Invited Review ArticlePollution and skin: From epidemiological and mechanistic studies to clinical implications
Introduction
Recently, published figures from the 2012 WHO Air pollution report 3.7 million deaths are attributed to ambient air pollution worldwide. This is double previous estimates and places air pollution as the world's largest single environmental health risk. Common anthropogenic pollutants arise from household combustion devices, motor vehicles, industrial facilities and forest fires. Outdoor air pollutants of major public health concern include particulate matter, volatile organic compounds, ozone, nitrogen dioxide and sulphur dioxide. Composition and concentrations vary in both developed and developing countries. In some regions, household air pollution remains mainly a rural issue, while ambient air pollution is predominantly an urban problem. Also, in some continents, many countries are relatively unaffected by household air pollution, while ambient air pollution is a major concern [1].
Researchers are increasingly interested in the various effects of pollutants on human health. Recently, large epidemiological studies identified that both long- and short-term exposure to air-borne pollution, including exposure to both particulate matter and ozone increases respiratory and cardiovascular morbidity [2], [3]. Long-term exposure has even been associated with the development of certain cancers [4].
Although, epidemiological and clinical studies highlight the adverse effects of pollution on human health, very little research is available to date concerning cutaneous effects. The skin is another organ, of which the outermost barrier is in direct contact with various air pollutants.
Sensitive skin is known to be associated with barrier dysfunction [5] and the prevalence of reported sensitive skin is increasing within industrialized countries including Asian skin types [6], [7], [8].
This subgroup within the population may therefore need specific management in urban areas particularly with high levels of ambient pollution.
In this article we attempt to provide a state-of-the-art review on what is currently known about the effects of common pollutants on skin. We will also discuss these data in the context of sensitive skin and eventually would like to suggest some cosmetic measures that could prevent or relief skin damage caused by environmental pollutants. We also believe that this topic might be of particular relevance to countries where mainly fossil fuels are consumed, with a fast growing automobile market and industry.
Section snippets
Methods
A Eurasian board of experts was formed at the beginning of 2014, composed of one European Dermatologist and specialist in Environmental Medicine (JK), two Chinese dermatologists (LW, LL), a public health specialist (XP) and three scientists from L’Oreal research (MC, GS, SS). A literature review was performed using PubMed, using combinations of the following words: air pollution, health effects, skin, cutaneous symptoms, respiratory disease, cardiovascular disease, lung cancer, dermatological
Key pollutants and worldwide variations and concentrations
The WHO defines pollution as contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere [9]. Pollution is usually related to either an internal or an external environment. Ambient pollution refers to air pollution in outdoor environments and is the focus of this review. Outdoor pollution comes from fixed, usually industrial sources, and mobile sources such as road and air traffic. These sources
Health problems associated with pollution exposure
Environmental toxicologists and epidemiologists continue to study the effect of pollution on human health. In Europe, [15] the USA [16] and China [17], [18], [19] studies repeatedly show that the acute and long-term effects of ozone and particulate matter exposure are associated with increased cardiovascular [2] and respiratory mortality and morbidity [20]. Additionally, there is growing evidence that other organs might also be affected by air-borne particle pollution. Recent reports indicate a
Possible mechanisms of action
Current research suggests that each individual air pollutant most probably has a specific, toxic action on the skin (Fig. 1). From a theoretical point of view, this might be due to an outside-inside effect, e.g. penetration of PM and/or organic compounds bound to PM into the skin. Another possibility could be an inside–outside mechanism. Accordingly, it is well established that PM exposure might cause systemic effects as a consequence of (i) particles penetrating the lung and subsequently the
Sensitive skin: a condition at a higher risk for risk pollution-induced damage
The concept of sensitive, reactive and intolerant skin was originally developed by Kligman et al. Although sensitive skin is not clearly defined as a dermatological pathology, continued reports of related symptoms led to this current definition: An onset of subjective complaints of discomfort, (stinging, itching, burning, dryness erythema desquamation, papules, or scaling) without an immunological response. It is defined as a multifactorial, inflammatory syndrome with signs of non-immunological
Implications for skin care
In general, cosmetic strategies to protect human skin against pollution-induced damage include general and specific approaches. General strategies include the topically applied products, which help to reduce particle load on skin or, which improve skin barrier function to reduce cutaneous pollutant penetration. Examples include rinse-off products as well as typical products known to reduce transepidermal water loss and thus increase skin barrier function such as emollients. Also, there is
Role of funding
La Roche-Posay Pharmaceutical Laboratories, China provided funding for the board meeting, and medical writing support to draft and edit the manuscript.
Acknowledgement
Amy Whereat, Speak the Speech Consulting provided drafting and editing assistance.
Jean Krutmann, MD, was on 3rd April 1959. Currently, Jean Krutmann is Professor of Dermatology and Environmental Medicine and Director of the IUF – Leibniz Research Institute for Environmental Medicine at the Heinrich-Heine-University Düsseldorf. Furthermore, he is a coordinator of the Leibniz Research Alliance “Healthy aging” (a strategic alliance of 23 Leibniz institutes). His research is in the field of dermatotoxicology and immunodermatology with special emphasis on environmentally-induced
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Jean Krutmann, MD, was on 3rd April 1959. Currently, Jean Krutmann is Professor of Dermatology and Environmental Medicine and Director of the IUF – Leibniz Research Institute for Environmental Medicine at the Heinrich-Heine-University Düsseldorf. Furthermore, he is a coordinator of the Leibniz Research Alliance “Healthy aging” (a strategic alliance of 23 Leibniz institutes). His research is in the field of dermatotoxicology and immunodermatology with special emphasis on environmentally-induced skin diseases and skin aging. He is author or co-author of more than 200 papers. He is the recipient of the International Arnold-Rikli-Award, the Albert Fleckenstein Award, the Paul Gerson Unna Award, the Oscar Gans Award, the C.E.R.I.E.S. Research Support Award and the Dermopharmacy Innovation Award. He is a visiting and adjunct professor of dermatology at the Nagoya City University, Japan, Case Western Reserve University, Cleveland, OH, USA and University of Alabama, Birmingham, AL, USA. He is a member of the National Academy of Science of Germany and Xu Guang Qi Lecturer, Shanghai Institute for Biological Sciences (CAS), Shanghai, China.