Air Pollution: Absorption Into Our Skin And Body

Air pollution has a significant impact on human health, and the skin, being the largest organ in the body, is constantly exposed to harmful compounds in the environment. These compounds can exist as solids, liquids, gases, and particulate matter, and they are absorbed into the body through various routes, including direct transcutaneous absorption into the subcutaneous tissue or indirectly through the systemic distribution of inhaled or ingested pollution via the blood. While the skin acts as a physical, chemical, and immunological barrier, the prolonged or repetitive exposure to high levels of pollutants may have detrimental effects on skin health.

Air pollution is absorbed into the skin via direct and indirect routes

Air pollution is a growing threat to human health worldwide, and the skin is one of the main targets of pollutants. The skin acts as a physical, chemical, and immunological barrier against environmental factors. However, air pollutants can be absorbed into the skin via direct and indirect routes, causing various adverse effects.

Direct routes of absorption include transcutaneous uptake, where pollutants penetrate the skin directly. This can occur through the skin's surface, hair follicles, and sweat/sebaceous glands. The skin is exposed to a variety of environmental stressors, including solids, liquids, gases, and particulate matter. These pollutants can induce severe interference with the normal functions of lipids, DNA, and proteins in the skin, leading to oxidative damage.

Indirect routes of absorption occur through the systemic distribution of inhaled or ingested pollution via the blood. Pollutants such as polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and particulate matter (PM) can enter the body through inhalation or ingestion and then affect the skin from within. The intensity of the pollutants and the length of exposure can also impact the skin.

Air pollution has been linked to a range of skin conditions, including premature aging, skin cancer, inflammatory diseases such as atopic dermatitis, cellulitis, and psoriasis, acne, hair loss, and pigmentation disorders. It can also exacerbate allergic skin conditions such as eczema. Additionally, air pollution can affect vitamin D synthesis by reducing UVB radiation, which is essential for the production of vitamin D3 and its derivatives.

Overall, the impact of air pollution on the skin is complex and multifaceted. While the skin acts as a protective barrier, it is also vulnerable to the harmful effects of pollutants. Understanding the direct and indirect routes of absorption is crucial for mitigating the adverse effects of air pollution on skin health.

Air pollution causes oxidative stress and inflammation in the skin

Human skin is constantly exposed to harmful compounds in the environment as the first line of defence. As the largest organ in the body, it is one of the main targets of pollutants, which reach the superficial and deeper skin layers by transcutaneous and systemic routes.

Air pollution can induce or exacerbate various skin pathological conditions and systemic diseases. These include premature skin ageing, skin cancer, inflammatory skin diseases (atopic dermatitis, psoriasis, and cellulitis), acne, alopecia, and pigmentary disorders.

The skin's normal barrier function can be interrupted by exposure to high concentrations of environmental factors, including ultraviolet (UV) radiation, outdoor air pollutants, and indoor air pollutants. The intensity of the pollutants and the length of exposure are contributing factors to the impact on skin health.

Air pollution elicits an oxidative stress response in the skin, which activates inflammation and drives skin and systemic pathologies. Oxidative stress occurs when the formation of reactive oxygen species (ROS) overwhelms the cell's antioxidant defences. Free radicals and ROS are generated, interacting with the lipid-rich plasma membrane to initiate the lipid peroxidation reaction cascade. ROS also stimulate the release of pro-inflammatory mediators, resulting in a cycle of further free radical generation.

Oxidative stress initiates complex biological processes, resulting in genetic damage, activation of transcription factors, and signalling pathways. The altered redox homeostasis from air pollution contributes to a cycle of skin oxinflammation.

Air pollution is linked to inflammatory skin diseases

Human skin is constantly exposed to harmful compounds in the environment, including air pollutants. Airborne pollution has been linked to respiratory and cardiac health issues, but its impact on the skin is less understood. However, the skin is one of the main targets of pollutants, which can reach the deeper layers of the skin through transcutaneous and systemic routes.

Air pollution has been shown to play a role in the development of inflammatory skin diseases. Studies have indicated that exposure to high concentrations of air pollutants can interrupt the skin's normal barrier function and induce or exacerbate a range of skin conditions. These include inflammatory diseases such as atopic dermatitis, cellulitis, and psoriasis, as well as acne, hair loss, and even skin cancers. The specific inflammatory skin diseases that have been linked to air pollution include:

• Atopic dermatitis (AD)
• Airborne contact dermatitis (ABCD)
• Allergic contact dermatitis
• Psoriasis
• Acne
• Alopecia
• Cutaneous lupus erythematosus (CLE)
• Scleroderma

The pathogenic mechanisms of air pollutants on skin diseases include the AhR pathway, oxidative stress, and skin barrier impairment. Air pollution can also affect the skin microbiome and inflammasomes, which are involved in the pathogenic process. Additionally, the intensity of the pollutants and the length of exposure can contribute to the development of skin diseases.

Overall, air pollution is a significant risk factor for inflammatory skin diseases, and understanding the complex effects of air pollutants is crucial for developing strategies to mitigate their negative impacts on skin health.

Air pollution affects skin ageing

As the largest organ in the human body, the skin is the first line of defence against harmful compounds in the environment. It is exposed to various environmental factors, including air pollutants and ultraviolet (UV) light.

Air pollution is a growing threat to human health worldwide, and the skin is one of its main targets. It reaches the superficial and deeper skin layers through transcutaneous and systemic routes. Pollutants such as particulate matter (PM), ozone, heavy metals, and cigarette smoke can induce oxidative stress and inflammation in the skin, leading to premature ageing and skin pathologies.

The impact of air pollution on skin ageing has been the subject of numerous studies. Research has shown that exposure to high concentrations of air pollutants, including polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), particulate matter (PM), heavy metals, and gaseous pollutants such as carbon monoxide (CO), nitric oxides (NOx), sulfur oxide (SO2), and ozone (O3), can interrupt the skin's normal barrier function and induce or exacerbate skin ageing.

The association between traffic-related air pollution and skin ageing has been well-established. Studies have found links between exposure to particulate matter, soot, and nitrogen dioxide (NO2) and premature skin ageing. Additionally, there is evidence that tropospheric ozone contributes to wrinkle formation, independent of other factors such as NO2, PM, and UV radiation.

The interaction between pollutants and the skin can vary depending on the specific characteristics of each agent. However, damaging the skin barrier is often associated with increased reactive oxygen species (ROS) production, oxidative stress, and inflammatory responses. These processes contribute to premature skin ageing and the development of skin disorders and pigmentation issues.

Overall, air pollution is a significant factor in skin ageing, and its effects can be amplified by exposure to ultraviolet radiation (UVR) and other environmental factors. While the specific mechanisms are still being studied, the available evidence indicates that air pollution has detrimental effects on skin health and ageing.

Air pollution impacts the skin microbiome

Human skin, as the body's largest organ, is constantly exposed to harmful compounds in the environment. These compounds include outdoor and indoor air pollutants, such as polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), particulate matter (PM), heavy metals, and gaseous pollutants like carbon monoxide (CO) and nitrogen dioxide (NO2).

Airborne pollutants can reach the superficial and deeper skin layers through transcutaneous and systemic routes. While the impact of air pollution on respiratory and cardiac health is well-established, its effects on the skin and the skin microbiome are less understood. However, studies have indicated that exposure to high concentrations of air pollutants can interrupt the skin's normal barrier function and induce or exacerbate a range of skin conditions, including inflammatory diseases, acne, hair loss, and even skin cancers.

The skin microbiome refers to the diverse population of microorganisms, including bacteria, fungi, and viruses, that reside on the skin. This microbiome plays a crucial role in maintaining skin health and protecting against pathogens. However, chronic exposure to air pollutants can disrupt the delicate balance of the skin microbiome, leading to potential skin issues.

A study by Boonpethkaew et al. (2024) found a link between air pollution and skin barrier dysfunction, suggesting that chronic exposure to PAHs alters the skin virome composition and virus-host interactions. Another study by Du et al. (2024) investigated the impact of climate change on cellulitis, a common skin infection, and its relationship with air pollution. These studies highlight the potential influence of air pollution on the skin microbiome and its role in skin health and disease.

Furthermore, a study by Fitz-Gibbon et al. (2013) explored the association between the skin microbiome and acne, specifically examining the role of Propionibacterium acnes strain populations. Additionally, the impact of UV-induced immune suppression on the skin microbiome has been explored, given the interaction between certain pollutants and ultraviolet radiation. These studies underscore the complex interplay between air pollution, the skin microbiome, and skin health, warranting further investigation.

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