The human immune system can be compromised by indoor and outdoor air pollutants. This can lead to a range of clinical conditions, including acute respiratory tract infections, reduced heart rhythm variability, and skin problems. Subclinical deficiencies of micronutrients can exasperate these effects. This review (1) examines the use of the micronutrient vitamins A, D, E, C, B6, B12, folate, and the trace elements copper, iron, selenium, and zinc to restore the oxidant-antioxidant balance in subjects affected by poor air quality.
Airborne pollution leads to increased pulmonary intake of reactive oxygen species (ROS). When we inhale, particulate matter (PM) enters the respiratory (lung) system, causing coughing and sneezing. The finest particulate matter, PM2.5, travels all the way to the alveoli and causes local and systematic harm, including increased oxidative stress and increased inflammation. In addition, there is evidence of specific mechanisms whereby PM2.5, traffic-related or combustion-related air pollution exposure can affect the cardiovascular system (2).
At low levels, ROS are essential for the human metabolism ; they are vital for several signaling pathways, the modulation of gene expression, and the regulation of antibody or cytokine biosynthesis. However at high concentrations, ROS produce a condition known as “oxidative stress”, causing cell damage by reacting with important functional and structural molecules, and rendering them unavailable . The intake of antioxidants can restore the oxidant-antioxidant balance to a steady state and thus protect against cell damage. Air pollution increases the risk of acute respiratory tract infection and is thought to contribute towards seven million premature deaths globally each year (WHO, 2014), particularly in developing countries.
Nutritional status is one of the most important factors in modulating immune function. Essential micronutrients are able to function synergistically and serve as cofactors in the development, maintenance, and expression of immune response (1). Micronutrient deficiencies can suppress normal immune function, leading individuals to be more at risk from infection and the effects of chemical pollutants in the environment. Immune dysregulation increases with age, meaning the elderly are two to 10 times more likely to die from an infectious disease than their younger counterparts:
- Vitamin A is important for innate, cell-mediated immunity and antibody response. Retinoic acid in particular imprints protective T-cells and B-cells into intestinal tissues.
- Vitamin D, in the active form of 1,25(OH)2D3, is a potent immunomodulator. In addition, it enhances innate immunity by increasing the differentiation of monocytes into macrophages.
- Vitamin E is a key, fat-soluble antioxidant capable of protecting cell membranes from oxidative damage. It also enhances T-cell-mediated functions. Vitamin E is an integral component of the alveolar surface of the lung and directly affects lung function.
- Vitamin C is a key, water-soluble antioxidant which helps maintain the redox balance inside cells. It also helps regenerate vitamin E as well as stimulating the transit of neutrophils and monocytes. Vitamin C is particularly important inside the lungs to help counter the presence of inhaled oxidative substances.
- Vitamins B6, B12, and folic acid modulate immune function by means of nucleic acid and protein biosynthesis.
- Selenium has an important role in redox regulation via glutathione peroxidases by removing excess ROS. Zinc, iron, and copper are critical components of enzymes which are required for the correct functioning of immune cells.
Micronutrient intake is important with regard to the sensitivity of an individual to air pollution ; it affects the composition and quantity of antioxidants in the respiratory tract lining fluid (RTLF) of the lungs.
It is thought that Sick Building Syndrome (SBS) can be regarded as indoor pollution, with its symptoms being associated with oxidative stress. Poor ventilation, office equipment, and decor can lead to the buildup of volatile organic compounds (VOCs), dust, mould spores, and carbon dioxide. A study by the author in 2010 (1) on a cohort of Jakarta office workers showed that daily supplementation with a multivitamin containing vitamins A, B6, B12, C, D, and E (together with trace elements: selenium, zinc, copper, and iron) over three months had a significant effect on the development of symptoms of SBS. In the intervention group, far fewer subjects reported symptoms such as headaches, sore eyes, sore throats, nasal congestion, and tiredness.
Possami et al. (3) conducted a daily intervention of 500mg vitamin C and 800mg vitamin E in a randomized, controlled trial involving a cohort drawn from people living or working in a large, coal-fired power plant in Southern Brazil who were subject to high levels of particulate matter emissions. It had been suggested that high levels of airborne contamination containing particular matter exposes individuals to potential serious diseases due to the over-generation of reactive oxygen species. The antioxidant intervention saw several biomarkers of oxidative stress be restored back to normal control levels.
A study by Baccarelli et al. (4) found that compromised heart rate variability caused by particulate matter (PM2.5) air pollution in a cohort of older men from Boston MA could be improved through supplementation with a combination of vitamins B6, B12, folic acid, and methionine.
Exposure to PM2.5 is a health threat compared with a typical level of 10 µg/m3. 35 µg/m3 causes 15% higher mortality rates but can be attenuated by supplementation with certain vitamins. Studies have shown that supplementing a micronutrient-deficient individual back to a state of sufficiency can restore immune function and increase resistance to infection (1).