19712
In the present study , the cytotoxicity of two different sized aluminium oxide nanoparticles ( ANP ( 1 ) , mean hydrodynamic diameter 82 . 6 +/- 22nm and ANP ( 2 ) , mean hydrodynamic diameter 246 . 9 +/- 39nm ) towards freshwater algal isolate Chlorella ellipsoids at low exposure levels ( <= 1 mu g / mL ) using sterile lake water as the test medium was assessed .
 Chemical: aluminium oxide
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: aluminium oxide 
Answer:
 Chemical: aluminium oxide