Brake fluid is a hydraulic fluid necessary for a vehicle’s braking system, transferring force from the brake pedal to the wheel cylinders or calipers. However, due to its chemical composition, it is highly toxic and dangerous if ingested or absorbed through the skin. Any exposure should be treated as a medical emergency requiring immediate professional attention.
Chemical Basis of Toxicity
Most brake fluids (DOT 3, DOT 4, and DOT 5.1) are formulated with glycol ethers and polyglycol compounds. These chemicals are toxic, but the most severe danger arises after absorption and processing by the liver. Components like ethylene glycol and diethylene glycol are metabolized by the alcohol dehydrogenase enzyme, converting them into destructive byproducts.
This metabolic process yields substances such as glycolic acid and, ultimately, oxalic acid, which are far more toxic than the parent compounds. The accumulation of these acids causes a severe disruption in the body’s pH balance, known as metabolic acidosis. The less common DOT 5 brake fluid is silicone-based and does not contain these toxic glycols, resulting in a lower toxicity risk.
Routes of Exposure and Immediate Symptoms
The most dangerous route of exposure is ingestion, which can occur accidentally due to the fluid’s sweet taste, particularly in children or pets. Immediate symptoms often mimic alcohol intoxication, including nausea, vomiting, and abdominal pain. The absorbed glycols can quickly lead to central nervous system (CNS) depression, presenting as slurred speech, confusion, drowsiness, and lack of coordination.
Dermal contact is the most likely route for occupational exposure, though acute systemic toxicity from this route is unlikely because absorption is limited. Glycol-based fluids have a defatting action on the skin, which can lead to irritation, redness, and dermatitis with prolonged exposure. The fluid should be washed off immediately to prevent irritation and minimize absorption.
Inhalation exposure is the least common route, as the fluid has a low vapor pressure at ambient temperatures. However, exposure to mists or sprays in confined or poorly ventilated spaces can cause upper respiratory tract irritation. Symptoms may include headache, dizziness, or a burning sensation in the nose and throat.
Systemic Damage to Major Organs
The delayed and most severe consequences of brake fluid poisoning result directly from the toxic metabolites circulating in the bloodstream. The most pronounced effect is on the kidneys, which attempt to filter these toxic acids.
As the body breaks down the glycol compounds, the resulting oxalic acid combines with calcium to form insoluble calcium oxalate crystals. These crystals deposit directly in the renal tubules, causing acute tubular necrosis and severely impairing the kidney’s ability to filter waste. This can rapidly lead to acute kidney failure, which may require hemodialysis and result in permanent kidney damage or death if left untreated.
The central nervous system is also significantly impacted, progressing from initial intoxication to more severe neurological effects. If metabolic acidosis is not corrected, the patient may experience seizures, coma, and potential brain damage. Severe poisoning can also affect the cardiovascular system, leading to changes in heart rate, low blood pressure (hypotension), and myocardial depression. The most severe kidney symptoms are delayed, often taking 24 to 72 hours to fully manifest, and should not lead to a false sense of security after initial symptoms subside.
Emergency Response and First Aid Protocols
Brake fluid exposure is a medical emergency, and the most important action is to contact professional medical assistance immediately. Call the National Poison Control Center at 1-800-222-1222 or 911 without delay; do not wait for symptoms to worsen. Be prepared to provide the exact name and type of brake fluid involved (e.g., DOT 3, DOT 4, or DOT 5.1).
For ingestion, do NOT induce vomiting unless specifically instructed by a medical professional. Vomiting risks aspiration of the toxic fluid into the lungs or a second round of chemical burns to the esophagus. Instead, immediately rinse the mouth. If the victim is conscious, they may be given a small amount of water to help dilute the substance, as advised by Poison Control.
In the event of skin or eye contact, the contaminated area must be flushed immediately with copious amounts of water. Flush the eyes for at least 15 minutes, holding the eyelids apart to ensure thorough irrigation. Wash the skin with soap and water. Any contaminated clothing should be removed immediately to prevent further exposure.