Use of Correct and Appropriate Concentration of Disinfectant

Though I am not a professional in sanitation and public hygiene, being in a chemistry profession I would like to share to our esteem readers the appropriate concentration to be used while preparing the disinfectant. With the outbreak of the covid-19 pandemic, we see many frontline workers and other field workers in the municipalities sacrificing their life and are tirelessly working and sanitising all the potentially contaminated public places for the safety of our people. And with the partial relaxation of lockdown and with the advisory issued by the central and state government to ensure proper cleaning and frequent sanitisation of all the workplaces, it may not be within the reach of the professional sanitation team to sanitise all the public places, offices, institutions, colleges, schools and down to the village level community hall, panchayat hall, churches etc. Until a cure is found against this unseen novel coronavirus, all the frequently used places and potentially contaminated premises and areas, vehicles etc in all the districts need be cleansed frequently for general precautionary measures using products containing antimicrobial agents known to be effective against viruses. Although there is lack of specific evidence of the effectiveness of sodium hypochlorite against 2019-ncov virus, as per WHO report, the test carried out with SAR-Cov showed that sodium hypochlorite is effective. Therefore proper use of sodium hypochlorite bleach and other common disinfectants product should be made aware down to the local village level workers.

Household bleach is a strong and effective disinfectant. Its active ingredient, sodium hypochlorite, NaOCl is a strong oxidising agent. It denatures protein in micro-organisms and is therefore effective in killing bacteria, fungi, and viruses. Household bleach works quickly and is available at a low cost. Besides household bleach sodium hypochlorite, solid calcium hypochlorite commonly called bleaching powder or chlorine of lime [Ca(OCl)2] is also a type of disinfectant which produces hypochlorite.

Bleach irritates mucous membranes, the skin and airway, decomposes under heat or light and reacts with other chemicals. If mixed with acidic solutions chlorine gas is produced, and mixing with ammonia based solutions give rise to chloramines solution both of which contribute to toxic effects, and therefore caution should be exercised in the use of it. Improper use of bleach may reduce its effectiveness and overuse of bleach or using a bleach solution that is too concentrated results in the production of toxic substances which can be harmful to health, pollute the environment and disturb ecological balance.

Household bleach are available in different concentrations depending on the manufacturers such as; 3.5%, 5%, 5.25%, 6-6.15%, 10% sodium hypochlorite. The household bleach may contain upto 10% sodium hypochlorite, while industrial bleaches may be more concentrated upto 50% sodium hypochlorite. Due to inappropriate dilution or mixing, accidental exposures to chlorine are relatively common. Thus appropriate dilution of bleach is recommended for the disinfection of the environment.

-Always check the % conc. of sodium hypochlorite in bleach and accordingly prepare the desired % conc. of chlorine.

-Always use freshly prepared bleach solution, the effectiveness goes down on standing.

According to WHO guidelines and the MoHFW, Govt. of India, the chlorine concentration is recommended as 0.5% and 1% respectively for sanitising the outer surfaces etc.

The following chart may be helpful as ready reference for dilution/preparation of bleach to make the required % chlorine and be used for disinfectant (as per WHO & MoHFW, GOI)

-Precaution while Handling: Use PPE, Hand gloves, mask, Goggle or face protector

-Avoid: Mixing of bleach with acidic solution, it becomes toxic (e.g commonly used toilet cleaner harpic which is acidic )

-Side effect: Skin allergy, eye infection, sore throat , gastro intestinal problems

-Do not throw away bleach in the sanitary septic, throw the left over in the mud pit

Stay safe
Dr.T.Tiakaba Jamir
Chemistry dept, Kohima Science College, Jotsoma