Industrial wastes primarily enter coastal waters from terrestrial (land-based) activities. Industries, like municipalities and other entities that generate wastes, dispose of many liquid wastes through wastewater systems (and ultimately to waterbodies), whereas they dispose of their solid wastes in landfills.
The quantity and characteristics of industrial wastewater depends on the type of industry, its water and wastewater management, and its type of waste pretreatment (if any) before delivery to a wastewater (sewage) treatment plant. Because industrial waste frequently goes down the same sewers as domestic and commercial nonindustrial waste, sewage often contains high levels of industrial chemicals and heavy metals (e.g., lead, mercury, cadmium, and arsenic).
Substances that are not removed by wastewater treatment processes are discharged via the treated effluent to a receiving stream, river, or coastal outlet. Inland waters ultimately reach the ocean, carrying with them some residual chemical that are not attenuated, stored, or degraded during their journey through the watershed. Other land-based sources of industrial pollutants in the ocean are pipeline discharges and transportation accidents, leaking underground storage tanks, and activities at ports and harbors. Intentional, illegal dumping in inland watersheds and in inland waterbodies also can deliver industrial wastes to drainageways, and ultimately to the ocean.
In coastal watersheds, some industries discharge their wastes directly to the ocean. Like industries located inland, these industries must first obtain a permit under the Clean Water Act. Industrial pollutants also can directly enter the ocean by accidental spills or intentional dumping at sea.
Wet and dry deposition of airborne pollutants is a sometimes overlooked, yet significant, source of chemical pollution of the oceans. For example, sulfur dioxide from a factory smokestack begins as air pollution. The polluted air mixes with atmospheric moisture to produce airborne sulfuric acid that falls on water and land as acid rain. This deposition can change the chemistry and ecology of an aquatic ecosystem. The major transport of PCBs to the ocean, for example, occurs through airborne deposition.
Industrial chemicals can adversely affect the growth, reproduction, and development of many marine animals. Pollutants are appearing not only in the Pacific, Atlantic, and Indian Oceans and their marginal seas, but also in the more remote and once-pristine polar oceans. An array of contaminants have been found in the flesh of fish and marine mammals in polar regions. In addition to the environmental and ecological issues, there is growing concern over the potential human health impacts in aboriginal communities whose residents depend on fish and marine mammals for daily sustenance.
A major public health concern is the safety of seafood as it relates to the chemical pollution of waters used for commercial and recreational fishing and mariculture . Heavy metals (e.g., copper, lead, mercury, and arsenic) can reach high levels inside marine animals, and then be passed along as seafood for humans. A well-known case of human poisoning occurred in Japan, where one industry dumped mercury compounds into Minimata Bay from 1932 to 1968. Methyl mercury that accumulated in fish and other animals was passed along to humans who consumed them. Over 3,000 human victims and an unknown number of animals succumbed to what became known as "Minimata Disease", a devastating illness that affects the central nervous system.
Monitoring by fisheries, environmental, and public health agencies can prevent or minimize cases of human illness caused by chemical contaminants in seafood. Some shellfish-producing areas off the U.S. coasts have been either permanently closed or declared indefinitely off-limits by health officials as a result of this type of pollution. A large percentage of U.S. fish and shellfish consumption advisories are due to abnormally high concentrations of chemical contaminants in seafood.
