18229
This research supports the hypothesis that endogenously produced reactive species , including acetaldehyde , are always present and constitute the majority of the observed biological effects following very low exposures to exogenous acetaldehyde .
 Chemical: acetaldehyde; Chemical: acetaldehyde
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: acetaldehyde, acetaldehyde 
Answer:
 Chemical: acetaldehyde; Chemical: acetaldehyde