2018 Air Monitoring Network Report

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Executive Summary

In February 2011, the California Department of Pesticide Regulation (DPR) implemented a multi-year statewide air monitoring network to measure pesticides in various agricultural communities. This pesticide 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 eighth volume of this study and contains AMN results from January 1, 2018, to December 31, 2018.

In 2018, DPR, with the assistance of staff from the California Air Resources Board (ARB) and the Santa Barbara County Agricultural Commissionerís Office, monitored a total of 31 pesticides and 5 pesticide breakdown products in eight 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 temporarily expanded to include eight sites for a two-year period. Not all eight sites were operational at the start of 2018; however, all eight sites were in operation by the end of 2018. Monitoring for the communities of Cuyama, Lindsay, Oxnard, and San Joaquin began at different dates partway through 2018. Therefore, monitoring data from these locations were not sufficient to determine 2018 annual air concentrations.

One 24-hour sample was collected each week at each monitoring location. Sampling start dates were randomly selected each week to produce variation in the sampling day while sampling start times ranged between 9:00 a.m. to 2:00 p.m.

Of the 12,058 analyses1 conducted, 93.8% (11,316) did not return a detectable concentration. Seven hundred forty-two (6.2%) of the analyses returned a detectable (trace or quantifiable) concentration, while 152 (1.3%) of all analyses had quantifiable concentrations. A quantifiable concentration refers to a concentration above the analytical limit of quantitation.

Eight of the 36 chemicals monitored were not detected; of the remaining pesticides, 17 were only detected at trace levels. Eleven compounds were detected at quantifiable levels. These were 1,3-dichloropropene (1,3-D), chloropicrin, chlorothalonil, chlorpyrifos, chlorpyrifos oxygen analog (OA), chlorthal-dimethyl, dimethoate OA, malathion, methyl bromide, MITC, and trifluralin. The chemicals with the highest number of quantifiable detections from all eight sites were MITC, 1,3-D, and chloropicrin, respectively.

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 measured air concentrations of a pesticide to its health screening levels or regulatory targets for 1- or 3-day (depending on the pesticide), 4- or 13-week (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 based on 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.

Results from the monitoring performed during the 2018 calendar year showed that the highest 13-week rolling average concentration of 1,3-D (5.6 ppb) exceeded the established subchronic screening level of 3.0 ppb at the Shafter sampling location. This 13-week rolling average was largely influenced by a single 24-hr 1,3-D air concentration of 50.5 ppb measured in Shafter on January 21, 2018. DPR is in the process of developing regulations to reduce exposures to 1,3-D in ambient air. None of the 30 other pesticides or five breakdown products exceeded any of their health screening levels or regulatory targets.


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