2017 Air Monitoring Network Report

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Executive Summary

In February 2011, DPR implemented a multi-year statewide air monitoring network to measure pesticides in various agricultural communities. This Air Monitoring Network (AMN) is the first multi-year air monitoring study conducted by DPR. The goals of the AMN are to provide data that assists in assessing potential health risks, developing measures to mitigate risks, and measuring the effectiveness of regulatory requirements. This annual report is the seventh volume of this study and contains AMN results from January 1, 2017 to December 31, 2017.

In 2017, DPR monitored a total of 31 pesticides and 5 pesticide breakdown products in four communities. Pesticides monitored in the AMN were selected based primarily on potential risk to human health. Higher-risk pesticides were prioritized and selected for inclusion in the AMN based on higher use, higher volatility, and higher toxicity. The AMN originally provided monitoring for three communities, but with the passing of the Budget Act of 2016, it was expanded to include a total of eight sites for a two-year period. Four sites were operational in 2017 while the other four were added to the AMN in 2018. The four operational AMN monitoring sites were in the communities of Shafter (Kern County), Santa Maria (Santa Barbara County), Watsonville (Monterey County), and Chualar (Monterey County).

One 24-hour sample was collected each week at each of the four sites. Starting dates were randomly selected each week to produce variation in the sampling day while sampling start times were left to the discretion of field sampling personnel.

Of the 7,396 analyses1 conducted, 92.9% (6,868) had no detectable concentrations. Five hundred twenty-eight (7.1%) of the analyses had a detectable (trace or quantifiable) concentrations, while 122 (1.6%) of all analyses had quantifiable concentrations. A quantifiable concentration refers to a concentration above the limit of quantitation for the respective pesticide.

Nine of the 36 pesticides and breakdown products monitored were not detected; of the remaining pesticides, 17 pesticides and breakdown products were only detected at trace levels. Ten compounds were detected at quantifiable levels. These included 1,3-dichloropropene, chloropicrin, chlorothalonil, chlorpyrifos and its oxygen analog, chlorthal-dimethyl, DDVP, EPTC, malathion, and methyl isothiocyanate (MITC). The chemicals with the highest number of detections from all four sites were chlorthal-dimethyl (39%), MITC (34%), and chlorothalonil (27%).

No state or federal agency has established health standards for pesticides in ambient air. Therefore, DPR estimates the potential for adverse health effects by comparing the air concentrations to its health screening levels or regulatory targets for 1-day, 28- or 90-days depending on the pesticide, 1-year, and lifetime exposure periods. DPR devised health screening levels based on a preliminary assessment of possible health effects; they are used as triggers for DPR to conduct a more detailed evaluation. Regulatory targets are established after a complete assessment of possible health risks and supersede the screening levels. DPR puts measures in place based on the regulatory target to limit exposures so that adverse effects can be avoided. Exceeding a regulatory target does not necessarily mean an adverse health effect occurs, but it does indicate that the restrictions on the pesticide use may need to be modified. For 2017, no monitored pesticide exceeded any screening level or regulatory targets at any of the AMN sampling locations.


1 Number of analyses = Number of samples multiplied by number of chemicals analyzed in each sample.