6253
Titanium dioxide exposure resulted in 31 ( bulk ) and 22 fold ( nano ) increases in the Ti concentrations of gill tissue compared to controls , but there were no measurable increases of Ti in the internal organs including the brain .
 Titanium dioxide, Ti, Ti
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Titanium dioxide, Ti, Ti