Air Pollution: Skin Cancer's Unseen Enemy

Air pollution is a serious health risk, and it is estimated that more than 7 million people die prematurely each year due to its effects. It is a mixture of particles and gases that can reach harmful concentrations both outside and indoors.

Air pollution can affect the skin in various ways, including premature ageing, skin cancer, and inflammatory skin conditions such as atopic dermatitis, eczema, and acne.

Ultraviolet radiation (UVR) is a physical pollutant that can cause skin ageing and skin cancer. Polycyclic aromatic hydrocarbons (PAHs) are among the most dangerous organic pollutants and can be found in cigarette smoke, vehicle emissions, and industrial activities. PAHs are absorbed through the skin and can lead to skin pigmentation, cancers, and acne.

Particulate matter (PM) is another harmful pollutant that can penetrate the skin and cause oxidative stress, leading to premature ageing and skin cancer.

Ozone (O3) is a highly reactive oxidant that can cause oxidative stress and inflammation in the skin.

Volatile organic compounds (VOCs) are emitted from paints, vehicle refinishing, and industrial facilities. They can cause allergic reactions such as atopic dermatitis and eczema.

Nitrogen oxides (NOx) and sulfur dioxide (SO2) are also air pollutants that can cause oxidative damage and allergic reactions.

Overall, air pollution can have significant effects on skin health, and it is important to take measures to reduce exposure and protect the skin.

Air pollution can increase the risk of skin cancer by causing oxidative stress and DNA damage

Air pollution is a mixture of gases and particles that can reach harmful concentrations both outside and indoors. The skin is the largest organ of the human body and acts as a physical, chemical, and immunological barrier against environmental factors. However, the protective ability of the skin is not unlimited, and problems can arise when an abnormal exposure to environmental stressors exceeds the skin's normal defensive potential.

Air pollutants can induce severe interference of normal functions of lipids, DNA and/or proteins of the human skin via oxidative damage, leading to skin aging, inflammatory or allergic conditions such as atopic dermatitis, psoriasis, and acne, and skin cancer.

Oxidative stress is an imbalance of free radicals and antioxidants in the body, which can trigger the production of reactive oxygen species (ROS) and cause damage to DNA, proteins, and lipids. Oxidative stress can initiate complex biological processes resulting in genetic damage, activation of transcription factors, and signalling pathways involved in cell growth and differentiation and in the degradation of the connective tissue of the dermis.

Air pollution can cause oxidative stress in the skin, which can, in turn, activate inflammatory responses. The aryl hydrocarbon receptor (AhR) can act as a sensor for small molecules such as air pollutants and plays a crucial role in responses to (photo)pollution. AhR activation can induce the production of inflammatory and immunosuppressive cytokines in cutaneous keratinocytes and fibroblasts, resulting in the accumulation of neutrophils and other phagocytic cells that further generate free radicals, creating a vicious cycle of inflammation and metabolic impairments.

Some air pollutants, such as polycyclic aromatic hydrocarbons (PAHs), are photoreactive and can be activated by ultraviolet radiation (UVR). The activation of PAHs by UVR exposure would enhance their deleterious effects on the skin. PAHs can lead to acneiform eruptions due to the presence of 2,3,7,8-tetrachlorodibenzo-p-dioxin, a polyhalogenated aromatic hydrocarbon. PAHs can also be found in cigarette smoke and are highly lipophilic, allowing them to easily penetrate the epidermal skin barrier.

Cigarette smoke is a highly complex aerosol composed of thousands of chemical substances, including reactive oxygen species, carbon monoxide, reactive nitrogen species, and electrophilic aldehydes. It can cause oxidative stress or secondary oxidative events and inhibit antioxidant mechanisms. Chemical substances from cigarette smoke increase transepidermal water loss, degeneration of connective tissue in the skin, and upregulation of matrix metalloproteinases, which degrade collagen and elastic fibres.

Overall, air pollution can increase the risk of skin cancer by causing oxidative stress and DNA damage, leading to inflammatory responses, genetic damage, and the activation of transcription factors and signalling pathways involved in cell growth and differentiation.

Air pollution can cause skin ageing by inducing oxidative stress and reducing antioxidant defences

Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) and the ability of the body to neutralise them. Air pollution can increase the amount of ROS in the body, which can lead to oxidative stress.

Oxidative stress can be caused by exposure to air pollutants such as cigarette smoke, volatile organic compounds, and polycyclic aromatic hydrocarbons. These pollutants can be absorbed through the skin or inhaled.

The skin has antioxidant defences, including enzymatic and non-enzymatic antioxidants, which can neutralise ROS. However, air pollution can deplete these defences, leading to an increase in oxidative stress.

Oxidative stress can damage the skin by causing inflammation and tissue injury. This can lead to skin ageing, as well as other skin conditions such as atopic dermatitis, psoriasis, and acne.

Air pollution can increase the risk of atopic dermatitis by causing oxidative stress and inflammation

Air pollution is a complex mixture of solids, liquids, and gases that can directly harm skin barrier function and homeostasis, contributing to the development and exacerbation of cutaneous diseases. Atopic dermatitis (AD) is an inflammatory skin disease in which patients have underlying skin barrier defects and a heightened immune response to irritants and allergens.

Oxidative stress can also deplete the skin's antioxidant defenses, including enzymatic (glutathione peroxidase, glutathione reductase, superoxide dismutase, and catalase) and non-enzymatic (vitamin E, vitamin C, and glutathione) antioxidants. This depletion can lead to lipid peroxidation, which is the oxidation of lipids in cell membranes, and further tissue injury.

Oxidative stress also initiates complex biological processes resulting in genetic damage, activation of transcription factors, and signaling pathways involved in cell growth and differentiation and in the degradation of the connective tissue of the dermis.

In addition, air pollution can cause inflammation by activating the AhR pathway, which can lead to increased artemin expression and inflammatory processes in murine epidermal cells. Artemin is a neurotrophic factor that causes hypersensitivity to itching and is coded by Artn, an AhR target gene.

Overall, the scientific literature suggests a significant role of air pollution in the pathogenesis of AD, but our understanding is still incomplete due to limitations in the available literature.

Air pollution can increase the risk of acne by causing oxidative stress and inflammation

Air pollution is a mixture of particles and gases that can reach harmful concentrations both outside and indoors. It is a growing environmental health risk, responsible for killing millions of people prematurely every year.

The skin is the largest organ of the human body and acts as a physical, chemical, and immunological barrier against environmental factors. However, prolonged or repetitive exposure to high levels of air pollutants may have profound negative effects on the skin.

Air pollutants can enter the skin through hair follicles and sweat/sebaceous glands, causing oxidative stress and inflammation. Oxidative stress is caused by an increase in reactive oxygen species (ROS) and free radicals within the cell and its mitochondria, which overcome the skin's innate antioxidant defenses. This can lead to lipid peroxidation, which unleashes proteolytic activity and causes further tissue injury.

Oxidative stress also initiates complex biological processes, resulting in genetic damage, activation of transcription factors, and signaling pathways involved in cell growth and differentiation and the degradation of the connective tissue of the dermis.

Air pollutants, such as polycyclic aromatic hydrocarbons (PAHs), can be absorbed on the surface of suspended particulate matter in the air in urban areas. PAHs are highly lipophilic, allowing them to easily penetrate the epidermal skin barrier. They can be converted into quinones, redox-cycling chemicals that produce reactive oxygen species (ROS).

Cigarette smoke is a highly complex aerosol composed of thousands of chemical substances, including reactive oxygen species (ROS), carbon monoxide, reactive nitrogen species, and electrophilic aldehydes. It causes oxidative stress and inhibits antioxidant mechanisms, leading to increased transepidermal water loss, degeneration of connective tissue in the skin, and upregulation of matrix metalloproteinases (MMPs) that degrade collagen and elastic fibers.

Additionally, air pollution can affect vitamin D synthesis by reducing UVB radiation, which is essential for the production of vitamin D3, tachysterol, and lumisterol derivatives.

Overall, air pollution can increase the risk of acne by causing oxidative stress and inflammation through various mechanisms, including the generation of ROS, activation of transcription factors, and degradation of connective tissue.

Air pollution can increase the risk of psoriasis by causing oxidative stress and inflammation

Air pollution is increasingly being recognised as a risk factor for skin disorders, including psoriasis. Psoriasis is a chronic autoimmune condition that causes thick, scaly patches on the skin. It is characterised by abnormal skin cell growth and inflammation, and can be triggered by a mix of genetics, immune responses, and environmental factors.

Recent studies have shown that people living in polluted areas are more likely to develop skin problems, including psoriasis. A study published in the *JAMA Network* showed that long-term exposure to pollutants like nitrogen dioxide (NO2), nitrogen oxides (NOx), and fine particulate matter (PM2.5 and PM10) was associated with an increased risk of psoriasis.

Air pollution can cause oxidative stress and inflammation, which are thought to be key mechanisms linking pollution to psoriasis. Pollutants can enter the skin and trigger oxidative stress, which occurs when there is an imbalance between free radicals and antioxidants in the body. Over time, this can weaken the skin barrier, making it more vulnerable to irritation and inflammation.

Genetic factors also play a role in the development of pollution-induced psoriasis. Those with a family history of psoriasis are more likely to experience severe flare-ups when exposed to high levels of pollution. This is because genetic factors determine how the immune system reacts to environmental triggers like pollution, and so some people may be more susceptible to pollution-induced inflammation.

Tips to Protect Your Skin from Air Pollution:

• Moisturise regularly: This helps to prevent skin dryness and creates a protective layer over the skin, preventing pollutants from penetrating the surface.
• Cleanse your skin: This helps to remove pollution particles from the skin's surface, preventing them from clogging pores and causing irritation.
• Wear sunscreen: Harmful UV rays can amplify the damaging effects of pollution on the skin.
• Invest in an air purifier: This can help to reduce your exposure to harmful indoor pollutants.
• Avoid high pollution areas: Try to limit your exposure to polluted areas, especially during peak pollution times, such as rush hour.

Frequently asked questions