Aquatic environments can be polluted with harmful chemicals from human activities, which can harm aquatic life and even human health. A study looked at pollution levels in rivers and lakes, finding that sediments in a city lake had the highest contamination levels. The main sources of pollution were vehicle and industrial emissions. Surprisingly, even highly polluted areas showed only moderate risk to aquatic life, suggesting some organisms can adapt to contamination. The study also found that pollution levels did not always match with the health of the ecosystem, as some heavily polluted areas had relatively healthy aquatic life. To fully understand pollution effects, a combination of different assessment methods is needed.