4376
A significant increase in female mouse lung tumors was observed at the lowest exposure concentration of 12 . 8 ppm , whereas a small , but not statistically significant increase was observed in female rats only at the highest exposure concentration of 80 ppm .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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