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Toxic Pollution

The Problem

  • Toxic pollution occurs when synthetic chemicals are discharged or natural chemicals accumulate to toxic levels in the environment, causing reductions in wildlife numbers, degrading ecosystem functions and threatening human health.
  • Among the many naturally-occurring substances involved are certain metals (such as mercury, lead, chromium) and petroleum. Synthetic, or human-made, chemicals include, among others, pesticides, PCBs and dioxins. A large group of these, known collectively as persistent organic pollutants, or POPs, are complex compound-all containing hydrogen and carbon and many containing chlorine-that persist unchanged in the environment for long periods. Human activities are also responsible for environmental contamination by radioactive substances, some of which are natural and some synthetic.
  • Once in the living food chain, many of these substances are accumulated to ever-higher concentrations in the tissue of the animals that consume them. Some of the known effects on marine animals include cancer, lesions, genetic and developmental deformities, behavior abnormalities, reproductive failures, sex changes, and death.
  • Because water is such an effective solvent, much toxic pollution that humankind generates eventually ends up in the ocean. After entering the marine environment, many chemical substances concentrate in the sediment and the sea surface microlayer.
  • Humans may be exposed to toxic pollution from a variety of sources, including airborne emissions and contaminated water or food. Except in the case of workers who are exposed to large amounts of a single toxic material, the cumulative effects from all sources are the most problematic for human health.
  • Among documented and postulated maladies are reproductive problems, declines in fertility, developmental and learning problems, and suspected links to cancer.

The Causes

  • Toxic pollution occurs as a result of a variety of human activities. Industries and sewage treatment plants discharge wastes which contain toxic substances directly into waterways, These direct pipeline discharges are called point sources.
  • Air emissions from manufacturing; from fuel combustion in cars and other motors, homes and buildings; and from power plants contain numerous chemicals that drift in the atmosphere and rain down upon or absorb into the surface of the ocean and other bodies of water. Plutonium processing plants, nuclear power plants, nuclear submarines and nuclear waste dumps are the sources of radioactive contamination. Incinerated, spilled and discharged wastes can also cause marine pollution.
  • Toxic pesticides are dispersed through the environment by rain running off chemical-treated land and flowing into lakes, rivers, estuaries and coastal waters. Other sources of pollutants in rainwater run-off include material from numerous human-made surfaces-roads and parking lots, city streets and buildings, cars and houses. These sources of run-off pollution are called non-point sources.
  • Household cleaning and disinfecting products are flushed into sewage systems and out through treatment plant discharge, or are washed from property and septic tanks into groundwater and streams.
  • Oil drilling and transport, mining and maritime operations all result in the accidental introduction of significant amounts of toxic materials into the marine environment, as does leakage from storage tanks and pipelines, and seepage from waste dumps.

The Context

  • Naturally-occurring toxic substances occur in the environment in concentrations that arc generally not problematic to wildlife Even natural oil seeps on the ocean floor support dense mats of microbes that break the oil down. The use of these substances by humans, however, usually results in unnaturally large, localized concentrations.
  • All synthetic chemicals are of concern, because wildlife and humans are not resistant or adapted to them.
  • There are an estimated 70,000 chemicals in commerce in the US, with an additional 1,000 or so new chemicals produced each year.
  • We still do not know the effects of most of these manufactured chemicals-because, among other reasons, of the sheer number of contaminants, because of the lack of information on biological effects of complex mixtures, because different chemicals affect different species in different ways, and because the nature and extent of negative effects varies according to the magnitude, timing and duration of exposure, and the susceptibility of the organism.
  • These uncertainties have delayed or prevented regulatory action, particularly since the onus is on government and society to prove damage' rather than on the chemical producer, user or polluter to prove safety.

The Solutions

  • Although the United States has historically addressed toxic pollution through the use of environmental standards-limits on emissions and discharges, and on concentrations of toxic substances in air and water-this may only have limited results. Dischargers may simply dilute their emissions rather than reducing them; and standards for concentrations in the environment may not take into account that the sources of the pollution may be far removed and difficult to identify and regulate.
  • Consumers can play a role by being aware of manufacturing processes and "clean" alternatives to products. For example, paper can now be manufactured without using polluting bleaches and without the toxic by- product dioxins; and printing can be done with non-toxic inks.
  • International treaties can initiate stronger efforts to reduce toxic pollution worldwide. A new treaty banning the production and use of certain persistent organic pollutants is being negotiated as a result of an Intergovernmental Conference on the Prevention of Marine Pollution Caused by Activities on Land, held in Washington, D.C., in 1995.
  • However, such treaties can only address a fraction of the total contaminants being produced. Another approach is through prevention by preventing or reducing waste discharge when it has a potential for causing pollution, rather than regulating it only after it has caused pollution. In other words, a potential pollutant is considered "guilty" until proven "innocent"' this approach inspires the development of new industrial processes that do not create toxic wastes or toxic products-processes known as clean production.