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Polluting or toxic chemicals may be released from several sources :
- industrial wastes (e.g.: chemical industry)
- transportation (e.g.: oil tankers)
-agriculture ( fertilizers, herbicides, pesticides)
-consumption (e.g.: paints, PVC bottles)
-civil waste (e.g.: detergents)
Of course, the problem has to be
approached at several levels ( local, national, supernational) :
A primary requirement is to know and list the polluting sources: in some countries (USA, Canada, Australia, UK, Japan) have been carried out and published Pollutant or Toxic Release Inventories, that can provide real gains towards reducing pollution and protecting the environment.
Exporting dangerous wastes (Basel Convention)
Exporting dangerous wastes in developing countries has been common practice in the recent past : developed countries used to solve the industrial wastes problem comfortably and at low cost.
The countries receiving the wastes were often unprepared to a safe treatment, with clear increase of the environmental risks.
The Basel Convention has forbidden transportation of any dangerous waste from developed countries (members of OECD) to developing countries (not members of OECD). The ban (named Basel Ban) is effective from December 31, 1997.
According to the environmentalists, these decision will accelerate the reduction of toxic wastes, leading to the development of industrial products and processes more environmental friendly, or encouraging recycling.
Lists of dangerous chemicals.
Some toxic chemicals are resistant to degradation and, due to their environmental persistence, may move long distance and concentrate very far from the emission sites, or, being fat-soluble, bio-accumulate in the tissues of humans or animals (at the top of food chain).
The most common among these substances, DDT and PCB (Poly Chlorinated Biphenyls), are widely contaminating the Oceans: they have been found in whales and other marine mammals.
PCBs persist in the environment for years and may bio-accumulate up to 70,000 times.
It is reasonable to believe that many other POPs, Persistent Organic Pollutants, contaminate the Oceans.
An initial list of POPs to be banned has been agreed under the auspices of UNEP ( United Nations Environment Protection); 12 toxic chemicals (or better, chemical families) are included, primarily first generation chlorinated pesticides (dieldrin, DDT, toxaphene, chlordane), and industrial chemicals (PCBs):
These 12 POPs have been recently banned by the Stockholm Convention (May 2001), with a partial exemption for DDT (necessary for malaria control in some countries)
On a regional base, other initiatives have been taken : among them, it is specially relevant the OSPAR commission, for the marine environment of the North East Atlantic, active from March 22, 1998 : as first step towards total elimination of the emission of dangerous substances into the marine environment, a list of 15 chemicals to be prioritized has been defined: among these, the polyaromatic hydrocarbons ( PAHs ), the short chained chlorinated paraffins, mercury ond organomercury compounds, cadmium, lead and organolead compounds, organotin compounds (including TBT -tributiltin-, used in naval paints), and some phtalates (dibutylphthalate, di-etyl-hexyl-phthalate).
Many other chemicals (including the ones listed by UNEP) are presently under examination by OSPAR.
The "precautionary principle".
Often there is little scientific evidence of widespread ill health or ecosystem damage caused by manufactured chemicals, apart from special cases (ozone layer depletion, and acute impacts, such as from accidents or local spillages).
"No evidence" does not necessarily mean "no effects": damages due to toxic chemicals may be evident, often in an irreversible way, after long exposure time at low dosage.
A particularly famous case is the Minamata disease, in Japan, due to a diet rich in fish coming from water polluted by industrial wastes containing mercury.
As a consequence, it is now introduced,
in many international agreements, the "precautionary