Environmental pollution is the introduction of foreign and potentially

harmful elements into the environment. The consequences are particularly

important when they damage ecosystems and human societies, especially
with regard to health.

Pollution is not a human prerogative: volcanoes, for example, also emit

pollutants. It is, however, certain that our species is contributing massively
to environmental pollution, and this has increased over the past centuries.

Types of pollution
There are different types of pollution.

 The first to be studied were those in which pollutants had physical

elements: air pollution, water pollution and land pollution.

 Later, by analogy, definitions were provided

for noise pollution, light pollution, thermal pollution,
and electromagnetic pollution: in these cases, no material
substances are introduced into the environment, but intangible
agents – such as electromagnetic waves (including light) or sound –
are.

Often the different types of pollution interact with each other: for example,
some pollutants in the atmosphere fall back to earth in the form of acid rain,
thereby contaminating soils and oceans.

Air pollution
Air pollution is the most prominent case. The most visible phenomenon
is smog (a portmanteau word, a combination of “smoke” and “fog”), formed
by gases such as nitrogen oxides and sulfur dioxide.

Even when it cannot be seen, however, pollution is both present and

harmful. In the long run, the most dangerous pollutants are the greenhouse
gases (mainly carbon dioxide), which are responsible for climate change.
The air in our cities is also polluted by other gases (such as carbon
monoxide) and atmospheric particulate matter (i.e., fine particulate matter),
which can be classified into PM10 (particles smaller than 10 microns in size)
and PM2,5 (smaller than 2.5 microns).

Finally, the air is often polluted inside homes as well, due to cigarette
smoke, insecticide sprays, and especially, in many countries, kitchens with
ovens fueled by coal or other highly polluting fuels.

Water Pollution
Water pollution now affects virtually all the world's seas, oceans, lakes and
rivers. In the sea, the most egregious cases are oil spills from shipping
disasters, but the problem of pollution from plastics and particularly
microplastics is becoming increasingly urgent.

Fresh water accounts for only 2.5% of all water on Earth – it is the most
precious resource for human life. Very often, however, running water is
contaminated with chemicals, particularly those known as PFAS
(Perfluorinated and Polyfluorinated Alkyl Substances).

Soil Pollution
Pollution, along with erosion, is now the main threat to soil on our planet,
and it has now reached every corner of the world: it has even been found in
the most uninhabited areas, such as Antarctica.

Soil pollution is caused both by macroscopic objects such as waste left by

humans and by substances that are present in the form
of microscopic and therefore invisible particles.

Electromagnetic pollution
Electromagnetic fields are often of natural origin: for example, the Earth's
magnetic field, or the electric field generated by lightning. Today, however,
we speak of electromagnetic pollution when the causes are human: even if
they do not contaminate the environment with harmful substances, they still
alter the natural conditions on the planet.
This is the case, for example,
with broadcasting and telecommunications equipment (including cell
phones), which are in fact designed to emit electromagnetic waves.

Light Pollution
Since light is transmitted as electromagnetic waves, a special case of
electromagnetic pollution comes in the form of light pollution. Artificial
lighting systems often emit excessive brightness into the environment due
to inefficient lamp design, so light is not concentrated downward, on
streets or where it is most useful, but is scattered in all directions.

In addition to depriving urban dwellers of stargazing, light pollution makes

astronomical observations problematic and, above all, it interferes with the
life cycles of many animals.

Noise Pollution
Like light pollution, noise pollution is also caused by human activities that
do not emit material substances into the environment but waves, in this
case sound.

This mostly affects city dwellers (e.g., in nightlife districts) but also, in
general, anyone living in areas with a high density of road, rail or aviation
traffic, as well as in industrial areas. And, as is the case with light
pollution, noise pollution also creates more or less severe disturbances for
many animal species.

Thermal Pollution
Last but not least, thermal pollution occurs when human activities affect the
environmental temperature. The effect is direct when heat is emitted: for
example, water poured by many industries into waterways. It isn’t
necessarily polluted but is at a high temperature.

Heat pollution is indirect when the increase in heat is a consequence of

other activities: e.g., deforestation, which reduces the cooling effect of
vegetation, or overbuilding, so much so that we speak of an "urban heat
island" in cities, where the temperature is significantly higher than in
surrounding areas. In the long run, the most worrisome indirect
consequence is climate change triggered by greenhouse gases.

The main causes of pollution

Virtually every human activity produces some form of pollution.

 The oldest economic activity, agriculture, today makes extensive

use of substances such as pesticides and fertilizers, which are
among the main contributors to soil and water pollution.

 Industries, and especially large factories, are a major source of air

pollution due to gaseous emissions, but also, with their solid and
liquid wastes, soil and water pollution. Furthermore, they are among
the main contributors to noise and thermal pollution.

 The energy sector has historically relied on fossil fuels, which are
among the main contributors to climate change. Today the
contribution of renewable sources is increasing, but in many
countries, such as China, the use of coal, the most polluting fuel, is
still predominant.

 Another significant contributor to the greenhouse effect comes

from transportation, but it also emits other polluting gases, such as
carbon monoxide produced by vehicular traffic. Moreover,
transportation is one of the leading causes of noise pollution.

 Waste – industrial waste but also waste produced by individuals –

has a major impact on the environment, especially if it isn’t managed
properly. At a local level, landfills are a major source of soil pollution,
while on a larger scale so is waste (such as plastic) that reaches the
sea via waterways.

The effects of environmental pollution

Environmental pollution has a harmful effect on human health.
According to World Health Organization (WHO) estimates, air pollution is
responsible for 7 million premature deaths a year due to respiratory,
cardiovascular, and immune system ailments. The damage caused by
polluted indoor air must also be taken into consideration.

Water pollution is so widespread that nearly two billion people, or a quarter

of the world's population, drink contaminated water on a daily basis.

Furthermore, pollutants such as waste from the pharmaceutical and

cosmetics industries, when dispersed into the environment, cause an
increase in bacterial resistance to antibiotics.

Climate change also means an increase in extreme events such

as cyclones, floods and drought.

On a planetary scale, the most lasting effects of environmental pollution are

on biodiversity, so much so that there is talk of a new mass extinction that
is already underway. The main causes, alongside intensive hunting and
fishing, include climate change, but all other forms of pollution, from soil
pollution to plastic contamination in the oceans, as well as thermal, noise
and light pollution, also contribute to a lesser extent.