Sure — I may be mixing abstractions here, so let me spell out what I had in mind.
A 1000× reduction means that, in expectation, the protected environment has 1/​1000 of the relevant airborne particle concentration compared with the outside environment. So if an unprotected person would inhale 1000 relevant particles over some period, a protected person would inhale about 1 over the same period, ignoring spatial variation, time dynamics, leakage events, deposition, behavior, etc.
My intuition was then: if the minimum infectious/​lethal dose were effectively 1 particle, and if we wanted lifetime infection/​death risk inside the protected space to be below ~1%, then the protected person’s expected inhaled dose would need to be on the order of <0.01 infectious particles over the relevant period. With only a 1000× reduction, that corresponds to an outside unprotected expected inhaled dose of only ~10 infectious particles over that same period.
That seems surprisingly low compared to my own work on mirror bacteria. So I was wondering whether the 1000× target assumes one or more of the following:
the relevant environmental concentrations are expected to be quite low;
the true infectious/​lethal dose is meaningfully above 1 particle;
the 1000× PM10 reduction is only one layer, with additional reductions from UV, glycol vapor, surface controls, masks, behavior, etc.;
the target is meant as a practical near-term benchmark rather than a complete risk-reduction target.
So my question is basically: what outside concentration /​ dose /​ acceptable-risk model makes 1000× the right threshold?
I don’t quite follow, can you spell out the reasoning a bit more?
Sure — I may be mixing abstractions here, so let me spell out what I had in mind.
A 1000× reduction means that, in expectation, the protected environment has 1/​1000 of the relevant airborne particle concentration compared with the outside environment. So if an unprotected person would inhale 1000 relevant particles over some period, a protected person would inhale about 1 over the same period, ignoring spatial variation, time dynamics, leakage events, deposition, behavior, etc.
My intuition was then: if the minimum infectious/​lethal dose were effectively 1 particle, and if we wanted lifetime infection/​death risk inside the protected space to be below ~1%, then the protected person’s expected inhaled dose would need to be on the order of <0.01 infectious particles over the relevant period. With only a 1000× reduction, that corresponds to an outside unprotected expected inhaled dose of only ~10 infectious particles over that same period.
That seems surprisingly low compared to my own work on mirror bacteria. So I was wondering whether the 1000× target assumes one or more of the following:
the relevant environmental concentrations are expected to be quite low;
the true infectious/​lethal dose is meaningfully above 1 particle;
the 1000× PM10 reduction is only one layer, with additional reductions from UV, glycol vapor, surface controls, masks, behavior, etc.;
the target is meant as a practical near-term benchmark rather than a complete risk-reduction target.
So my question is basically: what outside concentration /​ dose /​ acceptable-risk model makes 1000× the right threshold?
Thanks, I follow you now.