In the 1930s, a peculiar phenomenon startled farmers in New Zealand: trousers spontaneously caught fire or even exploded while being worn. The underlying cause was the use of sodium chlorate as a herbicide, which reacted dangerously with the natural fibers in clothing when exposed to heat or friction.

This chemical mishap led to unexpected fires and left many puzzled until the connection between sodium chlorate and flammable trousers was uncovered. The story of the exploding pants remains a notable example of how overlooked chemical reactions can have surprising and sometimes hazardous consequences in everyday life.

Overview of The Exploding Pants Incident

The sudden combustion of farmers' trousers in 1930s New Zealand drew national attention and confusion. These incidents highlighted unusual risks from the use of newly adopted agricultural chemicals.

Origins of the Chemical Mystery

The core of the incident involved farmers using sodium chlorate, a potent weed killer. Sodium chlorate is highly reactive and, when absorbed by organic material such as cotton or wool, can make fabrics extremely flammable. Farmers often wore these trousers while spraying weeds, leading to direct chemical exposure.

After use, many workers dried their chemically contaminated pants near open flames or heaters, a common household practice at the time. The combination of residual sodium chlorate and heat sources caused some trousers to ignite or even explode unexpectedly.

Early attempts to identify the source of these fires included informal experiments by affected farmers. Inquiries revealed that improper handling and drying of sodium chlorate-affected clothing directly contributed to the hazard. Authorities began issuing warnings about the dangers of sodium chlorate and its interaction with everyday fabrics.

Historical Context During World War II

Widespread use of sodium chlorate in New Zealand’s agriculture coincided with World War II. The war drove the need for increased food production, pushing farmers to adopt chemical weed control methods due to labor shortages and the need for efficiency.

Supply constraints from the war also encouraged improvisation with chemical treatments and equipment. Many chemicals previously regulated were distributed more freely, increasing the risk of unsafe handling. War-related rationing led some to reuse clothing contaminated with agricultural chemicals, magnifying the danger.

Although the war was not the direct cause of the incidents, the context accelerated the adoption of hazardous agricultural practices. Farmers, lacking detailed safety knowledge, faced new chemical risks as they tried to meet wartime food demands. The exploding pants serve as a case study of the unforeseen consequences of rapid technological and chemical adoption during periods of economic and social stress.

Key Chemicals and Compounds Involved

The case of exploding pants centers on the interaction of industrial chemicals with natural fibers in clothing. Sodium chlorate, sulfur, and benzene each played significant roles in the resulting hazards.

Role of Industrial Chemicals

Industrial chemicals, particularly sodium chlorate, were widely used by farmers in the 1930s as weed killers. Sodium chlorate is a strong oxidizing agent, making it effective at destroying unwanted vegetation.

However, this same property made it extremely dangerous when it came into contact with organic materials like wool and cotton fibers in clothing. These fibers can act as fuel, and the sodium chlorate can trigger a chemical reaction leading to ignition or even explosion under certain conditions, such as heat or friction.

Exposure to sunlight, fire, or even stored heat was enough to cause treated trousers to burst into flames. Farmers often dried their clothes near fires, significantly increasing the risk of combustion.

The Use of Sulfur and Benzene

Sulfur and benzene are common industrial chemicals with various agricultural uses. While sodium chlorate was the primary cause of ignition in most cases, sulfur was also used in some weed control mixtures.

Benzene, a volatile aromatic hydrocarbon, was occasionally present as a solvent or component in chemical mixtures. It is highly flammable and can increase the overall risk when combined with other reactive compounds. Use of any of these chemicals on clothing or equipment heightens flammability and exposes users to hazardous reactions.

Key chemical properties:

Sulfur: Yellow, odoriferous solid, flammable, can contribute to slow-burning fires.
Benzene: Clear, volatile liquid, extremely flammable, toxic on inhalation.

Toxic Chemicals and Their Properties

Many of these chemicals are classified as toxic due to their health and safety risks. Sodium chlorate is not only a potent oxidizer but also hazardous to human health if inhaled or ingested.

Benzene is a well-known carcinogen and can cause long-term health problems if chronically exposed. Sulfur dust can irritate the eyes and respiratory system. Each chemical’s toxicity and reactivity played a role in the dangers associated with using them in agricultural practices.

Table: Chemical Properties

Chemical Nature Toxicity Flammability Sodium chlorate Oxidizer High Ignites organic Sulfur Nonmetal Moderate Flammable Benzene Hydrocarbon Carcinogenic Highly flammable

The Science Behind the Explosions

The phenomenon of exploding trousers can be traced to a combination of agricultural chemistry and accidental ignition. Early investigations focused on the use of sodium chlorate herbicides and their interactions with organic fibers in clothing.

Laboratory Investigations

Laboratories began examining samples of contaminated trousers to identify the underlying cause of combustion. Scientists tested fabrics exposed to sodium chlorate, noting how the chemical residue interacted with both cotton and wool.

Routine testing revealed that even slight friction or heat application could trigger rapid ignition. In controlled settings, researchers documented cases where minor sparks from fireplaces or even sunlight reflected through glass intensified the risk.

Researchers used standard chemistry experiments to simulate the real-world handling of herbicide-soaked clothing. Their observations highlighted the importance of material composition and storage conditions in contributing to the explosions.

Chemical Reactions and Mechanisms

Sodium chlorate (NaClO₃) acts as a strong oxidizing agent. When it comes into contact with organic fibers such as cotton or wool, the potential for chemical reaction increases, particularly if the fabric is damp or exposed to friction.

The equation for the main reaction is:

Organic Fiber + Sodium Chlorate + Heat/Impact → Combustion Products (CO₂, H₂O, Energy)

The oxidizer accelerates the decomposition of the fibers, releasing energy rapidly. Even a small spark or friction from walking could provide enough activation energy to start the combustion process.

This rapid reaction distinguishes chlorate-induced fires from typical fabric fires, which require more heat to ignite. The unique vulnerability came from the direct contact between the oxidizing chemical and combustible material.

Experimentation and Findings

Researchers replicated typical farming scenarios to assess the exact risks. They rubbed treated fabrics against each other, exposed them to sunlight, and tested various ignition sources like matches and heat lamps.

Key findings included:

Friction alone could ignite chlorate-soaked trousers
Moisture sometimes increased the instability of the chemical
Untreated clothing did not combust under identical conditions

Lab results were consistent—chlorate-treated garments combusted much more easily than untreated ones. These findings confirmed that sodium chlorate residue fundamentally altered the ignition characteristics of ordinary clothing. This experimental approach provided a clear understanding of why explosions occurred in the field.

Health and Safety Implications

The use of sodium chlorate on farms caused an unexpected health crisis, with numerous cases linked to chemical exposure. Affected individuals faced burns, symptoms of poisoning, and other serious health issues.

Medical Center Responses

Medical centers in regions affected by exploding trousers saw an increase in cases involving unusual chemical burns and inhalation injuries. Staff reported patients presenting with burns to the legs, thighs, and lower torso, some requiring hospital admission and specialized wound care.

Treatments focused on cooling burns, pain management, and treating possible secondary infections. In severe cases, wound debridement or skin grafts were necessary. Reports also mention respiratory complications, as inhalation of combustion byproducts from burning trousers could cause irritation or lung injury.

Hospitals in rural areas where sodium chlorate use was common developed protocols for recognizing and responding to chemical burns related to herbicide exposure. This included staff education on handling contaminated clothing and reducing the risk of secondary contamination in the medical facility.

Exposure Risks and Health Outcomes

Exposure to sodium chlorate, particularly when combined with organic fibers like wool or cotton, dramatically increases the risk of violent reactions and fires. Farmers, field workers, and even family members faced contact through direct handling, laundering, or wearing contaminated clothing.

The main routes of exposure included skin contact, inhaling fumes from combustion, and, less commonly, ingestion from contaminated hands. Health outcomes ranged from acute chemical burns to symptoms of poisoning like nausea and headaches. Children and those with pre-existing respiratory conditions were especially vulnerable.

There were reports of burns resulting from what seemed to be minor heat sources, such as sunlight, friction, or even proximity to stoves. This unpredictability increased the public health risk and made effective prevention more challenging for both the workforce and the medical community.

Burns, Cancer, and Other Health Effects

Burn injuries were the most frequent and immediate health consequence, with some classified as second- and third-degree burns. Immediate care was essential to limit tissue damage, infection risk, and long-term disability.

Unlike some herbicides, sodium chlorate is not classified as a carcinogen. However, chronic exposure could contribute to cumulative health risks—particularly through the formation of toxic gases during fires. Concerns included respiratory illnesses and potential skin sensitization.

In addition to burns, chemical exposure posed risks of systemic toxicity. Symptoms ranged from skin irritation to, in rare cases, effects on kidney and blood function. Public health initiatives focused on restricting sodium chlorate use and educating farm workers about safer practices to reduce the incidence of severe injuries.

Government and Community Responses

Exploding pants incidents in New Zealand drew urgent attention from both authorities and local residents. These reactions focused primarily on immediate safety, accident response, and steps to safeguard public health in rural communities.

Accidents and Emergency Measures

After the first reports of trousers catching fire spontaneously, local authorities began documenting accident cases. Fires often started when contaminated trousers were drying near open flames or heat sources—common practices at the time.

To mitigate risks, fire brigades implemented rapid response protocols, prioritizing rural properties known to use sodium chlorate. Public information posters were distributed, advising the safest ways to handle, wash, and store work clothes exposed to the chemical.

Community meetings hosted by local councils allowed farmers to share first-hand accounts. Health officers warned about the dangers of inhaling fumes from burning clothing and encouraged the immediate disposal of contaminated items. Emergency medical care was recommended for any burns or smoke inhalation injuries.

Evacuation Protocols

In regions where incidents escalated, local officials established evacuation procedures for at-risk farmhouses. These plans included identifying likely hotspots and setting clear muster points for affected families and livestock.

A typical evacuation checklist used by rural authorities:

Step Action Sound alert Use local bell or siren Remove people and animals Guide to pre-set safe area Secure flammable materials Store away from buildings Report to emergency contacts Notify local fire brigade

Public health notices emphasized the importance of prompt evacuation in the event of clothing fires or chemical spills. Local schools were instructed on fire drills linked specifically to chemical hazards, ensuring broader community readiness and reduced risk of injury or property loss.

Legacy and Environmental Impact

The use of sodium chlorate for weed control in the 1930s created significant new risks for farmers and the environment. Chemical contamination of soil and water supplies had effects that lasted well beyond its period of popularity.

Superfund Cleanup Initiatives

Most cases involving sodium chlorate occurred before modern chemical regulation, so few direct Superfund cleanups targeted affected farmlands in New Zealand or elsewhere. However, similar hazardous sites in the United States involving persistent agricultural chemicals later required Superfund action.

Key elements of these cleanups include:

Removal of contaminated topsoil
Containment of hazardous waste
Monitoring of groundwater quality

Communities near contaminated sites often experienced higher risks of soil and water pollution. Remediation efforts aimed to restore land usability and protect public health by reducing exposure to legacy chemicals.

Long-Term Lessons Learned

Experience with sodium chlorate demonstrated the dangers of widespread use of untested agricultural chemicals. Key lessons led to the development of stricter government regulations for chemical safety and higher standards for environmental review.

Important outcomes:

Increased monitoring of chemical residues in food and water
Education campaigns for safe chemical use among farmers
New regulations under public health and environmental agencies

Scientific understanding of environmental persistence and human health risks improved as a result. Lessons from the "exploding pants" incidents continue to influence modern practices in weed management and chemical regulation.

The Exploding Pants: A Chemical Mystery Behind the Bizarre Farming Incident