The health case for urgent action on climate changeBMJ 2020; 368 doi: https://doi.org/10.1136/bmj.m1103 (Published 30 March 2020) Cite this as: BMJ 2020;368:m1103
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Air pollution become the biggest global killer and the developing world is most affected by it.  Global mortalities from air pollution exceeded 3 million annually , including 1.4 million annual deaths in China and 0.65 million annual deaths in India.  Due to smog thousands of death per annum occurred in Indonesia.  Haze also causes annual 40,000 premature deaths globally.  Air pollution causes 180 deaths per day in Iran, and more than 8 deaths per day in Afghanistan.  Due to haze, Iran and India declared health emergency in 2015 and 2016 respectively. [2,3] About 70 Asian cities are listed among 100 most polluted cities of the world.  Top 10 out of 15 worst polluted spots of world exist within India having 153 PM 2.5 mcg/ m3 of air. While 11 cities in China have faced red alerts. 
Tran-boundary smog from Indonesia due to forest burning mantles Malaysia, Philippines, Singapore and Thailand for several months every year and affects the health of billion of people.  Many cities in south Asian countries like Bangladesh, India and Pakistan have the worst air pollution.  Egypt has 100 times appalling condition than the safety standards of World Health Organisation. Some cities of west Asian countries such as Qatar, Abu Dhabi, Saudi Arabia also have higher air pollution. [1,5] Annual mean of air pollution in United Arab Emirates is 80 PM 2.5 mcg/ m3 of air. 
Many toxic components in air such as black carbon, nitrates, ozone and sulphates initially cause the cough, dermatological and ophthalmic irritation. [1,4] While prolong exposure causes respiratory diseases such as asthma, chronic obstructive pulmonary disease, rhinitis and lungs cancer, it also increases the risk of heart diseases and stroke. [1,2] While some new studies revealed that progression of diabetes mellitus, pediatric mental health, neural diseases of adults and other neurodegenerative diseases like Alzheimer's are also associated with air pollution. [2,4] Due to haze, the annual cost of illness is increasing globally and estimated about US$ 5000 billion.  There is an imperative need of industrial smoke reduction, use of renewable energy resources by collective efforts and life style modification.  Guidelines and in-depth involvement of United Nations Environment Programme (UNEP) can play effective role. Abrupt and absolute control over haze is impossible. However, incessant awareness of community about safety precautions during hazy milieu will reduce the risk of maladies; enhance the quality of health and life expectancy in Asia. Every country should initiate a large scale public intervention and educational programme.
1. Vidal J .Beijing and 10 other Chinese cities have issued red alert warnings. The Guardian May 11, 2016 https://www.theguardian.com/environment/2016/may/12/air-pollution-rising... (accessed, Nov 21,2016)
2. Carrington D. New inhaler protects lungs against effects of air pollution. The Guardian Sep 16,2016 https://www.theguardian.com/environment/2016/sep/16/new-inhaler-protects... (accessed, Nov 21,2016)
3. Vidal J. Air pollution: a dark cloud of filth poisons the world’s cities. The Guardian. Jan 16, 2016 https://www.theguardian.com/global-development/2016/jan/16/winter-smog-h... (accessed, Nov 21,2016)
4. What causes South East Asia's haze?. BBC. Oct 26, 2015. http://www.bbc.com/news/world-asia-34265922 (accessed, Nov 21,2016)
5. Underwood M. The grey area over air pollution. The Nation.UAE. July 29,2015 http://www.thenational.ae/uae/environment/the-grey-area-over-air-pollution (accessed, Nov 21,2016).
Competing interests: No competing interests
Air pollution in the Po Valley, especially particulate matter (PM) has received increasing attention in the past years, since exposure to PM2.5 and PM10 is notoriously associated with a number of adverse health effects, ranging from respiratory and cardiovascular to neurological and metabolic diseases or even premature death.  At the same time, a number of studies have shown that airborne transmission route could spread viruses even further the close contact with infected people. [2-15] An epidemic model based only on respiratory droplets and close contact could not fully explain the regional differences in the spreading of the recent severe acute respiratory syndrome COVID-19 in Italy, which was fast and dramatic only in Lombardy and the Po Valley.
The higher mortality rates associated with COVID19 observed in these areas, already characterized by atmospheric stability and high humidity, were proposed on March 16th 2020 in the Italian Society of Environmental Medicine (SIMA) Position Paper to be associated with the peaks of fine particulate matter concentrations, frequently exceeding the legal limit of 50 µg/m3.  A significant correlation was found between the geographical distribution of the daily PM10 exceedances in 110 Italian Provinces and the spreading of the COVID-19 infection during the time-lapse of the study, with the number of PM10 exceedances being much more frequent in Lombardy and in cities located in the Po valley than those registered in Rome and Southern Italy, where the diffusion and lethality of the virus was significantly lower if compared with that observed in Northern regions.  Research carried out by the Harvard School of Public Health seems to confirm an association between increases in particulate matter concentration and mortality rates due to COVID-19. 
These first observations suggest that particulate matter could be regarded as an indicator of the severity of COVID-19 infection in terms of diffusion and health outcomes. Further experimental studies could assess the possibility that particulate matter may act as a “carrier” for the viral droplet nuclei, impressing a boost effect for the spreading of the viral infection, as it has been shown for other viruses.
Indeed, Paules et al. (2020) highlighted that airborne transmission of SARS-CoV can occur , besides close distance contacts. For different pathogens, it has also been reported how they can reach long distances thanks to airborne transport [5-7]. Reche et al. (2018) described the aerosolization of soil-dust and organic aggregates in sea spray that facilitates the long-range transport of bacteria - and likely of viruses - free in the atmosphere. In particular, virus deposition rates were positively correlated with organic aerosol <0.7 µm, implying that viruses could have longer permanence times in the atmosphere and, consequently, will be dispersed further .
Moreover, Qin et al. (2020) analyzed the microbiome of the airborne particulate matter (PM2.5 and PM10) in Beijing over a period of 6 months in 2012 and 2013, putting in evidence a variability of the composition that depended on the months . Temporal distribution of the relative abundance of the microbiome on the particulate matter (PM) showed the highest presence of viruses in January and February, just in coincidence with highest concentration of particulate matter. Chen. et al (2017) demonstrated the relationship between short-term exposure to PM2.5 concentration and measles incidence in 21 cities in China . Their meta-analyses showed that the nationwide measles incidence was significantly associated with an increase of 10 µg/m3 in PM2.5 levels.
Other recent studies have also reported associations between particulate matter concentrations and infectious diseases (e.g., influenza, hemorrhagic fever with renal syndrome) because inhalation could bring PM deep into the lung and virus attached to particles may invade the lower part of respiratory tract directly, thus enhancing the induction of infections, as demonstrated by Sedlmaier et al. in 2009 . Zhao et al. (2018) showed that the majority of the positive cases of highly pathogenic avian influenza (HPAI) H5N2 in Iowa (USA) in 2015 might have received airborne virus, carried by fine particulate from infected farms both within the same State and from neighboring States . Ma et al. (2017) observed a positive correlation of the measles incidence with PM10 in western China during the period 1986-2005. 
The condensation and stabilization of the bio-aerosol, generating aggregates with atmospheric particles from primary (i.e. dust) and secondary particulate, has been indicated as mechanisms able to transport airborne bacteria and viruses to distant regions, even by the inter-continent-transported dust.  Ferrari et al. (2008) described measles outbreaks occurring in dry seasons and disappearing at the onset of rainy seasons in Niger , but Brown et al. had already found that the most severe measles epidemic in the United States occurred in Kansas in 1935 during the Dust Bowl period . Coming to recent specific studies, laboratory experiments of Van Doremalen et al. (2020) indicated that airborne and fomite transmission of SARS-Cov-2 is plausible, since the virus can remain viable and infectious in aerosol for hours .
Based on the available literature, there is enough evidence to consider the airborne route, with a possible role of particulate matter, as a possible additional infection “boosting” factor for interpreting the anomalous COVID-19 outbreaks observed in Northern Italy – known to be one of the European areas characterized by the highest PM concentration . Therefore, there is the rationale for carrying out experimental studies specifically aimed at confirming or excluding the presence of the SARS-CoV-2 (and its potential virulence) on particulate matter of Italian cities as well as at European and international level. Urgent actions must be adopted to counteract climate changes and the alteration of ecosystems that might trigger new and unexpected threats to human health such as that of COVID-19, which we are so dramatically experiencing worldwide.
1. European Environment Agency (2019) Air quality in Europe. EEA Report No 10/2019. https://doi.org/10.2800/822355 (2019)
2. World Health Organisation, Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations, Scientific brief. https://www.who.int/news-room/commentaries/detail/modes-of-transmission-... (29 March 2020)
3. Cai J, Sun W, Huang J, Gamber M, Wu J, He G. Indirect virus transmission in cluster of COVID-19 cases, Wenzhou, China, Emerg. Infect. Dis.
https://doi.org/10.3201/eid2606.200412 (2020 June)
4. Paules, C.I., Marston, H.D., Fauci, A.S. Coronavirus infections – More than just the common cold. JAMA, 323 (8), 707-708. https://doi.org/10.1001/jama.2020.0757 (2020)
5. Sorensen, J. H., Mackay, D. K. J., Jensen, C. Ø., Donaldson, A. I. An integrated model to predict the atmospheric spread of foot-and-mouth disease virus Epidemiol. Infect., 124, 577–590 (2000)
6. Glostera, J., Alexandersen, S. New Directions: Airborne Transmission of Foot-and-Mouth Disease Virus Atmospheric Environment, 38 (3), 503-505 (2004)
7. Reche, I., D’Orta, G., Mladenov, N., Winget, D.M., Suttle, C.A. Deposition rates of viruses and bacteria above the atmosperic boundary layer. The ISME Journal. 12, 1154-1162 (2018)
8. Qin, N., Liang, P., Wu, C., Wang, G., Xu, Q., Xiong, X., Wang, T., Zolfo, M., Segata, N., Qin, H., Knight, R., Gilbert, J.A., Zhu, T.F. Longitudinal survey of microbiome associated with particulate matter in a megacity. Genome Biology. 21, 55 (2020)
9. Chen, G., Zhang, W., Li, S., Williams, G., Liu, C., Morgan, G.G., Jaakkola, J.J.K., Guo, Y. Is short-term exposure to ambient fine particles associated with measles incidence in China? A multi-city study. Envirnmental Research. 156, 306-311.
10. Sedlmaier, N., Hoppenheidt, K., Krist, H., Lehmann, S., Lang, H., Buttner, M. Generation of avian influenza virus (AIV) contaminated fecal fine particulate matter (PM2.5): genome and infectivity detection and calculation of immission. Veterinary Microbiology. 139, 156-164 (2009)
11. Zhao, Y., Richardson, B., Takle, E., Chai, L., Schmitt, D., Win, H. Airborne transmission may have played a role in the spread of 2015 highly pathogenic avian influenza outbreaks in the United States. Sci Rep. 9, 11755. https://doi.org/10.1038/s41598-019-47788-z (2019)
12. Ma, Y., Zhou, J., Yang, S., Zhao, Y., Zheng, X. Assessment for the impact of dust events on measles incidence in western China. Atmospheric Environment. 157, 1-9 (2017)
13. Ferrari, M.J., Grais, R.F., Braiti, N., Conlan, A.J., Wolfson, L.J., Guerin, P.J., Djibo, A., Grenfell, B.T., Bjornstad, O.N. The dynamic of measles in sub-Saharan Africa. Nature. 451, 679-684 (2008)
14. Brown, E. G., Gottlieb, S., Laybourn, R.L. Dust storms and their possible effect on health, with Special reference to the dust storms in Kansas in 1935. Public health Rep. 50 (40), 1369-1383. https://doi.org/10.2307/4581653 (1935)
15. Van Doremalen, N., Morris, D.H., Holbrook, M.G., Gamble, A., Williamson, B.N., Tamin, A., Harcourt, J.L., Thornburg, N.J., Gerber, S.I., Lloyd-Smith, J.O., de Wit, E., Munster, V.J. Aerosol and surface stability of SARS-Cov-2 as compared with SARS-Cov-1. The New England Journal of Medicine. . https://doi.org/10.1056/NEJMc2004973 (2020)
16. Italian Society of Environmental Medicine (SIMA) Position Paper on Particulate Matter and COVID-19, available at: http://www.simaonlus.it/wpsima/wp-content/uploads/2020/03/COVID_19_posit...
17. Xiao Wu, Rachel C. Nethery, M. Benjamin Sabath, Danielle Braun, Francesca Dominici, Exposure to air pollution and COVID-19 mortality in the United States, available at: https://projects.iq.harvard.edu/files/covid-pm/files/pm_and_covid_mortal...
Competing interests: No competing interests