Spraying of Disinfectants to Large Outdoor Areas

Spraying of disinfectants

Sri Lanka College of Microbiologists would like to bring attention to the practice of spraying disinfectants to large outdoor areas such as streets and public areas as a method of preventing spread of COVID-19.

SARS-CoV2, the causative agent of COVID-19, has been shown to survive from hours to days on contaminated surface, particularly, frequently touched surfaces. Therefore, considering the possibility of hand to face transfer of the virus, which can result in spread of the disease, decontamination of such surfaces is required. The Sri Lanka College of Microbiologists (SLCM) is of the view that disinfectants should be applied on surfaces that are highly or frequently touched by public, such as hand railings, door knobs, poles on transit vehicles, elevator buttons, park/ street benches, counters etc. Rather than spraying large quantities of disinfectants on streets and public areas, we suggest that frequently touched surfaces should be wiped down or cleaned with appropriate disinfectant solutions. 

Large scale spraying of disinfectants to environment may have serious consequences on human health. Further, this practice may result in negative effects on the environment, fauna and flora as well. 

Chemical disinfectants such as hypochlorite-based products, alcohol and glutaraldehyde/ formaldehyde are used for spraying/ fogging of the environment. Some of the hazardous effects of widespread use of disinfectants in the environment are mentioned below;

  1. Inhalation of chlorine-based disinfectants may cause irritation of the respiratory tract and worsening of asthma in humans (1,2). They may also be irritating to skin and eyes. Studies show that widespread use of chlorine compounds in Africa during and the aftermath of the Ebola outbreak has led to adverse health impact in humans (3). Further, the World Health Organization (WHO) does not recommend spraying of chlorine compounds on humans and animals at any point (4).
  2. Concerns have been raised on the use of disinfectants in agriculture and aquaculture (5,6). Therefore, the release of large volumes of disinfectants into the environment as an infection prevention strategy is likely to have similar consequences and concerns.
  3. Some disinfectants have shown a dose dependent negative impact on the environment under experimental conditions in toxicity bioassays (7).  The heavy use of the disinfectants on roads and other public places results in increase of the load of chlorine released into the environment. A high concentration of sodium hypochlorite is generally used for disinfection and the level may reach up to 5000 ppm.  Therefore there is a possibility of environmental toxicity.
  4. When released to the environment, bleach releases chlorine that readily reacts with organic matter present in soil and water generating organochlorine compounds. These compounds are highly toxic to the humans, environment and wildlife. These organic byproducts have toxic effects on human health, such as, hormone related conditions (endometriosis, infertility), cancer of male and female reproductive system, developmental toxicity, neurotoxicity and immunotoxicity (8,9).
  5. Some of the residual disinfectants seep into the soil while the rest is carried away with runoff water into waterways Therefore, the organochlorine compounds may finally end up in water table.
  6. When the disinfectants are sprayed to the environment, exposure to suboptimal levels of disinfectants by the environmental bacteria may lead to development of antibiotic resistance in these bacteria, worsening the public health crisis the world has been facing during the past few years (10).
  7. With widespread disinfectant spraying, saprophytic beneficial soil microorganisms can be destroyed affecting the decomposition of waste and treatment of sewage.
  8. Further, there is a significant fire hazard when alcohol is used in large quantities to spray the environment due to their highly inflammable nature. Inhalation of alcohol also has been shown to have side effects such as irritation of nose, throat as well as detectable levels in blood (11,12).
  9. When glutaraldehyde/ formaldehyde are used in spraying or fogging, they can have acute health effects such as irritation of the eyes and skin with contact. Breathing glutaraldehyde/formaldehyde can irritate the nose, throat, and respiratory tract, causing coughing and wheezing, nausea, headaches, drowsiness, nosebleeds, and dizziness. With chronic exposure they can cause a skin allergy, chronic eczema and worsening of asthma symptoms (13). In addition, The International Agency for Research on Cancer (IARC) classifies formaldehyde as a human carcinogen (14).

Chlorine-based disinfectants (which are commonly used in Sri Lanka) are usually unstable in both concentrated and diluted forms, as they are affected by heat and light. Therefore, to be effective, hypochlorite containing solutions, need to be freshly prepared and should be available in the concentration needed to achieve the desirable effects. Further, there should be an adequate wet contact time. Presence of organic matter and dirt is known to reduce the effectiveness of these compounds. Therefore, cleaning with a detergent is generally encouraged before use of these preparations, even in healthcare settings. Therefore, their effectiveness on outside environment is debatable (15). Further, disinfectants may disintegrate or degrade with exposure to different environmental conditions such as sunlight.

Spraying large quantities in to environments, as a measure to prevent COVID-19, done as a once or twice a day practice in crowded public places such as in bus stands/ depots, train stations, public/ private transport, schools, gymnasiums etc.  may not be effective, since these areas and surfaces are constantly being contaminated by the people touching the surfaces. For it to be effective in destroying the virus, and breaking the chain of transmission of COVID-19, these frequently/ highly touched surfaces in public areas should be disinfected very frequently. Therefore, frequent fogging/ spraying disinfectants in crowded public places may not be a practical solution, and also during fogging/ spraying all the people should be evacuated from these areas. Hence, the practical solution would be to wipe the highly/ frequently touched surfaces in these public places with a disinfectant. Further, spraying in large quantities of disinfectants result in wastage of these disinfectants, when they can be put to much better use in preparing hand sanitizers and for surface disinfection in healthcare and other high-risk environments.

Other countries and experts have started to actively discourage the spraying of roads and public places with chlorine based disinfectants (16,17). Further, China, where this practice was initially started, has also issued warnings against it now. (18).

The World Health Organization, in their document dated 15th May 2020 has also stated clearly that spraying/ fogging of indoor and outdoor environments is likely to be ineffective and harmful to humans. Hence, in their document, practices such as spraying or fogging of indoor and outdoor spaces as well as spraying of disinfectants directly on humans are not recommended (19). 

Considering the available evidence and global consensus, the Sri Lanka College of Microbiologists wishes to emphasize the need to disinfect frequently touched surfaces in public areas while strongly discouraging widespread spraying of public places and strongly condemning spraying disinfectants directly on to humans or animals.


  1. World Heath Organization (WHO). Environmental Health Criteria 216. DISINFECTANTS AND DISINFECTANT BY-PRODUCTS. 2000. Available from https://apps.who.int/iris/bitstream/handle/10665/42274/WHO_EHC_216.pdf;jsessionid=6AE3D38F4C158B588BD8EF71C196420D?sequence=1. Accessed on 16/06/2020
  2. Hoyle GW, Svendsen ER. Persistent effects of chlorine inhalation on respiratory health. Ann N Y Acad Sci. 2016 Aug;1378(1):33-40. doi:10.1111/nyas.13139.
  3. Mehtar S, Bulabula AN, Nyandemoh H, Jambawai S. Deliberate exposure of humans  to chlorine-the aftermath of Ebola in West Africa. Antimicrob Resist Infect Control. 2016 Nov 14;5:45. eCollection 2016. PubMed PMID: 27895903; PubMed Central PMCID: PMC5109677.
  4. WHO. Spraying and introducing bleach or another disinfectant into your body WILL NOT protect you against COVID-19 and can be dangerous. Coronavirus disease (COVID-19) advice for the public: Myth busters. Available from https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public/myth-busters . Accessed on 16/05/2020
  5. FAO. Environmental aspects of aquaculture in the tropics and sub-tropics. Available from http://www.fao.org/3/ad002e/AD002E01.htm . Accessed on 16/05/2020
  6. Bruins G, Dyer JA. Environmental considerations of disinfectants used in agriculture. Rev Sci Tech. 1995 Mar;14(1):81-94. Review. PubMed PMID: 7548974.
  7. Agnelo L, Leonel LP, Silva NB, Candello FP, Schneider J, Tonetti AL. Effects of wastewater disinfectants on the soil: Implications for soil microbial and chemical attributes. Sci Total Environ. 2020 Mar 1;706:136007. doi: 10.1016/j.scitotenv.2019.136007. Epub 2019 Dec 9. PubMed PMID: 31846886.
  8. Solomon KR Chlorine in the Bleaching of Pulp and Paper.  Pure & Appl. Chem., Vol. 68, No. 9, pp. 1721-1 730, 1996. https://www.researchgate.net/publication/237300446
  9. Kleanthi1 G, Katerina L, Evaggelia P, Andrea L. Mechanisms of actions and health effects of organochlorine substances: a review. Health Science Journal https://www.hsj.gr/medicine/mechanisms-of-actions-and-health-effects-of-organochlorine-substances-a-review.php?aid=3667
  10. Nasr AM, Mostafa MS, Arnaout HH, Elshimy AAA. The effect of exposure to sub-inhibitory concentrations of hypochlorite and quaternary ammonium compounds on antimicrobial susceptibility of Pseudomonas aeruginosa. Am J Infect Control. 2018 Jul;46(7):e57-e63. doi: 10.1016/j.ajic.2018.04.201. Epub 2018 May 31. PubMed PMID: 29778432.
  11. National Research Council (US) Committee on Toxicology. Emergency and Continuous Exposure Limits for Selected Airborne Contaminants: Volume 2. Washington (DC): National Academies Press (US); 1984. No abstract available. PubMed PMID: 25032441.
  12. MacLean RR, Valentine GW, Jatlow PI, Sofuoglu M. Inhalation of Alcohol Vapor: Measurement and Implications. Alcohol Clin Exp Res. 2017 Feb;41(2):238-250. doi: 10.1111/acer.13291. Epub 2017 Jan 5. Review. PubMed PMID: 28054395; PubMedCentral PMCID: PMC6143144.
  13. OSHA;Glutaraldehyde. https://www.osha.gov/SLTC/etools/hospital/hazards/glutaraldehyde/glut.html
  14. International Agency for Research on Cancer (June 2004). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans Volume 88 (2006): Formaldehyde, 2-Butoxyethanol and 1-tert-Butoxypropan-2-ol. https://publications.iarc.fr/106
  15. CDC. Rationale and Considerations for Chlorine Use in Infection Control for Non- U.S. General Healthcare Settings. Available at https://www.cdc.gov/vhf/ebola/clinicians/non-us-healthcare-settings/chlorine-use.html.  Accessed on 15/05/2020
  16. Health Department, Republic of South Africa, COVID-19 Disease: Infection Prevention and Control Guidelines Version 1 April 2020. Available from https://www.idealhealthfacility.org.za/docs/Manuals-and-Handbooks/COVID%2019%20Disease%20Infection%20Prevention%20and%20Control%20Guidelines%20Version%201%20-%20%20April%202020.pdf
  17. Reuters, Mass disinfections to combat coronavirus pose another health hazard. https://www.reuters.com/article/us-health-coronavirus-disinfection/mass-disinfections-to-combat-coronavirus-pose-another-health-hazard-idUSKBN21I1PB. Accessed on 15/05/2020 
  18. Xinhua Agency, China. Available from http://www.xinhuanet.com/english/2020-03/02/c_138835959.htm and http://www.china.org.cn/china/Off_the_Wire/2020-03/02/content_75765503.htm  . Last accessed on 15/05/2020. Also available in Chinese as an official press release in Chinese language at http://www.nhc.gov.cn/jkj/s3577/202002/d1ae51c7899d4faaa763a2e67ebbd2e5.shtml?fbclid=IwAR1RnyaClZB0JeSeDRklgcD6P9iuelnNQ6PwyBD8q34Lppd0vfzjmMZe3lw . Last accessed on 16/05/2020  
  19. World Health Organization. (‎2020)‎. Cleaning and disinfection of environmental surfaces in the context of COVID-19: interim guidance, 15 May 2020. World Health Organization. https://apps.who.int/iris/handle/10665/332096. License: CC BY-NC-SA 3.0 IGO

Author: SLCM

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