In this blog, we discuss how air quality affects the blood pressure of an individual. Furthermore, we shall elaborate on the various chemicals that have been shown to affect blood pressure.
Does air quality affect blood pressure?
Studies have shown that short term exposure to poor air quality can cause variation in blood pressure. Therefore, air quality affects blood pressure. Elevated blood pressure is the top leading risk factor for morbidity and mortality in both men and women.
Every 20 mmHg increase in systolic BP (or 10 mmHg increase in diastolic BP) has been shown to be associated with more than a two-fold increase in cardiovascular mortality.
Air quality refers to the measure of cleanliness of the ambient air. Lower pollution levels imply good air quality. Pollutants in the form of gases or particles from natural as well as anthropogenic (human-based) sources degrade air quality.
What does research suggest?
Several studies have taken place in order to investigate the relation between degradation of air quality and fluctuation of blood pressure.
There are many ways in which air pollution manifests fluctuation of blood pressure. These mechanisms include oxidative stress, arrhythmia, and vasoconstriction and vasodilation, which refers to constriction and dilation of blood vessels, respectively.
Variation in blood pressure levels caused due to short term exposure usually resolve themselves once the causative agents are removed, but repeated exposure can cause hypertension, which refers to high blood pressure.
As stated before, hypertension is a serious issue, since if it is not treated adequately, it can give way to more serious issues in the cardiovascular system.
What pollutants affect blood pressure
Poor air quality contains a variety of pollutants gases and particles that can cause varying degrees of variation in blood pressure, and these include:
- Ozone (O3)
- Carbon Monoxide (CO)
- Particulate matter (PM)
- Nitrogen dioxide (NO2)
- Sulphur dioxide (SO2)
We shall discuss each of the pollutants mentioned above in detail.
Ozone is a highly reactive gas that is composed of three oxygen atoms. In nature, it is formed in the upper layers of the atmosphere, when light with oxygen to form ozone.
Ozone in the upper levels of the atmosphere serves an important purpose of blocking the harmful UV rays from reaching the ground, where it affects both plants and animals.
However, ozone formed in the ground level atmosphere is a major pollutant, as it can have serious adverse effects that include functional, morphologic, immunologic, and biochemical alterations.
Ozone has been shown to elevate blood pressure when a person is subjected to short term exposure. For people with pre-existing hypertension, the effects were more pronounced.
Ozone causes oxidative stress. Increased serotonin-induced vasoconstriction, and reduced acetylcholine-induced vasodilation are two proposed mechanisms relating high blood pressure with O3 exposure.
Carbon monoxide (CO)
Carbon monoxide is a serious air pollutant, and in higher concentrations, it can prove to be lethal. It is a colorless, odourless gas, therefore it is hard to detect its presence.
Carbon monoxide is formed from incomplete combustion of fossil fuels and wood. It is also formed from smoking cigarettes.
Carbon monoxide forms a strong bond with haemoglobin, the compound present in red blood cells (RBCs), which is responsible for transportation of oxygen from the lungs to the tissues, and carbon dioxide from the tissues back to the lungs.
Studies have shown that CO has a negative relationship with blood pressure i.e., exposure to CO causes decrease in the blood pressure of subjects.
Endogenously generated CO appears to contribute to vasorelaxation in the cerebrovascular circulation, according to research.
Particulate matter (PM)
Small sub-micron particles suspended in the air are referred to as particulate matter. There are two forms of particulate matter: coarse particulate matter (PM10), and fine particulate matter (PM2.5).
Particulate matter is a common contaminant in today’s world, since it comes from a variety of natural and manmade sources. It has been demonstrated to have major consequences for human health, especially the cardiovascular system.
Soot is the most harmful of the several forms of PM. Soot, often known as black carbon, is amorphous particles made solely of carbon atoms that are produced as a result of fossil fuel and firewood burning.
Several studies have looked at the short-term effects of particulate matter, specifically PM2.5, in the ambient air pollution on the development of high blood pressure, and the results have been very consistent.
One particular study in Canada found out that each 4.5 g/m3 increase in daily PM2.5 was related with 0.5 mm Hg increases in both systolic blood pressure and diastolic blood pressure.
Nitrogen dioxide (NO2)
Nitrogen dioxide is a component of the nitrous oxide (NOx) family of chemicals, which includes a variety of molecules containing nitrogen and oxygen atoms in variable amounts.
These are a significant contaminant because they raise the risk of illnesses pertaining to the respiratory as well as the cardiovascular system.
Because nitrogen dioxide is released via vehicle exhaust, it is largely a traffic-related contaminant. They are also released by coal-fired thermal power plants (CTPPs), steel and iron mills, and can occur naturally following lightning strikes.
Certain studies have shown mixed results regarding the short term effects of NO2 on blood pressure. However, a study done by Kang et al. which involved more than 90,000 subjects found that NO2 causes an elevation of the blood pressure.
Sulphur dioxide (SO2)
Sulphur dioxide is a significant contaminant in the atmosphere. Natural causes, such as volcanic eruptions, as well as human activities, such as fossil fuel burning and industrial emissions, produce it.
Studies have shown that SO2 has a negative relationship to blood pressure variation, similar to that of carbon monoxide. This is attributed to the fact that SO2 acts as a vasodilator.
SO2 blocks the entry of calcium ions through both potential-dependent and receptor-operated calcium channels, as well as intracellular calcium ion release.
Who is at risk?
Poor air quality can affect anyone’s health. However, certain groups of people are more vulnerable than others. This includes:
- Children and adolescents
- Older people
- People with pre-existing illnesses
- People in polluted environments
Children and adolescents
Poor air quality can cause fluctuations in blood pressure levels of children as well as adolescents. Since their cardiovascular systems are still developing, their risk of illnesses when subjected to air pollution are higher than that of adults.
Children, especially infants, have a higher rate of breathing compared to adolescents and adults. Therefore, they are more vulnerable to the effects of poor air quality on blood pressure.
Studies have found that children and adolescents, especially those in the metropolitan cities, or areas where annual air quality is predominantly poor, are at a high risk of developing hypertension, which refers to elevation in the basal blood pressure.
With the onset of age, the various systems of our body become more susceptible to diseases caused by foreign substances.
This also includes health issues that are linked to the cardiovascular system, which thereby can affect the blood pressure.
With age, poor respiratory muscle strength, decrease in elastic recoil, and greater rigidity of the chest wall become common. So, in order to compensate, the breathing rate becomes higher than that for younger people.
People living in polluted environments
An average American individual spends more than 90% of their total lives indoors. Hence, indoor air quality can also affect blood pressure.
Indoor air can get polluted from indoor sources such as common household items, combustion of fuels, smoking, or can get polluted when outdoor air enters inside the house through doors and windows.
Hence, for people that live closer to streets, especially the ones which are prone to traffic congestion, can be affected by the poor air quality, which in turn could cause variation in blood pressure.
People with pre-existing illnesses
People with pre-existing illnesses, especially the ones with diagnosed issues pertaining to the cardiovascular system or the respiration system, are more prone to effects of pollution on blood pressure.
In the study done by Kang et al, there were two groups on which the effect of certain pollutant species on blood pressure were observed – one group had a normal range of blood pressure, while the other comprised people diagnosed with hypertension.
It was found out that the effects of pollution on blood pressure were observed in both groups. However, the group that comprised people with high blood pressure showed a higher range of fluctuation in blood pressure.
What are the sources of the contaminants that affect blood pressure?
There are various sources of contaminants that are responsible for affecting blood pressure. These are prevalently generated from anthropogenic activities, and we shall discuss them below.
Over the past years, the number of automobiles used for transport has risen significantly. Traffic is one of the biggest polluters in metropolitan cities.
The exhaust gases released from vehicles contain pollutants such as ozone, NOx species such as NO2, SO2, soot, heavy metals, carbon monoxide, and so on. These species have been shown to affect the air quality, and can affect blood pressure when subjected to acute exposures.
In industrial areas, the air quality is much worse than compared to other places. The main contributors are steel and iron manufacturing plants, coal-based thermal power plants (CTPPs), brick kilns, chemical manufacturing plants, and so on.
The majority of emissions from industries comprise PM, SO2, NOx species, and even carbon monoxide. Workers in such industries often present headaches and other symptoms related to poor air quality.
Other FAQs about Air Quality that you may be interested in.
Studies have shown that short term and long term exposure to poor air quality can adversely affect blood pressure. These pollutants originate mainly from sources such as traffic and industrial emissions.
These effects are more pronounced in certain groups, such as children and adolescents, older people, people living in polluted environments, and lastly, people with pre-existing illnesses.
How can I keep my indoor environment clean?
The best way to deal with indoor air pollution is by the following methods:
Improving ventilation of the house, which would help to dilute the indoor air pollution level by introducing outdoor air, and carry the pollutants out of the house. Furthermore, you can install exhaust fans at your windows or in the central air ducts to improve the efficiency of ventilation.
Using an air dehumidifier to reduce the relative humidity of the home. A high humidity level can promote the growth of mold and mildews, which give rise to spores, which can cause issues such as wheezing, irritation in the throat, difficulty in breathing, asthma, etc.
Avoid smoking or combustion of fuels inside the house, as these processes adversely affect the indoor air quality. Cigarette smoke contains several toxins, which can act as irritants to the airway and affect the respiration system, thereby triggering an asthma attack.
You can invest in an air purifier. The best method for reducing PM concentrations is by using an air purifier. Depending upon the size of the basement, an adequate air purifier should be used.
Air purifiers with HEPA (High-Efficiency Particulate Air) filters are best suited for indoor purposes. The presence of an activated charcoal filter and a UV light further increases the efficiency of the filters.
Can exposure to cigarette smoke affect blood pressure?
Yes, exposure to cigarette smoke can affect blood pressure. This is because cigarette smoke contains lots of pollutants such as PM and CO, which have been shown to affect the blood pressure.
The active ingredient of cigarettes, nicotine, is known for its effects as a vasoconstrictor and increases the heart rate. This in turn causes an elevation of blood pressure.
- Choi, YJ., Kim, SH., Kang, SH. et al. Short-term effects of air pollution on blood pressure. Sci Rep 9, 20298 (2019). https://doi.org/10.1038/s41598-019-56413-y
- Giorgini P, Di Giosia P, Grassi D, Rubenfire M, Brook RD, Ferri C. Air Pollution Exposure and Blood Pressure: An Updated Review of the Literature. Curr Pharm Des. 2016;22(1):28-51. doi: 10.2174/1381612822666151109111712. PMID: 26548310.
- Giorgini, Paolo; Di Giosia, Paolo; Grassi, Davide; Rubenfire, Melvyn; D. Brook, Robert; Ferri, Claudio (2015). Air Pollution Exposure and Blood Pressure: An Updated Review of the Literature. Current Pharmaceutical Design, 22(1), 28–51. doi:10.2174/1381612822666151109111712
- M. Huang, J. Chen, Y. Yang, H. Yuan, Z. Huang, Y. Lu. Effects of Ambient Air Pollution on Blood Pressure Among Children and Adolescents: A Systematic Review and Meta Analysis. https://www.ahajournals.org/doi/10.1161/JAHA.120.017734
UNEP. Young and old, air pollution affects the most vulnerable.