1557
Furthermore , it was observed that urinary GST - alpha levels increased by about 10 % over the 8 - year course of the study among individuals with an average exposure to amalgams among the study subjects from the amalgam group , in comparison with study subjects with no exposure to dental amalgams .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None