40 people were poisoned in Thuong Phuc commune, Thuong Tin district, Hanoi, after inhaling chlorine gas that leaked from a chemical cylinder at one family's scrap collection business. This marks the first mass poisoning incident involving chlorine gas from a scrap cylinder.

Doctor Nguyen Huy Hoang, a member of the Vietnam Undersea and Hyperbaric Medicine Association, stated that chlorine is widely used in water disinfection, chemical production, and industry. However, in its gaseous form, this substance is highly toxic when inhaled.

Chlorine is a yellowish-green gas with a pungent odor that irritates the eyes and nose. Upon contact with moisture on the mucous membranes of the eyes and respiratory tract, chlorine reacts to form strong acidic and oxidizing substances, damaging cells. "This is not merely an irritation from an unpleasant smell but can be actual chemical damage," explained Doctor Hoang.

At mild levels, individuals exposed to chlorine gas may experience eye irritation, watery eyes, sore throat, coughing, or chest tightness. In more severe cases, chlorine causes bronchospasm, airway edema, and deep damage to the alveoli – the site of oxygen exchange between the lungs and blood. When the alveolar protective barrier is damaged, fluid floods the air sacs, leading to pulmonary edema. Patients then suffer severe shortness of breath, oxygen deficiency, and respiratory failure, requiring emergency care, even intubation and mechanical ventilation.

A dangerous characteristic is that symptoms do not always appear fully and immediately. Individuals who initially only experience coughing, a sore throat, or discomfort may develop progressively worsening shortness of breath after several hours. Therefore, reduced eye irritation or less coughing does not mean the danger has passed.

Doctor Hoang stated that the extent of damage depends on the chlorine concentration in the air, exposure duration, distance from the leak source, and the individual's health status. High concentrations can cause severe damage in a short period.

Toxicology documents note that concentrations of about 1-10 ppm can cause irritation to the eyes, nose, throat, and coughing. Ppm is a unit of concentration, simply understood as the number of parts of chlorine gas in one million parts of air. At higher concentrations, the risk of airway constriction and pulmonary edema increases.

The US Agency for Toxic Substances and Disease Registry (ATSDR) estimates that inhaling approximately 430 ppm of chlorine gas for 30 minutes can be fatal. However, this is reference data, not a safety limit or a countdown for every individual.

"We cannot smell the gas to know its concentration, nor can we rely on our tolerance to decide to stay longer," Doctor Hoang said, advising that upon experiencing eye irritation, choking cough, or shortness of breath in an area suspected of toxic gas, one must leave the source of exposure immediately, without trying to finish tasks.

Chlorine gas is heavier than air and can accumulate in pits, trenches, basements, and enclosed, poorly ventilated areas. Therefore, when a leak occurs, going to a lower spot or into a depressed area to avoid the gas can actually increase exposure.

Children, individuals with asthma, chronic lung disease, or heart conditions require special attention due to a higher risk of severe progression. After the acute phase, some individuals may experience persistent coughing, wheezing, or increased sensitivity to cigarette smoke, dust, and cold air.

Common symptoms of inhaling chlorine gas include: red, irritated eyes, watery eyes, burning in the nose and throat, coughing, chest tightness, wheezing, and shortness of breath. Some people may experience nausea or vomiting. If shortness of breath rapidly worsens, accompanied by stridor, clear hoarseness, blue lips, confusion, fainting, or coughing up pink frothy sputum, the patient requires immediate emergency medical attention.

Authorities handle the chemical leak area in Thuong Phuc on 19/10 – where 40 people were poisoned. Photo: Tien Thanh

Authorities handle the chemical leak area in Thuong Phuc on 19/10 – where 40 people were poisoned. Photo: Tien Thanh

What to do if you suspect chlorine gas poisoning?

The top priority is to leave the toxic gas source without further exposing yourself or others, moving to an area with clean air. If the gas leaks indoors, quickly exit the area if it is safe to do so. Do not return to retrieve items, search for the leak source, or bend down to sniff. For outdoor incidents, follow evacuation or shelter-in-place instructions from authorities; do not assume any direction is safe.

Do not attempt to rescue individuals in the toxic gas zone without proper protection. Ordinary cloth masks, surgical masks, wet cloths, and N95 respirators do not protect against chlorine gas. Accessing a gas leak area requires trained personnel equipped with appropriate breathing apparatus.

If eyes are irritated, rinse them with clean, gently flowing water continuously for at least 15 minutes; remove contact lenses if present and easy to remove. Do not rub your eyes, self-administer medication, or use chemicals to neutralize the exposure. Remove contaminated clothing and wash skin thoroughly with plenty of water and mild soap.

There is no specific antidote for chlorine poisoning. Treatment depends on the extent of the damage. Patients may require blood oxygen monitoring, chest imaging, or respiratory support. After examination, if coughing increases, chest tightness, or shortness of breath recurs, the patient must seek medical attention immediately.

Le Nga