Pragmatic method based on on-line leaching and inductively coupled plasma mass spectrometry for risk assessment of the impact of short-term pollution

A method was devised to assess the impact of short-term pollution. It was demonstrated with a natural toothbrush, known as miswak, which is used as chewing stick in Middle-Eastern countries. To this end, miswak sticks collected from one tree were treated differently. One was immediately placed in a ziplock plastic bag whereas the others were driven 180 km away to a market on the side of a busy road. After a few days, one of the unsold sticks was placed in a ziplock bag. Analysis by inductively coupled plasma mass spectrometry following acid digestion revealed that the polluted miswak had significantly higher concentrations of As, Cd, Pb, Fe and Cu than miswak bagged upon collection. The temporal profiles obtained for Cd and As using on-line leaching of ground miswak with artificial gastro-intestinal fluids (saliva, gastric juice and intestinal juice) at 37 degrees C, which provide information on bio-accessibility, included a double peak, indicating two different sources. Furthermore, plotting the leaching profiles of the elements against each other confirmed two different sources of As, Cd and Pb. The on-line leaching approach thus provides information that cannot be obtained by batch methods. In this example, bagging miswak upon collection would significantly reduce contamination.