The Global Challenge

Population Reports, Fall, 2000

Another powerful secondary pollutant is acid rain, formed when sulfur dioxide and oxides of nitrogen combine with water vapor and oxygen in the presence of sunlight to form a diluted "soup" of sulfuric and nitric acids. They can fall as both wet (acid rain) or dry deposition. Other harmful pollutants include sulfur dioxide, suspended particulate matter (soot, ash, and smoke from fires), carbon monoxide from vehicle exhausts, and lead, mainly from the exhaust of vehicles that burn leaded gasoline (262).

Air pollution is not only a health hazard but also reduces food production and timber harvests, because high levels of pollution impair photosynthesis. In Germany, for example, about US$4.7 billion a year in agricultural production is lost to high levels of sulfur, nitrogen oxides, and ozone (227).

Water Pollution

Globally, 2.3 billion people suffer from diseases linked to water. Providing safe drinking water and adequate sanitation would have major health benefits. Some benefits include an estimated 2.1 million fewer deaths from diarrheal diseases, 150 million fewer cases of schistosomiasis, and 75 million fewer cases of trachoma (63, 261).

Water-borne diseases, also known as "dirty water" diseases, result from using water contaminated by human, animal, or chemical wastes. These diseases cause an estimated 12 million deaths a year, 5 million of them from diarrheal diseases. Most of the victims are children in developing countries (46, 222, 227).

In many places both surface and ground waters are fouled with industrial, agricultural, and municipal wastes. According to the World Commission on Water for the 21st Century, more than half of the world's major rivers are so depleted and polluted that they endanger human health and poison surrounding ecosystems (117). In many large cities in the developing world the drinking water supply is contaminated. Only half of Southeast Asia's 550 million people have access to safe drinking water (237).

Pollution from Heavy Metals

Illnesses traced to heavy metals date back to ancient Rome, where lead pots, pipes, and smelters were held responsible for loss of intelligence among children and for brain damage and abnormal behavior among adults (181). Heavy metals released into the environment today come from uncontrolled emissions by metal smelters and other industrial activities, unsafe disposal of industrial wastes, and lead in water pipes, paint, and gasoline.

The heavy metals most dangerous to health include lead, mercury, cadmium, arsenic, copper, zinc, and chromium. Such metals are found naturally in the soil in trace amounts, which pose few problems. When concentrated in particular areas, however, they present a serious danger. Arsenic and cadmium, for instance, can cause cancer. Mercury can cause mutations and genetic damage, while copper, lead, and mercury can cause brain and bone damage (262).

Lead additives in gasoline cause widespread health problems in some countries. In Thailand, for example, a 1990 study found that some 70,000 children in Bangkok risked losing four or more points of IQ (Intelligence Quotient, based on standardized tests) because they were heavily exposed to lead emissions from motor vehicles. In Latin America some 15 million children under the age of two are at risk of ill health from lead pollution (227).