Air pollution and neurological diseases


In close collaboration with a group of experts, Generali, an official partner with COP21, stresses the links between climate and health throughout the summit

“In its capacity as an insurance company, Generali has a wide-ranging concern with climate change (cyclones, storms, precipitation, droughts and heat waves, etc.) and its impacts both on us and our clients and in the way in which these new risks have to be taken into account. The harms will continue to grow and the impacts on health will be significant. We nevertheless have powerful levers at our disposal for supporting attenuation and adaptation policies regarding climate change, both in terms of orienting our asset management policies and encouraging more responsible behaviour by our customers. That is the reason for our commitment as an official partner to COP21” explains Hélène N’Diaye, Technical Risks Director, Generali, France.

By Jean-Baptiste Renard, Research Director at the CNRS (National Centre for Scientific Research)

Pollution occurs when gases such as ozone and nitrogen oxide and fine particles are released into the air.
These particles may be produced directly by industrial activity and traffic, but are also formed as a result of polluting gases. Amongst all of these particles, the most dangerous to health are carbon particles, whose dimensions range from a few nanometres to a few micrometres. In addition to the pollution, these particles also play a role in climate change.

Reducing industrial waste, and therefore CO2 emissions, should enable a reduction in concentrations of fine particles in the air. But in fact it is also possible to reduce CO2 emissions when burning hydrocarbons by increasing the rate of fine particles emitted.
It is therefore essential to combine research on pollution with research into climate, and to develop new monitoring systems for measuring concentration of fine carbon particles in the atmosphere.

Some key data: Fine particle pollution in Paris in 2015 has exceeded the information threshold (50 micrograms per m³) on about ten days so far. In Peking, the average value is over 100 micrograms per m³ with peaks at 1 milligram per m³!

3 Questions to Pr. Boller, Professor of Neurology at the George Washington University Medical School in Washington DC

What are the effects of this air pollution on diseases of the central nervous system and neuropathological diseases?
We can see that there is growing evidence pointing to the role played in such diseases by air pollutants. Dementia (Alzheimer’s, vascular diseases, etc.) and deterioration in cognitive functions in the elderly, representing a cost to society which is certainly not negligible, may be correlation with such pollutants.  
Two recent scientific research studies highlight this correlation.

What do these research studies show?
The first, carried out in Umeå in Sweden by Anna Oudin et al. shows an undeniable correlation between exposure to air pollution and frequency of dementia.
The research study was based on a health profile (blood samples, blood pressure, sensory assessments etc.) and on a cognitive assessment of the participants (wide range of cognitive processes and memory systems) followed over a period of 15 years.
Result: 302 of the 1,806 participants were diagnosed as suffering from Alzheimer’s or vascular disease.
It is clear that the proportion of patients [suffering from these diseases] increases proportionately to concentrations of nitrogen oxide, one of the main air pollutants, in the air.

The second, carried out in the in the USA by Melinda C. Power et al., analysed the impact of concentrations of black carbon (linked to traffic, as with fine particles) on cognitive functions. The research was based on analysis of 680 men who came regularly, over a period of 11 years, for a battery of 7 cognitive tests assessing a variety of cognitive areas: attention, memory, executive functions, language, visual-motor abilities, etc.
Result: exposure to black carbon is associated significantly with the risk of weak scores in cognitive tests.


How can this phenomenon be explained?
Two biological mechanisms can explain the harmful effects of air pollution linked to traffic on cognitive functions:

  • Fine particles are so small that they can cross the blood-brain barrier and are able to cause translocation in the brain, leading to inflammation of the neurones and oxidative stress.
  • Fine particles linked to traffic also exert indirect effects on cognitive functions via effects on cardio-vascular health (for they increase the risks of cardio-vascular diseases).