Polluted air and our immune system in winter… Dr. Tsvetelina Velikova in front of FACTI

What happens to our immune system in winter, how does the air affect us after people start using domestic heating… Immunologist Dr. Tsvetelina Velikova speaks in front of FACTI.

- Dr. Velikova, we are on the verge of winter and people are starting to heat themselves with wood. Air pollution and the immune system - is there a direct relationship?
- Yes, domestic heating, together with the increased use of personal cars for transportation, contribute to greater air pollution during the cold months. In recent years, we have very convincing evidence that pollutants in the air - especially fine dust particles PM2.5 and PM10 - directly alter the functioning of the immune system. When the air is polluted, inhaled particles reach deep into the alveoli and nearby lymph nodes, causing oxidative stress, chronic inflammation and disrupting immune regulation.

This leads to reduced antimicrobial protection, which children and adults can experience as more frequent respiratory infections, but we also observe more allergies and exacerbation of chronic diseases.

The good news is that people are increasingly becoming interested in the impact of polluted air on their health and are linking their complaints such as eye and throat irritation, headaches, malaise and others to periods of more polluted air. This was also shown by our surveys conducted in cities traditionally suffering from polluted air, together with the Medical Network “Air for Health“ and environmental associations “Breathe, Ruse“ and Breathe, Dimitrovgrad“. However, there is still little talk about the impact of polluted air on the immune system.

- How do fine dust particles, nitrogen and sulfur oxides affect us… Basically everything we breathe…
- Each air pollutant has its own mechanism of damage. For example, fine dust particles with a size of up to 2.5 microns and 10 microns reach the alveoli in the lung, activate immune cells, disrupt the balance between protective and inflammatory mechanisms.

Something more – It turns out that these pollutants can pass through the bloodstream to distant areas of our body and thus lead to systemic effects.

These pollutants are at increased risk of developing and exacerbating pre-existing asthma, chronic obstructive pulmonary disease and autoimmune diseases. But also due to immune suppression, fine dust particles are associated with increased susceptibility to infections.

Gases such as NO₂, SO₂, CO irritate the respiratory system, increase oxidative stress and stimulate the release of pro-inflammatory cytokines, which leads to impaired immune system functions and chronic inflammation.

The polycyclic aromatic hydrocarbons and heavy metals in polluted air have toxic, mutagenic and immunosuppressive effects. The combination of all these substances makes the air an active “stressor“ on the immune system.

- Polluted air, unhealthy food, bad habits – what do we subject the immune system to in today's times…
- It's true – we only think about having an immune system when its work is hampered. In addition to polluted air, lack of sleep, taking certain medications, diseases such as diabetes, respiratory, kidney and others, malnutrition (heavy diets, etc.), smoking, alcohol, lack of exercise and unhealthy eating have a negative impact.

- We are also entering the flu season, like every year. But what have we learned about the immune system after COVID. What a test of humanity's immunity was the coronavirus…
- COVID-19 has shown us that the immune system can react either too weakly or too strongly, which depends on both the type of virus and the genetic terrain of the given person. We often underestimate the importance of good barrier function of mucous membranes as protection against infections. COVID-19 still exists, and in addition to prevention through vaccines, it is important to know the long-term consequences of the infection, incl. post-covid and autoimmune conditions.

The pandemic has highlighted the need for prevention, vaccines, care for the chronically ill, and responsibility for one's own health.

These are the lessons we need to take with us, as well as those we can use to be prepared for future epidemics and pandemics.

- Why does vitamin D deficiency occur in people in cities with high levels of pollution?
- A completely true observation. This happens for two main reasons: dirty air blocks the UV rays needed for the synthesis of vitamin D in the skin, and people in big cities spend less time outdoors, which further reduces the production of vitamin D. On the other hand, patients with vitamin D deficiency suffer more often from infections and are more likely to have autoimmune diseases. We still do not have prospective studies on whether vitamin D supplementation can protect against the harmful effects of polluted air on the immune system.

- How much can we afford to strain our immune system in an urban environment and how does stress and fatigue affect it?
- The immune system has a large capacity, but it is not infinite. Chronic stress and lack of rest lead to suppression of lymphocytes, impaired antibody production, slower reactions of innate immunity, chronic inflammation. Thus, in an urban environment, the strain is higher due to the combination of pollution, stress, noise and lack of quality sleep. What we can do for our own health and that of our children is to influence these factors, as much as possible - to eat healthily, get enough sleep, have sufficient physical activity, spend more time outdoors in nature, etc.

- You often mention that we need regular prophylaxis of the immune system. Why?
- Prevention is important because immunity is affected daily by the environment we inhabit. Prevention has three goals:
-- to maintain low levels of inflammation or no chronic inflammation at all;
-- to strengthen the body's barrier functions;
-- to prevent damage caused by pollutants.
It is especially important in children, the elderly and the chronically ill, who are most vulnerable.

- How is prevention done…
- Prevention of the immune system is always individual – we take into account the condition of the child or adult.
In practical terms, I can recommend the following:
-- Minimizing exposure to polluted air
-- Maintaining good ventilation in the home
-- Healthy and balanced nutrition, consumption of foods rich in antioxidants – green leafy vegetables, nuts, fruits, fish
-- Physical activity to improve circulation and immune cell function
-- Sufficient sleep – at least 8-10 hours a day
-- Correction of vitamin D deficiency, after examination, if necessary
-- Annual preventive examinations and vaccines according to recommendations

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Dr. Tsvetelina Velikova, MD, is a clinical immunologist, Master of Public Health and Health Management. Leading researcher at Sofia University “St. Kliment Ohridski“ and head of the GROWTH scientific group. Member of the medical network “Air for Health“ for 2 years and editor at the Central Medical Library of MU-Sofia. Author of scientific publications and lecturer in the field of immunology, clinical medicine and public health. Author of the book “Children's Immunity“ (Ciela, 2022).