When it rains in the Amazon, as it so often does, a man made problem is that affect the environment is the fact that it rains down acid rain. The water within the clear water areas do in fact tend to be neutral and even sway more toward being alkaline rich. The water in other areas such as blackwater areas tend to be highly acidic; reaching levels sometimes as low as four and four tenths on the pH scale. This acidity can be very harmful to the animals living in this water. Acid rain is caused by pollutants which are man made going into the atmosphere and raining upon the landscape and flowing into the vast river.