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The cyanobacterial beta - N - methylamino - L - alanine ( L - BMAA ) is described as a low - potency excitotoxin , possibly a factor in the increased incidence of amyotrophic lateral sclerosis ( ALS ) and Parkinsonism - dementia complex ( PDC ) in Guam .
 beta - N - methylamino - L - alanine, L - BMAA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 beta - N - methylamino - L - alanine, L - BMAA