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Junior Member News - October, 2019

Air Pollution and its Effects on Allergic Diseases: A New Story in Developing Countries

Air pollution has recently emerged as a worldwide problem, especially in developing countries. Recently, air quality has been worsen in Southeast Asia (SeA), and the countries located in SeA are enveloped by a blanket of smog containing pollutants, such as particulate matters (PMs) and volatile organic compounds (VOCs)1. In September 2019, the air quality in the large cities of Viet Nam, such as Ha Noi and Ho Chi Minh City exceeded red warning level, with AQI over 2002. According to the unpublished records from those cities, numbers of patients visiting hospitals with allergic diseases, including asthma, atopic dermatitis and urticaria were dramatically increased. That has prompted the scientists in SeA countries to focus on investigating the effects of air pollutants on respiratory and cutaneous allergic diseases.

PMs are main elements of polluted air that have significantly negative effects on human organ systems. Among PMs, PM 2.5 (fine particles with diameters under 2.5 µm) has been widely investigated and expresses various biological effects on human cells and tissues. PM 2.5 is known to trigger respiratory diseases by inhalation, such as asthma and COPD. Nevertheless, its effects on human cutaneous system have not been fully understood. The skin is the largest organ of the human body that is always exposed to polluted particles in the environment. Association studies have shown that exposures to PMs and VOCs could aggravate inflammatory skin diseases, including psoriasis and atopic dermatitis (AD). Moreover, prenatal exposures to PMs could be associated with the development of AD in children3. Limited studies have been performed to elucidate the mechanisms how PMs induce skin inflammation. PMs could damage the skin barrier by inducing oxidative stress, which further stimulated keratinocytes to produce pro-inflammatory cytokines such as TNF-alpha and IL-8. In addition, PM exposure induced the production of matrix metalloprotease (MMP)-1, MMP-2 and MMP-9, which caused the degradation of collagen4. A recent in vivo study in Korea has shown that PM could penetrate through the barrier-disrupted skin and go to the intercellular space of the epidermis, which then induced skin inflammation. Moreover, PM could accumulate in the secondary lysosomes of keratinocytes, induce oxidative stress and the production of pro-inflammatory cytokines such as IL-8 and MMP-15.

Although there are in vitro and in vivo data showing the mechanisms how PMs induce skin allergic inflammation, the localization of PMs on human skins and its communication with the skin immune system in allergic diseases are not understood and remain to be elucidated. In addition, before the national authorities establish policies to reduce air pollution, methods to prevent its harms on human body are crucial. Young scientists in the University of Medicine and Pharmacy at Ho Chi Minh City, Viet Nam, are conducting studies to investigate the effectiveness of low-cost protection methods against air pollution, e.g. wearing N95 masks, or thick and long sleeve clothes, as well as daily body cleansing behaviors, in respiratory and skin allergic diseases. Those studies would be very helpful for people living in developing countries, where pollution level is high and average income is low. Junior members of WAO could conduct or join in those researches, as well as utilize public media to raise the awareness of people about air pollution and its negative effects on allergic and other diseases.

References:

  1. https://thediplomat.com/2019/09/southeast-asias-deadly-annual-haze-is-back/
  2. https://vietnamnews.vn/society/536158/air-pollution-in-ha-noi-exceeds-red-warning-level.html
  3. Ahn K. The role of air pollutants in atopic dermatitis. J Allergy Clin Immunol 2014; 134: 993-9)
  4. Kim KE, Cho D, Park HJ. Air pollution and skin diseases: Adverse effect of airborne particulate matter on various skin diseases. Life Sci 2016; 152:126-34.
  5. Jin SP, Li Z, Choi EK, et al. Urban particulate matter in air pollution penetrates into the skin barrier-distrupted skin and produces ROS-dependent cutaneous inflammatory response in vivo. J Dermatol Sci 2018; 152:126-134.

Duy Le Pham, MD., PhD
Faculty of Medicine
University of Medicine and Pharmacy at Ho Chi Minh City
Ho Chi Minh City, Viet Nam