Maintaining differential pressure gradients does not increase safety inside modern BSL-4 laboratories

Link post

This is a linkpost for Kurth 2022.

Context

After listening to Alison Young discussing biosafety failures with Luisa Rodriguez on The 80,000 Hours Podcast, I got curious about whether there had been any cost-benefit analyses on improving the biosafety of BSL-3 or BSL-4 labs. I had in the back of my mind past examples where opportunities to improve biosecurity had been exagerated.

I did not find any cost-effectiveness analyses[1]. However, I came across Kurth 2022. It says “directional airflow or a differential pressure gradient in airtight rooms within a secondary BSL-4 containment do not increase biosafety, and are not necessary”. I have not investigated the claims made in the article, but I found its conclusion surprising. I got the impression listening to the podcast that directional airflow, and a differential pressure gradient were critical safety measures even today. In any case, they may become much more important in the near future as bio capabilities increase[2], so do not start replacing expensive airflow systems with duct taped doors just yet!

It is also worth noting that optimal number of biosafety failures (and maybe even pandemics?) is not 0. As Bryan Caplan said:

Whenever there is a disaster, the normal reaction is, “Something has to be done to stop this from ever happening again.” Again, the question is: Maybe we should just stay the course, because this is the right number of disasters to have? Which horrifies people. But look, we shouldn’t have earthquake codes so strict that no building ever collapses, no matter what, because the effect on housing costs would be astronomical. So why don’t you tell me what is the correct number of houses to collapse in earthquakes [or biosafety failures]? And then we’re only going to cover it in the media if we exceed that number. You just imagine people’s heads exploding, like, “No, we have to cover every single one so that we can have the proper reaction!” This proper reaction is what makes housing costs too high.

Of course, it still makes sense to be aware of the risks, and I think it is great that Alison has contributed to that!

Abstract

This article discusses a previously unrecognized contradiction in the design of biosafety level-4 (BSL-4) suit laboratories, also known as maximum or high containment laboratories. For decades, it is suggested that both directional airflow and pressure differentials are essential safety measures to prevent the release of pathogens into the environment and to avoid cross-contamination between laboratory rooms. Despite the absence of an existing evidence-based risk analyses demonstrating increased safety by directional airflow and pressure differentials in BSL-4 laboratories, they were anchored in various national regulations. Currently, the construction and operation of BSL-4 laboratories are subject to rigorous quality and technical requirements including airtight containment. Over time, BSL-4 laboratories evolved to enormously complex technical infrastructures. With the aim to counterbalance this development towards technical simplification while still maintaining maximum safety, we provide a detailed risk analysis by calculating pathogen mitigation in maximum contamination scenarios. The results presented and discussed herein, indicate that both directional airflow or a differential pressure gradient in airtight rooms within a secondary BSL-4 containment do not increase biosafety, and are not necessary. Likewise, reduction of pressure zones from the outside into the secondary containment may also provide sufficient environmental protection. We encourage laboratory design professionals to consider technical simplification and policymakers to adapt corresponding legislation and regulations surrounding directional airflow and pressure differentials for technically airtight BSL-4 laboratories.

  1. ^

    Millett 2017 discusses the cost-effectiveness of mitigating bio extinction risk at a higher level, but does not go into specifics of improving biosafety. I encourage you to supplement a read of Millet 2017 with David Thorstad’s commentary.

  2. ^

    Although other safety measures should also be expected to improve.