Currently, aluminum in various forms is the most commonly licensed adjuvant whose use is generally regarded by the pharmaceutical industry and various government regulatory agencies as safe. Research on this topic suggests that toxic encephalopathy is rare, and that the exact neurocognitive effects of such toxic exposure to aluminum is unclear. Generally, the research suggests that the aluminum levels found in most vaccines do not cause in serious or long term effects, as found by Offit and Jew (2003) after they conducted a meta-analysis of the available literature on this topic. Molloy, Standish, Niboer, and Turbull (2007) found similar results and that aluminum ingestion does not produce acute effects on cognition or adverse long-term effects. In the case of chronic toxic encephalopathy, which is characterized by long term, occupation exposure to solvents, there is some evidence of increased psychological complaints and significantly worse performance on tests of speed of information processing and memory and learning (van Hout, Schmand, Wekking, and Deelman, 2006). However, even these findings are tenuous, as the writers noted a high rate of suboptimal effort exhibited by their participants.