On Environmental Health

Is environmental health the same as ecological health? Can we reconcile the tools we use to protect the environment with the ones we use to protect human life?

It is indisputable that the construction and expansion of human society have come at a cost to parts of the environment, and human health and environmental protection are sometimes at odds. In this context, what efforts have been made to improve our understanding of changes in the environment, what are we actually measuring as we try to understand the environment, and how are these measurements applied to change policy?

Environmental health is a branch of public health that concerns all aspects of the natural and built environment that affect human health. The WHO describes the elements included in environmental health as, ”Clean air, a stable climate, adequate water, sanitation and hygiene, safe use of chemicals, protection from radiation, healthy and safe workplaces, sound agricultural practices, health-supportive cities and built environments, and a preserved nature.” The public health aspect of environmental health is made clear by the fact that up to 24% of global deaths can be attributed to modifiable environmental risks. As the environment continues to be affected by the growing human population, intensive agriculture, and a warming climate, this figure is bound to go up.

Environmental and human health are thus inseparably linked and share one fundamental goal: the survival and health of the human species. Monitoring human health aims to help people avoid diseases and survive them if they are afflicted. The goal of monitoring and protecting environmental health is also primarily about ensuring human health, rather than actually ensuring the survival of the Earth, its ecological systems, or non-human organisms. This is different from ecological health which looks at preserving certain ecosystems or endangered species without necessarily concerning itself with human welfare.


The Birth of Environmental Biomarkers
In the 19th century, when industrialization led to widespread pollution, the link between the degraded environment and health problems forced the creation of public health efforts to address these mounting issues through sanitation and clean water initiatives. However, in the mid-20th century, the relationship between the environment and health crystallized and pushed the government to create new agencies (e.g., the U.S. Environmental Protection Agency (EPA) in 1970) that began to regulate pollutants and conduct environmental health research. Part of this work involved setting up new measurement systems and relevant markers of environmental dysregulation.

The following are a small sample of measures used to monitor environmental health:

Air quality markers
Particulate Matter (PM2.5 and PM10)—describing fine particles suspended in the air with diameters less than 2.5 micrometers (PM2.5) and 10 micrometers (PM10); nitrogen dioxide (NO2)—a gaseous air pollutant primarily produced from combustion engines; or sulfur dioxide (SO2)—a gas resulting from the burning of fossil fuels containing sulfur. Each are important as inhalation of these particles can lead to respiratory and cardiovascular diseases, as well as premature death.

Water quality markers
Biological Oxygen Demand (BOD)—indicates the amount of oxygen required by aerobic microorganisms to decompose organic matter in water; Chemical Oxygen Demand (COD)—measures the total quantity of oxygen required to oxidize both organic and inorganic substances in water; Heavy Metals (Lead, Mercury, Cadmium); and Pathogen Indicators (E. coli, Enterococci) which may indicate fecal contamination in water. All these measurements at high levels can harm human life in the short or longer term.

Soil quality markers
Soil pH; nutrient levels (Nitrogen, Phosphorus, Potassium); organic matter content; contaminant levels (pesticides, heavy metals). These markers affect nutrient availability, microbial activity, plant growth, and water retention and can pose risks to human health through food chain contamination.

Ecosystem health markers
Biodiversity Index—measures the variety and abundance of species in a given area; Indicator Species are species whose presence, absence, or abundance reflects specific environmental conditions; and Habitat Quality, which assesses the suitability of an area to support its native species.

These markers are essential elements of environmentalists’ toolkits. They identify areas of concern, provide a scientific basis for policy-making, and help guide sustainable development and environmental conservation efforts. Integrating these measures into a broader framework that balances environmental concerns, human development and health is a challenge and keeps evolving.


From Biomarkers to an Integrated Multi-System Approach
Based on these environmental biomarkers and others, a landmark study published in 2023 in Nature entitled “Safe and just Earth system boundaries” brought much attention to environmental health by setting new standards for what should be considered safe system boundaries. Importantly, the study went beyond the safety of maintaining a habitable Earth by incorporating ideas of justice in a rapidly changing world. It considered three types of justice to complement biophysical considerations: between different species (rejecting human exceptionalism and a real departure from traditional environmental health), between generations, and between countries and communities.

This ambitious approach aimed to combine vital signs of planetary health with indicators of human welfare, attempting to do an interdisciplinary science assessment of the entire people-planet system. In particular, it sought to protect the most vulnerable populations from disproportionate impacts of environmental degradation such as extreme temperatures and sea-level rise. These concepts were originally developed by Kate Raworth, an economist at the University of Oxford, who proposed “doughnut economics” as a framework for sustainable development for humanity, balancing ecological sustainability and social foundations (such as food security, health, education, etc.).

In some cases, boundaries calculated for safety (for example, what are the limits of  carbon dioxide emissions, ocean acidification, chemicals and air pollution for human safety?) align perfectly with ones for justice, but in others, maintaining justice requires more stringent boundaries regarding the effects of climate change and the use of aerosols, for example. Scientists acknowledge that our planet faces growing crises of water availability, nutrient loading, ecosystem maintenance, and air pollution, and while the situation is grim in almost every category, it is not beyond hope. More specifically:

Climate
The authors identify safe boundaries for warming by minimizing the likelihood of triggering climate tipping elements, maintaining biosphere functions, and accounting for previous interglacial climate variability. While they agree with the consensus that limiting the increase to 1.5°C above pre-industrial levels is essential to prevent severe climate impacts, particularly for vulnerable populations, they note that even then, significant harm could occur, especially for communities already facing high exposure to climate risks. Hence, climate actions must prioritize both reducing emissions and enhancing adaptive capacities of the most vulnerable.

Biosphere
The study highlights the urgent need to halt biodiversity loss and protect ecosystems. It distinguishes between two distinct settings: (1) the area of largely intact natural ecosystems and (2) the functional integrity of all ecosystems, including urban and agricultural ecosystems. These are treated differently as they provide different functions directly linked to environmental stability and human welfare. The authors emphasize that biodiversity is crucial for maintaining ecosystem services that support human life.

Water
As the term “rival” is derived from the Latin rivalis, originally “person using the same stream as another,” coming from rivus or “stream,” the importance of access to fresh water cannot be overstated in maintaining social order. The study proposes two spatially defined safe boundaries: (1) flow alteration boundaries for surface water, and (2) drawdown boundaries for groundwater. The authors stress that current water usage patterns are unsustainable and disproportionately impact poor and marginalized communities.

Nutrients
Nutrient cycles are heavily disrupted by agricultural practices and lead to soil exhaustion and toxic runoffs. The study sets safe boundaries for agricultural nitrogen and phosphorus surpluses to minimize eutrophication of surface water and dead zones in aquatic systems. Optimizing fertilizer use, recycling nutrients, and supporting agricultural practices that maintain soil health are required to reduce pollution and ensure that agricultural systems do not exceed planetary boundaries.

Air pollution
Air quality is a major concern, with aerosol pollution from industrial and urban activities affecting climate and human health. The study uses the difference in aerosol optical depth (AOD) between the northern and southern hemispheres as the main marker of pollution. The AOD measures how much direct sunlight is prevented from reaching the ground by aerosol particles. Scientists compare AODs because a rising north/south hemisphere difference can trigger tipping points and cause substantial adverse effects on hydrological cycles. Preventing excessive air pollution and major differences between regional AODs should reduce the threats to human health and improve social equality.


Environmental health recommendations have evolved based on our understanding of complex climate and ecological models but also on the weight we attribute to other considerations. The study presented here is in no way a comprehensive work on integrating all knowledge, but it is a systematic effort to combine many environmental models and set up a clear framework for policymakers based on ethical considerations beyond human welfare. The scorching temperatures that took hold of vast swaths of the US (and the rest of the world) is another reminder that the time for action is now, and developing precise yet tractable and understandable environmental markers is key for immediate and future global actions and policies.

– Jonathan Friedlander, PhD  & Geoffrey W. Smith



Engineering Biology
Jacob Oppenheim, PhD, and Entrepreneur-In-Residence at Digitalis Ventures, writes Engineering Biology at Digitalis Press:

This month, Jacob wrote about a number of surprising results concerning the success of machine learning in biology; ones that throw into question whether our models are learning biology at all. The implication of this work is that perhaps it is not Machine Learning that matters, but instead Active Learning as defined by the Design/Build/Test cycle.  Active Learning requires neither omniscient nor perfectly accurate models. Only that the representations used, and the models built on top of them, are faithful enough. If anything, these assumptions are weaker than we have traditionally thought.  The transformation of processes designed for solo scientists into active-learning-driven industrial discovery will demand a new set of tools and systems, most of which do not yet exist.



First Five
First Five is our curated list of articles, studies, and publications for the month.

1/ Fasting to beat cancer (not to starve it)
A team of researchers at Memorial Sloan Kettering Cancer Center has uncovered a new effect of intermittent fasting. Natural Killer (NK) cells undergo metabolic reprogramming, helping them survive in the harsh environment in and around tumors while also improving their cancer-fighting ability. The study published in Immunity shows again the importance of diet both in cancer treatments and in shaping the immune system more generally.

2/ Getting nutrients straight to cancer cells
Another orthogonal approach linking diet to cancer treatment is delivering certain nutrients specifically to the cancer microenvironment. A recent Nature Nanotechnology publication shows how packaging tyrosine into lipid nanoparticles and delivering it directly to tumor cells activates some metabolic pathways that slow down rapid proliferation in melanoma. A great example of food as medicine.

3/ Spatial biomarkers!
The effects of space travel on human health are actively studied. Unsurprisingly, our immune system is also altered by life in microgravity and a Nature paper aims to create a database of all these changes. By experimenting in microgravity in the international space station, they created the Space Omics and Medical Atlas (SOMA), highlighting all the differences between samples (and mice) who traveled in space and their earthling twins.

4/ E pluribus unum
A new single-cell sequencing technology called Strand-seq enabled scientists to show that about 1 in 40 human bone marrow cells carry massive chromosomal alterations without causing any apparent disease or abnormality. The study, published in Nature Genetics, suggests there may be more genetic differences between individual cells in our bodies than between different human beings. It shows that mosaicism is more common than we knew and not necessarily a driver of disease.

5/ And another study about whether coffee is good for you
Given how many studies have been dedicated to this subject, one might think it is one of the most important questions agitating the human mind. This GWAS study adds a (minor) piece to the edifice. While the article, published in Neuropsychopharmacology, convincingly shows that coffee consumption is genetically inherited, it still can’t say much about its effect on human health despite the large cohort size. Could it be time to retire the subject?



Did You Know?
In this section of our newsletter, we hope to demystify common terms and notions in our work as investors.

‍Investment Deal Flow
Deal flow is a term used by investment professionals (venture capitalists, private equity investors, investment bankers, angel investors, etc.) to describe the rate at which they received investment pitches and business proposals.  Investment professionals sort through the inflow of investment pitches and business ideas to determine what they consider to be the most profitable investments.  If they decide to move forward with an investment, they can provide not only the funding but also guidance and expertise to the entrepreneurs. While not a quantitative measure, the term indicates whether a business is going well or poorly.  Deal flow typically follows a cyclical pattern that can coincide with economic/market trends.

– Haiming Chen  & Dylan Henderson