What is Nitrogen Dioxide Toxicity?
Nitrogen is a gas that is colorless, tasteless, and smell-less, making up to 78% of the air we breathe. It’s typically inactive and doesn’t directly harm our bodies. However, nitrogen can change into different forms, known as nitrogen oxides (including nitric oxide and nitrogen dioxides). These changes can occur during various processes, such as reactions involving nitric acid, the burning of a type of compound called nitrocellulose, explosions, or when rocket fuel breaks down.
People may come into contact with nitrogen oxides in various situations, such as while electric arc welding, during the process of electroplating and engraving, or from engine exhaust. They can also form when silos are filled with grain that has a high nitrite content. Nitric oxide, one form of nitrogen oxide, can react with the oxygen in the air to form another type, nitrogen dioxide.
What Causes Nitrogen Dioxide Toxicity?
Nitrogen oxide gases can be created by ice resurfacing machines (known as “Zamboni machines”) when they burn propane, their fuel source. This could be a major risk in indoor ice-skating rinks if they don’t have good ventilation. As an example, in 1987, 116 people at an ice hockey game in Minnesota experienced various symptoms – from coughing to coughing up blood – because of a high level of nitrogen dioxide exposure.
Nitrogen dioxide toxicity is often referred to as “silo filler’s disease”. This condition happens when a person breathes in nitrogen dioxide gas that gathers when silage (stored, fermented fodder) decomposes. Depending on how long they are exposed and how concentrated the nitrogen dioxide is, they could experience a range of symptoms.
If they’re exposed to a high amount at once, they might have symptoms like difficulty breathing, coughing, or even symptoms similar to acute respiratory distress syndrome (ARDS), a severe condition that causes fluid to build up in the lungs. However, it’s important to note that symptoms of nitrogen dioxide toxicity might not appear right away and might show up even when they’re away from the site where they were exposed.
Risk Factors and Frequency for Nitrogen Dioxide Toxicity
Inhaling various gases, dust, or fumes could lead to lung problems, difficulty breathing, or other health issues. The use of harmful industrial chemicals is increasing. Each year, an estimated million plus workers in the U.S. risk irritation to their lungs through their jobs. Workers, especially those exposed to nitrogen oxides, are often at risk of harmful effects. These workers may not realize that they’re being exposed for long periods, allowing more of these harmful gases to reach their lungs, potentially causing damage.
Silo filler’s disease is a job-related illness caused by inhaling nitrogen oxides. These gases form when agricultural storage towers, or silos, are filled with organic materials like corn or other grains. The highest risk of exposure happens in the first month after the silos are filled. This is because nitrogen oxides are heavier than air and tend to accumulate above the stored materials. Workers get exposed when they go into the silo or open the hatch without wearing the right breathing protection. Importantly, silo filler’s disease can be completely prevented by using the correct safety equipment and workplace controls. Therefore, if someone gets silo filler’s disease, it could mean those health and safety rules aren’t being followed, and public health authorities might need to be informed.
Signs and Symptoms of Nitrogen Dioxide Toxicity
Nitrogen dioxide, due to its low water solubility, can expose people for a long time without showing any obvious symptoms. Early warning signs may include slight cough or feeling sick. If exposed to large amounts of nitrogen dioxide, one might experience symptoms like burning eyes, sore throat, or cough. Within 24 hours after exposure, chemical lung inflammation can develop, leading to low blood oxygen levels and fluid in the lungs. In some cases, this condition may progress into a serious lung disease several days after exposure. Other serious symptoms can be similar to respiratory distress syndrome, severe infection, or acute heart failure. Therefore, knowing the details of any nitrogen dioxide exposure is crucial.
Nitrogen dioxide toxicity often unfolds in three stages. The first stage might include symptoms like coughing, wheezing, difficulty breathing, chest pain, fever, sweating, and weakness. During a physical examination, wheezing and crackling sounds in the lungs could be noticed. A chest X-ray might show fluid in the lungs or appear normal. In the second stage, the patient might not show any symptoms. The third stage, which can occur 2 to 8 weeks later, might lead to severe lung disease. At this stage, symptoms could include fever, chills, wheezing, cough, difficulty breathing, chest pain. The chest X-ray at this stage might appear normal or show small widespread nodules.
Testing for Nitrogen Dioxide Toxicity
People exposed to nitrogen dioxide should be regularly checked for vital signs, like heart rate and temperature, and for any changes in behavior or consciousness. Doctors often use devices to continuously measure the amount of oxygen in the blood and the amount of carbon dioxide that is breathed out. To diagnose nitrogen dioxide toxicity, doctors mainly depend on whether the patient has had exposure to it, as there are no specific lab tests or X-ray findings that can confirm this. Asking about the patient’s work environment might provide clues if they work in industries known to have nitrogen dioxide exposure. In an emergency setting, they might conduct a blood test to measure gases in the blood and do a chest X-ray.
A blood test that measures gases in the blood can show if a patient has too little oxygen. Nitrogen dioxide can cause a chemical reaction in the blood, transforming the normal oxygen-carrying molecule, oxyhemoglobin, into a different molecule that can’t carry oxygen well. Chest X-rays might show areas that look fuzzy or cloudy, indicating potential damage. Pulmonary function testing can assess lung health and identify conditions like bronchiolitis obliterans, which is a severe and irreversible disease that blocks the small airways in the lungs.
Doctors should also consider a diagnosis of methemoglobinemia in patients who have too little oxygen and have a blue or purple color to their skin. Methemoglobinemia is the presence of abnormal hemoglobin, known as methemoglobin, in the blood. This abnormal hemoglobin can’t carry oxygen well, leading to a lack of oxygen in the body. Certain chemicals—including nitrites and nitrates—can lead to the formation of methemoglobin. Signs of methemoglobinemia include blood that appears “chocolate brown,” especially when the percentage of methemoglobin is greater than 15%, and the presence of too little oxygen in the blood undeterred by the administration of extra oxygen. A blood test, known as co-oximetry, is the best way to diagnose methemoglobinemia. Patients with levels less than 15% typically don’t show symptoms. Levels between 15% to 20% can cause a blue or purple color to the skin, and the patient may show mild symptoms. At 20% to 45%, the blue or purple color is more pronounced, and the patient will exhibit more symptoms. If levels reach 45% to 50%, patients may show severe symptoms. Anything above 70% is life-threatening. Treatment usually includes removing the patient from the environment causing the exposure, providing extra oxygen, and treating with a medication called methylene blue.
Treatment Options for Nitrogen Dioxide Toxicity
If you breathe in a lot of nitrogen dioxide, or other similar gases, you should get to an emergency room as soon as possible. It’s also a good idea to call your local poison control center for advice. In the United States, the number is 1-800-222-1222.
When a person has been exposed to nitrogen dioxide, a quick response is essential to help their body start to recover. Doctors’ main focus will be to make sure you can breathe and that your heart is pumping enough blood. Getting away from the exposure source as soon as possible is crucial to prevent further damage. However, it’s important for anyone trying to help to avoid also becoming exposed to the gas. As soon as you’re clear of the exposure, you should breathe in fresh air or be given additional oxygen. There’s no need to worry about decontamination nor about the gas spreading to other people or patients.
Even if you don’t immediately feel unwell after nitrogen dioxide exposure, you should still be monitored by medical professionals for at least 24 hours. This is because symptoms can develop later, such as chemical pneumonitis, which is inflammation of the lung tissues.
Treating chemical pneumonitis involves providing extra oxygen, using inhalers to open up the airways and reduce inflammation, and the use of a machine to help with breathing if necessary. While corticosteroids, which are a type of medication to reduce inflammation, are not usually helpful in cases of acute lung injury, they might be beneficial for delayed lung injuries.
For instance, in one case, a patient was introduced to nitrogen dioxide during a metal plating process and was given a corticosteroid through an IV. This treatment was reported to dramatically improve the person’s breathing by the 5th day in the hospital.
What else can Nitrogen Dioxide Toxicity be?
When diagnosing delayed lung inflammation after exposure to gases, doctors may consider a variety of causes. These could include exposure to different types of gases such as nitrogen oxides, chlorine gas, chloramine gas, ammonia, phosgene, sulfur oxides, hydrogen sulfide, cadmium, or metal fume fever due to zinc oxide fumes among other irritant gases. Other conditions that could present similar symptoms to nitrogen dioxide exposure include severe pneumonia, sepsis, acute heart failure, or any form of acute respiratory distress syndrome (ARDS). Knowing a patient’s occupational or environmental exposure history could help in identifying the exact cause of the illness.
Here are some conditions that doctors might consider:
- Acute respiratory distress syndrome
- Cardiogenic pulmonary edema (fluid accumulation in the lungs due to heart problems)
- Congestive heart failure and pulmonary edema
- Asthma
- Upper respiratory tract infection
- Lower respiratory tract infection
- Methemoglobinemia (a blood disorder)
- Farmer lung (a type of allergic reaction)
- Smoke inhalation
- Carbon monoxide poisoning
- Miliary tuberculosis (a type of lung infection)
- Chlorine gas poisoning
- Hydrogen sulfide poisoning
- Phosgene poisoning
What to expect with Nitrogen Dioxide Toxicity
The outcome can change based on how intense, how long, and how often someone is exposed to nitrogen dioxides. However, if you’re exposed to nitrogen dioxide just once, you can usually expect to fully recover as long as you receive the right medical care. In severe cases, advanced medical support may be required. This could include use of a mechanical ventilator to help you breathe, or a treatment called extracorporeal membrane oxygenation (ECMO). These treatments can help manage and reduce the harmful effects of the exposure, giving your body time to heal and recover.
Possible Complications When Diagnosed with Nitrogen Dioxide Toxicity
After the first severe reaction to chemical pneumonitis, a patient may go through a third phase which typically happens 2 to 8 weeks later. During this stage, they might develop a condition called bronchiolitis obliterans. The individual could feel symptoms like fever, chill, trouble in breathing, chest pain and also encounter wheezing and coughing. It’s important to note the chest X-Ray could appear normal or display small, scattered lumps. There are some unconfirmed reports suggesting that this phase of the illness may improve with the use of systemic corticosteroids.
Common symptoms:
- Fever
- Chills
- Wheezing
- Cough
- Trouble breathing (dyspnea)
- Chest pain
- Normal or scattered lumps in chest X-ray
Preventing Nitrogen Dioxide Toxicity
The American Conference of Governmental Industrial Hygienists (ACGIH), which is an organization that provides guidelines for work-related health and safety, suggests an average nitrogen dioxide level of 3 parts per million (ppm) over a certain amount of time (known as a time-weighted average or TWA). They also recommend a short-term exposure limit (STEL) of 5 ppm, meaning this is the maximum level that is safe to be exposed to in a brief period.
The National Institute for Occupational Safety and Health (NIOSH), another organization focused on work health and safety, recommends a permissible exposure limit (PEL) of 5 ppm, which is the maximum amount of nitrogen dioxide someone can be exposed to without it being harmful.
The U.S. Environmental Protection Agency (EPA) has its own standards for the amount of nitrogen oxides (air pollutants) in the environment. They have set a daily maximum limit of 100 parts per billion (ppb), with an annual guideline set at 53 ppb.
The World Health Organization (WHO), an internationally recognized authority on public health, suggests an average annual level of nitrogen dioxide of 40 micrograms per cubic meter (mcg/m^3). They also have a threshold for short-term exposure, which is 200 mcg/m^3 within any given hour.
