For California’s agricultural commissioners, the “Guidance Manual: Methyl Bromide (In Combination with Chloropicrin) – Field Soil Fumigation” is the go-to resource for vital permit decisions. This essential manual empowers staff to confidently issue restricted materials permits for methyl bromide, strictly adhering to Title 3, Division 6, Subchapter 4 of the California Code of Regulations. 

It’s packed with the critical information commissioners need to meticulously review and evaluate applications for methyl bromide, whether applied alone or in combination with chloropicrin or other agents for field soil fumigation, offering everything from detailed methods and procedures to indispensable charts and tables necessary for precisely calculating appropriate buffer zone sizes and durations at any intended fumigation site. 

Ultimately, this comprehensive guide is the definitive tool for streamlining the permitting process and ensuring safe, compliant field soil fumigation practices. 

Chloropicrin and Methyl Bromide Mixture Overview 

Chloropicrin and methyl bromide mixtures are powerful soil fumigants used in agriculture to control a broad spectrum of pests including nematodes, fungi, insects, bacteria, and weed seeds. These fumigants are typically applied as pre-plant treatments before crop planting. The mixtures range from 33% methyl bromide with 67% chloropicrin (“33/67”) to 80% methyl bromide with 20% chloropicrin (“80/20”). 

Primary Uses 

1. Agricultural Applications

Chloropicrin and methyl bromide mixtures serve multiple purposes: 

• Pre-plant soil fumigation at agricultural sites, greenhouses, and tree replant areas 

• Control of soil-borne diseases including Verticillium wilt in strawberries and other high-value crops 

• Nematode management and pest control across various crop systems 

• Warning agent function – chloropicrin’s strong, pungent odor serves as a warning when mixed with odorless methyl bromide 

 

2. Application Methods

The fumigants can be applied through several methods: 

• Shank injection into soil at depths of 8-18 inches depending on application type 

• Drip irrigation systems for controlled application 

• Broadcast applications with or without plastic tarps 

• Bed fumigation for raised bed agricultural systems 

 

Major Health Hazards 

1. Acute Health Effects

Chloropicrin Exposure: 

• Severe eye irritation causing intense tearing and pain 

• Respiratory irritation affecting nose, mouth, throat, and lungs 

• Gastrointestinal symptoms including nausea, vomiting, and diarrhea 

• Pulmonary edema at high exposure levels – a life-threatening emergency 

Methyl Bromide Exposure: 

• Central nervous system effects including headaches, dizziness, confusion, and hallucinations 

• Respiratory symptoms ranging from coughing to pulmonary edema 

• Cardiovascular complications including hypotension and ventricular fibrillation 

• Delayed onset symptoms that can appear 48 hours to several months after exposure 

2. Chronic Health Effects

Long-term exposure to these fumigants can result in: 

• Nervous system damage affecting vision, speech, coordination, and mental function 

• Respiratory disorders including chronic bronchitis and persistent breathing difficulties 

• Kidney and liver effects with potential for permanent organ damage 

• Potential carcinogenic effects – chloropicrin shows evidence of carcinogenicity in animal studies 

 

Exposure Limits and Monitoring 

1. Regulatory Standards

Current exposure limits include: 

• Methyl bromide: OSHA ceiling limit of 20 ppm (short-term), ACGIH TLV of 1 ppm (8-hour TWA) 

• Chloropicrin: OSHA PEL and NIOSH REL of 0.1 ppm (8-hour TWA) 

• Skin notation applies to both chemicals, indicating significant dermal absorption risk 

2. Air Monitoring Requirements

Continuous monitoring is required during fumigation: 

• Breathing zone samples collected every hour for mixtures with less than 20% chloropicrin 

• Action levels: Operations must cease if chloropicrin exceeds 1.5 ppm or methyl bromide exceeds 5 ppm 

• Detection equipment includes colorimetric detector tubes and electronic monitoring devices 

 

Safety Measures and Protective Equipment 

1. Personal Protective Equipment (PPE)

Respiratory Protection Requirements vary by mixture composition: 

• For mixtures with ≥20% chloropicrin: Full-face or hood-style respirators with organic vapor/acid gas cartridges 

• For mixtures with <20% chloropicrin: Half-face, full-face, or hood-style respirators required at all times 

• Emergency situations: Self-contained breathing apparatus (SCBA) required for spill response or equipment failure 

Additional PPE Requirements: 

• Chemical-resistant gloves and apron when handling liquid fumigant 

• Chemical-resistant footwear and protective eyewear 

• Long-sleeved shirts and long pants as minimum clothing requirements 

2. Buffer Zones and Application Restrictions

Mandatory buffer zones must be established around fumigated areas: 

• Minimum distance: 25 feet, with actual distances based on application rate, field size, and equipment used 

• Duration: Buffer zones remain active for minimum 48 hours after application completion 

• Exclusion requirements: All non-handlers must be excluded from buffer zones during active periods 

3. Application Safety Protocols

Good Agricultural Practices (GAPs) include: 

• Soil preparation: Proper tillage to 5-8 inches depth and removal of crop residue 

• Injection depth requirements: 8-18 inches depending on application method and tarping 

• Tarp management: Minimum 5-day waiting period before tarp perforation 

• Equipment maintenance: Proper sealing to prevent fumigant leakage 

 

Emergency Procedures and Spill Response 

1. Immediate Response Actions

In case of spills or leaks: 

• Evacuate all personnel from the immediate area 
• Approach upwind wearing appropriate PPE including respirators 
• Contain the spill using absorbent materials like vermiculite, sand, or earth 
• Monitor air concentrations before allowing reentry 

2. Emergency Equipment Requirements

Essential emergency supplies include: 

• SCBA equipment for emergency entry into contaminated areas 

• Absorbent materials for spill containment 

• Air monitoring devices for concentration measurement 

• Emergency contact information and fumigant management plans 

 

3. Medical Emergency Procedures

If exposure is suspected: 

• Remove from exposure area immediately and move to fresh air 

• Contact emergency services and certified applicator 

• Provide product labels and Safety Data Sheets to medical personnel 

• Monitor for delayed symptoms which can appear hours to days after exposure 

 

Training and Certification Requirements 

1. Handler Training

All fumigant handlers must receive: 

• Pre-application training on safe handling procedures 

• Worker Protection Standard (WPS) certification for pesticide handlers 

• Respirator fit testing and medical clearance according to OSHA standards 

• Emergency response training including spill procedures and first aid 

2. Applicator Certification

Certified applicators must have: 

• State-specific certification for restricted use pesticides 

• Specialized soil fumigation training beyond basic certification 

• Fumigant Management Plan (FMP) preparation and implementation 

• Ongoing education on safety protocols and regulatory updates 

3. Regulatory Compliance

Legal requirements include: 

• EPA registration – both chemicals are classified as restricted use pesticides 

• Incident reporting – all exposure incidents must be reported to EPA 

• Record keeping of applications, monitoring data, and safety measures 

• Buffer zone compliance with state and federal regulations 

 

This comprehensive safety framework reflects the serious hazards posed by chloropicrin and methyl bromide mixtures while providing essential guidance for their safe and effective use in agricultural applications. Strict adherence to all safety protocols, proper training, and regulatory compliance are crucial for protecting workers, bystanders, and the environment.