Chlorine (Cl) has an atomic weight of 35.5. Chlorine gas is a yellow-green, highly irritating gas. It is soluble in water and alkaline solutions and readily dissolves in organic solvents such as carbon disulfide and carbon tetrachloride. When chlorine gas reacts with water, it forms hypochlorous acid and hydrochloric acid, which then decompose into nascent oxygen. Under high pressure, chlorine gas liquefies into liquid chlorine. Chlorine gas is highly corrosive, and equipment and containers are easily corroded, leading to leaks. Industrial exposure to chlorine can occur during its production or use if equipment or pipelines are not tightly sealed or during maintenance. Leaks of large amounts of chlorine gas can also occur during the filling, transportation, and storage of liquid chlorine if cylinders are poorly sealed or malfunction. Chlorine is primarily encountered in industries such as salt electrolysis, the production of various chlorine-containing compounds, papermaking, textile printing and dyeing, and water disinfection. The effects of chlorine gas on the human body include acute poisoning and chronic damage. Clinically, acute poisoning can be further classified into irritant reactions, Grade I, Grade II, and Grade III poisoning.

bubble_chart Clinical Manifestations

Acute chlorine poisoning is clinically classified into irritant reaction, grade I, grade II, and grade III poisoning based on the severity of respiratory system damage.

1. Chlorine irritant reaction: Transient eye and upper respiratory tract irritation symptoms occur. There are no positive signs in the lungs or occasional scattered dry rales, which generally subside within 24 hours.
2. Grade I poisoning: Mainly manifests as bronchitis or peribronchitis, with symptoms such as cough, expectoration of a small amount of sputum, and chest tightness. Scattered dry rales or wheezing sounds are present in both lungs, and a small number of moist rales may be heard. Chest X-ray shows increased and thickened lung markings with blurred edges, typically more pronounced in the lower lung fields. Symptoms usually resolve within 1–2 days with rest and treatment.
3. Grade II poisoning: Mainly manifests as bronchopneumonia, interstitial pulmonary edema, or localized alveolar pulmonary edema. Eye and upper respiratory tract irritation symptoms worsen, accompanied by chest tightness, dyspnea, paroxysmal choking cough, and sputum production, sometimes including pink frothy sputum or blood-streaked sputum. Other symptoms include headache, lack of strength, nausea, loss of appetite, abdominal pain, and abdominal distension and fullness. Grade I cyanosis is present, with dry or moist rales in both lungs or diffuse wheezing sounds. These symptoms gradually improve and subside after 2–10 days of rest and treatment.
4. Grade III poisoning: Any of the following clinical manifestations or chest X-ray findings qualifies as grade III poisoning.
   1) Clinical manifestations include: (1) Pulmonary edema occurring within minutes to hours after inhaling high concentrations of chlorine, with copious white or pink frothy sputum, dyspnea, chest tightness, obvious cyanosis, and diffuse moist rales in both lungs; (2) Severe asphyxia due to laryngeal or bronchial spasm or edema; (3) Shock and grade II or deep unconsciousness; (4) Sudden death caused by reflex respiratory center suppression or cardiac arrest; (5) Severe complications such as pneumothorax or mediastinal emphysema.
   2) Chest X-ray findings: Mainly show extensive, diffuse pneumonia or alveolar pulmonary edema. There are large, uniformly dense shadows or patchy shadows of varying sizes and densities with blurred edges, widely distributed in both lung fields, some appearing as butterfly-wing patterns. After grade III chlorine poisoning, bronchial asthma or asthmatic bronchitis may occur. The latter is caused by organized scars formed by hydrochloric acid corrosion, which are difficult to resolve and may progress to pulmonary emphysema.

bubble_chart Diagnosis

The diagnosis of acute chlorine poisoning can be made based on the rapid onset of symptoms after short-term exposure to high concentrations of chlorine gas, combined with clinical signs, symptoms, and chest X-ray findings, after excluding other respiratory diseases with similar presentations.

bubble_chart Treatment Measures

Basic Treatment

1. General Management: Immediately remove the patient from the scene and move them to an area with fresh air. If the eyes or skin are contaminated, rinse thoroughly with clean water or saline solution. Administer 0.5% cortisone eye drops and antibiotic eye drops. For skin acid burns, apply a wet compress with a 2–3% sodium bicarbonate solution. Patients exposed to a certain amount of chlorine gas should remain under hospital observation, with monitoring including respiration, pulse, and blood pressure changes. Early blood gas analysis and dynamic chest X-ray observations should be prioritized.
2. Correct Hypoxia: Administer oxygen and ensure the airway remains unobstructed.
3. Prevention and Treatment of Pulmonary Edema: (1) Nebulize neutralizing agents, such as 5% sodium bicarbonate for local inhalation. (2) Use glucocorticoids appropriately. For outpatient preventive treatment, administer dexamethasone via intramuscular injection or oral prednisone for 1–2 days. Hospitalized patients may receive dexamethasone 20–60mg intravenously or via drip, depending on their condition.

1. Oxygen Therapy: Oxygen therapy is one of the key measures for treating pulmonary edema and improving hypoxia. Ensure the partial pressure of oxygen in the blood is maintained around 80mmHg while avoiding the toxicity of high-concentration oxygen.
2. Nebulized Inhalation: Use a mixture of gentamicin 80,000–160,000 units, dexamethasone 5mg, aminophylline 0.25g, and 5% sodium bicarbonate 20ml, diluted with 0.9% saline to 50ml. Administer via nebulization every 4 hours, 10–15ml each time.
3. Reduce Pulmonary Capillary Permeability: Early, adequate, and short-term use of adrenal glucocorticoids is crucial for treating pulmonary edema. On the first day, for Grade I pulmonary edema, administer dexamethasone 10–20mg or hydrocortisone 200–400mg intravenously or via drip. For Grade II, use dexamethasone 20–30mg or hydrocortisone 400–600mg. For Grade III, administer dexamethasone 30–50mg or hydrocortisone 600–1000mg, then adjust the dosage based on the patient's condition. Glucocorticoids are typically used for 2–5 days, but for severe chlorine poisoning (Grade III), they may be used for an extended period under close observation.
4. Relieve Spasms and Clear Foam, Maintain Airway Patency: Administer aminophylline 0.25g in 10% glucose solution 20ml intravenously. For severe pulmonary edema with airway obstruction by foam, use defoaming agents (e.g., dimethicone) via nebulization.
5. Vasodilators: Some reports suggest vasodilators are effective in rescuing toxic pulmonary edema. Consider trying sodium nitroprusside, nitroglycerin, phentolamine, or anisodamine.
6. Treatment of Complications: Toxic pulmonary edema often leads to pulmonary infections, requiring early, adequate, and combined antibiotic therapy. Acidosis is common in pulmonary edema, and respiratory alkalosis may occur with mechanical ventilation or hyperventilation. Prevent and promptly address acid-base imbalances.