17702
The PHC5 for copper was then estimated ( 6 . 8 micro g / L ; 95 % confidence interval [ CI ] , 1 . 8 - 13 . 6 micro g / L ) , by fitting a log - normal distribution to the population threshold concentrations obtained .
 copper
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 copper