Effects

Effects on health
Pollutants can have an effect on the human body at different levels :

• skin - this particularly applies to irritant vapours and allergies,
• mucous membranes,
• alveoli of the lungs. Pollutants dissolve and pass into the blood or the superficial liquids,
• organs - certain toxins transported by blood may accumulate in the body organs.

The time it takes for pollutants to have an effect :

• immediate effects, such as those observed after historic incidents,
• short-term effects,
• long-term effects, found after chronic exposure to concentrations which may be very low.

The limit values for the concentrations of certain pollutants (SO₂, particles, NO₂, Pb, O₃) in the air, laid down by EU Directives, take these effects into account. The World Health Organisation (WHO) establishes rules to be followed for the various pollutants.

Particles : the finer the particles, the deeper they penetrate into the respiratory system and the longer they stay there. They have a double effect - caused by the particles themselves and the pollutants that they carry (metals, hydrocarbons, sulphur dioxide, etc.). They irritate the human respiratory system and can contribute to causing acute respiratory diseases.

SO₂ : SO₂ leads to inflammation of the bronchi with spasms that cause a deterioration in the respiratory functions.

NO-NO₂ : NO₂ is toxic (40 times more than CO, 4 times more than NO). NO₂ penetrates deeply into the lungs. Peak levels are more damaging than the same dose over a long period. NO is a gas that irritates the bronchi and reduces the oxygenating power of the blood.

VOCs : certain organic compounds, such as aromatics and alkenes, cause irritation of the eyes. Aldehydes strongly irritate mucous membranes. Certain VOCs, such as benzene, are carcinogenic.

CO : CO fixes on the haemoglobin in the blood. The phenomenon is irreversible. Many people have been killed by inhaling CO from ill-functioning gas heaters.

OZONE : Ozone is a powerful oxidant. It irritates the eyes, throat and bronchial tubes. Its effects are exacerbated by physical exercise.

Effects on materials
Basically, materials are affected by acid pollution which erodes buildings and monuments. Atmospheric pollution threatens our cultural heritage and requires expensive work to be carried out to clean buildings and restore monuments.

Effects on forest ecosystems
Trees are alive, and they die from many varied natural causes including old age. But the sudden decline observed since 1980 seems to come from quite exceptional causes. Experts consider that atmospheric pollution is one of many elements contributing to the decline in woodland areas. In France, the DEFORPA programme (decline in forests related to pollution of the atmosphere) and also laboratory research have shown that the causes of declining woodlands are very complex. They include poor soil quality, abnormal drought, and the presence of pollutants in the atmosphere (principally acid pollution and ozone).

Effects on fresh water ecosystems
The acidification of lakes and watercourses sometimes leads to irreversible destruction of pond-life. The lowering of the pH level causes leaching out of naturally-occurring metals from the soil, such as aluminium which, in its dissolved form, is toxic to almost all living organisms.