Toxicology of hydrogen fluoride in relation to major accident hazards

A major industrial accident involving the release of hydrogen fluoride has the potential to cause serious injury and possibly death in the surrounding human population. Given the potential for such serious and large-scale eff ects, there is a need for scientifically based risk assessments for determi ning appropriate on-site risk control measures, as well as for informing of f-site emergency plans and land-use development decisions. Within Great Bri tain, the Health and Safety Executive (HSE) has the statutory responsibilit y for providing land-use planning advice in the vicinity of major accident hazard sites. The advice is based on quantified assessment of the individua l risk of exposure to a specified amount of the toxic substance. Among othe r things this requires a consistent, reliable, and transparent understandin g of the major hazard toxicology of the substance concerned. An assessment of the toxicology of hydrogen fluoride in relation to major accident hazard s, based on conventional inhalation toxicity studies, was published by HSE in 1993. Recently, studies have been reported in which rats inhaled hydroge n fluoride via a mouthpiece attached to an endotracheal cannula. HSE has ex plored the use of this "mouth-breathing" rat model as a possible basis for human health risk assessment for hydrogen fluoride in the context of major accident hazards. A number of uncertanties in the use of this animal model have been identified that warrant caution in the use of this model for regu latory purposes. Overall, the results from the "mouth-breathing'' rat model did not lead to a change in the HSE assessment of hydrogen fluoride, which remains based on experimental data obtained following "mainstream" toxicol ogical practices. (C) 1999 Academic Press.