Removal of Arsenic and Mercury Contamination in Museums using a Natural Environmentally Benign Chemical (2006-02)

Summary

Some natural science specimens and ethnographic artifacts in museums were historically treated with arsenic and mercury salts. This has created an environmental concern for museum workers and the public who may be exposed to these toxins. In addition, museums are frequently being asked to return sacred objects under the Native American Graves Protection and Repatriation Act (NAGPRA). Artifacts that are otherwise well contained and rarely handled are being returned to tribes for culturally appropriate use which may involve direct human contact. The need for a method to decontaminate artifacts and museum surfaces without causing degradation to the surfaces or exposure to personnel poses limitations on the methods that can be employed. The cultural beliefs of the Native American people also limits appropriateness of potential techniques, as some objects may be considered to be living spiritual beings.

α-Lipoic acid is a natural environmentally benign chemical that is integral to all plants and mammals and is patented as an agent for the cure of many diseases. It has also been demonstrated that α-lipoic acid acts in-vivo for the detoxification of both arsenic and mercury in biochemical studies dating back to the late 1950’s (Reiss et al (1958); Reiss et al (1958); Grunert (1960); and Wagner (1956)). It is known that α-lipoic acid does not require reduction to bind to mercury (Brown, 1968), however, the literature does not indicate whether reduction is required for binding to arsenic. It has been demonstrated that reduced α-lipoic acid binds strongly to arsenic in water (Spuches et al, 2005). Thus, due to the attributes of α-lipoic acid as a natural healing and detoxification agent and its known ability to react with arsenic and mercury, it is deemed to be the most appropriate cleaning agent for artifacts.

In this study, aqueous α-lipoic acid solutions were developed and reduced using natural sunlight and laboratory ultra violet lamps. The solubility in various organic and inorganic solutions were examined, and variables that may impact the reduction and solubility, such as pH and temperature, were examined. Arsenic and mercury on natural materials such as cotton, wool, paper and feathers were studied using a Niton handheld X-ray Fluorescence Spectrometer (XRF) to monitor contamination levels. A processing sequence that optimized decontamination was developed by running a series of full factorial experiments, which were analyzed using analysis of variance (ANOVA) techniques.

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