Use of a luminescent bacterial biosensor for biomonitoring and characterisation of arsenic toxicity of chromated copper arsenate (CCA)

Abstract

The increase of arsenic (As) concentration on the earth’s surface is due both to natural sources, such as volcanic activity and weathering processes, and to anthropogenic sources, such as mining activities, agricultural and forestry applications. One example of anthropogenic arsenic contamination in the environment is the use of arsenic-containing wood preservatives. The most extensively used wood preservative is chromated copper arsenate (CCA), which is pressurised into the wood through a process called ‘Wolmanizing’ [1]. Wood intended for marine uses receives 24–40 kg CCA per cubic meter of wood to prevent its destruction by bacteria, fungi and insects. Each of the three chemicals in CCA is known to be toxic to aquatic biota at concentrations above trace levels, and found to be leached from the treated wood in both fresh and sea water [2–4]. Chemicals leached from CCA-treated wood can affect organisms that grow on the wood itself and those that live adjacent to the CCA-treated bulkheads, and also be adsorbed onto sediments, where they can be slowly released or taken up by benthic organisms [4–6]. The rate of metal accumulation in sediments and in benthos differs with each chemical in the order: Cu>As>Cr, and decreases with distance and time [1, 7]. Benthic organisms living near CCA-treated bulkheads were found to contain elevated levels of Cu and As. The number of individuals, as well as the species diversity, were also decreased at sites adjacent to CCA-treated bulkheads [1]. Pathologic and genotoxic effects have also been observed in oysters (Crassostrea virginica) living on CCA-treated wood [8]. In addition, CCA was shown to affect the growth of PCP-degrading bacterial species and their ability to degrade PCP [9, 10]. Thus, monitoring of bioavailable amounts of CCA released by the treated wood, is important in order to detect and rectify its toxic effects. Among the three chemical constituents of CCA, arsenic is the most abundant in the environment, and known to have carcinogenic and teratogenic effects on humans upon chronic exposure [11, 12]. Therefore, the focus of this study is on biomonitoring of arsenic toxicity.