Particulate matter (PM), particularly PM2.5, was found to be harmful to aquatic invertebrates. These aquatic invertebrates include fish, crustaceans, and Mollusca. In a study by Han et al, the effects of PM<2.5 micrometers on life history traits and oxidative stress were observed in Tigriopus japonicus. Exposure to particulate matter of less than 2.5 micrometers in diameter led to significant changes in ROS levels, indicating that particulate matter exposure was a causative agent of oxidative stress in Tigriopus japonicus. In addition to aquatic invertebrates, negative effects of particulate matter have been noted in mammals as well. Following acute exposure to ambient particulate matter, rats showed a significant increase in neutrophils and a significant decrease in lymphocytes, indicating that particulate matter exposure can result in activation of the sympathetic stress response.