Even animal studies have suggested that tryptophan itself "when ingested by susceptible individuals either alone or in combination with some other component in the product, results in the pathological features in EMS".At the time of the outbreak, Showa Denko had recently made alterations to its manufacturing procedures that were thought to be linked to the possible origin of the contaminants detected in the affected lots of tryptophan. A key change was the reduction of the amount of activated charcoal used to purify each batch from >20 kg to 10 kg. A portion of the contaminated batches had also bypassed another filtration step that used reverse-osmosis to remove certain impurities. Additionally, the bacterial culture used to synthesize tryptophan was a strain of Bacillus amyloliquefaciens that had been genetically engineered to increase tryptophan production. Although the prior four generations of the genetically engineered strain had been used without incident, the fifth generation used for the contaminated batches was thought to be a possible source of the impurities that were detected. This has been misused to argue that the genetic engineering itself was the primary cause of the contamination, a stance that was heavily criticized for overlooking the other known non-GMO causes of contamination, as well as for its use by anti-GMO activists as a way to threaten the development of biotechnology with false information.
Eosinophilia–myalgia syndrome is a rare, sometimes fatal neurological condition linked to the ingestion of the dietary supplement L-tryptophan. The risk of developing EMS increases with larger doses of tryptophan and increasing age. Some research suggests that certain genetic polymorphisms may be related to the development of EMS. The presence of eosinophilia is a core feature of EMS, along with unusually severe myalgia (muscle pain). Signs and symptoms
The initial, acute phase of EMS, which last for three to six months, presents as trouble with breathing and muscle problems, including soreness and spasm, but which may also be intense. Muscle weakness is not a feature of this phase, but some people experience muscle stiffness. Additional features can include cough, fever, fatigue, joint pain, edema, and numbness or tingling, usually in the limbs, hands and feet.The chronic phase follows the acute phase. Eosinophilic fasciitis may develop, primarily in the limbs. CNS signs may appear, including numbness, increased sensation, muscle weakness, and sometimes cardiac or digestive dysfunction. Fatigue is present to some degree, while the muscle pain (which may be extremely intense) and dyspnea continue in this phase. Causes
Subsequent epidemiological studies suggested that EMS was linked to specific batches of L-tryptophan supplied by a single large Japanese manufacturer, Showa Denko. It eventually became clear that recent batches of Showa Denkos L-tryptophan were contaminated by trace impurities, which were subsequently thought to be responsible for the 1989 EMS outbreak. The L-tryptophan was produced by a bacterium grown in open vats in a Showa Denko fertilizer factory.