Effects on humans
White phosphorus can cause injuries and death in three ways: by burning deep into tissue, by being inhaled as a smoke, and by being ingested. Extensive exposure in any way is fatal.
Effects of exposure to WP weapons
Incandescent particles of WP cast off by a WP weapon's initial explosion can produce extensive, deep (second and third degree), burns. Phosphorus burns carry a greater risk of mortality than other forms of burns due to the absorption of phosphorus into the body through the burned area, resulting in liver, heart and kidney damage, and in some cases multi-organ failure. These weapons are particularly dangerous to exposed people because white phosphorus continues to burn unless deprived of oxygen or until it is completely consumed. In some cases, burns are limited to areas of exposed skin because the smaller WP particles do not burn completely through personal clothing before being consumed. According to GlobalSecurity.org, quoted by The Guardian, "White phosphorus results in painful chemical burn injuries" .
Exposure and inhalation of smoke
Burning WP produces a hot, dense white smoke. Most forms of smoke are not hazardous in the kinds of concentrations produced by a battlefield smoke shell. Exposure to heavy smoke concentrations of any kind for an extended period (particularly if near the source of emission) does have the potential to cause illness or even death.
WP smoke irritates the eyes and nose in moderate concentrations. With intense exposures, a very explosive cough may occur. However, no recorded casualties from the effects of WP smoke alone have occurred in combat operations and to date there are no confirmed deaths resulting from exposure to phosphorus smoke.
The Agency for Toxic Substances and Disease Registry has set an acute inhalation Minimum Risk Level (MRL) for white phosphorus smoke of 0.02 mg/m³, the same as fuel oil fumes. By contrast, the chemical weapon mustard gas is 30 times more potent: 0.0007 mg/m³ .
The accepted lethal dose when white phosphorus is ingested orally is 1 mg per kg of body weight, although the ingestion of as little as 15 mg has resulted in death. It may also cause liver, heart or kidney damage. There are reports of individuals with a history of oral ingestion who have passed phosphorus-laden stool ("smoking stool syndrome")