Thursday 9 January 2020

Atmospheric Pollution and Vitamin D – bad air & ultra-fine particles

Bad Air – Miasma 

During the nineteenth century the population of London, like the populations of many European cities, suffered from several epidemics of cholera. The cause of these epidemics was put down to “Miasma”, that is “bad air”. Miasma was the current paradigm in Europe, in that it was the explanation and assumed cause of all sorts of diseases including epidemics. The air was certainly bad, with a “stench” as well as smoke. The physicians of the day were impotent; they could hardly be expected to clean the air. There was no provision for the population at risk to be moved to a location of clean air. 
19th century representation of Miasma

There was no possibility of reducing or prohibiting the burning of coal, but it was the smell of the air ("the great stink") that was considered to be the main factor of miasma. Sir Edwin Chadwick, the first public health physician in England, took action by organising the construction of drains to take the foul-smelling waste into the River Thames and thus rid the populated parts of the city of “miasma”. Unfortunately the drains entered the Thames above the water intake.

Dr John Snow and the Broad Street pump

During the 1854 epidemic of cholera in London a thoughtful young physician Dr John Snow, unlike Sir Edwin Chadwick, was not content with the miasma paradigm. The paradigm was the result of the philosophical approach to medicine – thinking about the problems. Snow had a scientific approach – research. 

Dr John Snow, 1813–1858
His data collection identified the geography of the epidemic, its epidemiology. The cluster of cases of cholera pointed to a specific water pump, the one situated in Broad Street. His advice to stop using the pump went unheeded: everyone (including all other physicians) accepted that the disease was due to miasma, and of course the people wanted water from a convenient pump close to home. The story goes that Snow removed the handle of the Broad Street pump, thus making it unusable. Following this the epidemic came to an end.

Paradigm change

The miasma paradigm came to an end in the latter years of the 19th century but only because there was a new paradigm to take its place: transmission of disease, and specifically cholera, is due to water-borne micro-organisms.

The germ theory opened a new era of medical research, the new science of microbiology. Many new bacteria were to be identified and classified, and linked to a large number of human and animal diseases. Viral and fungal diseases were identified later. By the 1960s when I was a medical student it might have been thought that all of microbiology was known, but this was very far from reality.

Bad air again

The miasma concept did not completely disappear and it is now being revived. During the latter half of the 19th century and the first half of the 20th century “bad air” was a very serious problem in Europe. Whereas clean water was the priority in the 1880s, clean air became the priority in the 1950s. 

A major effect of air pollution by smoke was and still is the inhalation effect causing chronic lung disease, chronic bronchitis, later called chronic obstructive pulmonary (lung) disease (COPD). It was because of the large number of deaths from what was then called chronic bronchitis that the UK Government introduced the Clean Air Act in 1956, and it turned out to be the very effective

Sunlight and immunity

During the 19th and early 20th centuries, the other major health effect of air pollution was recognised as being a reduction of sunlight penetration to ground level, resulting in vitamin D deficiency and rickets. The knowledge of this seems to have been lost in recent years.

Robert Koch had demonstrated tuberculosis (called consumption, phthisis, or even Koch’s Disease) to be caused by a bacterium – Mycobacterium tuberculosis, or Koch’s bacillus. However here we find an interaction between bacterial infection and the susceptibility of individual people. 

Towards the end of the 20th century it became obvious that reduced immune competence (as in AIDS) makes tuberculosis more likely to occur, and this is also an effect of vitamin D deficiency. Blockage of sunlight by polluted air (or by staying indoors) has serious effects on immunity, and an increased risk of tuberculosis is just one of them. 

It had been demonstrated by Niels Fyberg Finsen in 1905 that tuberculosis of the skin (lupus vulgaris) could be healed by exposure to UV light.

Bad air today

I remember that when I was a young boy in Manchester, UK, it was possible in the winter months to look directly at the sun, which was often just a pale disk in the sky. 

Taj Mahal in polluted air

This is now a feature in the newly industrialising countries, particularly China and India. On a "cloudless" day in many cities such as Beijing and other industrial cities of China it is not possible to see the sun due to the high level of pollution, and things are similar in Delhi and other Indian cities. In fact most heavily polluted atmospheres are in Indian cities. The health consequences of this are yet to emerge, but vitamin D deficiency can be predicted.

This is no longer the case in the UK and other European cities today and the air quality is very much improved compared to what it was in the 1950s. The carbon particles are now different. The pollution today is with ultra-fine particles and these cannot be seen. They do not seem to block the sun and the air appears to be clean.

London 2018

In London and other European cities in the mid-20th century, the main pollutant was the industrial and domestic burning of coal. Coal had a high content of sulphur, and major pollutants were sulphur dioxide and sulphurous acid, both very toxic to the lungs.

Motor car fuels, with petrol and diesel, have also been responsible for the release of toxic sulphur gases into the atmosphere, mainly in the cities. However legislation has resulted in the the purification of fuels for road vehicles to virtually eliminate the sulphur content. 

Decline of sulphur content of road traffic fuel in UK since legislation

January 1st 2020 will see the introduction of rules by the International Maritime Organisation to allow shipping to use only low sulphur fuels.

"Toxic air" – Ultra-fine particles

In the EU the air has become much cleaner since the mid-20th century, but despite this obvious change we are told that our air is "toxic" and is causing enormous damage to us in a large number of ways. Ultra-fine particles apparently pass through the bronchial tree and into the depths of the lungs, then entering the body. However undesirable this might be, it cannot be assumed that they are causing disease. The fact is that in the UK and the EU in general, life expectancy continues to rise. We are healthier than ever before.

PM – Particle Matter
Ultra-fine particles cannot be seen with the naked eye but they can be measured in a laboratory. A detailed summary was produced by a UK government working group in 2018. Ultra-fine particles have a diameter less than 100 nanometers, or <0.1 microns. With the improvement of fuel quality and combustion processes there has been a significant reduction during the early years of the 21st century and a further reduction is anticipated, especially if there is a major reduction in the use of carboniferous fuels.

Decline of ultra fine particles

I am not proposing that we should be complacent. There is a serious problem of too many cars on our roads, but like everyone else I want to keep mine! It will be many years before we change to electric vehicles and domestic heating by electricity. Even though more than half of electricity generated in the UK in 2019 was from non-carbon sources, the source of additional generation of electricity in the future remains uncertain. 

Microplastic pollution 

There is also concern about plastics. The effect of large plastic waste products on sea life is obvious and very tragic. However there is also a problem with microplastic pollution. It has been observed that these are present in the seas and in sea life, but recent studies have detected microplastic particles in the air. They are present in many cities with London having the highest recorded levels. 

Once again it is not clear whether they are toxic or inert, and whether or not they have a detrimental effect on human health. A study in 1998 demonstrated microplastics in cancerous human tissue, but a causative role cannot be assumed. Apparently we consume about 50,000 microplastic particles per year. They decompose extremely slowly, and if they are toxic the effects will be with us for a long time.

Disease attributed to air pollution

I cannot help thinking of the miasmic theory when I read assertions that present-day diseases "are the result of" atmospheric pollution. I find it perfectly reasonable to accept that 41% of global deaths from chronic obstructive pulmonary disease (COPD) are the result of the inhalation of toxic air pollution. However to state that 20% of Type 2 Diabetes deaths are the result of air pollution stretches credibility. 

Similarly it is stated that 19% of deaths from lung cancer are due to air pollution. We know that most lung cancer has been caused by cigarette smoking, but atmospheric pollution has not been an accepted cause. At present, at least in the UK, there seems to be a significant epidemic of lung cancer in "never-smokers", and 80% of cases are in women. This is a great worry but there has been no good evidence that it is the result of atmospheric pollution. The possible role of microplastics requires further evaluation.

To state that 16% of deaths from coronary heart disease (CHD) are the result of atmospheric pollution is very suspect. Which 16% ?Are these deaths in countries that experience a high level of air pollution? Is there really a link? The reality is that deaths from coronary heart disease have shown a major epidemic of the latter half of the 20th century, and the epidemic is now effectively at an end. To link atmospheric pollution to the major decline in coronary heart disease deaths at the present time would not be realistic. I have expressed my conclusion that coronary heart disease must be due to micro-organisms.

On November 18th 2019 we read in the UK press that: "Air pollution from homes, industry and cars kills five people a week in Bristol", and  up to 36,000 per year in the UK. Who are these people? What was the precise cause of death, remembering of course that "air pollution" is not a recognised cause of death. This is poor quality research that adds very little but as a scare story, it creates headlines. Once again there is the proposal that air pollution contributes to asthma, lung cancer, heart disease, stroke and diabetes. Of these only a link to asthma has plausibility. The others are purely speculation without any direct plausible mechanism.

Earlier in the year a delightful 9 year-old girl in Lewisham, south London, died as a result of asthma. It was claimed by her mother that the cause of death was air pollution, and this has received a great deal of attention by the national press. Air pollution is not a recognised cause of death, and the reality is that the child died in a severe attack of asthma. She had experienced 24 admissions to hospital on account of asthma during the previous 3 years. I can understand the concern of the mother as the family lived 25 metres from the notoriously busy South Circular Road. Asthma is not due to air pollution, but inhalation of smoke and other chemicals can precipitate a severe attack. It would not have been possible stop traffic movement outside the house, but perhaps there could have been assistance to the family moving into a rural environment.

On Thursday November 28th 2019, the national press reported that the "Impact of air pollution on health may be far worse than thought.... almost every cell in the body may be affected by dirty air". It suggested that atmospheric pollution might have a causative role in heart failure, urinary tract infections, strokes, brain cancer, miscarriage, and mental health problems

This newsfeed is based on a recent British Medical Journal paper, which draws on USA Medicare data concerning hospital admissions and discharges. There is no reason to suspect that the findings cannot be applied to other countries. 

At the same time we learned that 90% of the world's population are exposed to air pollution above the WHO recommended upper limit.  We are told that air pollution increases the risk of glaucoma, a condition in which the pressure inside the eye increases and this can lead to loss of vision if not treated.

A press release on December 19th 2019 informs us that depression and suicide are linked to air pollution, and that "cutting the air pollution around the world to the EU's legal limit could prevent millions of people becoming depressed." It was pointed out that intermediary mechanisms are unknown, and thus only conjectural.

City life

Life is much more pleasant in a rural environment: the contrasting health between the citizens of Manchester and Salford, UK, and those of surrounding villages was first investigated and publicised almost 300 years ago, as I described in an earlier Post. As it was then, so it is now and employment tends to be concentrated in growing cities and not in the countryside. For those in employment, rural living usually means a long commute, mainly by car.

Stalybridge, Manchester in 1950

Stalybridge, Manchester in 2018

There is clearly a health advantage to rural rather than inner city living but the health issues and reasons for this are complex. Can the visible air pollution in major cities in India and China be equated to the invisible ultra-fine particle pollution in London and other similar cities in Europe and North America?

Is the air in London "toxic" or are there other reasons for health disadvantages? The wide range of illnesses associated with air pollution suggests common susceptibility rather than true cause.

If it the result of atmospheric pollution, could the susceptibility be the result of reduction of sunlight penetration to ground level?  This will certainly be the case very in the major cities of India and China in which there is very obvious visible air pollution. 

It is strange that in the many recent articles that I have read on the subject of the  detrimental health effects of air pollution, I have not seen any mention of the interference of penetration of sunlight to ground level. It is as though there is a conspiracy to ignore the obvious great importance of the sun to human health and the role of the sun and vitamin D in maintaining good immunity and good health.

The importance of the sun.

We know that the sun has at least four metabolic effects on our bodies, three of which will have a protective effect on the cardiovascular system. They are as follows.
  • Vitamin D is synthesised in the skin from 7-dehydrocholesterol  by the action of the sun. Vitamin D in its twice-activated form calcitriol activates (via the intracellular vitamin D receptor) specific genes that are involved in turn in activating immune defensive processes. Immunity is very important in the control of infection and in the prevention of CHD.
  • It has become clear that there is a cardiovascular benefit from sunlight acting on the skin that is independent of vitamin D synthesis. The action of the sun on the skin synthesises nitric oxide from nitrates circulating in the blood and passing through the skin. The role of nitric oxide is not completely understood but it appears to have a significant role in control of arterial health and blood pressure.
  • It also appears that skin cells (keratinocytes) are activated by sunlight to in turn activate immune mechanisms within the body. Once again this will be of benefit in CHD.
  • Finally, the sun, acting through the eyes  stimulates the pineal gland within the brain to secrete melatonin. This is of importance to brain activity but it does not at present appear to be of direct cardiovascular benefit.

Intermediary mechanisms

However I emphasise the point that understanding the link between air pollution and disease is essential, as without it we have no plausibility. We have great experience of the effects of air pollution in the UK in the 19th and 20th centuries, and the benefits of pollution controls. The major problem was obstruction to sunlight with vitamin D deficiency: this will indeed affect "almost every cell in the body".

The insistence that bad air causes so much premature death without  any clear intervening mechanism effectively brings us back to the miasma theory, which was replaced by the germ theory more than a century ago. But the germ theory is being ignored by those who are understandably concerned about the effects of air pollution. This is at the time of a huge expansion of the germ theory. The identification of the immune-enhancing effects of the sun would bring together air pollution and the germ theory.

New analytical techniques have demonstrated many more varieties of micro-organisms that are part of the human microbiome. Many have be linked to a variety of human diseases, most chronic, but “proof” will be very difficult in the absence of transmission studies and long-term follow-up. 

However it is looking as though a large number of human diseases are the result of changes to our microbiome. This must be linked to immune mechanisms, and acknowledge the importance of air pollution and the importance of sun exposure.

Sunset – Conwy Estuary, North Wales


  1. Thank you Dr. Grimes for this insightful synopsis. The other limb of this, if I may comment, is the potential effects of the "pristine environment" on health. I believe one Japanese groups has demonstrated that exposure to the forest environment, enhances the immune system; which in turn could have a positive effects on say CHD. Suggestive studies; more trials studies are indicated.

    As always, always a delight to read your blogs.

    Have a wonderful day.


  2. I too enjoy reading your blogs. Always insightful. I have just listened to an excellent podcast by Dr Ben Bikman who was discussing the effects of pollution (traffic) on health. It compliments all that you have said about the effects of modern day pollution.