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Toxic
Pollution
- 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, leach,
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.
- 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.
- 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.
- 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.
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