Big if true: Three health interventions worth a closer look

[Deena Mousa]

Link post

There is some (inconclusive) evidence that biodiversity conservation, replacing dirt flooring, and reducing environmental noise exposure might be much more cost effective areas for global health funding than we currently price in. These findings are, in my view, ‘big if true’ - with a big ‘if’.

If you know of additional important research on these topics or are working on any of these areas, I’d be interested in your thoughts!

[NickLaing]

Love this.Has there really not been an RCT on floor replacements yet? That surprises me as it would be a relatively easy RCT to do. EarthEnable from Rwanda just won the 2 million dollar Skoll award doing this at scale.

GiveWell must have considered it I would have thought?

[Mo Putera]

Deena’s post only mentioned “of at least one large RCT underway, with results expected in a few years” without further reference, but on cursory googling it might be the CRADLE trial?

The Cement-based flooRs AnD chiLd hEalth trial is an individually randomised trial in Sirajganj and Tangail districts, Bangladesh. Households with a pregnant woman, a soil floor, walls that are not made of mud and no plan to relocate for 3 years will be eligible. We will randomise 800 households to intervention or control (1:1) within geographical blocks of 10 households to account for strong geographical clustering of enteric infection. Laboratory staff and data analysts will be blinded; participants will be unblinded. We will instal concrete floors when the birth cohort is in utero and measure outcomes at child ages 3, 6, 12, 18 and 24 months.

The primary outcome is prevalence of any STH infection (Ascaris lumbricoides, Necator americanus or Trichuris trichiura) detected by quantitative PCR at 6, 12, 18 or 24 months follow-up in the birth cohort. Secondary outcomes include household floor and child hand contamination with Escherichia coli, extended-spectrum beta-lactamase producing E. coli and STH DNA; child diarrhoea, growth and cognitive development; and maternal stress and depression.

We will report findings on ClinicalTrials.gov, in peer-reviewed publications and in stakeholder workshops in Bangladesh.

While GiveWell doesn’t seem to have looked into this specifically, this 2015 review of GiveDirectly mentioned that lack of cement floors was in one of GiveDirectly’s two sets of eligibility criteria for its standard campaigns:

Thatched roofs: To date, GiveDirectly has used housing materials to select recipients in all of its standard campaigns, enrolling households who live in a house made of organic materials (thatched roof, mud walls, and a mud floor) and excluding households with iron roofs, cement walls, or cement floors.170 In GiveDirectly’s campaigns in Kenya, about 35-45% of households have been eligible based on these criteria, while in Uganda about 80% of households have been found to be eligible.171 …

Happier Lives Institute’s 2021 annual review did mention cement flooring among the “micro-interventions” they wanted to look into (alongside deworming, cataract surgery, digital mental health interventions, etc), but I haven’t seen anything by them since on this, so I assume it didn’t pass their internal review for further analysis.

[Ulf Graf 🔹]

Happier Lives Institute made an analysis of EarthEnable which was in their chapter in the latest World Happiness report. I guess they will make a report about it in the near future but I am not sure. So they have looked at flooring and housing. :)

[Mo Putera]

Ah, I missed this, thanks! And I appreciate the pointer to EarthEnable in particular. Although it looks like their analysis stopped at the shallow level, so maybe no future report…

EarthEnable looks quite impressive by their own lights: 35,000+ “housing solution projects” completed or in progress benefiting 200,000+ people, and over 1,000 jobs created in East Africa (they “developed training curriculum for masons to learn to build our products to earn a livelihood of 2-3x the median income”). I also appreciate how most of their senior team seems local at a glance.

Just posting HLI’s chart here for others’ benefit:

Quoting their qualifier too:

Note that our task was to bring together all the work that had already been done. All the research had the same output (WELLBYs per dollar) but the inputs were ‘lumpy’: some analyses were much deeper than others. It was out of scope to re-analyse and update all the pre-existing estimates. So take this as the first word on the topic, not the last!

[Larks]

Thanks for sharing, some very interesting ideas.

I’m skeptical about the biodiversity point, at least at that level of generality. It makes sense there are some species that are important for human welfare, maybe in ways that are not initially appreciated, but it seems like a big jump to go from this to biodiversity in general being important.

The improvements to flooring and noise pollution make a lot of sense to me. One interesting intervention I’ve heard of for the latter is improving the regulations about backup warning alarms on trucks and other vehicles.

[Tristan D]

I have the opposite intuition for biodiversity. People have been studying ecosystem services for decades and higher biodiversity is associated with increased ecosystem services, such as clean water, air purification, and waste management. Higher biodiversity is also associated with reduce transmission of infectious diseases by creating more complex ecosystems limiting pathogen spread. Then we have the actual and possible discovery of medicinal compounds and links with biodiversity and mental health. These are high level examples of the benefits. The linked article gives the possibility of impact by considering two effects from bats and vultures. Multiply that effect by 1000+ other species, include all the other impacts previously mentioned and I can see how this could be high impact.

[Larks]

I don’t see how you can ‘multiply by 1000+ other species’ given these two examples were likely selected for being unusually large.

[Tristan D]

The point is, there are 8.7 million species alive today, therefore there is a possibility that a significant number of these play important, high impact, roles.

[Mo Putera]

I’m not seeing where Deena wrote that biodiversity in general was important?

Both studies suggest that protecting certain animal populations might have large, direct effects on human health that we’re overlooking. But there are good reasons to be cautious. These are outlier results; there isn’t much else in the way of evidence for estimates of this magnitude for the impact of biodiversity loss on human mortality. There’s also the possibility of publication bias. In particular, since both papers come from the same author, this may be driven by a file drawer effect, where a researcher looks at many potential similar cases but the null findings are less likely to see the light of day.

Still, if these effects are real, they could change how we think about conservation. Saving vultures or bats wouldn’t just be about biodiversity—it could also be a form of public health policy.

[Larks]

I think ‘biodiversity’ generally implies a commitment to maintaining a very large number of species, over and above the identifiable value each one provides. It’s not about protecting specifically identified valuable species.

[Mo Putera]

I think you’re right in general, you’re just pointing to a different thing than Deena is, so maybe tabooing “biodiversity” might be useful here. They’re at OP GHD so unsurprisingly the part of conservation loss they care about is human mortality impact.

A more biodiversity-as-you-said line of thinking fleshed out would probably look like this:

We are orienting to this issue at the ‘local systems’ level (see below). We acknowledge that many organizations are tackling related issues at the earth systems level (climate change) and individual level (animal welfare). We feel there are important, tractable and neglected strategies that emerge when operating at this level.

This table visualizes the relationships between ecosystems and other aspects of our world and core systems we speak to throughout this proposal.

Quantifying species diversity is an interesting mathematical problem in its own right. Tom Leinster’s slides make the case that the three popular measures of species diversity (species richness, Shannon entropy, Gini–Simpson index) all problematically diverge from intuitively-desired behavior in edge cases of consequence, so the formalisation you really want is Hill numbers, which depend on a so-called “viewpoint parameter” q that changes how the former are sensitive to rare species. (Your professed stance corresponds to low q; it’d be useful to know if your interlocutors prefer high q; Tom’s charts visualise this.) You can then extend this line of reasoning in ways that affect actual conservation policy.

[Dee Tomic]

Hi Deena, thanks for sharing this! As an occupational health epidemiologist, the point about environmental noise exposure particularly resonated with me.

In occupational settings, we take noise seriously: we monitor exposures, set enforceable thresholds, and implement controls. But in communities, chronic environmental noise often goes unmeasured and unaddressed – despite clear links to the health issues you mentioned.

There’s a lot we could borrow from occupational health to protect the public more effectively. A few examples:

1. Community noise mapping and thresholds: Just like exposure assessments at work, cities could monitor residential noise levels over time – especially at night – and act when WHO-recommended thresholds (e.g., 55 dB Lnight) are exceeded.

2. Zoning and built environment controls: Like engineering controls in workplaces, urban planning could prioritise noise buffers like green spaces, sound-insulating materials in construction, or rerouting traffic away from dense housing.

3. Noise fatigue tracking in high-risk populations: In occupational health, we monitor fatigue and hearing loss over time. A similar approach could be piloted in schools, elder care, or high-exposure neighbourhoods using wearable tech or longitudinal surveys.

Noise might be “invisible,” but it’s a modifiable risk factor. We just need to start treating it that way in public health.