Update on Lompoc
(Revised June 1999)

Back to Lompoc Air Monitoring Project

In 1997, the Department of Pesticide Regulation (DPR) formed the Lompoc Interagency Work Group (LIWG) to help investigate Lompoc residents' concerns (first voiced in 1992) about pesticide use as it relates to community health. DPR has sought answers to whether health symptoms in Lompoc (Santa Barbara County) are occurring at a high rate and if so, to determine whether pesticides may be the cause.

The hospital discharge data from 1991-1994 suggest that certain respiratory illnesses occur in Lompoc at higher rates than in other comparison areas. The State's Office of Environmental Health Hazard Assessment (OEHHA) evaluated this data and published its results in a 1998 report entitled, Illness Indicators in Lompoc, California: An Evaluation of Available Data. The evaluation indicated that the proportion of hospitalizations due to respiratory illnesses, in particular bronchitis and asthma, were elevated in Lompoc relative to the proportion of hospitalizations in the comparison areas, with some differences by age. The incidence of lung and bronchus cancers also was increased above the expected numbers based on regional rates. The purpose of the report was not to speculate on the cause of the illnesses; rather, it was to evaluate the incidence of specific illnesses. At the LIWG's April 1999 meeting, OEHHA presented additional analyses of the hospital discharge data that corroborated the initial report's findings.

The LIWG is composed of staff from federal, state, and county agencies as well as community representatives. The LIWG formed several subgroups to develop recommendations to address health concerns, to conduct a pesticide air monitoring strategy, and to consider potential exposures from other environmental factors, such as crystalline silica and radon. The pesticide exposure subgroup (now called the Technical Advisory Group, or TAG) developed a work plan that recommended comprehensive air monitoring in Lompoc during the growing season to determine whether applied pesticides migrate by air to adjacent residential areas. This exposure subgroup prioritized 46 pesticides based on their toxicity, use, and volatility.

The TAG recommended a comprehensive monitoring program to span the peak use periods for the top 23 chemicals in a two-phase program, with the first phase of monitoring during the summer of 1998 (if only partial funding was available), and the second phase early in the summer of 1999. Although funds are not available at this time to conduct phase two in the summer of 1999, DPR is actively seeking funding to conduct phase two monitoring. The monitoring recommendation was designed to measure maximum daily pesticide concentrations in air that could be compared to human health endpoints. The subgroup did not recommend monitoring for the bottom half of the list of 46 pesticides, realizing fiscal resources are limited. The LIWG accepted the TAG's recommendations and forwarded them to DPR in April 1998.

In August 1998, the Legislature passed Senate Bill 661 which provided funding to DPR to conduct the first phase of pesticide air monitoring. Accordingly, monitoring was conducted during August and September 1998. DPR released the draft pesticide air monitoring results for phase one to an executive session of the LIWG on January 22, 1999, and presented the results to the LIWG on April 22, 1999 in Lompoc.

Lompoc Pesticide Air Monitoring Project - Phase One

This packet contains the following documents that were distributed to the LIWG on January 22, 1999:

*The document has been updated since it was distributed in January 1999. This is the most recent version. ;

These documents include the available draft data from the air monitoring conducted in Lompoc last summer. These documents contain only very preliminary data; much of these data are still under review, and should not be considered final. In addition, several important elements such as data analysis and conclusions have not been completed. DPR plans to include these elements in its final report.

Study Design:

DPR selected 12 target pesticides for study in phase one. They included two fumigants, methyl bromide and methyl isothiocyanate (a metam-sodium breakdown product), and ten other pesticides-alachlor, chlorothalonil, chlorpyrifos, diazinon, dimethoate, disulfoton, fenamiphos, fonofos, oxydemeton-methyl, and permethrin. DPR selected these pesticides for three reasons: (1) they are among the 23 pesticides ranked highest by the LIWG (based on toxicity and potential for exposure including usage and vapor pressure), (2) validated sampling and analytical methods for these pesticides already existed or could be developed prior to the start of sampling, and (3) toxicological information was available. DPR also monitored for 29 metals and elements.

Fumigant Study Plan:

  • Monitored for two fumigants: methyl bromide and methyl isothiocyanate (MITC)
  • MITC monitoring coincided with application
  • No methyl bromide applied, background monitoring
  • Five monitoring sites: central, northeast, northwest, southwest, west
  • Pesticides collected on sampling tubes, analyzed by lab

Other Pesticides:

  • Monitored for ten pesticides
    • Alachlor - herbicide
    • Chlorothalonil - fungicide
    • Chlorpyrifos - insecticide
    • Diazinon - insecticide
    • Dimethoate - insecticide
    • Disulfoton - insecticide
    • Fenamiphos - insecticide
    • Fonofos - insecticide
    • Oxydemeton-methyl - insecticide
    • Permethtrin - insecticide
  • Sampled August 17 - September 14, 1988
  • Sampled five random days per week for four weeks
  • Five monitoring sites in Lompoc: central, northeast, northwest, northeast, west
  • Pesticides collected on sampling tubes, analyzed by lab

Metals Study Plan

  • Monitored for 29 metals and elements
  • Sampled August 17 - 29, 1998
  • Sampled three random days per week for two weeks
  • Three monitoring sites in Lompoc: central, east and southwest
  • Metals collected on filters, analyzed by lab

Meteorological measurements were also collected during the monitoring period.

DPR prepared screening levels for the pesticides monitored under phase one of the Lompoc pesticide air monitoring project: alachlor, chlorothalonil, chlorpyrifos, diazinon, dimethoate, disulfoton, fenamifos, fonofos, methyl isothiocyanate, methyl bromide, oxydemeton methyl, and permethrin. Although DPR developed these screening levels, consensus has not been reached with the TAG of the LIWG on what these values should be. DPR has provided preliminary copies of these screening levels to toxicologists from the LIWG and is continuing discussion.

DPR released the monitoring results to the LIWG on January 22, 1999. Since then, the TAG independently wrote a consensus summary (Attachment 1) that the LIWG, including DPR, endorsed.



  • Monitored single MITC application
  • MITC detected more frequently at night
  • Highest MITC concentration detected = 1,036 nanograms per cubic meter (ng/m3)
  • MITC detected at all five sites
  • Quality assurance data indicates concentrations underestimated
  • Methyl bromide data invalid, pesticide not applied

Other Pesticides:

  • Ten pesticides targeted
  • Two detected, confirmed, quantified: chlorpyrifos and diazinon
  • Two detected, unconfirmed, not quantified: dimethoate and oxydemeton-methyl
  • Four not detected, not applied: alachlor (not applied during monitoring), disulfoton, fenamiphos and fonofos (not applied during monitoring)
  • Three other chemicals detected, confirmed quantified: oxygen analog of chlorpyrifos, oxygen analog of diazinon, and cycloate
  • Concentrations of five pesticides confirmed and quantified:
    • chlorpyrifos maximum concentration = 83 ng/m3
    • chlorpyrifos oxygen analog maximum concentration = 8.5 ng/m3
    • cycloate maximum concentration = 760 ng/m3
    • diazinon maximum concentration = 18 ng/m3
    • diazinon oxygen analog maximum concentration = 5.3 ng/m3
    • quality assurance data indicates uncertainty in the results
  • Lompoc Pesticide Air Monitoring Phase I Results - Detections by Chemical (see Table 1, PDF) (4 kb)
  • Lompoc Pesticide Air Monitoring Phase I Results - Chlorpyrifos Time Trend (see Figure 1, PDF) (43 kb)

Quality Assurance:

  • Lab spike recoveries 93 - 143%
  • Trapping efficiency recoveries 78 - 133%
  • Storage stability tests show loss of MITC
  • Difference between field duplicates 1 - 7%
  • Trapping efficiency and field spikes show conversion to oxygen analogs 14 - 60%
  • Chain of custody broken for MITC, methyl bromide
  • No quality assurance for oxygen analogs, cycloate, DPR weather station, pesticide use data


  • Monitored for 29 metals and elements
  • Manganese is contained in the pesticides maneb and mancozeb. Aluminum is contained in the pesticide fosetyl-aluminum
  • Silicon levels were found close to the highest levels detected in the Air Resources Board's urban monitoring network
  • Metals data cannot be used to determine pesticide concentrations

Pesticide Use:

  • Fifty plus pesticides were applied
  • Twelve pesticides were targeted in this phase one pesticide air monitoring project
  • Five monitored during or near peak season (August or September were among highest three months): chlorpyrifos, chlorthalonil, permethrin, diazinon, and oxydemeton
  • Four monitored outside peak season: alachlor, dimethoate, fonofos, and methyl isothiocyanate
  • Three not used during 1998: disulfoton, fenamiphos, and methyl bromide


  • Wind direction predominantly from the west-northwest
  • Wind speed varied diurnally, 1 - 23 miles per hour
  • Temperature varied diurnally, 40 - 77 F
  • Inversion height 270 - 600+ feet (lowest measurable height = 50 feet)

Data Analysis:

  • Plotting locations of air concentrations and pesticide use
  • Using computer models to correlate air concentrations with pesticide use data and weather

DPR Screening Levels:

(Note: For the calculation of average air concentrations in phase one, DPR used ½ the detection limit for non-detects.)

The screening levels represent the first tier in a hierarchy of risk analysis (see DPR's Lompoc Exposure Data memo for a description of the methodology DPR used to develop these levels) and are based on currently available toxicology data. As described, wide variation in the strength and completeness of the toxicology data existed. Given the conservatism used in the methodology, approaching or exceeding these screening levels would not indicate a health hazard, but would prompt DPR to further evaluate exposure and refine the analysis. Every situation will be treated on a case by case basis. Monitoring data that are orders of magnitude below screening levels would indicate the lack of a health hazard.

As shown in the attached tables (DPR's Lompoc Exposure Data memo), the monitoring indicates that none of the pesticides exceeded the screening levels.

Cycloate was the only pesticide found that approached the screening level for seasonal exposure. This information (both analytical results and screening level) was developed after the original table on screening levels was constructed, so it was not included in that information.

For more information or questions about this project, please contact Madeline Brattesani at (916) 324-4082 [e-mail address <Madeline.Brattesani@cdpr.ca.gov>] or Randy Segawa at (916) 324-4137 [e-mail address <Randy.Segawa@cdpr.ca.gov>].