CDPR Releases New Report on 1,3-D

The California Department of Pesticide Regulation (CDPR) has just released its first air monitoring report for its 2024 regulations on 1,3-Dichloropropene (1,3-D). These regulations address 72-hour acute risk and 70-year lifetime cancer risk to residents and other non-occupational bystanders (adults and children) from 1,3-D. Known as Regulation 22-005, these requirements went into effect on January 1, 2024. Using worst-case application scenarios,  CDPR established requirements to minimize the release of 1,3-D in the air after its application in the soil.  These mitigation measures include acreage limits, minimum setback distances from an occupied structure to a treated field, totally impermeable films, deeper fumigant injections, an increase in soil moisture requirements, quarterly use summaries, and an annual report, among other requirements.

Now, pursuant to CDPR regulations, CDPR must prepare an annual report that evaluates the effectiveness of the 1,3-D regulations. The report identifies and evaluates the ten highest-use townships in California and evaluates the air concentrations at all six DPR’s 1,3-D monitoring stations. This first annual report also checks compliance with the 1,3-D regional use limit (township cap) of 136,000 adjusted total pounds (ATP) temporarily in effect.  If any of the modeled or monitored air concentrations are higher than expected in comparison to previous data, the report includes a description of action(s) DPR will take to address the high levels and a timeline for taking the actions. 

The townships identified and evaluated in this annual report represent the highest-use townships in each of the ten counties with the highest 1,3-D use, based on the ATP . The report identifies key factors influencing usage levels and air concentrations within the specified ten townships and includes detailed modeling to estimate the maximum 1,3-D air concentrations over periods of 24 hours, 72 hours, and 1 year average.  In 2024, 7,008,972 pounds of 1,3-D were used on 43,736 acres statewide, corresponding to 4,053,244 ATP and 1,296,684 pounds of emissions. This is the lowest 1,3-D use and acreage since 2009. The crops with the most use were almonds, strawberries, sweet potatoes, and carrots.

Modeling results showed that the highest estimated air concentrations were 26.8 ppb, 15.1 ppb, and 0.41 ppb for the 24-hour, 72-hour, and 1-year time periods, respectively. These concentrations were below DPR’s regulatory target concentrations of 55 ppb (72-hour average) and 0.56 ppb (70-year average). Additionally, the highest measured air concentrations at the monitoring stations were 7.19 ppb and 0.21 ppb for the 24-hour and 1-year time periods, respectively. These concentrations were below the thresholds of 55 ppb (24-hour average) and 0.27 ppb (1-year average) that trigger additional evaluation.

In summary, DPR’s pesticide use report (PUR) data analyses of high-use townships and ambient air concentrations from air monitoring stations within DPR’s Air Monitoring Network (AMN) indicate that current regulatory measures are functioning as intended. In summing up the report CDPR commented “There is no evidence at this time to suggest that additional actions are necessary to meet regulatory goals of DPR Regulation 22-005.”