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.