Consensus Summary of TAG Evaluation of Phase I Data Attachment 1

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The Phase I study was intended to test pesticide sampling and analysis methods and to determine if a subset of the total pesticides in use in the area could be measured in air. With some exceptions, these goals were achieved. The study was most successful in developing and demonstrating the multiple-pesticide sampling and analysis method. Due to the limited nature of the Phase I sampling, these results are not appropriate for risk assessment.

Over 50 pesticides were used in or near Lompoc during the August-September 1998 monitoring period. Air monitoring was conducted for twelve pesticides with recorded use in those months in prior years. Of the 12, five were not applied during the 1998 monitoring period, and were not detected in air samples. The remaining seven were detected in air samples. Many of these detected concentrations were between the sample "detection limit" and "quantitation limit," meaning that the existence of the pesticide in a sample, while likely, was too low to be assigned a numerical value. For example, chlorpyrifos, the most frequently detected pesticide, was detected in 55/119 samples above the quantitation limit of 4 ng/m3, and in an additional 60/119 samples between the quantitation limit and the detection limit of 1 ng/m3.

The results for MITC are estimates due to poor quality assurance/quality control of the samples. Qualitatively, the results probably represent an underestimate of the MITC actually present in the samples. The highest concentrations of MITC were the result of one application of 720 pounds of metam sodium (the parent compound) on 7.5 acres approximately one mile west of Lompoc.

Cycloate was not one of the 12 pesticides on the monitoring list, but was detected during laboratory screening. Concentrations of cycloate are considered to be estimates because of limited laboratory quality assurance.
The metals analyses were originally intended as surrogates for pesticides containing metals (aluminum in fosetyl-Al, and manganese in maneb and mancozeb). In retrospect, these analyses are not capable of discriminating between natural background sources, e.g. soils, and airborne pesticides. Results should not be interpreted as indicative of the presence or absence of these metal-containing pesticides in air.

Silicon was tested for and found in Lompoc air during the monitoring period. Levels were found as high as 17,000 ng/m3, close to the highest levels measured in California urban areas during recent years.
The TAG is generally of the opinion that detection limits and quantitation limits should always be reported in a data summary, along with estimates of mean concentrations. For the Phase I data, the TAG recommends that values between the detection limit and the quantitation limit be reported as detects. For Phase II the TAG will develop recommendations for the presentation and interpretation of air monitoring results.