We continue our series on guiding you through Environmental Indicators relevant to a Life Cycle Assessment (LCA) methodology, this time diving into factors with a direct effect on the environment & human health (find part one of our series here: Climate Change indicators).
These indicators help assess the impact from three different aspects: the reaction of sunlight with emissions from fossil fuel combustion, the retreat of oxygen in freshwater systems and the consequential suffocation of its fauna and flora, and the reduction in the pH of the ocean. Let’s take a closer look:
Photochemical Oxidation Potential (POP)
On Earth, pollution mixed with heat and sunlight creates a concentration of Ozone (O3 gaz) in the atmosphere (stratosphere + troposphere). This gaseous element, when released in the stratosphere, acts like sunscreen for all living organisms, shielding the Earth’s surface from most of the sun’s UV light (unless it creates depletion in the atmospheric layer, see here for Ozone Depletion Potential).
However, when this concentration remains at ground level in the troposphere, it affects the air that we breathe as humans and therefore starts becoming a health hazard. When inhaled, ozone reacts chemically with many biological molecules in the respiratory tract, leading to a number of adverse health effects.
We call this secondary air pollution Photochemical oxidation, also known as Summer Smog. Chemically speaking, photo-oxidant formation is a photochemical creation of reactive substances: it is formed in the atmosphere by nitrogen oxides and volatile organic compounds in the presence of sunlight, often the consequence of emissions from fossil fuel combustion. POP calculates the destructive effects of ozone in the troposphere over a time horizon of 100 years.
Eutrophication Potential (EP)
Eutrophication calculates the destructive effects of ammonia, nitrates, nitrogen oxides and phosphorus (emitted in air and waters) on freshwater systems. In inland waters, it is one of the major factors that determine the ecological quality of an aquatic environment.
This process of pollution occurs when a lake or stream becomes over-rich in plant nutrient – as a consequence, phytoplankton increases, and the water becomes overgrown in algae and other aquatic plants. The plants die and decompose, robbing the water of oxygen so that ultimately the lake, river, or stream becomes lifeless.
While eutrophication occurs naturally in freshwater systems, man-made eutrophication occurs over millions of years and is caused by organic pollutants from man’s activities, like effluents from industries and homes.
Acidification Potential (AP)
Acidification is an environmental problem caused by acidified rivers/streams and soil due to anthropogenic air pollutants such as ammonia, nitrogen oxides and sulphur dioxide. When acids are emitted, the pH factor falls and acidity increases, which for example can involve the widespread decline of coniferous forests and dead fishes in lakes in Scandinavia.
In the ocean, we define acidification as a reduction of the pH over an extended period of time, and it is caused primarily by an uptake of carbon dioxide (CO2) from the atmosphere: the ocean absorbs the extra amount of CO2 emitted in our atmosphere. We are already observing this change in the deep ocean, especially at high latitudes.
It affects marine organisms, with a consequence on the ecosystems they belong to in and above water: disrupting the food chain (increase of the mobilisation and the leaching behaviour of heavy metals in soil), altered prey availability (for example, krill for whales), impact on habitats (lower pH destroys coral reefs), but also the amplification of noise pollution by a modification of the underwater acoustics.
As an indicator, Acidification Potential calculates the impact of the potential change in acidity in the soil due to the atmospheric deposition of sulfates, nitrates, phosphates, and other compounds.
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