The major kinds of pollution, usually classified by environment, are air pollution, water pollution, and land pollution. Modern society is also concerned about specific types of pollutants, such as noise pollution, light pollution, and plastic pollution.
Water pollutants can be divided into three major categories:
(1) substances that harm humans or animals by causing disease or physical damage;
(2) substances or situations that decrease the oxygen content of water, leading to anaerobic decay and the death of aquatic life; and
(3) substances that are indirectly harmful, by making water unpleasant to use or destroying the natural beauty and health of lakes, rivers, and oceans (Table 13.8).