To date the available data on the effect of AgNPs in mammals in vivo is very less. The existing results have portrayed that AgNPs can cause toxicity to test animal model. This was studied by experimenting on Sprague-Dawley rats. In the first experiment Sprague-Dawley rats showed no significant changes in lungs and nasal cavity at a high dose of 1.32 X 10 6 particles cm -3 AgNPs in an inhalation chamber for 4 weeks. However, Goblet cells containing neutral mucin was affected and hence they increased in size and number. This suggest that AgNPs affects the neutral mucin in respiratory system . In the second one, lung inflammation was reported. In this Sprague-Dawley rats undergoes inhalation exposure at a dose of 2.9 X 10 6 particles cm -3 for 6 hours per day this was done for 90 days (13 weeks). After 13 weeks, inflammation in the lungs was reported in rats, also the lung functional test showed significant decrease in tidal volume and minute volume. This experiment indicates that AgNPs may cause lung damage and affect their normal function . No significant changes were observed in body weight, hematology and blood biochemistry for both male and female Sprague-Dawley rats after 4 weeks (28 days of exposure at high dose of 1.32 X 10 6 particles cm -3 , implying that AgNPs having concentration near sliver dust (1X10 6 μ cm -3 ) did not produce any remarkable health effects on Sprague-Dawley rats .