Métox

The métox (abbreviation of me ic rates tox ) is an index quantifying some Pollution S poisons of the Eau X soft, brackish, salted, surface or underground. It was developed and used in particular to calculate the royalties that certain pollutants (generally industrial) must pour with the agencies of water (these taxes being used to finance the Agencies and to fight against the water pollution).

Definition

The métox is not a total indicator of Pollution, nor really description.

He considers and adds individually with the values estimated for eight major and nonbiodegradable pollutants which are: the Arsenic and seven heavy metals: mercury, Cadmium, Lead, Nickel, Copper, Chromium and Zinc.

It does not take into account the Synergie S which exist between these pollutants or these pollutants and others, nor the fact that the receiving medium is already more or less polluted and thus more or less sensitive to an additional pollution. The métox is a unit which expresses a relative level of pollution by poison durable, in effluents.

Each element quoted above is analyzed in water. It is affected of a all the more high coefficient as its long-term toxicity is important, according to the scientific data available.

The multiplying coefficients are the following:

  • mercury and cadmium are multiplied by 50,
  • arsenic and lead by 10,
  • nickel and copper by 5
  • chromium and zinc by 1.
Each coefficient was calculated starting from biological tests and on validation of experts. The métox is expressed by the average sum per unit of time (generally the day) of the mass of elements multiplied respectively by the coefficients defined above. For example a rejection of 2 g/j of mercury and 10 copper g/j gives: 2 × 50 + 10 × 5 = 150 G of métox/j

A flow of métox is expressed in equivalent living (ex: average rejection of 0,23 g/j per capita).

Limits of this way of calculating

The Métox does not integrate all the pollutants (it can seriously underestimate the toxicity of a rejection), but it allows a certain comparison of rejections different containing several from the pollutants quoted above. For the following reasons, it does not allow any true ecotoxicological interpretation of the results:
  • it does not take into account possible synergies and/or antagonisms between pollutants or pollutants and other substances.
  • it surpondère not the speciations (the chemical shape of the elements) most toxic: ex Chromium VI is much more toxic than chromium, but the same coefficient is allotted to them.
  • the métox does not differentiate either the Biodisponibilité pollutants (ex: methyl-mercury is much biodisponible than mercury, but it keeps the same value as mercury for the calculation of the métox).

See too

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