.ca.gov. All other questions concerning this project should be directed to Madeline Brattesani at (916) 324-4100, or email mbrattesani@cdpr.ca.gov.
 

IV. STUDY DESIGN

DPR has selected 12 specific pesticides for study in stage one. In addition, several metals will be monitored because they are breakdown products of several pesticides. DPR selected these pesticides for three reasons: 1) they are among the 23 highest ranked pesticides by the LIWG (ranking based on use, volatility, and toxicity), 2) validated sampling and analytical methods for these pesticides already exist or can be developed prior to the start of sampling, and 3) comprehensive toxicological information is available. The 12 specific pesticides are alachlor, chlorothalonil, chlorpyrifos, diazinon, dimethoate, disulfoton, fenamiphos, fonofos, methyl bromide, methyl isothiocyanate (metam-sodium breakdown product), oxydemeton-methyl, and permethrin. The metal-containing pesticides are mancozeb, maneb, and fosetyl-Al.

The LIWG considers community outdoor air monitoring the most effective method to quantify the town's exposure to pesticides. Thus, five monitoring sites will be established in Lompoc, most on the outskirts of town near agricultural areas. DPR and ARB will select the monitoring sites based on the following criteria: 1) consent of the property owner, 2) closest distance from agricultural areas, 3) security of the site--samplers will be unattended for 24 hours a day, 4) electrical power available, and 5) proximity to other monitoring sites--sites should not be clustered in one area.

The LIWG recommends monitoring during the period of highest pesticide use, May - June. However, since funding for this project could not be secured until August, monitoring will begin as soon as sampling and laboratory preparation is completed and continue for four to six weeks. ARB will use the following sampling schedule for all pesticides except methyl bromide, methyl isothiocyanate, and metals. At each monitoring site, ARB will collect samples four to six days each week. At each monitoring site, one 24-hour sample will be collected on each day monitored. ARB will collect five duplicate samples each week to determine the sampling and analytical precision.

The same five monitoring sites will be used for methyl bromide and methyl isothiocyanate. Since these chemicals are applied infrequently and dissipate rapidly, sampling will not be initiated until the Santa Barbara County Department of Agriculture informs the sampling personnel that an application is scheduled. Once started, sampling will continue for four consecutive days. At each monitoring site, ARB will collect two sets of 12-hour samples for each day monitored.

DPR and ARB will select three sites for metals monitoring. Monitoring will begin as soon as sampling and laboratory preparations are completed, probably early August. At each of the three monitoring sites, ARB will collect samples two days each week for three weeks. At each monitoring site, one 24-hour sample will be collected on each day monitored. ARB will randomly select the two days each week for monitoring. ARB will collect two duplicate samples each week to determine the sampling and analytical precision.
 

V. SAMPLING METHODS

ARB will use the following sampling methods for all pesticides except methyl bromide, methyl isothiocyanate, and metals: Monitoring will be conducted with low-volume air sampling pumps (Thomas Industries, Model 607CA22). One sampler will be set up at each of the five monitoring sites. Each sampler will be fitted with a Teflon® cartridge containing 30 milliliters of XAD-4 resin. The cartridges will be shielded from sunlight and pointed down to prevent water from entering the cartridge. Sampler air flow rates will be set at approximately 15 liters per minute. Once samples are collected, the cartridges will be capped and the samples placed on dry ice and remain frozen until analysis. Chain of custody procedures will be followed to document all persons handling the samples. Temperature in the storage containers will be recorded during the entire storage period.

ARB will use the following sampling methods for methyl bromide and methyl isothiocyanate: Monitoring will be conducted using personal air sampling pumps (SKC model 224-PCXR8). A duplicate pair of samplers will be positioned approximately one meter apart at each of the five monitoring sites. Each sampler will be fitted with activated charcoal vapor collection tubes, stacked two in a series, consisting of a one-gram primary tube and a one-gram secondary tube for methyl bromide, or two-gram tubes for methyl isothiocyanate. The tubes will be shielded from sunlight and pointed down to prevent water from entering the tube. Sampler air flow rates will be set at approximately 0.1 liters per minute for methyl bromide, or 1.2 liters per minute for methyl isothiocyanate. Once samples are collected, each tube opening will be capped and the samples placed on dry ice and frozen until analysis. Chain of custody procedures will be followed to document all persons handling the samples. Temperature in the storage containers will be recorded during the entire storage period.

ARB will use the following sampling methods for metals: Monitoring will be conducted with low-volume air sampling pumps. One sampler will be set up at each of the three monitoring sites. Each sampler will be fitted with a 37-millimeter diameter Teflon® filter to collect particulates. Sampler air flow rates will be set at approximately five liters per minute. Once samples are collected, the filters will be placed individually in sealed containers and shipped to the laboratory. Chain of custody procedures will be followed to document all persons handling the samples.
 

VI. LABORATORY ANALYSIS

The University of California, Davis will perform the analyses for the semi-volatile pesticides alachlor, chlorothalonil, chlorpyrifos, diazinon, dimethoate, disulfoton, fenamiphos, fonofos, oxydemeton-methyl, permethrin, as well as some breakdown products. The pesticides trapped in the XAD-4 sample cartridges will be extracted using the solvent ethyl acetate. The initial extract will be split into three portions. One portion will be analyzed for chlorpyrifos, diazinon, dimethoate, and fonofos using a gas chromatograph equipped with a flame photometric detector. A second portion of the extract will be analyzed for alachlor, chlorothalonil, and permethrin using a gas chromatograph equipped with a mass selective detector. A third portion of the extract will be oxidized, reextracted, and analyzed for disulfoton, fenamiphos, and oxydemeton-methyl using a gas chromatograph equipped with a flame photometric detector.

The oxygen analogs, or oxons, are breakdown products of many organophosphorous pesticides. In general, the oxygen analogs are more toxic than the parent compounds. The laboratory will analyze for the oxygen analogs of chlorpyrifos, diazinon, dimethoate, disulfoton, and fonofos. While the methodology gives an accurate estimate of total concentration (parent plus oxygen analog), the sampling methodology gives an erroneously high proportion of the oxygen analogs and erroneously low proportion of the parent compounds. The quality control samples incorporated into the study should give sufficient information to correct the erroneous proportions. If this is due to the increased oxidation due to air flow, field spikes treated equally but without the air flow should account for the differences.

The University of Nevada, Reno will analyze for the volatile pesticides methyl bromide and methyl isothiocyanate (metam-sodium breakdown product). For methyl bromide, the charcoal samples will be placed into headspace vials with benzyl alcohol. The vials will be sealed and heated. A portion of the headspace will be withdrawn and injected into a gas chromatograph equipped with an electron capture detector. For methyl isothiocyanate, the charcoal samples will be extracted with a mixture of carbon disulfide and ethyl acetate. The extract will be filtered and analyzed with a gas chromatograph equipped with a thermionic specific detector.

ARB will analyze for metals, including manganese in the metal-containing pesticides maneb and mancozeb, and aluminum in the metal-containing pesticide fosetyl-Al. The filter samples will be analyzed by placing them in a vacuum and irradiating with X-rays. This X-ray fluorescence method will detect other metals and elements including: aluminum, antimony, arsenic, barium, bromine, cadmium, calcium, chlorine, chromium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, nickel, phosphorus, potassium, rubidium, selenium, silicon, strontium, sulfur, tin, titanium, uranium, vanadium, yttrium, zinc, zirconium.
 

VII. METEOROLOGICAL DATA

Two meteorological stations will be set up specifically for this study, in addition to the existing station operated by the Santa Barbara County Air Pollution Control District. DPR will set up one station in the agricultural area west of Lompoc for the duration of the monitoring. This station will record wind speed, wind direction, air temperature, and relative humidity at a height of approximately six meters every five minutes. Air temperature will also be recorded at a height of approximately two meters.

AeroVironment, Inc. will operate a second station, consisting of a mini-SODAR® system to measure the atmospheric mixing height (inversion height). This system will record horizontal wind speed, vertical wind speed, and horizontal wind direction. The wind parameters will be measured at five meter increments starting at an altitude of 15 meters to approximately 200 meters. Data will be recorded at the maximum rate of the system, approximately every four seconds. These data should provide general trends in wind speeds at different altitudes, and most importantly the mixing height.

The Air Pollution Control District meteorological station is located within Lompoc. This station provides wind speed, wind direction, and air temperature at a height of 10 meters.
 

VIII. PESTICIDE USE DATA

By law, all agricultural pesticide applications in California must be reported to the county department of agriculture. These pesticide use reports contain information regarding the pesticide(s) applied, the application rate, the number of acres treated, the crop treated, the date treated, the location of the site treated, the person making the application, the method of application, and other information. Some pesticide applications must be reported to the county department of agriculture within seven days of application, others must be reported monthly. The county department of agriculture in turn reports this information to DPR on a periodic basis for an annual statewide compilation. The Santa Barbara County Department of Agriculture has agreed to expedite processing of all pesticide use reports for the Lompoc area between May and September, 1998 and to send this information to DPR by late-October.

Certain pesticides are designated restricted materials. One of the requirements for use of restricted materials is that the county department of agriculture must be informed by the applicator prior to application. Methyl bromide and metam-sodium (methyl isothiocyanate parent compound) are restricted materials. The Santa Barbara County Department of Agriculture will inform sampling personnel when a methyl bromide or metam-sodium application is scheduled for the Lompoc area. ARB will initiate monitoring for these chemicals on the scheduled date(s) of application.
 

IX. QUALITY ASSURANCE/QUALITY CONTROL

For quality control, each laboratory will determine or document the pesticide dissipation in samples while stored prior to analysis (storage stability), the accuracy and precision of the sampling method (trapping efficiency), the accuracy and precision of the analytical method (method validation), and that the methods can quantify to the concentration levels needed for risk assessment (method detection limit determination). In addition, each laboratory will prepare and analyze quality control samples with each set of samples analyzed. These quality control samples will consist of samples containing no pesticides (blank samples) to check for contamination, and samples containing a known amount of pesticide (spiked samples) to check the precision and accuracy. Additional duplicate samples, field blank samples, trip spike samples, and field spike samples will be submitted to the laboratories.

Due to the low detection limits required for this study, most of the analytical methods do not unequivocally identify the chemicals detected. If detected concentrations are high enough, selected samples will be confirmed using an unequivocal method such as mass spectrometry.

Quality assurance personnel unassociated with the project will audit selected procedures and data for the study. These audits will ensure that the stated procedures are followed correctly and that the appropriate data are recorded. The quality assurance personnel will report their findings to DPR management.

The reviewing senior scientist will ensure that 1) the appropriate scientific methods are used for the study; 2) only valid data are used for the data analysis; and 3) the data support the conclusions of the study.
 

X. DATA ANALYSIS

All air concentrations will be reported as nanograms per cubic meter. Assuming that some pesticides are detected, DPR will compile the results by pesticide, sampling date, and location. DPR will compare the pesticide use reports to the monitoring data. DPR will determine if correlations exist between the dates and locations of pesticide applications, and the occurrence of pesticides at the monitoring stations. DPR plans to compare the monitoring data to meteorological parameters such as wind direction, wind speed, and inversion height.

ARB plans to compare the manganese monitoring results from Lompoc to the data collected from the urban area monitoring network. Elevated levels may indicate that maneb and mancozeb contribute to manganese air concentrations.
 

XI. STAGE TWO METHOD DEVELOPMENT

DPR (under a U.S. Environmental Protection Agency grant) will contract to develop sampling and analytical methods for the 23 pesticides ranked highest by the LIWG (ranking based on use, volatility, and toxicity) as listed below. The terms of the contract will be negotiated specifically for each chemical because of the technical difficulties inherent in some of the sampling and analytical problems associated with specific chemicals.

DPR's contractor will develop sampling methods based on the following performance measures: Chemicals - The contractor will attempt to develop sampling methods that will capture all the parent compounds as well as any breakdown products that are more toxic, such as the oxygen analogs of organophosphate pesticides. Sampling Media - The contractor will attempt to use trapping media and cartridges that are compatible with current DPR and/or ARB samplers. Trapping Efficiency - The contractor will attempt to develop methods that capture at least 70% of each pesticide from ambient air. Cost - DPR will attempt to develop methods whose development and monitoring study costs will not exceed the legislative and grant funding of the project. To minimize the cost, the contractor will attempt to develop multi-residue methods as opposed to single-pesticide methods.

DPR's contractor will develop analytical methods based on the following performance measures: Chemicals - The contractor will attempt to develop analytical methods that will detect and quantify all the parent compounds as well as any breakdown products that are more toxic, such as the oxygen analogs of organophosphate pesticides. Sensitivity - The contractor will attempt to develop methods with quantitation limits specified by DPR. These will either be the quantitation limit goals specified for stage one, or U.S. Environmental Protection Agency reference doses. Specificity - The contractor will attempt to develop methods that provide unequivocal identification of detected pesticides. Precision - The contractor will attempt to develop methods that have a coefficient of variation of 20% or less for replicate samples. Accuracy - The contractor will attempt to develop methods that have a recovery of at least 70% in laboratory-spikes. Cost - The contractor will attempt to develop methods whose development and monitoring study costs will not exceed the funding of the project.

The success of the method development will be judged by the number of pesticides for which methods can be developed that meet the goals stated above. If it is unlikely that the goals stated above can be met for all 23 pesticides, then the contractor will identify the specific problems or costs that make the development of methods beyond the fiscal scope of the contract.
 

XII. ESTIMATED TIMETABLE