=biology =medicine
Bleach is the most common disinfectant today. That's sodium hypochlorite,
made by absorbing Cl2 into NaOH. It's generally considered to kill bacteria
by disrupting cell membranes by oxidizing double bonds in fatty acids, but
like chlorine, it can also chlorinate tyrosine and amines. It's cheap and
works fairly well, but it releases chlorine gas, and can take a little while
to kill viruses.
Immune cells can also
produce
hypochlorite to kill bacteria they've "eaten". This is done by reacting
H2O2 with Cl-. A little bit of the hypochlorite can escape, and even that
can cause serious side effects.
That being the case, peroxyacids also
oxidize double bonds in fatty acids, so they should also work for
disinfection.
And they do. Peroxyacetic acid, which you can get by just mixing H2O2
and acetic acid, has occasionally been used as a disinfectant. But it's
volatile and smells even worse than bleach.
OK, so what if you use a
non-volatile acid instead? It also needs to be nontoxic and cheap, of
course. And it can't be too big, because it needs to be able to diffuse into
the bacterial cell membrane to some extent. Perhaps citric acid, or phthalic
acid?
And yes, peroxycitric acid
works fine as a disinfectant. But this is such "advanced technology"
that it was only figured out a few decades ago, and bleach production and
usage is apparently too entrenched for something that merely doesn't release
chlorine gas to compete. And the stability isn't bad; hydrogen peroxide is
normally more stable in acidic solutions anyway. This is less
storable than bleach powder in a sealed container, but bleach solution in a
plastic bottle doesn't last forever either, and refrigeration is fairly
effective at slowing peroxide solution decomposition.
Direct
sunlight is pretty good at killing most infectious bacteria. Pure blue light
can also kill bacteria without being particularly harmful to humans, by
catalytic production of radicals inside bacteria. "High
Intensity Narrow Spectrum light" disinfection with bright 405nm blue
light from LEDs is now being considered for use in some hospital rooms. You
could either pulse it, turning it on for a few seconds every few minutes
with a ramp up so people could close their eyes, or you could give people
blue-filtering glasses and run it continuously at the cost of more heat
generation and electricity usage, or you could control it manually. But this
does not kill viruses effectively; that basically
requires UV
light.
If you just want to kill viruses, a saturated solution of
CaCl2 should be highly effective at denaturing proteins. That has some
obvious disadvantages when used like most disinfectants:
- it will damage
skin by drying it
- if wiped on surfaces, it doesn't go away; it will
instead stay as a liquid or white powder, depending on conditions
However, it might make sense to use a bowl of saturated CaCl2 solution to
kill viruses on the outside of rubber gloves being worn.
- It should quickly
denature virus proteins.
- It's completely nontoxic in small amounts.
- CaCl2 is very cheap. (~$0.14/kg)
- It's nonvolatile, so it could be
kept in an open bowl.
CaCl2 is also somewhat soluble in ethanol; it
could potentially increase the disinfection effectiveness of ethanol, and
make denaturing it with methanol to prevent people from drinking it
unnecessary. There is
some
evidence of CaCl2 increasing disinfection effectiveness but it really
hasn't been studied much.