By: Delphine Farmer (@ChemDelphine) and Marina Vance (@marinavance)

With growing concerns over Coronavirus, more people are turning to the power of disinfectants to clean surfaces – and that is giving rise to a new set of indoor chemistry. While ordinary soap is surprisingly effective at breaking down the Coronavirus, bleach, alcohol, and ammonia are all rising in popularity – as are calls to poison control centers….

So what is bleach, and why can its improper use cause health problems? Chlorine bleach is a solution of sodium hypochlorite in water, which forms hypochlorous acid – HOCl. Hypochlorous acid is an oxidizing agent that attacks and destroys molecules in bacteria and viruses. Recent work has shown that hypochlorous acid causes proteins in bacteria to unfold – a process called denaturing.

But this same oxidizing potential that makes chlorine bleach such an effective disinfectant also makes it a powerful chemical agent in the environment – including the indoor environment of your own home.

When you apply a bleach solution in water to your floor or to a surface, the HOCl can volatilize and move from the water solution to the gas phase. Once in the air, it can react and oxidize the tissues of your lungs, but it can also go on to react with indoor surfaces to form the quite toxic molecular chlorine gas, Cl2.

Mixing HOCl with ammonia will lead to a particularly lethal set of molecules – the chloramines. These molecules are why chemists and bleach manufacturers warn you not to mix ammonia cleaners with chlorine bleach! But humans naturally emit ammonia – and the compounds that are part of dirt and food debris that we often have on our floor can also react with bleach and form an array of toxic compounds!

In fact, you shouldn’t mix chlorine bleach with any other cleaners. Mixing bleach with pine- or lemon-scented cleaners will start a cascade of chemical reactions that will form tiny particles in the air, while mixing chlorine bleach with alcohol will make chloroform. Even vinegar spurs the formation of that toxic molecular chlorine gas when added to bleach, so please just use bleach according to manufacturer’s instructions and make sure any room is well-ventilated with open windows and fans. Wear gloves, safety glasses, and whatever you do, don’t drink or ingest it at any concentration. While this compound is a powerful disinfectant and great at destroying microbes, you want to make sure your lungs and your skin are protected from it – and any of its toxic chemical products!