By Ross Walker

I have stated on repeated occasions that I believe the major problem on the planet is over-population. Until some authoritative world body addresses this issue, I suspect that, as a species, we only have somewhere between 50-100 years left. One of the major consequences of overpopulation is the overcrowding of urban areas and large cities, purely because this is where better facilities and infrastructure are available.

Another major consequence of so many people being squeezed into a relatively small space is air pollution. In Mumbai, where there are 24 million people living in a very concentrated area, the traffic and pollution are unmanageable. When I visited, it took two hours to drive 15km and I spent more time in the car than I did in meetings.

The health effects of pollution

Over the past decade, there have been a number of disturbing reports about the health effects of air pollution. One of the major culprits appears to be the fine particles (PM 2.5). These are particles that are around 30 times smaller than human hair and are very easily inhaled. They can be absorbed into the bloodstream. There appears to be a strong link with exposure to PM 2.5 and chronic lung conditions, heart disease, cancer and now, according a recent and very disturbing report, a major factor in the generation of Alzheimer’s disease.

The study

A recent study analysed the data from the Women’s Health Initiative Memory Study, looking at 48 US states and just under 3,650 women (aged between 65 and 79) who did not have dementia at the start of the study.

All women had their cognitive function assessed on an annual basis and the results of the study were very clear and very disturbing. It appears that those women who had the highest exposure to PM 2.5 compared with those with the lowest exposure had an 81% greater risk of global cognitive decline, along with a 92% increased risk for developing not only Alzheimer’s disease, but all other forms of dementia.

When analysing all of the data, it appears that air pollution is the probable cause for around 20% of dementia cases. I have often said, it’s your genes that load the gun and your environment that pulls the trigger. In this situation, it certainly appears to be the case.

There is a particular genetic abnormality that is quite common known as ApoE4. The women who had one copy of the ApoE4 gene had a much higher risk of developing Alzheimer’s disease, especially when they were exposed to air pollution. 

Interestingly, this study was also replicated in mice comparing those with the ApoE4 gene and those mice without the gene. Both groups were exposed to the equivalent of significant air pollution and the study showed exactly the same results as the Women’s study.

It has been estimated that one in eight deaths around the world are linked now to air pollution, whereas one in four deaths in China appear to be related to this increasing and worrying scourge. Although many people are debating the concerns around air pollution, it doesn’t appear that there is much action happening to reduce this increasing, and concerning, problem. 

The answer is clear, we need to bring in fair and reasonable strategies to start reducing the world’s population. It appears from all accounts that we can sustain the planet with a population of around 4 billion, but we’re rapidly approaching the 8 billion mark. Clearly, maintaining the health of the population is not sustainable if we continue in this fashion.