Thread by @jonlevyBU

1. What do exposure science and risk assessment, 2 core methods of environmental health, tell us about how to think about opening K-12 schools this fall?

THREAD

2. First, some definitions - exposure science involves the study of real-world contact with and uptake of toxic materials than can cause heath effects.

nature.com/articles/75004…

3. Risk assessment estimates the nature and probability of adverse health effects to people who may be exposed to toxic materials. And risk management tries to figure out what to do to reduce the risk.

4. A key tenet of risk assessment is the concept of risk-risk trade offs. Basically, you can’t get something for nothing, and you need to think about new risks you may be creating through your risk management efforts. And, most things in life involve some risk...

5. To schools - the only way to eliminate #COVID19 exposure risk is to never step foot in a school. But that doesn’t mean not to open schools. For one, it will create numerous other risks - mental health of kids, ability of parents to work, reduced learning, etc.

6. By analogy, the only way to eliminate car accident risk is not to drive, but we accept the risk for a desirable outcome. To extend the analogy, we are better off driving with seat belts, air bags, and rules of the road, to reduce risk. So how do we reduce risk in schools?

7. Exposure science has the concept of the hierarchy of controls, which we wrote about recently in the context of #COVID19

nature.com/articles/s4137…

8. Elimination of exposure is most effective, but is not always possible. Universal use of masks is incredibly important, but going upstream to administrative and engineering controls is key to truly reduce exposure risk.

9. This is where we need creative exposure-minded strategies. Improved ventilation systems are incredibly important but not always viable. But opening windows is easy and cheap. Or holding classes outdoors. Or repurposing large spaces like theaters.

10. De-densification is a key exposure-driven concept. But you can de-densify with fewer kids in the same space, or with a bigger space. And having adequate ventilation helps to address some (but not all) concerns with density.

11. Recapping - exposure science can help us figure out how to best reduce exposures, which are a function of intensity, frequency, and duration. It’s not one size fits all - the right solution will depend on case rates, outdoor temperatures, building configuration, etc.

12. But exposure science tells us that it is possible. We reduce exposures every day in occupational and public settings, through myriad measures the public never notices. It requires forethought, analysis, and yes, resources (which need to be provided to cash-strapped schools).

13. Risk assessment also reminds us that vulnerability varies across individuals, so the same exposure risk means different things to different people. At one level this is obvious - CDC high-risk categories - but there is also some variability that is not knowable.

14. What this means is that investment in exposure reduction will allow for increased frequency of use (more days in school), and will also allow for a wider range of people to find the risk tolerable with an adequate margin of safety.

15. This also means that we need to accept that what works for some people will not work for others. And that this will change over time as case rate changes, knowledge changes, and risk tolerance changes. We need flexibility.

16. Risk management also needs to keep equity front and center. If case rates are higher in low-income communities of color, and vulnerability is higher, narrow analysis might imply less in-person school there. But that would be inequitable in multiple ways.

17. Big picture, there is no magic bullet or one-size-fits-all solution. I can’t tell each individual school what to do. But I know that the disciplines of exposure science and risk assessment, applied thoughtfully and with local information, can get us there.

END

P.S. It bears repeating that, while a vaccine ends the pandemic, tools like exposure science and risk assessment will help us live through the pandemic with the smallest health burden and best quality of life possible.

P.P.S. Although this is a new context, it is in many ways a very old problem, with lots of relevant expertise. People like @j_g_allen @CorsIAQ @ShellyMBoulder have thought about healthy buildings for a long time. Lots of valuable guidance 👇

schools.forhealth.org/wp-content/upl…

P.P.P.S. I’m fully aware that what works in MA in Jan won’t work for AZ in Aug, what works for K won’t work for 12, and what optimizes health may not optimize education. Only by enlisting teachers, parents, and public health experts in true partnership can we figure this out.