White Phosphorus in Southern Lebanon: What the Incendiary Agent Does and Why Its Use Is Contested

White phosphorus has re-emerged as a focus of international concern amid Israel's military operations in southern Lebanon, where the incendiary substance has reportedly been deployed in areas where civilians live and work. An explainer segment produced by Al Jazeera, presented by correspondent Reem Takieddine and published on 29 September 2026, examined what the chemical agent is, how it affects people and land, and why its use in populated areas is restricted under international humanitarian law.

At its most basic level, white phosphorus is a waxy, translucent solid that ignites spontaneously on contact with oxygen in the air. Once alight, it burns at extremely high temperatures and produces a dense, choking smoke. Because the substance continues to react with oxygen, it can reignite even after flames appear to have been extinguished—particularly if particles embedded in clothing, soil or wounds are re-exposed to air. This self-igniting quality is what makes it distinct from many conventional incendiary materials.

The material is used by militaries for legitimate purposes, most commonly to create smoke screens that conceal troop movements or to illuminate targets. It can also serve as an incendiary weapon. The dual-use character of white phosphorus is central to the legal debate: the same chemical that generates harmless obscurant smoke on a battlefield can, when deployed against people or structures, cause injuries that are exceptionally difficult to treat.

The human toll is severe. White phosphorus can inflict deep thermal and chemical burns that may extend to the bone, and burning fragments can continue to smoulder inside tissue. Medical workers treating such injuries describe a painful and prolonged recovery process, with elevated risks of infection, disfigurement and death. Survivors may also suffer respiratory damage from inhaling the toxic smoke, which contains phosphorus oxides capable of irritating and injuring the airways and lungs.

Beyond the immediate harm to individuals, the use of white phosphorus carries lasting consequences for the environment and for civilian livelihoods. Fires ignited by the substance can spread across farmland, orchards and brush, destroying crops and grazing land. The residue left behind can contaminate soil and water sources, and the smoke can drift across residential areas far from the point of impact. In agricultural communities in southern Lebanon, where farming sustains many families, such damage compounds the direct dangers of the conflict.

The legal framework governing white phosphorus is not a blanket ban, which is a frequent source of confusion. International law prohibits the use of incendiary weapons against civilians and requires that they not be directed at military objectives located within concentrations of civilians. Under Protocol III of the Convention on Certain Conventional Weapons, there are also restrictions on air-delivered incendiary munitions in populated areas. The core obligation is the principle of distinction: combatants must separate military targets from civilians and civilian objects, and must refrain from attacks that are indiscriminate or disproportionate.

When white phosphorus is used in populated areas, those protections are directly implicated. Even if the agent is initially employed for a smoke-screen purpose, its effects are difficult to confine once fires spread or particles scatter. Critics argue that releasing an indiscriminate, persistent incendiary substance over towns and villages effectively places civilians at risk of burns, respiratory harm and displacement regardless of the intended target. Defenders of particular strikes maintain that the material was used for permissible military functions such as screening, and that any civilian harm is unintended.

The sensitivity of the issue is heightened in Lebanon because the country's south has already endured repeated rounds of hostilities. Communities there have faced displacement, destruction of homes and damage to agricultural land, which makes the reported use of white phosphorus a cumulative burden rather than an isolated incident. Each new deployment in a populated setting increases the strain on hospitals, civil defence teams and local authorities that are already stretched by conflict.

International monitoring bodies and human rights organisations have repeatedly called for investigations into allegations involving white phosphorus, arguing that documented patterns of use near civilian areas merit scrutiny under the laws of war. They stress the importance of preserving evidence, including soil samples, medical records and satellite imagery, so that responsibility can be established and victims can pursue accountability. Such calls often run up against political obstacles and the difficulty of access to active conflict zones.

For civilians in southern Lebanon, the practical consequences of these legal debates are immediate. Families in affected areas may face evacuation orders, the loss of crops and income, and the psychological weight of knowing that a weapon capable of reigniting could be present in the ground around them. Farmers returning to fields must contend with unexploded remnants and contaminated soil long after the fighting subsides, extending the harm well beyond the moment of impact.

The medical response to white phosphorus injuries also presents unique challenges for health systems. Burn units require specialised care, and embedded particles must be kept submerged or smothered to prevent reignition during treatment. Where health infrastructure is damaged or overwhelmed, the capacity to provide such care is limited, raising the likelihood of preventable deaths and long-term disability. Aid agencies have warned that the needs created by incendiary injuries can outlast the active phase of a conflict by months or years.

Al Jazeera's explainer situates the current concern within a broader pattern of questions about how Israel has employed white phosphorus in southern Lebanon. It highlights three linked issues: the physical properties that make the agent dangerous, the particular vulnerability of civilians and farmland in the affected zones, and the legal restrictions that apply when such weapons are used in or near populated areas. Each of these strands feeds into the wider debate about compliance with international humanitarian law in contemporary armed conflict.

Ultimately, the controversy surrounding white phosphorus reflects a wider tension in modern warfare between military utility and the protection of civilians. Weapons that are lawful in certain contexts can become unlawful when the circumstances of their use change, and the line between permissible smoke screening and indiscriminate harm is often contested in practice. In southern Lebanon, that contest is being fought over fields, villages and the health of the people who live among them—making the question of what white phosphorus is, and how it is used, far more than a technical matter.