What is Toluene Toxicity?

Toluene is a type of chemical that is a byproduct of benzene also known as methylbenzene, phenylmethane, or toluol. Long-term exposure to small amounts of toluene especially in the workplace or industrial setting can lead to harmful effects on your body. Toluene can be used as a volatile solvent, and it’s often misused or abused causing a group of symptoms related to sudden and severe poisoning. It is an aromatic hydrocarbon with the ability to induce a sort of sleep-like state and damaging effects on the nervous system and can lead to dependence or addiction. The exact way in which toluene works is not fully understood, but it seems to affect various types of ion channels, which are gate-like structures in our body’s cells.

Recent research suggests that toluene affects the firing of certain neurons related to dopamine from an area of the brain called the ventral tegmental area into the limbic and cortical structures. This can change the pathways in the brain that give feelings of reward.

Most studies focus on the commonness and harm related to sudden exposure to toluene. People who misuse solvents often see toluene as safe and it’s easily accessible in a variety of products for home use. Because of this, sudden poisoning by toluene is quite common. While we don’t have precise data on how often toluene poisoning happens, one emergency department reported 20 cases of sudden toluene poisoning within 2 years. However, this might be an underestimate since toluene is widely present in our society and many people who experience its harmful effects might not seek treatment or want to seek treatment.

What Causes Toluene Toxicity?

Toluene is a colorless liquid with a specific smell, that’s used a lot by industries. It’s used to make things like plastics, nylon (a type of plastic), and polyurethane (a type of foam), and can also be used as a solvent in paints, inks, adhesives (glues), fragrances, coatings, and cleaning agents. Toluene is also used in veterinary medicine to get rid of certain types of worms in animals, and by the military to create a type of explosive named 2,4,6-Trinitrotoluene (or just TNT). It can also be used to improve the quality of gasoline.

Each year, about 30 billion pounds or 13.6 million metric tons of toluene is produced. Because it’s used so much and in many different environments – like factories, building sites, nail salons, printing places, ships, and car repair garages – there are some strict rules about how much is safe to get exposed to.

The rules regarding safety limits for exposure to toluene are set by organizations like the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH). They have decided on safety limits for both short-term (low) and long-term (high) exposure to toluene. According to OSHA, it’s okay to be exposed up to a certain point, which is 200 ppm for eight hours, with a maximum concentration of 300 ppm and a peak beyond that is 500 ppm for 10 minutes. NIOSH suggests even stricter limits of 100 ppm for eight hours and a maximum of 150 ppm over 15 minutes.

Regarding safety rules for skin exposure to toluene, there isn’t a lot of data. But some studies have shown that repeated exposure can cause certain skin issues like defatting dermatitis (which is dry, itchy skin), itching, and thickening of the skin.

Apart from exposure at work, toluene can also be found in the environment like the air, water, and soil. Facilities that produce and process toluene release about 22 million pounds (or 10,000 metric tons) of it into the air each year. Places like newly built buildings or places with high gasoline emissions can have high levels of toluene in the atmosphere.

Toluene can also get into water sources, especially near industrial areas and places where hydraulic fracturing operations (which use water pressure to extract natural gas or oil) occur. It has been estimated that each year, around 54,000 pounds (or 245 metric tons) of toluene are released into water sources and about 1.3 million pounds (or 590 metric tons) go into the soil.

Other organizations have also provided their own limits for safe exposure to toluene. The Lower Olefins and Aromatics (LOA) REACH Consortium suggests limited exposure to 100 ppm over 15 minutes or 20 ppm over eight hours. If the level of exposure ever exceeds 500 ppm, it could cause a range of health issues, starting from an intense feeling of pleasure to failure of organs and even sudden death.

Risk Factors and Frequency for Toluene Toxicity

Toluene is usually the most misused type of volatile solvent. It tends to be most prevalent among 12 to 14-year-olds, decreasing significantly after the age of 18. More boys and young men misuse toluene than girls and young women. About 10% of American students from 8th to 12th grade have misused toluene, a rate that hasn’t changed much over the past two decades. Globally, Brazil and Australia see the highest misuse rates, while Canada and Japan have the lowest. Some communities are disproportionately affected, particularly indigenous groups in America, Australia, and Canada, where 50 to 60% have experienced toluene toxicity.

Toluene is commonly found in various sectors, including maritime, construction, and petrochemical industries. However, nobody knows how often or how many workers in these industries are exposed. Certain workers are more at risk of exposure, such as those near underground gasoline storage tanks, nail salon workers, construction workers using adhesives, solvents, and paints, and those involved in gasoline production.

Toluene is the most misused solvent.
Most misuse occurs between the ages of 12 and 14, with a significant decline after 18.
Toluene misuse is more common in boys and young men than girls and young women.
About 10% of American students from 8th to 12th grade misused toluene.
Globally, Brazil (16.5%) and Australia (10.3%) have the highest rates of misuse, while rates are lowest in Canada (3-5%) and Japan (1.2%).
Indigenous communities in America, Australia, and Canada are disproportionately affected by toluene toxicity, with rates between 50 and 60%.
Toluene is common in various industries, though the exact exposure rates among workers are unknown.
Workers near underground gasoline storage, nail salon workers, and construction workers who use adhesives, solvents, and paints are at increased risk of exposure.

Signs and Symptoms of Toluene Toxicity

When taking a patient’s history, it is crucial to consider potential exposure sources. This could be related to their occupation, travel history, or home renovations. Take into account the specifics of the exposure if provided by the patient. This could include details about what substance they breathed in and how their symptoms have evolved over time. The physical examination should cover all body systems as there are no specific findings that point directly to toluene toxicity.

After acute exposure to toluene, it is known to cause a series of effects. Initially, it can cause feelings of euphoria, excitability, lack of restraint, and impulsive behavior.

Neurological symptoms: This may include a headache, slurred speech, double vision, mood swings, loss of motor control, illusions, hallucinations, dizziness, and nausea. The disease can progress to more severe symptoms such as seizures, coma, and even death. Chronic users may suffer from impaired cognition, brain disease, and altered social behaviors.
Cardiac symptoms: Arrhythmias or irregular heartbeats can be detected by feeling or listening to the heartbeat.
Pulmonary symptoms: Chronic cough, difficulty breathing with clear, wheezy, or raspy breath sounds.
Renal symptoms: Presence of pus or blood in urine and painful urination.
Integumentary symptoms: Noticeably dry, sensitive skin, especially on the ends of the arms, mouth, and nose. These areas may be irritated and itchy.

Testing for Toluene Toxicity

The first step in checking someone’s health is to assess their breathing, make sure they’re not struggling for air, and check their circulation. The doctor will also check vital signs like body temperature. Other evaluations include checking the heart through an electrocardiogram, evaluating the lungs with x-rays and ultrasound and running blood or urine tests to identify any dysfunction in organ systems or any abnormalities in electrolytes. If a patient has specific neurological symptoms, imaging studies might be necessary.

Diagnosing hydrocarbon toxicity can be challenging because there’s no direct lab test that can confirm exposure. Doctors can sometimes identify volatile substances using gas chromatography, a technique to separate and analyze compounds, but it’s not a practical method for immediate assessments. However, finding high levels of a compound called hippuric acid in the urine is a reliable way to confirm toxicity from a substance called toluene, and this is typically how ongoing exposure is monitored in high-risk jobs.

Other signs that may suggest a person has been exposed to toluene include low levels of potassium (which can also affect the heart’s rhythm), low bicarbonate, high levels of creatinine phosphokinase (a marker of muscle damage), and blood in the urine.

Treatment Options for Toluene Toxicity

Toluene toxicity is a serious condition that can have harmful health effects. Treatment primarily focuses on managing the patient’s airway, correcting chemical imbalances in the body such as metabolic acidosis (a condition where your body produces too much acid) and electrolyte abnormalities (imbalances of essential minerals in the body), and educating the patient about the dangers of exposure to toluene. Usually, patients have to stay in the hospital for monitoring until their condition improves.

There are specific ways to treat toluene toxicity, too, although they’re mostly based on small clinical trials and individual case studies. For instance, some research suggests that the use of acetaminophen and aspirin might slow down the body’s processing of toluene, which limits the production of a harmful substance called hippuric acid. In one study involving 40 subjects, medications like carbamazepine and haloperidol reduced psychosis or behavioral changes by half.

Patients may also be given a lot of fluids, since the waste products from toluene breaking down in the body are water-soluble and can be removed by the kidneys. In severe cases of toluene toxicity, a patient might be treated with a technique called extracorporeal membrane oxygenation, which provides prolonged cardiac and respiratory support to the patient.

However, some commonly used treatments for poisoning, like stomach pumping (gastric lavage) or giving activated charcoal, are not recommended for toluene toxicity. This is because there’s a risk of these treatments causing the patient to inhale their vomit into their lungs (aspiration), and there’s only limited absorption of toluene through the stomach and intestines anyway. All cases of toluene toxicity should be reported to the local poison control center for appropriate treatment guidance.

The symptoms of toluene toxicity, which mainly include changes in mental state, lung inflammation (pneumonitis), and a type of blood disorder known as metabolic acidosis, can be quite general. This means that many other health conditions could cause similar symptoms, making toluene toxicity difficult to diagnose. So, a detailed medical history is really important. Some of the conditions that might be considered as possible causes of these symptoms include:

Substance misuse such as barbiturates, benzodiazepines, opioids
Overdose of certain medications like lithium, diuretics
Exposure to carbon monoxide
Inhalation of benzene
Severe lung condition called Acute Respiratory Distress Syndrome
Attempted suicide
Brain injuries
Toxic encephalopathy (a brain disease caused by exposure to toxic substances)
Primary aldosteronism (a hormonal disorder)
Thyrotoxicosis (condition caused by an excess of thyroid hormone)
A condition caused by consuming too much licorice with glycyrrhizin
Neurovascular or neuromuscular disorders
Pneumonia
Cancer (neoplasms)

What to expect with Toluene Toxicity

Toluene toxicity, which is poisoning from exposure to the chemical toluene, has a suggested death rate of about 15%. It’s difficult to know for certain because there aren’t a lot of studies that track this. If someone is exposed to toluene and they are diagnosed and treated quickly, the chances of long-term complications are quite low. However, having confusion, severe metabolic acidosis (too much acid in the body), and hypokalemia (too little potassium in the blood) can result in worse outcomes.

Long-term use of toluene can lead to a range of health problems. These can include shaking, issues with the nerves in the hands and feet, problems with normal movement and coordination, changes in mood, brain diseases, trouble with walking, dementia, and muscle tightness. There’s debate about whether or not these problems can go away if exposure to toluene is stopped.

People have been observed to improve greatly if they completely stop being exposed to toluene, especially if they are young, had less exposure to toluene, and showed initial symptoms. However, people with brain diseases have the toughest time recovering.

Possible Complications When Diagnosed with Toluene Toxicity

Exposure to toluene, a type of chemical, can lead to serious health problems. It can affect the lungs, causing severe breathing difficulties known as acute respiratory distress syndrome. It can also interfere with the heart’s normal rhythm, leading to potentially deadly heart rhythm disorders. Additionally, toluene can cause kidney failure. The effects of toluene on pregnant individuals are not fully understood, but there have been reports suggesting risks to reproduction and potential for harm to an unborn baby.

Main Health Risks:

Acute respiratory distress syndrome (severe breathing difficulties)
Deadly heart rhythm disorders
Kidney failure
Potential reproductive risks
Possible harm to an unborn baby

Preventing Toluene Toxicity

Toluene toxicity and the misuse and dependency on inhalants aren’t frequently discussed among the general public, possibly due to limited research on the topic. In 2010, a Cochrane review, a highly respected systematic review of studies, looked for high-quality studies (randomized control trials and controlled clinical trials) focused on treating inhalant misuse, but didn’t find any studies that met their selection criteria. This indicates there’s a lack of research into effective treatment methods.

In 2012, a systematic review, which is a thorough review of existing studies, searched for effective treatments for volatile substance misuse, which is the abuse of substances that easily evaporate, but didn’t find any. One study noticed a significant decrease in inhalant misuse after a year of cognitive-behavioural therapy (CBT). CBT is a therapy that helps a person understand and change thought patterns leading to harmful behaviours or uncomfortable feelings.

In conclusion, we need more research in this area to come up with effective ways to discourage inhalant misuse and to provide useful information to educate patients.