12 Estimating the Environmental Impact of Products: Life Cycle Assessment
All this favours monocultures and determines a loss of the plants that usually grow in poorer soil. In water it appears as excessive growth of algae and loss of aquatic fauna together with the contamination of water bodies that cannot be used any longer as a water supply (lakes) or for swimming (lakes and ocean). Eutrophication is caused by agricultural processes that involve phosphate and nitrate fertilisers. Thus, the consumption of intensively cultivated food products, as well as use of gardening fertilisers (phosphates and nitrates) also plays an indirect role. Also, drainage and sewage water and industrial waste (nitrates and phosphates) are important carriers of eutrophicating agents. This why it is hard to find on the market detergents that contain phosphates; in fact, this is one of the few cases, where the environmentalist lobby has managed to break through on an industrial level. Finally, the part street traffic plays in causing eutrophication (exhaust gases emitted by cars SO2, NOx).
12.1.7 Toxic Air, Soil and Water Pollution Many substances are hazardous to humans and ecosystems alike. The effects can be straight-forwardly lethal or appear after long years of exposure. There are, in fact, persistent toxic substances (non-degradable) that will create an effect after long-term accumulation. Sometimes, the carcinogenic or mutagenic effects are also hereditary. The food chain can cause the accumulation of toxic agents in tissues and thus return to humans the substances they discarded into nature. Persistent toxic agents can first accumulate in water3 or soil. Among those we can list heavy metals (mercury, lead, arsenic, cadmium, hexavalent chromium, nickel, selenium, zinc), chlorinated pesticides (DDT), chemical substances as polychlorobiphenyl (PCB) and polychlorotriphenyl (PCT), and of course oil and exhaust gases. The phenomenon of the percolation of toxic substances that are not properly impermeable in landfill sites, discharging into the water bodies industrial and urban waste water containing toxic metals (mercury, lead, arsenic, cadmium, hexavalent chromium, nickel, selenium, zinc), oil and its derivatives, exhausted oils, and radioactive and chemical waste. Via the so-called food chain all the toxic substances discarded into the environment can return and accumulate in the tissues. The lead for example can be acquired via polluted food (or directly via inhalation) and would cause poisoning (saturnism: irreversible neurological damage); similarly, the derivatives of mer3
Typical indexes of pollution degree are the Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). BOD is a parameter for estimating the biodegradable organic pollution of lakes and water basins; it is equal to the amount of oxygen necessary for decomposing biodegradable pollutants, usually organic substances coming from waste. COD measures the pollutant load in a flow that might extract oxygen from the water.
Published on Nov 17, 2010
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