Arsenic and cancer: the still unanswered question

Metals and the skin

Certain metals, and many metal-based compounds, are inherently toxic, and their presence in occupational and environmental settings raises appropriate questions concerning human exposure. Contact of these materials with the skin represents an important route of exposure, which is not well characterized. The purpose of this review, therefore, is to assemble the available, useful information pertinent to risk assessment following dermal contact. Specifically, we summarize here: (1) data relevant to the qualitative and (where possible) quantitative evaluation of metal compound permeation through the skin; (2) the role of each metal in metabolism, particularly with respect to the skin, and the potentially toxic effects that may result from dermal contact; and (3) the immunological characteristics (including allergenicity) of the metals and their derivatives. In total, information on 31 metals has been reviewed. It is clear that many diverse factors determine the ability of metal-based species to permeate biological membranes, not all of which have been fully defined. Therefore, considerably more experimentation, targeted at the development of high-quality transport data, will be required before the specification of practically useful structure-activity relationships are possible.

What do losses in selenium and arsenic bioavailability signify for health?

Levels of As and Se in human foods and animal feeds respectively have decreased in recent years as a result of official limits and other factors. The reduction of SeO2 by SO2 to Se0 results in less bioavailability in the food cycle. Acid rain further reduces the pH of Se-depleted soils and soluble forms of Se are bound by metal ions in fallout from burning of fossil fuels. However, there is evidence that Se and As act as essential nutrients with anticancer value. The need for As in nutrition was shown by three laboratories in four mammalian species. Selenium inadequacies among people, as well as animals, are being recognized worldwide in the form of Se-responsive diseases. Reported data indicate that we have yet to learn the optimal intake levels for Se or As and how their decreased bioavailabilities affect human health.

Chronic arsenic poisoning in the north of Mexico

1 We compared the prevalence of signs and symptoms of chronic arsenic poisoning in two rural populations. 2 The arsenic concentration in the drinking water of the exposed population was 0.41 mg/l, and 0.007 mg/l in the control population. 3 The arsenic was present mainly (70%) in its pentavalent form. 4 The objective was to quantitate health effects and risks derived from chronic ingestion of arsenic in contaminated water. 5 In the exposed population, 21.6% of the sample, showed at least one of the cutaneous signs of chronic arsenic poisoning against 2.2% in the control town. 6 Non-specific symptoms were more prevalent in the exposed population and they occurred more frequently in those individuals with skin signs. 7 The relative risk of suffering a particular manifestation of poisoning, ranged from 1.9 to 36 times higher in the exposed population. 8 We estimated the risks above mentioned, which were derived from exposure to minute quantities of arsenic in a known proportion of its oxidation states during a life time period.

Lung carcinoma induction in BD rats after a single intratracheal instillation of an arsenic-containing pesticide mixture formerly used in vineyards

A single intratracheal 0.1-ml instillation of a calcium-arsenate containing vineyard pesticide induced multi-focal bronchogenic adenocarcinomas and bronchiolar-alveolar-cell carcinomas in nine out of 15 treated BD rats. This seems to be the first experimental confirmation of carcinogenicity of arsenic-containing pesticides used formerly in vineyards.

The effects of sodium arsenate on the free amino acid levels in erythrocytes and plasma in rats

The effects of arsenate on the levels of free amino acids in rat plasma and red blood cells have been investigated. The biggest changes occur in the branched-chain amino acids valine, isoleucine and leucine which are markedly decreased. The levels of several other amino-acids also change. The effects on the amino acids are not due to a change in the food intake caused by dosing with arsenate. This has been shown by comparing the results with those on fasting rats (40 h). Branched-chain amino acids in particular are markedly increased in plasma of fasting rats as opposed to a decrease in arsenate-treated rats.

Mortality among shipyard workers in Genoa, Italy

The dockyards of Genoa are exposed to many known or suspect carcinogenic agents, namely, asbestos, silica, polycyclic aromatic hydrocarbons, and halogenated hydrocarbons; other possibly harmful substances are trace amounts of aromatic amines, welding smokes, paints, and lipid-removing solvents. A cohort study of causes of death of 2190 dockyard workers in Genoa was conducted between January 1, 1960 and December 31, 1975. Mortality rates were calculated for 20 different occupational categories, for which there exist different levels of exposure to noxious substances. Two control groups were selected: the general male population of Genoa and all male employees (462) of San Martino Hospital, Genoa for the same period of time. Causes of death that demonstrated significant excesses for both control groups were: cancer of the colon, excluding the rectum; cancer of the larynx; cancer of the lung, bronchus, and trachea; cancer of the kidney, urinary bladder, and other urinary organs; respiratory diseases; and cirrhosis of the liver. The data obtained from these 20 job categories revealed different types and levels of risk for various carcinogenic agents.