17890
Treatments included three different types of nano - TiO2 differing in their coating or crystalline structure but of similar primary size ( 20 nm ) plus a micron - sized bulk material , two exposure levels ( 1 , 10mg / l ) and two food ration levels of the microalgae Chlorella vulgaris that included a non limiting ( 1 . 5 mu gC / ml ) and a limiting one ( 0 . 3 mu gC / ml ) .
 Chemical: TiO2
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: TiO2