Chlorine gas leak from water treatment plant hospitalises over 600 in Iraq: How dangerous is it?

More than 600 Shiite pilgrims in Iraq were treated for respiratory problems after inhaling chlorine gas from a leak at a water treatment station, officials said on Sunday (August 10).
The leak occurred overnight along the main route between Najaf and Karbala, two of the country’s most important Shiite holy cities.

Millions of pilgrims are expected to converge on Karbala in the coming days to mark Arbaeen, the 40-day mourning period for Imam Hussein, the grandson of the Prophet Mohammed, and his brother Abbas.

Iraq’s health ministry said 621 people suffered asphyxiation following the leak, but all received treatment and were discharged in good health. Security forces protecting pilgrims said the chlorine escaped from a water facility on the Karbala–Najaf road.

How bad is inhaling chlorine gas for health?

Inhaling chlorine gas can cause a wide range of health effects depending on how much is inhaled and for how long, as the gas is highly irritant and corrosive.

When chlorine enters the airways, it reacts with moisture in the respiratory tract to form acids, which damage tissue and trigger inflammation. Even brief exposure to low concentrations can cause irritation of the eyes, nose, and throat, producing symptoms such as burning sensations, redness, watering eyes, and a sore throat.

Many people experience immediate coughing or choking as the airways react to the chemical, and some may develop nausea and vomiting due to its sharp, pungent odour.

More serious exposures can lead to pronounced shortness of breath, a feeling of tightness in the chest, and wheezing from bronchospasm. In high concentrations, chlorine gas can cause pulmonary oedema, a dangerous condition in which fluid builds up in the lungs, sometimes several hours after the initial exposure. This delayed reaction can be life-threatening without medical intervention.

The long-term effects of chlorine inhalation depend on the severity of the incident. Mild cases often resolve completely, but more severe exposures can leave lasting airway damage, leading to persistent coughing, wheezing, or a condition known as reactive airway dysfunction syndrome.

In the most serious cases, scarring of lung tissue can permanently reduce lung capacity. People with asthma, chronic respiratory diseases, or weakened immune systems are at greater risk of both immediate and lasting harm, and children and older adults tend to be more vulnerable to the effects of chlorine gas than healthy young adults.

Chlorine gas attacks in Iraq in the past

Several chlorine tanker trucks were used in bombings during the Iraq War, deliberately releasing chlorine gas in populated areas.

Insurgents in Iraq began weaponizing chlorine gas as early as October 2004, combining it with conventional vehicle-borne explosives (better known as “dirty bombs”), a tactic that continued through mid‑2007.

Two chlorine truck bombs exploded outside the Fallujah government center, injuring at least 15 Iraqi and US soldiers, with many suffering suspected chlorine poisoning.

A suicide truck bomb loaded with chlorine detonated at a police checkpoint in Ramadi, killing approximately 27 people.

In one of the deadliest chlorine-related attacks, a bombing at a Shia village market in Diyala Governorate killed between 32 and 45 people and injured about 60, making it the highest death toll from a chlorine bombing in Iraq at the time.

By early 2007, multiple suicide attacks using chlorine had occurred across Anbar Province, resulting in over 350 people suffering injuries or illness from chlorine exposure.

With inputs from agencies