MPP+ has been known since at least the 1920s, with a synthesis of the compound being published in a German chemistry journal in 1923.[4] Its neurotoxic effects, however, were not known until much later, with the first paper definitively identifying MPP+ as a Parkinson's-inducing poison being published in 1983.[5] This paper followed a string of poisonings that took place in San Jose, California in 1982 in which users of an illicitly synthesized analog of meperidine were presenting to hospital emergency rooms with symptoms of Parkinson's.[3] Since most of the patients were young and otherwise healthy and Parkinson's disease tends to afflict people at a much older age, researchers at the hospital began to scrutinize the illicitly synthesized opiates that the patients had ingested.[2] The researchers discovered that the opiates were tainted with MPTP, which is the biological precursor to the neurotoxic MPP+.[2] The MPTP was present in the illicitly synthesized meperidine analog as an impurity, which had a precedent in a 1976 case involving a chemistry graduate student synthesizing meperidine and injecting the resulting product into himself.[6] The student came down with symptoms of Parkinson's disease, and his synthesized product was found to be heavily contaminated with MPTP.[6]