The document discusses indicators used to measure water pollution in the Mekong Delta and Ho Chi Minh City areas. It outlines two types of indicators: biological indicators like benthic macroinvertebrates, and chemical indicators such as dissolved oxygen, nitrates, hardness, phosphates, carbon dioxide, and acidity. The presence of different classes of macroinvertebrates and levels of chemicals can provide information about the health of water bodies and potential effects on local ecosystems and human health. The document also examines common causes of water pollution like agricultural and industrial runoff and their environmental impacts.