The toxic oil syndrome: 20 years on.

With hindsight, it is easy to criticise the standards of food regulation of two decades ago. Nevertheless, when the Spanish toxic oil syndrome (TOS) appeared in 1981, there were many who asked why aniline was permitted as an official adulterant for imported French rape seed oil, and why such adulterated oils were often illegally refined in Spain and marketed without difficulty. This review brings up to date a comprehensive survey of the ensuing research published in 1995 and concentrates on recent significant findings. These include the identification of the refinery that produced the toxic oil, and the detection of oil contaminants with possible aetiological significance. Possible chemical links have been found between oil contaminants and those detected in L-tryptophan implicated in the eosinophilia-myalgia syndrome (EMS). There is good evidence that the initial pathogenetic mechanism is immunological. On metabolic evidence, it is suggested that not one, but a group of, toxic agents was responsible for TOS.

Thalidomide: 40 years on.

Thalidomide was marketed in the late-1950s as a sedative and tranquilliser of exceptionally low general toxicity, but in 1961 it was implicated separately by Lenz and MacBride as the cause of the epidemic of congenital malformations that had been puzzling the world for some years. It is a very potent teratogen in humans, but in few other mammalian species; damage to the embryo is produced at specific stages of gestation, but the mechanism of embryopathic action is still not understood. Following the withdrawal of the drug worldwide, it was consigned to the history of medical tragedies. In 1965, however, Sheskin discovered that it was effective in treating erythema nodosum leprosum, a distressing complication of leprosy. As the drug is neither an antibiotic nor an analgesic, its action was assumed to be immunosuppressive. In Brazil the drug was used widely with few regulatory controls, since when more than 100 cases of congenital malformation have appeared. Sheskin's discovery led to the experimental use of thalidomide in many other indications thought to possess some immunological component. In some cases, e.g. Behçet's syndrome, graft-versus-host disease and aphthous ulceration in HIV-positive patients, the drug has been shown to possess some efficacy. And there is some evidence that it inhibits the replication of one of the immunodeficiency viruses. The AIDS community in the US has exerted much pressure on the FDA to allow the drug on to the market, although the use of a potent immunosuppressive drug of unknown mechanism in an immunodeficiency condition raises further questions. Thalidomide is not always beneficial; its use is associated with an increased mortality in epidermal necrolysis. In 1991, D'Amato confirmed it possessed antiangiogenic properties and this led to further trials in malignant conditions. Results were mixed, but those in multiple myeloma gave some grounds for optimism. In 1998, the FDA announced its extraordinary decision to grant marketing approval for thalidomide.

Carcinogens in food: priorities for regulatory action.

A pragmatic possible approach to the prioritization of chemical carcinogens occurring as food contaminants is described, based on the carcinogenic risk to the population. This should be of value in ensuring that resources for assessment and management of carcinogens in food are directed to the most important areas with regard to carcinogenic risk to the population. Key components of this approach are an assessment of the carcinogenic hazard to humans combined with estimations of intakes per person and of the proportion of the population exposed. These are used to derive an index referred to as the Population Carcinogenic Index. Concerning the hazard assessment expert judgement is used to place the chemical in one of five categories. The highest category is for chemical carcinogens that are believed to act by a genotoxic mechanism. It is recognised that such compounds may vary enormously with respect to their potency and various approaches to ranking carcinogens on the basis of potency are reviewed. The approach adopted is to subdivide the genotoxic carcinogens category into high, medium and low potency based on the TD50 value. Methods of estimating intakes and exposed populations are considered and an approach which groups these into broad categories is developed. The hazard and exposure assessments are then combined to derive the Population Carcinogenicity Index.