 Hi, today we are facing unprecedented times with the coronavirus pandemic and there are a lot of new kind of issues we are struggling with on a daily basis. One of the issues which many of us have to deal with is how to keep our homes, our workplaces safe. And safe in the sense, infection free, particularly with respect to the coronavirus infection. One of the best practices is to keep social distancing in washing your hands on a regular basis. But also, if there is a exchange, if you have touched any surface, you have brought in something from outside, you are going to office place where other people are coming. How do you ensure that surfaces and living environment remain clean? One of the substance which we use and we are actively using these days are disinfectants and we are using them to ensure that we do not pick up the space around us remains clean. But many of us are not aware of the effects, rather harmful effects these disinfectants can produce. So, this presentation is about understanding science of these disinfectants, how they work, what are their properties and when to use them so that we can make wise decisions about their use. Before we understand disinfectant, first we must understand about the virus which we are trying to disinfect. In this context, I am going to present some information which is based on research literature which is available so far on the latest novel coronavirus. This data is not based on experiments done by me, but I will do my best to present the results. Please note that the results I am presenting are for external use on materials and human skin only and this does not apply for internal treatment. That means it cannot be taken for medicinal intake for patients inside the human body. The third thing, I am only discussing substances that are in common use at household level. I am not discussing certain substances which are recommended for clinical settings or surgical settings. So, we are largely talking about the novel coronavirus, however, there have been a lot of human coronaviruses known so far and sometimes talking about coronaviruses, many results get mixed up. To clarify first, let us try to understand the kind of human coronaviruses known so far. As you might have heard in many articles and many fora, coronaviruses are not new to humans. The first human coronavirus was identified in 1965 when a young boy was infected and the viral sample was isolated from his body. This coronavirus was titled as HCOV B814, HCOV stands for human coronaviruses and B814 was the code assigned to it, but the sample could not be preserved. However, later on, many coronaviruses were found prevalent in humans. One of the most prominent of these is HCOV 229e. This has been found in people from almost all continents of the world so far. Along with 229e, OC43, these two coronaviruses are now found to be causing common cold-like symptoms almost at the change of season and particularly in the cold winter months. They cause runny nose which goes on for seven to eight days, some in some people five days. Then later to other viruses, coronaviruses and then 63 NHQ1 were found to be causing lower respiratory tract problems. In general, these four coronaviruses are found quite prevalent, but they were not known to be factored. At the beginning of this century in the year 2002, severe coronavirus infection broke out in China in December 2002. The disease associated with was called severe acute respiratory syndrome or SARS and the coronavirus was labeled as SARS-CoV. This virus infected about 40,000 people of which 800 died. This was the first fatal case of coronavirus infection and it really made the research community and the public health community wake up to realize that coronaviruses can also be factored. Later on in 2012, in South Arabia, another variant of coronavirus which was called as MERS, Middle Eastern respiratory syndrome, CoV, in this case about 8,000 people were infected of which 858 died. The fatality rate was even higher than that of the 2003 variant. Now we all know the novel coronavirus which we are struggling with and this coronavirus is now called SARS-CoV-2 similar to the one which came emerged in China in 2002 and we all know the fatalities which we all are observing the whole in the whole world. The disease associated with this coronavirus is called coronavirus disease 2009 or CoV-19. Before we understand about inaguration, let's take a look at its structure. This kind of image you may have seen by now in many TV or internet videos and even many print media. Now the structure of coronavirus is relatively simple, chemically. It has three main components. It is roughly spherical in shape and outside the spherical shape you see these are their spike structures. These are proteins. These are also known as spike proteins. Then this the spherical envelope is made up of lipids. Lipids are a class of compound which involves fatty acids and fats. Yes, exactly the same compounds which we use as oils and fats. They are important structural components of biological cells to be more specific. Inside this lipid core is RNA, ribonucleic acid. There is not much inside this envelope other than RNA and liquid of protein. Now technically speaking viruses are not living organisms. We have been hearing about them infecting humans but they don't live, they don't eat, they don't excrete, they don't respire and they don't reproduce. Yes, technically they don't reproduce by themselves. What maximum they can do is they can attach themselves to a specific host cell and they can induce changes in the cell and furthermore and more specifically they can induce host cell to produce copies of itself and that is how they produce more viruses like itself. If you want to say that reproduction but technically it's not reproduction but this is how the virus is multiplied. So therefore they are very much unlike other microorganisms. I would rather call them complex chemical entities. Since they are not living organisms, killing a virus doesn't mean anything. A better word to use is inactivation and inactivation of virus would mean that you have to change or alter its chemical structure so that it becomes incapable of infecting another cell. Inactivation studies have been going on for all the cases of human coronavirus and there is quite a vast literature available about it. I will here focus on the 2003 coronavirus because structurally it's quite similar to the current novel coronavirus. For this coronavirus there are two major studies which are available so far. So one is what was done in 2004 and the second one was done in 2007. Both these studies could identify five conditions at least which could inactivate the coronavirus. One of it was heat treatment and particularly heat treatment above 70 degree centigrade. They found that if a sample of virus is exposed to a temperature greater than 70 degree centigrade for more than 30 minutes the virus could be completely inactivated. To help you better understand these reasons I would like to briefly explain what these two graphs means. Typically virus concentration is expressed in a number called virus titer. It's called titer because it's something similar to titration what we do in chemistry. So viruses cannot be counted directly. The way it is done is that you treat a sample of virus with a collection of cells whether it's a bacteria cell or mammalian cell those cells with this virus can infect and you let the virus infect the cells and then you count the population of cells which could be infected by this virus. So in a way it's like chemical titration. Now exact counting of cell is also not possible. It is done in order of magnitude and the numbers are expressed as a statistical value. So it's expressed in a logarithmic scale. So for example tcid of 6 would mean about 10 to the power 6 or 1 million viruses per 1 million of active viruses infectious viruses per ml of the sample. So now we come to this particular data when the sample was incubated at 75 degree centigrade within 15 minutes there was about 5 log reduction. 5 log reduction means the population fell by reduced by 10 to the power of 5 times or 1 lakh times reduction in population and after that in another sample which was incubated for about 30 minutes there was a slightly higher infective virus found. So in general they concluded that about 30 minutes are required for complete inactivation of virus. In the second study done in 2007 the samples which were incubated at 68 degree centigrade they lost their complete infectivity within 30 minutes. However the samples which were incubated at 58 degree centigrade lost their infectivity within 60 minutes. So therefore at 58 degree centigrade it took 1 hour for complete inactivation whereas at 68 degree centigrade it took approximately 30 minutes for complete inactivation. Now further studies when they were done at 25 degree centigrade which is supposed to be the standard room temperature and 37 degree centigrade which is the typical body temperature of a healthy human being they found that extremely acidic condition that is pH equal to 2 or lower than 3 and extremely alkaline condition that is pH above 12 were sufficient to inactivate this virus within 1 hour of period. They did not do small time scale studies for these conditions. They also tried formalin and butyraldehyde you may be knowing that these are two sterilizing agents which are used to store many biological samples and organs in biological labs they are quite toxic in nature. Even these substances were not very effective as compared to the acidic and alkaline substances they were not so effective in activating the SARS-CoV it took 1 to 2 days when mixed in these two substances to inactivate the virus. On the other hand ultraviolet light of wavelength 254 nanometer was sufficient to inactivate this virus within 10 to 15 minutes when the light was irradiated from a distance of about 3 centigrade. Another important piece of information was that at 4 degree centigrade inactivation was not complete in extreme acidic conditions and at in formalin formaldehyde and butyraldehyde. Therefore at lower temperature the virus was much more safe the 2007 study did further investigation of the alkyline pH conditions because they found these were more relevant and more interesting because these were also effective at lower temperature conditions. They found that at 37 degree centigrade at pH 11 there was negligible effect in the population of virus even for 1 hour. That means this was much more sturdier than other coronavirus to give you example that other coronaviruses particularly 229E and OC the other variants they were inactivated significantly above pH 9. And that is why many you may be hearing a lot in the current literature that alkyline solutions above pH 9 can help in activating coronavirus. This may not be true for current coronavirus and particularly for the 2003 variant we know that it requires stronger pH higher pH conditions. So at pH 12 there is a 5 log reduction in a period of 1 hour. Now when they went to pH 13 interestingly they found instantaneous 3 log reduction within first minute of treatment. Here you will see the initial virus titer taken was higher than what was there in the earlier study. Here you see a log scale of 10 which means 10 million viruses per MN which required much longer time for complete inactivation. So at pH 13 it took about 2 hours for complete inactivation at 13.5 and at pH 13 it took about 5 hours for complete inactivation. So if the surface has a lower infection as corresponding to 10 to the power of 6 virus per ML then it may be inactivated in less than 1 hour also. Now till March 2020 there were no study available on inactivation of the novel coronavirus. Therefore this journal of hospital infection a prominent journal in the field of public healthcare particularly in the hospital settings did a review of published a review of 22 studies on human coronaviruses, 6 coronaviruses which were known before SARS-CoV-2 and they found that certain substances could inactivate when they defined inactivation as 3 log reduction and they found these substances were 62 to 71 percent ethanolic formulation then 0.5 percent of hydrogen peroxide, 0.1 percent of sodium hypochloride and let me mention that concentration which are much lower than 0.1 percent for example 0.01 percent of hypochloride solution were not as effective for inactivation and 0.23 percent of povidone iodine solution were effective for inactivation of the earlier coronaviruses. Interestingly other biocidal agents namely benzylconium chloride and chlorhexidine dilucidate these are two common substances used for antiseptic in antiseptic washes and even cleaning of frozen surfaces they were less effective. For benzylconium chloride in one sample they found almost no inactivation of virus whereas in one sample they found close to 2 to 3 log reduction of the virus population. Now in early April 2020 the study came in Lancet microbe they did a lot of valuable studies on inactivation of the novel coronavirus so I am presenting those studies here. Now in the temperature dependent studies they did let me remind you that Andy refers to experiment not done and you refers to when there was no virus detectable in the sample taken. So when the study was taken at 4 degree centigrade almost no inactivation was observed even after 14 days. Please note that the value represented here is on the log scale that means the value of 6.5 represents 10 to the power 6 virus per ml. At 22 degree centigrade this is a temperature we typically keep we are comfortable at this temperature we set for air conditioning in rooms typically. So at this temperature condition the virus starter was detected for at least 7 days that means the virus was stable under these conditions for about 7 to 10 days. At 37 degree centigrade the virus was stable for about one day. At 56 degree centigrade the virus was stable for about I would say 15 to 30 minutes and at 70 degree centigrade the virus was completely inactivated in less than 5 minutes. Please note that if you compare to the SARS-CoV-1 this virus was relatively easier to inactivate. In earlier case it took one hour at 56 degree centigrade. In this case 30 minutes were sufficient for complete inactivation of virus and at 70 degree centigrade here 5 minutes exposure was sufficient for complete inactivation whereas in the earlier case about half an hour of it at least 15 minutes of exposure was required. Now they did stability studies on several surfaces so on paper and tissue paper they found the virus was stable for about one to two hours at least. On wood and cloth the stability was of the order of one day. On glass and bank note interestingly the stability was of the order of three to four days. On stainless steel and plastic the virus was stable for the most longest period and that was about five to six days. If you compare these surfaces it looks like the virus was more stable on the smooth surface as compared to rough surface. For example if you take paper and bank note both are made of paper but bank note has polymeric coatings along with the paper to keep for its preservation and that is possibly one of the reason why the virus survives longer on bank notes. They also did studies on N95 mass and they found that on the inner layer of the mass the virus is stable for more than four days and on the outer layer the virus is stable for more than seven days and this is a crucial information too. Another study came in the last month where they also looked at some more surfaces in particular copper and cardboard so interestingly they found that the survival of the novel coronavirus and copper is much less than plastic and stainless steel. This could be because copper in general is a reactive surface it's a surface which tarnishes much faster and it has the the surface is in general rough even though how much ever smooth you take it it ruffles on its own and stainless steel and plastics are made to be more inert surfaces and therefore the survival is longer longer on these surfaces. They also did study on aerosols that means if you sneeze for example or you sing or shout loudly then if there is a spray of droplets from your mouth or nose in the air then it might the virus may be active for about three to four hours in that space. Actual timescale in an environment would depend upon the viral load and the actual environmental condition in general for coronavirus is drier at environment with low humidity make the virus faster inactive as compared to higher humidity environment. Now this group also looked at stability of the novel coronavirus with several disinfectants so they found that the household bleach was effective at inactivating the virus at even in five minutes. Interestingly they found that hands-off solution was effective in activating the virus within 15 minutes but in one sample they found there was significant population of virus left even it at five minutes. This could be because sometimes in viral suspensions virus make clumps and the soap may not be able to enter the viruses which were I mean it may inactivate the virus from the surface it may not be able to access the virus which are inside the clump and it takes slightly longer time on its own to inactivate all the viruses and that is why washing hands with soap or scrubbing the surface with soap solution it is advised to do gentle scrubbing so that at least if there is a cluster of viruses it comes in the solution phase and at least leaves the surface and then when it remains in the solution it will get inactivated on its own within few minutes. Now 70% ethanonic solution covidone iodine solution interestingly chlorozylonol chlorhexidine and benzalconium chloride solutions were also effective in inactivating this virus this is important information to note because these substances were relatively ineffective for the SARS-CoV-1. Now this showed that SARS-CoV-2 is inactivated by a wider range of disinfectant as compared to the earlier known normal coronaviruses in particular SARS-CoV-1 some of the other coronaviruses could also be disinfected by other substances but we are comparing SARS-CoV-1 and SARS-CoV-2. This is a good news in a way that we have a wider range of disinfectants which can sort inactivate the normal coronaviruses but we have to be now extra careful in dealing with disinfectants because now we are using disinfectants on an unprecedented scale and there are impacts. Let's start with the decision making process so whenever we have to make a call about using a certain disinfectant we have to first choose what formulation to make usually many of these disinfectant readymade formulations are available in the market but we need to be aware of the formulation secondly we have to know about how much and in what concentration this formulation or the disinfectant has to be used how frequently we should use it and then in what should be the mode of application there are many ways in which you can do it you can take a solution and spray it in the air the second way is you spray directly on the surface and then mop it the third way is you take a disinfectant solution you dip a cloth or a wipe in it and then use use it to scrub the surface and the fourth thing you can use it that you can soak a surface your hands or whatever has to be disinfected in a solution and leave it for a few minutes another important aspect which have to be looked at is the safety protocol or the safety procedure which must be followed by a worker doing the cleaning in this particular presentation I'm going to talk more about the properties of these disinfectant which can help you make decisions as per your needs and as per the substances available to you an important issue now we come to are the health concerns from disinfectant uses so here I'm reading a paragraph from a toolkit which is prepared for early care and education for green cleaning and sanitizing this is a program which is developed by University of California San Francisco School of Nursing so what they're seeing and leaving access we're constantly learning more about the potential health problems of cleaning sanitizing and disinfecting products some of these chemicals affect air quality and can cause or trigger health problems such as asthma for example 11 percent of people with work related asthma in California connected their asthma to cleaning and disinfecting products over half of these patients never had asthma before being exposed to these products inhaling the products caused asthma four out of five people diagnosed with work related asthma in these studies were bystander these were people who were not the persons doing the cleaning they were just either the users of this facility or they were just passing by so now we have to be really careful that these chemicals can directly cause health hazard a second important thing is the risk to covid patients and non-covid patients due to secondary infections and that too secondary infections that are picked up from spaces which are disinfected spaces for example hospitals and public health facilities for those of you are hearing for the first time this might sound counterintuitive to you so I'll elaborate a little bit so if you use a particular chemical in a space for a long time initially it has a killing effect on many microbes but over time many microbes including viruses can undergo changes or changes and they can slowly adapt themselves so that this is known as resistant to a disinfectant or anti-virus and so that they are no more affected by this particular chemical now in that space so you are you may be using a disinfectant you think that we have killed all the microbes and removed all the viruses but some of those resistance bacteria and viruses may still be there and when they cause the infection then those infections are not easily treatable by the commonly used medicines and other substances which have been used for dealing it earlier and as we know that many of the morbidities which are happening to covid patients are not just not just because of the covid disease but also of the secondary complications which are done another important aspect which is which I would like to highlight here is that there are a large number of viruses which exist inside and outside our body which are very important for controlling bacterial infections in humans for example even within the oral cavity there are large number of viruses which are called bacteriophages or bacteriophages depending upon how you pronounce it these pages keep a check on the bacterial population in a single day a normal human being excretes in the fecal sample about 10 to 10 to the power 12 to 10 to the power of 14 bacteriophages so this is not a small population and remember when we are using chemicals with the aim of killing all microbes and all viruses around us we are actually removing or inactivating the phages also hopefully not and if we are doing so then we are increasing the chance of developing infections and decreasing natural mechanisms which exist to fight these infections so apart from human health risk there are other issues which we have to be careful about using disinfectant and the second issue is that even though we may be using high concentration and high amount of disinfection disinfection may not be happening okay and this depends on the method of application i'm going to talk a little bit more about it in the coming slides then the third point is that many of these are active chemical substances and they also decay with time so they lose potency on storage or on the way you value them or you apply them and therefore we have to ensure that the substance being used retains its potency fourth point is that these chemical substances react with different materials and sometimes they may be causing damage to the material on which we apply so you cannot apply all disinfectants to all surfaces and sometimes the products which are formed after this reaction can also be harmful to the materials fifth and very important point is that these chemicals harm natural environment and ecology and we cannot ignore this point because the covid disease as we know is has its origin in ecological imbalance in the world which we have to see today now let's take a look at some of the common chemicals which are used in disinfecting and sanitizing substances and particularly which are effective for SARS-CoV-2 so first look at the substance which are effective for SARS-CoV-2 and we start with alcohols among the alcohols ethanol and isopropyl alcohol are propanol are known to be most effective in general disinfection and also effective against the current coronavirus their structure chemical structures are shown here the way they work is by denaturing and coglating proteins so in particular in this virus there are spike proteins so alcohols can coglate protein what is very important to note that the alcohols are effective in denaturing proteins at concentration of 60 to 90 percent so if you have a formulation which has alcohol less than 60 percent it alone may be effective in in activating the virus and the most important thing please note this carefully most important thing is that pure alcohol by itself is ineffective in inactivating it needs some water to denature the protein so please note that in some places you may be using a pure alcohol from a laboratory reagent water and then you apply anything that you have done even a better job of disinfection that's not true so you need some amount of water in that alcohol formulation for it to be effective second important thing to note is that alcohols are not effective against bacterial sports so sometimes if you are using this for disinfecting a space for a patient's skin which there is another wound or another clinical problem alcohol by itself will not be sufficient there have been cases where there have been outbreaks of infection just because the person used alcohol based disinfectant and felt that everything is safe and then the sports did the job certain precautions to be taken care when alcohols are used so alcohols evaporate fast and minimum of 20 second contact is required when you're using alcohol based sanitizer disinfectant or sanitizer so sometimes you may be using very little amount of this formulation or you may be applying to a surface that's hot so the 20 second of contact time is not achieved and therefore disinfection is not achieved second important feature which you have to be careful about is that alcohols are flammable and sometimes the flame of alcohol may be too faint to be visible but yet it's there it must be stored in cool and well ventilated area away from easily flammable substances secondly a sanitizer or disinfectant water containing ethanol must not be stored or used near hot appliances last two months we have come across news or cases of people who use kept this bottle in kitchen they applied alcohol based sanitizer on their hands and immediately switched on the gas stove and their hands called fire so this is a serious issue now many institutions are opening and in some places you may be using machines ovens furnaces or cooking stuffs and please make sure that you do not keep alcohol based sanitizers close to these spaces alcohols can react with certain plastics and rubbers and therefore they can damage certain parts of instruments so you cannot use alcohol based sanitizers or disinfectant on many of these surfaces only glass or plastics which are relatively inert or stainless steel you can use this alcohol based sanitizers next we look at sodium hypochloride disinfectant which is being recommended for a larger number of applications it's true it's very effective it's also known as hypo sodium sodium oxychloride or bleach solution it's an ionic compound which when dissolved in water it breaks into any plus and OCl minus it reacts with water to produce ectocel and NaOH so NaOH is a strong alkali therefore these solutions are slightly alkaline in pH the mode of action there have people have been writing that nascent oxygen or nascent chlorine may be produced that may be true partially but majority it is the HOCl species which reacts directly with protein enzymes DNA and lipids and it inactivates most microbes and viruses within 0.1 second so it's a very fast acting disinfectant no doubt about it but it's also highly reactive and it has highest reactivities with acids if you mix it with hydrochloric acid even very dilute it produces chlorine gas which is very toxic and if you mix it with even other dilute acids it produces other oxychlorides which are also equally and sometimes more toxic now another problem with sodium hypochloride is that these solutions are not stable over time in particular it decomposes below pH level as I said therefore it should never be mixed with any acid for any kind of cleaning unless done under expert guidance it decomposes easily about 25 degrees centigrade even at 25 degrees centigrade there is a very slow decomposition which is going on therefore it must be stored at cool places avoid hot places if by chance you have no option you have to keep a can or a bottle containing sodium hypochloride concentrated solution in a hot place you may want to wrap a wet cloth around it so that it remains cool contact with metal can also break down this chemical so don't store or dilute in metal container please be careful about it and light exposure also makes this solution to pick up as I said that sodium hypochloride has risk to human and other organisms a very important thing to note about sodium hypochloride is common disinfectant which has been used for about 100 years now and this or associated you know bleaching powder l-cemoxychloride they are used in disinfecting water supplies coming to our household taps so that means a lot of our environments living environments are already exposed to certain doses of chlorine and there are a lot of bacteria which are known to develop resistance to chlorine for hypochloride therefore this cannot be taken as a complete disinfecting substance this must be used after cleaning using soap and detergent for solution and this has to be used as a secondary second round cleaning now we look at hydrogen peroxide this is a solution you may have come across when you visit dentist this is the colorless solution which is given for you to rinse or gargle after any procedure is done it is also used in many laundry and household cleaning formulation also used as a bleaching agent now the way it works is that it has a same component as water oxygen in hydrogen it breaks down to produce OH radical of the hydroxyl radicals is hydroxyl radicals are extremely reactive species they can attack lipids which are there in the membranes in the outer envelope of a virus or bacteria it can attack membranes and nucleic acids now one thing we have to understand about free radicals is that many biochemical processes involve free radicals and these processes are mediated by enzymes so whenever a free radical external free radical encounters an enzyme enzyme can neutralize it and therefore stop it from acting many bacteria and pathogens have developed mechanisms to release enzymes particularly defend themselves against free radicals because free radicals can cause what is commonly known as oxidative stress or oxidative death to the cells now to overtake these defenses sometimes higher concentration of hydrogen peroxide we need it so if you use recently high concentration of hydrogen peroxide in certain situations a higher concentration will be desired you can use it against all microbes whether yeast fungus pores and viruses the nice thing about hydrogen peroxide is that it decomposes to give you water and oxygen and these the final products are safe for human beings and in general other higher in vaporized form in particular please note this is a recent study which has come that hydrogen peroxide spray can be used to disinfect N95 mass very important the surgical mass also which cannot be cleaned or disinfected using alcohol or please solution because this can affect the performance of this mask another problematic thing about hydrogen peroxide which to pay attention is that it is not effective on biofilms to give you ideas some of you may be knowing about biofilms those of you are not familiar biofilms are thin slimy layers which develop on any surface which is exposed to bacteria or microbes for a certain period of time so for example if you leave a bucket full of water in your bathroom many times you will find a slimy layer developing on the surface of the bucket okay in kitchen counters and bathrooms on the walls tiles you will see many times slimy layer of the things so these are polymeric layers which are created by bacteria and bacteria usually reside in these polymeric layers which are relatively safer places for bacteria in addition there may be viruses and phages which may be residing inside these spaces so biofilms if you have a very reactive substance like hydrogen peroxide it is very fast to react so it reacts with substances on the surface of biofilm so it is not able to penetrate or diffuse into the biofilms and therefore a lot of infections may remain if you just wash with hydrogen peroxide without scrubbing if you are able to do the scrubbing yes you can deal with this problem as well and just like sodium hydrochloride solution hydrogen peroxide solutions also break down over time so all solutions may have lower strength in particular if you have an organic matter which has certain enzymes present so enzymes can trigger or make the breakdown faster of hydrogen peroxide now other conditions are similar that temperatures about 25 degree centigrade context with metal or light exposure can easily reduce the concentration of the substance therefore you might have noticed that this substance is stored in almost dark black colored bottles and also kept in dark spaces now let's look at povidone iodine solution or this is also popularly known as betadine solution this is a solution of iodine complex with povidone so povidone is a water soluble polymer of vinyl pyrrolidine this is the structure of this polymer I'm showing here the purpose of this polymer is to keep iodine bound and complex so that the concentration of free iodine is very low the reason why this formulation was developed because earlier tincture iodine was in wider use and tincture iodine had high concentration of iodine which sometimes may be toxic in certain situations so tincture iodine was a formulation of iodine mixed with potassium iodide and dissolved in ethanol and water mixture now in povidone iodine small concentration of iodine exists at any time when this is consumed or reacted with any external substance then more iodine is released from the way from the polymer based on equilibrium and therefore its toxicity level under all conditions remain low usually iodine solutions are less used in disinfection because color stains may appear reaction wise iodine has similar reactions as chlorine but they are relatively less mild it reacts with lipids and membrane compounds in microbes it also blocks respiratory chain and coagulates nuclear material that is the DNA RNA present in any microbiome virus this can be used as a hand disinfectant important to note that because it has slightly lower reactivity than chlorine based substances it doesn't react fast and therefore it diffuses deeper into skin if you are using for hand wash or any surface it diffuses deeper and therefore it effect disinfecting effect persists for long for example if you are using alcohol or other disinfectant the effect may go may be persistent on your skin for about one to two hours whereas with povidone iodine solution the disinfecting effect is persistent for about 20 hours so this can be a very useful hand disinfectant particularly when you are working in a setting where you are exposed to infection for long hours for example waste management settings people who are handling medical waste or even other kind of a precious waste it has low toxicity and there are very rare cases known for allergies by povidone iodine and the most interesting thing is that iodine solutions have been in use in hospital settings and many other healthcare settings for more than 150 years and yet this is one substance for which they are least known cases of resistance bacteria developing in the planet this is a good news because that means we can use it particularly in spaces where we doubt resistance bacteria may be developing and important thing is that this substance is also active over biofilms this is because because iodine is slow reacting therefore a lot of it can diffuse within the biofilms and then act on the viruses and bacteria which is hiding inside the biofilms okay let's look at chlorozylonone it's also known as paraclorometozylonone PCMX this is the component of detal antiseptic wash is known for more than 90 years the chemical structure of this compound is shown here the way it acts is that the hydroxyl group on the phenyl ring reacts with membrane proteins and it changes the structure of the membrane proteins and hence causing leaks that causing leaks in the membrane of virus or bacteria and the other molecules can enter the membrane and then react further with protein and nucleic acid therefore reactivate them however complete mechanism of action of this substance is not fully known and it's known to be active on many bacteria fungi and viruses but not sports and there are contradictions in results on efficacy with bacteria and safety for users it's quite interesting that this is substances in use for more than 90 years and yet there's not complete clarity on its mechanism of action this is a compound which has low water solubility and low volatility and therefore the formulations are prepared in small amount of ethanol in water as a compound this is stable in light low heat and humidity therefore you may have known that detal or other chlorozylonone based formulations can be stored for one to two years without any loss in potency it's a good thing now the same property can also become problematic because if you have a spray of this solution in sunlight then in air it is stable even in sunlight for more than 24 hours it doesn't leak in sewage it has been found to be stable for more than seven days this can be particularly concerning because as you may be aware that sewage treatment plants in country and in the world are designed to have a hydraulic retention time of about three to four days typically you maybe have some plants having lower retention time and some very good plants which do up to tertiary treatment in a very elaborate manner may have a retention time up to nine days what it means is that the complete sewage will pass through that plant within that particular time period now if you have a substance which is persistent in sewage for more than seven days and this substance keeps on keeps on filling bacteria then it creates problem for the sewage treatment because sewage treatment is done by bacteria and microbes which feed on sewage and breaks it down this is one of the reason that we are using disinfecting substances in toilets and other household spaces on a regular basis that sewage is taking much longer to break down and therefore even though the sewage treatment plants were designed for effective treatment you have you are seeing effluents in which there is unnecomposed sewage now in US the regulation there is US EPA prohibits its discharge in sewage or water bodies without notification because if any facilities using this substance on a large scale then they must inform the sewage so that they can modify their treatment plant accordingly however in India we don't have any such notifications available and as a whole as a public we have to be aware to use it in a very controlled manner wherever necessary only there another important thing to note is that this substance is also used in paint emulsions, stemper and adhesive and therefore this is already prevalent in our urban environments this chlorozylonol has been found to develop resistance in pseudo-bonus orginosa this is a common pathogen in humans it caused many stem on related disorders and many other health complications in humans and there are many modes which have developed resistance to this substance let's next look at benzalconium chloride this is active ingredient in many lysol-based formulations for toilet cleaners although not all lysol formulations have this substance this is a long chain organic compound with the positive charge it's a part of category of compounds called quaternary ammonium salts this is a part of cationics affected surfactants category the way this work is that they disrupt negatively charged lipid bilayers in microbes or even in viruses and the mechanism is very similar to soaps these are salts as you can see and therefore they are non-volatile usually they are white solid and highly water soluble interestingly benzalconium chlorides are also used in eye drops nasal and ear drops though they have been controversy about its safety for human health inducing in these formulations what is interesting about this substance is that extended use of this substance induces resistance to many antibiotics and not just to itself it's not that the bacteria just stop caring about this substance or develops resistance to it there are many mechanisms many direct pathways it induces and makes bacteria fight or stay alive in presence of many other antibiotics and this research is this is a recent research which has shown that how these mechanisms operate this substance is toxic to many fishes and small animals but it has low toxicity to humans I must mention though that it has a unlike chlorozylonal it does undergo biodegradation relatively faster than the chlorozylonal next let's look at chlorhexidine dichlorobluconate it's also a quaternary ammonium salt that's a cationic surfactant it is water soluble and it's used in surveillance antiseptic products if you look at its chemical structure it looks quite complicated to draw your attention to that this substance has about 10 active nitrogen centers as compared to one center in the quaternary ammonium salt so it has multiple sites at which it can get protonated from the dichloronate the the acid which is available and it can therefore bind to the negatively charged liquid walls at multiple sites and therefore it is much faster in causing leaks and then it coagulates cytoplasmic proteins also this is also a part of mouth washes and skin washes it has been known to be not safe for eyes but it is very common in many mouthwash formulations that you may also be using this is has a very fast and high activity as I mentioned against bacteria and envelope virus and therefore it is active against novel coronavirus as well but not so much against pores fungi and non-enveloped viruses it has high residual activity because it it doesn't evaporate fast it doesn't wash is away extremely fast it can stick to your skin or surfaces for some time although few but there are some studies which have found resistance in some pathogens although the studies also claim that higher doses which are used in clinical settings are sufficient to deal with those infections now we come to soaps and detergents so technically soaps and detergents are not disinfectants the what they do is that they they are long chain fatty acids or sulphonic acid these are negatively charged entities as compared to the positively charged entities as you saw in the fortnery ammonium salts now these dissolve the lipid lipid layers and proteins and form mice you may have read about this in your high school science textbooks they are cleaning agents but as I have described they have inactive inactivating effect on most by bacteria and viruses but it's important I must mention that scrubbing is required because they do they are not very fast acting so as I was observed for the the novel coronavirus case it may take few minutes to dissolve all the bacteria and viruses particularly if they are present in clusters therefore scrubbing helps to at least get the a pathogen or virus in the solution phase it is important to note that some microbes can survive and actually thrive in soaps and detergents this can be important because we use soaps and detergents on a daily basis on such a large scale that all water all the sewage and all water bodies receive large quantities of these substances and there have to be bacteria in nature which can digest and break it down because if we have insufficient population of these bacteria in our environment what you see is a lot of foam and surfactant coming up in water bodies this is what is this is what we are actually observing in many rivers and lakes these days and therefore it's important equally important to sustain bacteria which can break this down. Second thing about soaps and detergents is that we have to be careful about using antibacterial soaps as I have said for dealing with the infection antibacterial soaps may be used but if used on a regular basis then antibacterial soaps can also kill bacteria in the surrounding and hence cause problems in the breakdown of these substances and also enhance cases of antimicrobial resistance in the surrounding now I come to important class of compounds which are nowadays not talked much about disinfectant but they have been classic disinfecting agents these are alkalis classic alkalis are NaOH, caustic soda, washing soda, sodium carbonate, calcium oxide lime, AOH and K2CO3 as we have just seen that most bacteria and viruses cannot survive over pH 9 but SARS-CoV does it survives in pH 12 now SARS-CoV once survives in pH 12 and above pH 12 it starts deactivating so we are extrapolating based on that that the SARS-CoV-2 is slightly easier to inactivate as compared to SARS-CoV-2 and quite similar to structure therefore it must also be responding to strongly acidic conditions and get deactivated. Now classically these has been used to clean and disinfect highly infected buildings inactivation by alkalis is a slow process it is actually a saponification process soap making process that these OH minus species reacts with lipids these are the fatty acids particularly in the membrane they form soap in C2 and then they use that soap to break down the membrane further this is a very interesting mechanism but it's a slow process we must remember that if you're using alkaline solution to mop a surface then a residual layer of very thin whitish layer of alkali may be observed after mocking and this layer if left as such can also provide further protection from pathogenic buildup or even biofilm development on surface if it is not hazardous to that or it is not corrosive to that surface and in particular we are now going to deal with monsoon season with lot of rains and for floors if compared to detergent mop surfaces alkaline mop surfaces may be slightly better because they are relatively less slippery than detergent particularly if not brought in contact with skin but in shoes and slippers certain precautions to be taken with alkali is that the solutions react with atmospheric carbon dioxide which cause the pH to reduce over time therefore if the solution is if the solution is prepared it must be stored in closed container and these solutions can be corrosive to metals therefore they cannot be stored or prepared in metallic containers but these are not corrosive to stone or cemented floors so they can be properly appropriately used on the same floors important thing to note is that alkalis can cause skin allergies and that was one of the reason why use has decreased over a period of time therefore if you use hand protection like gloves then we can use alkalis on many surfaces importantly there are lot of common alkaline substances that are used for cleaning which cannot be used for the novel coronavirus infection possible disinfection of surfaces so one of them is ammonia solutions ammonia solutions even if you take concentrated solutions it gives you a solution of pH 10 to 12 if you want to mix some strong alkali like sodium hydroxide to increase the pH further then ammonia will start get coming out of the solution and therefore ammonia will not be very helpful as disinfectant in this particular case similarly baking soda a lot a lot of people are recommending baking soda because it gives you a slightly alkaline solutions which are relatively safe which have pH of about 8 to 9 but as such this solution is not fully effective against the novel coronavirus similarly borax solution which is also known as suhaga in hindi in many places in india then this borax solution also cannot give you so cannot have pH higher than 10 therefore this is not so effective in this case some of easy to make alkali solutions with pH 12 are what is caustic soda solution caustic soda may be available as solid or even in solution form in hardware shop which is used to clean clogged sinks and water pipes so if you take about 2 gram per liter solution it will give you pH above between 12 to 13 please note that even 0.5 gram per liter solution is sufficient to give you pH 12 but i am giving a number which is slightly on the higher side to take into account if there are any impurities in the substance which you have procured washing soda solution if you take 11 gram per liter solution of sodium carbonate it will give you pH between 11 to 12 but it's very difficult to go about pH 12 with washing soda solution so if you take a slightly lower concentration of washing soda about 10 gram per liter and add about half a gram or even slightly less of caustic soda in it it will give you a solution pH greater than 12 an advantage of this solution over the caustic soda solution is that it has buffering properties and therefore the pH drop would be slow as compared to the caustic soda solution even on prolonged usage a third easy to make solution alkaline solution is if you take a well burned ash from burned wood or dried biomass such as cattle done cakes and if it's it must be fully burned like greyish white ash has to be used if you take 50 gram of this ash and mix it in one liter of solution and filter this solution through a filter paper or a very coarse tight cloth then if the clear solution will have pH above 12 or higher in some case if you have pieces of one burn biomass then you may acquire higher amount of ash getting the same pH if ash is too black that means it is not fully burned it's partially burned or the ash of the extract obtained is strongly colored which may indicate presence of heavy metals in the solution then this solution must not be used and second thing if you are dealing with hard water then sometimes higher amount of italy may have to be used one suggestion is that in hard water sometimes you can add a little bit of edity or even citrates of citric acid to deal with this hard water problem we must not forget the heat treatment that in warm seasons the surface is exposed to sunlight can easily develop temperatures about 56 50 degree centigrade so if we have exposure to more than 56 degree centigrade for half an hour then that is sufficient to deactivate the novel coronavirus so we can we must know that surfaces which are outside the roads the buildings which have been exposed to sunlight are already disinfected if they are exposed to sunlight higher temperatures reduce the deactivation time so now we have autoclaving steam cleaning or cleaning with closed very hot temperature water even treatment two to five minutes will be highly effective in disinfecting a surface wherever possible this should not be forgotten so here except for alicline solution as i've said formulations for other disinfectants are already commercially available you may have to do adjustment for according to local conditions so i would suggest if there are local labs chemistry labs in school colleges they can do optimization and then circulate to local people the appropriate quantity and dilutions to be used this is important particularly in some local markets concentration and purity which is available maybe slightly different and temperature and the quality of water may be different so after looking at disinfectants let's look at let's look at some of the common application practices and what are the practices to be avoided and what to be encouraged in the last two months you may have heard that in an effort to ensure disinfectant in public places particularly people coming and going out of institutions several places sanitization sprays have been done and particularly sanitization tunnels were set up in which people entering were sprayed with disinfectant solutions however later even ministry of health and family welfare government of india issued advisory against disinfectant tunnels because there was a possibility that these disinfectant solutions can cause harm to eyes skin and if inhaled they can also cause respiratory problems allergies which can further complicate matter in covid as well as non-covid cases the US department of health and human services has already been recommending against disinfectant fogging even in patient care areas so this is a recommendation I'm quoting from the current website but the recommendation exists since year 2003 now WHO also in May 15 very recently issued an advisory against disinfection fogging in public spaces and they gave a very important reasoning about it they mentioned that organic matter can impede direct contact of a disinfectant to a surface and inactivate the mode of action of several disinfectants as I have already mentioned that many of the disinfectants are reactive substances and when you spray them in air and they go and react to a surface they may first react with a lot of organic matter and debris which exist on the surface and they get they may get used up and no disinfectant is left over for completely inactivating a particular virus or a bacteria which we intend to do they have gone further to write that in indoor spaces I'm reading from portions of that advisory in indoor spaces routine applications of disinfectant to environmental surfaces by spraying or fogging is not recommended for covid-19 if disinfectants are to be applied this should be done with the cloth or a wipe that has been soaked in disinfectant because there may be this organic matter there may be biofilms or many other things so if you wipe with the cloth it will remove that film and ensure that disinfectant comes in direct contact with the surface wherever we intend to disinfect secondly they have mentioned that some countries have approved no-test technologies for applying chemical disinfectants which involve vaporized hydrogen peroxide, UV radiation chambers and devices now they mentioned that these technologies supplement but do not replace the need for manual disinfecting and disinfecting procedures so this is very important to note that we cannot even though we have no-test technologies but we cannot completely rely on that they cannot ensure complete disinfection spraying or fumigation of outer spaces such as streets or marketplaces is also not recommended to kill the covid-19 virus or other pathogens because again as the similar reason the disinfectant is inactivated and it's not feasible to clean manually and remove all organic matter from such places and more importantly what they have mentioned that street and sidewalks are not considered to be reservoirs of infection to covid-19 so we have to be very careful that are we wasting a lot of our efforts in doing efforts doing things spraying at spaces where actually it's not needed rather we want to focus our efforts on disinfectant practices which will help achieving the necessary disinfection I would also like to mention and declaration by association of occupational and environmental chemist clinics in USA they have declared sodium hypochloride as an asthmogen because it can irritate it can cause oxidative oxidative damage to inner lining of our respiratory system and cause many allergic problems in many people so while we have been recommending what not to do let's look at what are the best practices for cleaning and disinfecting so generally during all times if we are to clean our hands or surfaces with a particular cleaning agent gentle stripping is always recommended because it ensures that whether there is a biofilm or there is a cluster of viruses or pathogens which are sticking to the surface they get cleaned out which doesn't just does not happen by near contact with the soap solution secondly cleaning or cleaning mobs or clothes should be well soaked for 10 minutes in soap or detergent solution before and after cleaning this is to ensure that no active virus gets transferred from one surface or from cloth to the surface you're going to soaking in 5 to 10 minutes in a soap solution ensures that even if there is a little virus or pathogen left if we get dissolved in the soap solution third thing is that if you if at all we are using aggressive solutions such as hypochloride or peroxide it must be used after a cleaning by soap or detergent solution because it can supplement you know the disinfection of space but it cannot take the place of soap and detergent cleaning and fourthly safety gears must be used gloves and particularly face mask whenever we are using relatively more aggressive cleanings now we come to extremely infected space because for example if you have a patient at home where there is a likelihood likelihood of infection spreading or you are managing a public space or workspace where you have a lot of people coming in and going out some of them may be infected in general we should not forget that soap and detergent must be used for general purpose cleaning hypochloride iodine solution hydrogen peroxide or other fast acting disinfectants may be used whenever fast disinfection is required alcohol based sanitizers povidone iodine solution and soaps should be used for hand sanitization as we some of us already know it's being recommended these cause dryness to skin therefore moisturizing cream or oils may be used for adding skin dryness in confined spaces if significant disinfection is noted spraying may be done using hydrogen peroxide preferably or less preferably hypochloride and if it is done it must be done in absence of patient and there must the space must be left free for about few hours about 10 hours before another the any patient or any person comes to inhabit that space then wherever possible steam or hot water treatment must be considered for cleaning or treating heat stable surfaces particularly metallic surfaces ceramic surfaces because these do not leave any residue and eventually the place is much safer and for such spaces all cleaners must be given full body protection at least for face hands and feet and the clothes which they wear they it might be nice if they can wear a overcoat or something to protect their regular wearing clothes and whatever clothes they are wearing must be washed after they have done disinfection of the space or cleaning of the space now for regular cleaning of space particularly homes and public spaces as I already mentioned I will add a few more important things soaps and detergent again for regular cleaning of clothes hands and high contact surfaces for example door handles water taps in bathrooms and toilets these are particularly important thing for every time we don't have to clean these spaces the high contact surfaces with a disinfectant soap cleaning is quite sufficient for most cases now we may want to consider alkaline solutions for cleaning and persistent sterilization of surfaces particularly of floors cooking and eating areas such as canteens and bathrooms because these are the places where biofilms can usually tend to develop more often and if the water is hard some small amount of EDTA or even citric citric acid can be mixed to to deal with the hard water problem as we have mentioned that coronavirus coronavirus is in general and this novel coronavirus is quite stable at cold surfaces therefore cold objects and surfaces should be paid more attention with respect to cleaning for example cold food packets such as milk packets storage spaces such as refrigerators should be cleaned with soap water hydrogen peroxide or any other alternatives based on food safety considerations wherever possible at other places heat or steam treatment should be considered the spaces must be ventilated we should try wherever it's possible to expose a room or a space to direct cell lines for at least half an hour to an hour in a day simple water based cleaning must be done wherever no infection is suspected for example if there is a room which is very little used or where you are only the household members are staying they are not going out too much then water based cleaning is sufficient there is no need of using disinfectant regularly if at all at some places disinfectants have to be used it is recommended to use multiple methods of cleaning and disinfectant must be used in cycles to prevent antimicrobial resistance for example if you are using cyclohexanone or benzylconium chloride based formulation use them every two to three weeks and in the on a daily basis you can use simple water cleaning or other soap or detergent cleaning as per the requirement maybe now in busy market places and Mondays this is this is one of the biggest concern nowadays where a lot of crowd comes and a lot of vendors also come for selling and in some such places many vendors may not be able to afford more sophisticated sanitization practices one simple solution could be to keep cotton clothes or towels that are wetted with soap detergent or alkaline solutions which may be provided by the local market authorities or any other non-volatile disinfectants and then these clothes can be relatively you know they should not be dripping with water and these clothes can be used for covering food stocks such as food baskets or something and also for quick wiping of common use surfaces for example payment counters because these are constantly touched by shopkeeper as well as customers this practice is similar to what we commonly do with disposable disinfectant wipes but here I'm not recommended disposable wipes because again that would increase the waste and moreover we are already dealing with a big waste problem I'm just coming to that such a practice can really create transmission barriers in busy market places and prevent food stocks from getting contaminated so there is there is a lot of other public surface infrastructure that needs to be regularly sanitized because of high use by patients or service staff who are interactive with the public health services protocols have been suggested by NIOA in government of India now here I'm suggesting alternatives because they are one of the common disinfectant which is suggested is hypochloride yes it is it will work but there are some other safer alternatives which if available can be used for example for containers being strollies which carry medical waste or any other kind of infectious waste washing soda or lime powder may be used even as a dry powder may not be in the solution form and if you leave little bit of washing powder at the bottom of the container and with a waste bag on the top of it this lining can also help produce order in this waste bucket for the bin and intermittently the bins can be washed with hypochloride with or hot water solution hot water solutions are also quite effective in such situations next we have vehicles which are used to transfer to transfer sometimes the waste sometimes other sensitive material and also which have high risk of getting contaminated so the storage spaces in these vehicles can be cleaned with detergents solutions on the regular basis hypochloride or hot water may be used on occasional basis one more material which can be used for these spaces hydrogen peroxide if it is available now we come to vehicles and particularly sitting areas for example in cars trucks or in public buses their hydrogen peroxide sprays can be done on the seats a better alternative would be if it's possible to use cotton sheets to cover the seats and after the user has used them these can be washed regularly with detergents and particularly the high surfaces such as door handles window window surfaces should be cleaned with the soap or detergent water not by directly putting the water but with the drag which is soaked in these soap solutions intermittently if regular cleaning of a sheets covers is not possible then the covers may be cleaned with chlorozylonal or chlorhexidine washes intermittently because these persist on the surface and in such emergency situations these disinfectant can provide a long-term barrier to infection from spreading from one person to another if other options are not available now we come to toilets particularly public toilets because these are high risk spaces for spread of infection so in toilets on a daily basis detergents and alkaline substances can be used for cleaning which are highly effective for removing biofilms they they along with them sometimes citric acid or sodium citrate wash can be used if it is possible particularly if the water is hard and intermittently these spaces can be cleaned with acidic toilet cleaners and hydrogen peroxide because sometimes alkaline substances may produce overuse slight linings of salt deposits which can be easily removed by acidic toilet cleaners for personal protective equipments and aprons sometimes alcoholic washes may not be the most appropriate thing in such cases I've already mentioned hydrogen peroxide can be used to clean them on a routine basis by some times as short spray and with whenever it is possible or if it is appropriate then detergent and hot water washing can also be done to the protective or aprons which are used by healthcare providers and particularly the people handling based on a regular basis another recommendation I would like to make for sewage effluent treatment particularly now sewage is being considered as one of the possible means of community transmission and as I mentioned sometimes effluent coming from treatment plants may not be fully I mean we still have bacterial load and one of the treatment which is recommended is hypochloride or chlorine treatment of this effluent another option which is possible is ozone treatment which ozone on reaction with water produces hydrogen peroxide and hydrogen peroxide as I mentioned we have seen it's quite effective against the novel coronavirus and ozone producing machines are quite easily available in the market they are being used in dealing with several lakes lakes which had got severely polluted it has really helped in bringing back the ecology of the lakes we have to be very careful that the ozone concentration must be well controlled because high concentration of ozone sometimes can cause problems health problems to humans animals and also plants in the nearby vicinity so apart from using disinfectant there are many other preventive strategies that can help us in these times one I have already mentioned keeping spaces well ventilated minimizing closed and confined spaces secondly we have to be very particular about minimizing waste production in these times because as you know all municipalities are already under a lot of stress in dealing with the waste and they are dealing with low human resources to deal with more waste being generated and we have to be very particular about not producing single use disposable waste because as you all know no one bothers about disinfecting or cleaning a single use disposable before throwing it can it is true for whether we use face mask whether we use a spoon for example if you have used a spoon to eat something you would not bother about washing and cleaning it off before throwing it away and now I don't need to explain that this is a very important and very likely source of community transmission as plastic surfaces are plastic surfaces are big as coronavirus has long persistent time several days of persistent time on plastic surfaces these sometimes you go to close to dumpsters you can find these single use disposable bin thrown anywhere on the sides of streets or in heaps and we have to do our responsibility in ensuring proper use and not just disposable disposal of waste which we are producing through our house courts and offices by ensuring wherever possible to do proper repair by recycling of materials and chemicals whatever we use in homes and offices and trying to address chemical biological waste that we are producing by composting it at on site whether in homes or offices and wherever the waste is infectious it should be incinerated now since the pandemic which we are dealing with is a result of ecological imbalance and harm we have to take active steps to nurture health ecologies we have to do whatever we can to ensure diversity of plants wild animals and other animals birds insects fungi bacteria and viruses in our surroundings one thing which you can easily do is maintain composting units because composting unit does not just help in dealing with waste but they are also rich sites for microbial diversity we should also try to think of gardens and public green spaces and not just for planting few varieties of trees for aesthetic purposes but also see them as wild ecological spaces where multiple species of plants animals birds and other creatures can create micro ecological niches further we should try to think about using healthy microbial cultures for example acrobasilis is a very good example in whatever environmental practices we can for instance in gardening and agriculture there are many many options being available nowadays so in summary I would like to say that sanitize and disinfect your surrounding but do with the awareness of the chemicals and their properties and wherever it is necessary do it otherwise try to opt for other options including simple water cleaning I would be happy to receive your comments questions and any corrections in anything I have said or mentioned on this presentation you can send them to my email address mentioned here and I would like to close by thanking my colleagues at Homi Baba Centre for Science Education for the valuable discussions and feedback they have given on this presentation thanks a lot