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To better model the effects of arsenic on ATP - mediated Ca ( 2 + ) signaling under conditions of natural exposure , we cultured tracheal epithelial cells obtained from mice exposed to control or 50 ppb Na - arsenite supplemented drinking water for 4 weeks .
 Chemical: arsenic; Chemical: ATP; Chemical: Ca ( 2 + ); Chemical: Na - arsenite
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: arsenic; Chemical: ATP; Chemical: Ca ( 2 + ); Chemical: Na - arsenite