Air Pollution and Skin Aging

Introduction:

The human skin acts as a barrier against environmental stresses. Therefore, it is responsible for causing the skin to age and inflammatory or allergic skin diseases such as atopic dermatitis, eczema, psoriasis, acne, and even skin cancer. However, prolonged exposure to these environmental factors negatively affects the skin. Major air pollutants that influence skin aging includes ultraviolet radiation (UVR), polycyclic aromatic hydrocarbons (PAHs), nitrogen oxides, particulate matter (PM), and cigarette smoke.

How Does Air Pollution Cause Skin Aging?

The air pollutants which induce skin aging include:

Ultraviolet Radiation:

• The solar spectrum consists of ultraviolet A, B, and C. Approximately 95 % of ultraviolet A and one to five percent of ultraviolet B reach the earth's surface. At the same time, the ozone layer and oxygen absorb most ultraviolet C in the atmosphere.

• The stratospheric ozone depletion by environmental pollutants, including photochemical smog, supersonic aircraft flights, and refrigerant gasses, poses a threat to human health as it causes an increase in the penetration of the ultraviolet radiations of shorter wavelengths to the ground level.

• The severity of ultraviolet radiation effects on human skin depends on the wavelength.

• Exposure to ultraviolet A is linked with extrinsic skin aging (photoaging). Photoaging clinically manifests as coarse wrinkles, solar elastosis, and pigment irregularities.

• Aging results from the combined action of both intrinsic and extrinsic factors. The intrinsic aging of the skin is genetically determined and naturally occurring, bypassing time. Whereas extrinsic aging, on the other hand, is induced by lifestyle and environmental factors.

Polycyclic Aromatic Hydrocarbons (PAHs):

• Polycyclic aromatic hydrocarbons are one of the most widespread and dangerous organic pollutants.

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• The atmospheric polycyclic aromatic hydrocarbon benzo(a) pyrene is mainly found in residual wood burning. The other sources include automobile exhaust, diesel fumes, metallurgical industry, production of plastics, pesticides, dyes, cigarette smoke, and smoke from the combustion of organic material.

• These pollutants are associated with extrinsic skin aging, pigmentation, cancers, and acneiform eruption. In addition, prolonged skin exposure to particulate matter-bound PAHs through a hair follicle or transepidermal absorption may lead to oxidative stress and skin aging.

Cigarette Smoke:

• Cigarette smoke is a complex aerosol composed of various chemical substances such as reactive oxygen species, carbon monoxide, reactive nitrogen species, and electrophilic aldehydes.

• Reactive oxidants and free radicals from cigarette smoke cause oxidative stress and inhibit antioxidant mechanisms.

• Smoking causes premature aging, which is characterized by deeper periorbital wrinkling. The term "smoker's face" refers to premature facial skin aging in smokers, with a characteristic pattern of wrinkling and orange-purple skin discoloration. Heavy cigarette smokers are 4.7 times more likely to develop facial wrinkles or lines than nonsmokers, independent of sun exposure.

Particulate Matter (PM):

• Particulate matter is air pollutants consisting of complex and varying mixtures of different sizes and composition particles suspended in the air.

• The primary sources of particulate matter include factories, power plants, refuse incinerators, automobiles, construction activities, fires, and natural windblown dust.

• Particulate matter penetrates the skin either through hair follicles or transdermal mode. Prolonged exposure to particulate matter causes coarse wrinkles and pigment spots on the face and nasolabial folds.

• The generation of oxidative stress by particulate matter contributes to extrinsic skin aging in humans.

Oxides:

• The significant sources of nitrogen oxides are mobile and stationary combustion. They react with ozone or radicals in the atmosphere to form nitrogen dioxide.

• Among nitrogen oxides, nitrogen dioxide is responsible for oxidative damage, leading to free radicals that oxidize amino acids in tissue proteins and initiate lipid peroxidation of polyunsaturated fatty acids.

• Atmospheric sulfur dioxide is another pollutant from fuel combustion from industrial processes and natural sources such as volcanic activity and forest fires.

• Carbon monoxide, formed from incomplete combustion of mobile sources, acts on cell metabolism, which binds to heme and alters its function and metabolism. Flexural eczema is associated with traffic-related air pollutants, including nitrogen oxides and carbon monoxide.

Ozone:

• Ozone, a ubiquitous pollutant, exists in the stratosphere and the troposphere. Usually, ozone is present at ground level in low concentrations. However, ozone formed as a by-product of the interaction of sunlight (UVR) and hydrocarbons.

• Volatile organic compounds and nitrogen oxides are major active components of photochemical smog. In addition, ozone can damage the barrier function.

• The epidermis decreases the level of antioxidants such as tocopherols (vitamin E) and ascorbic acid (vitamin C).

• When combined with ultraviolet A rays and cigarette smoke, ozone acts as a powerful oxidizing agent of squalene. Oxidation of squalene produces a peroxidized form of squalene by-products, leading to comedogenesis, which aggravates inflammation. In addition, the epidermal lipids are oxidized, and the activity of matrix metalloproteinases is disturbed, which clinically manifests as wrinkling and extrinsic skin aging.

How to Minimize the Risk of Air Pollution?

Natural sources of pollution such as volcanic eruptions or forest fires are difficult to prevent. However, there are some ways by which human-made sources of air pollution can be controlled.

These strategies include:

• Less use of personal vehicles.

• More use of carpools and public transport.

• Supply of low-sulfur petrol, shifting industries in outskirts of the cities.

• Usage of eco-friendly industrial machines and methods.

• Avoidance of burning garbage in the open.

• Avoiding cigar smoke.

• Avoid using wood and crop residues as fuel for household cooking and heating.

• Reduce traffic-induced pollution. For instance, all public transport vehicles use biofriendly fuels such as compressed natural gas. The odd-even formula for private cars is an excellent example of steps taken.

• As a cleaner and greener alternative, using electric vehicles such as electric scooters and cars is a good approach to sustainable transportation. They are fuel-efficient and cost-effective.

How to Protect Skin From Air Pollution?

Some easy ways can be beneficial for personal protection, such as:

• Wash skin before bedtime using a cleanser to eliminate the pollutants accumulated on the skin.

• Use sunscreens before stepping out of homes.

• Reducing exposure to air pollution by avoiding areas around industries and public smoking.

• Use topical antioxidants, such as vitamin C and E, and sunscreen.

• Use of indoor air purifiers and ventilators while cooking.

• People working in high occupational risk areas such as traffic police, street vendors, and sweepers should wear masks.

Conclusion:

Skin is an essential organ of the human body. Protecting the skin from environmental stresses is necessary as any factor affecting the whole body impacts it. Major air pollutants affecting the skin include solar ultraviolet radiation, polycyclic aromatic hydrocarbons, nitrogen oxides, particulate matter, ozone, and cigarette smoke. Ultraviolet radiation, cigarette smoke, and ambient particulate matter are the main factors causing extrinsic skin aging. Human-made sources of air pollution can be controlled by taking crucial, environment-friendly steps. Some personal protection strategies to minimize skin aging risk can be helpful.

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