Does runoff from rolled zinc generate a risk for the environment?
Generally, emissions of zinc in rainwater that has been in contact with rolled zinc constructive systems do not generate a risk for the environment.
Zinc is naturally present in the environment and has always been used by humans for development and growth, making zinc the 3rd most important trace element after iron and magnesium for human beings.
When zinc is released into the environment, a significant quantity reacts with the other components of the environment such as oxides or organic matter (speciation), leaving a small quantity of zinc available for utilisation by living organisms (bio-availability). Generally, in the soil, over 90% of zinc released binds to soil particles and only 10% remains available for utilisation by living organisms; in water, 70% of zinc released binds to sediments (4).
The behaviour of zinc in the environment was modelled and the modelling was incorporated into the environmental risk assessment methods used at European level. In any case, for a given project, regardless of the envelope materials used, it is vital to conduct an environmental impact study if direct evacuation of rainwater into the environment is envisaged.
(4) “Atmospheric corrosion, runoff and environmental effects of zinc-based materials” I.Odnevall et Al. Workshop “Galvanizing of steel stip” Luxembourg February 27-28th, 2002
In Europe, do the levels of zinc in the environment generate a risk for humans and the environment?
No. Several years ago the European commission launched a Risk Assessment for zinc and its compounds at European level. The objective of this assessment was to identify the various sources of zinc emissions, assess the potential risks for humans and the environment and, if necessary, propose strategies to reduce emissions.
The conclusions of this Risk Assessment are that there is no regional risk for humans or the environment and that it is not necessary to reduce the use of products made from zinc or containing zinc used on the European market (fertilisers, pneumatics, paints, building products, etc.) (5).
(5) European Risk Assessment for zinc and zinc compounds – CASE n° 7440-66-6 and EINECS n° 231-175-3<:em>
Is zinc a natural element?
Yes, zinc is a natural element in the earth's crust; it is an integral part of our environment. Zinc is naturally present in rocks and soil, as well as in the air, water and the biosphere. Plants, animals and human beings contain and consume zinc.
Minerals and metals are generally obtained from the earth's crust. The average concentration of zinc in the earth's crust is 70 mg/kg (dry weight), with a range of concentrations generally varying between 10 and 300 mg/kg (Malle 1992).
In certain parts of the earth's crust, zinc is present in very high concentrations because of geological and geochemical processes (5-15% or 50,000-15,000 mg/kg). These concentrations of zinc found on the surface of or deep in the earth's crust can be subject to mining.
Is zinc an essential element?
Yes, zinc is an essential element, which means it is absolutely vital for the life of all living organisms.
For humans, zinc is the 3rd most important trace element after iron and magnesium. The OMS recommends a 15 mg daily dose of zinc for men and 12 mg for women.
For humans, zinc contributes to numerous metabolic reactions involved in:
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Growth and cell division,
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Fertility,
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The immune system,
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Taste, smell and appetite,
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Skin, hair and nail renewal,
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Eyesight,
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Etc.
What are the main parameters affecting runoff from rolled zinc?
The main parameters affecting runoff from rolled zinc are:
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Atmospheric sulphur dioxide content (the higher the sulphur dioxide content the greater the runoff).
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Atmospheric chloride content (the higher the chloride content, the greater the runoff).
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The slope of the constructive system (the greater the slope, the smaller the runoff).
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The surface aspect of the rolled zinc (natural runoff > preweathered runoff > coated runoff)
What does the term “Runoff” for a building product mean?
“Runoff” from a building product corresponds to the emission of substances from this product into rainwater that has come in contact with it.
What is the zinc concentration of rainwater having trickled off a rolled zinc roof?
The corrosion and runoff mechanisms of rolled zinc are today well known and documented. This knowledge makes it possible to assess runoff precisely according to a certain number of parameters (atmospheric sulphur dioxide concentration, slope and orientation of the constructive system, surface aspect of the rolled zinc).
Generally speaking, after 5 years of exposure and annual rainfall of between 470 and 790 mm:
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The concentration of zinc in rainwater having trickled off a rolled zinc roof is 4 mg/L (1),
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This concentration is reduced by 30 % in the case of preweathered rolled zinc such as QUARTZ-ZINC® or ANTHRA ZINC® (1).
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This concentration is reduced by 95% in the case of coated preweathered rolled zinc such as PIGMENTO® (2).
So the concentration of zinc in rainwater having trickled off a rolled zinc roof is generally lower than the drinkability threshold in zinc, set at 5 mg/L in national and international regulations (3) – where this threshold exists, because many regulations relating to the quality of water for human consumption do not set a threshold for zinc, such as the European directive.
(1) “Occurrence and fate of corrosion induced zinc in runoff water from external structures”, Sophia Bertling et al, Science of total environment n°367, February 2006.
(2) Umicore Building Products France internal report
(3) U.S. Environmental Protection Agency (EPA) - National Primary Drinking Water Regulation, French regulation ‘Decree n° 89-3 of 3 January 1989, modified (Appendix I.1) on the limits of quality of water for human consumption” and Danish Regulation