Answer and Explanation: Some areas of the Amazon River are fairly polluted, particularly areas of the river close to large cities. These large cities (such as Manaus, Macapa, and Santarem) have been known to dump trash, sewage, plastics, oil, and chemicals into the Amazon River.

The "dirty" or "cafe-au-lait" appearance of the Amazon River is actually a natural phenomenon caused by a massive load of suspended sediment and organic matter, not necessarily man-made pollution. The river originates in the Andes Mountains, where fast-moving water erodes rich, mineral-heavy soils and carries them downstream. These fine particles of clay and silt remain suspended in the water, giving it a turbid, brownish-yellow color. This sediment is actually vital for the ecosystem, as it provides the nutrients that support the lush rainforest along its banks. However, in 2026, ecologists have noted that human activity—specifically illegal gold mining and deforestation—is worsening the water quality by introducing heavy metals like mercury and increasing runoff. While the "brown" color is a sign of a healthy, nutrient-rich river, the presence of these industrial pollutants is a growing concern for the biodiversity of the Amazon basin, making the water "dirty" in a much more dangerous, chemical sense.