Environmental risk assessment of white phosphorus from the use of munitions - a probabilistic approach

White phosphorus (P(4)) is a highly toxic compound used in various pyrotechnic products. Ammunitions containing P(4) are widely used in military training areas where the unburned products of P(4) contaminate soil and local ponds. Traditional risk assessment methods presuppose a homogeneous spatial distribution of pollutants. The distribution of P(4) in military training areas is heterogeneous, which reduces the probability of potential receptors being exposed to the P(4) by ingestion, for example. The current approach to assess the environmental risk from the use of P(4) suggests a Bayesian network (Bn) as a risk assessment tool. The probabilistic reasoning supported by a Bn allows us to take into account the heterogeneous distribution of P(4). Furthermore, one can combine empirical data and expert knowledge, which allows the inclusion of all kinds of data that are relevant to the problem. The current work includes an example of the use of the Bn as a risk assessment tool where the risk for P(4) poisoning in humans and grazing animals at a military shooting range in Northern Norway was calculated. P(4) was detected in several craters on the range at concentrations up to 5.7g/kg. The risk to human health was considered acceptable under the current land use. The risk for grazing animals such as sheep, however, was higher, suggesting that precautionary measures may be advisable.