trans-1,3-Dichloropropene

1,3-Dichloropropene (1,3-D) was developed by Dow Chemical in the 1940s and commercialized under the trade name Telone as a broad-spectrum soil fumigant that kills plant-parasitic nematodes before crop planting. [1] Commercial Telone is a mixture of cis- and trans-1,3-D isomers (approximately 55:45 ratio), with the trans isomer (CAS 10061-02-6) being separately tracked. Telone became particularly important in California's vegetable and orchard crops, where nematode control is critical for yields of carrots, strawberries, almonds, and other high-value produce. By the early 1970s, 1,3-D was one of the most widely applied fumigants in California, but in 1977 the state suspended its registration after animal bioassay data showed it caused forestomach tumors, liver tumors, and other cancers in rodents. [2] After extensive negotiations and Dow's investment in exposure mitigation measures, California reinstated Telone use in 1990 with significant restrictions including buffer zones, use caps (maximum amount per county per year), and treatment restrictions near schools. The EPA classifies 1,3-D as a probable human carcinogen. Community air monitoring near Telone application areas in the San Joaquin Valley has documented ambient concentrations exceeding EPA risk thresholds, and studies have associated residence near fumigant-heavy agricultural areas with elevated cancer rates. [3] The compound is volatile (vapor pressure ~25 mmHg) and readily migrates from treated soil into ambient air, making it a significant inhalation hazard for farmworkers and nearby communities.

Inhalation of volatilized 1,3-D from treated fields is the primary pathway for both farmworkers and community residents living near treated fields. Direct applicator exposure during injection into soil using specialized equipment is a significant occupational exposure. Community members downwind of active fumigation operations or recently treated fields may inhale ambient 1,3-D. The compound does not persist in soil (half-life 1–4 days), but volatilization during the first 5–7 days post-application creates a transient but potentially significant exposure window for nearby residents.

Multi-site carcinogenicity in animal studies (forestomach, liver, lung, and other organs) drove the probable carcinogen classification and California's registration suspension. [2] The mechanism involves metabolic activation by cytochrome P450 and glutathione S-transferase to reactive epoxide and thioether intermediates that form DNA adducts. Community-level cancer risk assessments in California's agricultural counties have identified 1,3-D as a significant contributor to cumulative cancer risk from pesticide air emissions. Acute effects include irritation of the eyes, nose, and throat; dermal absorption can cause systemic toxicity.

Farmworkers applying Telone or working in treated fields during the post-application volatilization period face the highest occupational exposures. Residents (especially children) living within 1 mile of fumigated fields are at increased risk from ambient air exposure. Schools and residences in high-use agricultural counties (Fresno, Kern, Tulare in California) are particularly affected.

1. California requires large buffer zones (100–300+ feet) around Telone applications near schools and residences; verify these are being enforced in your area. 2. Avoid outdoor activities near fields during and immediately after fumigation (within 5 days). 3. Keep windows closed and use indoor recirculation on HVAC during nearby fumigation events. 4. Farmworkers should use supplied-air respirators during application; re-entry intervals must be strictly observed. 5. Community organizations can request access to DPR pesticide use reporting data to monitor local fumigant application volumes.