Planetary health and WASH: causes and consequences

What is planetary health?

Humanity is emitting too much CO2 and using ever-increasing amounts of energy and water. The human population is set to swell for the foreseeable, requiring both more food and the water to grow it. At the same time, climate change is threatening progress across the board.

These trends have spurred a new way of thinking about the health of humans and our world: planetary health. First articulated in a Lancet commentary in 2014, the concept was expanded upon in a 2015 Lancet Commission, which defined planetary health as “the health of human civilisation and the state of the natural systems on which it depends”. This emphasises the interconnectedness of societies and ecosystems. Climate change understandably dominates planetary health discourse, but its other major themes include soil/food, water resources, and biodiversity.

How does planetary health relate to WASH?

WASH services, particularly sanitation, contribute to pollution of water and greenhouse gas (GHG) emissions, predominantly methane. On the other side of the coin, WASH services are likely to be harmed by climate change and other environmental degradation. I tried and failed to find an existing conceptual framework combining this “cause and consequence” perspective, so made my own (Figure 1).* Click here for a higher resolution version.

All of the consequences are likely to have knock-on impacts on human health, quality of life and livelihoods, which is part of the point of planetary health. Another angle is that better WASH services, including having multiple options available, can make people more resilient to shocks. However, in this post I focus on the consequences for WASH services to keep things manageable – this paper provides a useful review including some of the climate-related health consequences. I have seen little work explicitly applying the planetary health concept to WASH, though reams of it touches on the issues without using the term. Notable exceptions are this report on sanitation and planetary health, and this feature on planetary health approaches for dry cities.

WASH causes

Taking the climate aspect of planetary health first, sanitation is an important contributor to GHG emissions via methane (and nitrous oxide) from wastewater treatment and pit latrines. Methane emissions contribute to about a third of today’s anthropogenic warming, because it is about 30 times better at trapping heat in the atmosphere than CO₂. Wastewater contributes about a tenth of all anthropogenic methane emissions globally. This is likely to grow (emissions more than doubled over 15 years in China), but the relative contribution of methane emissions from pit latrines and septic tanks remains unclear.

In considering the impact of WASH services on climate, recall that infrastructure development of any kind currently uses fossil fuels and concrete. Operating water supply and sanitation assets also uses energy. Turning to other aspects of planetary health, human urine and faeces also contain phosphates and nitrates which contribute to eutrophication if discharged untreated, potentially harming biodiversity.

WASH consequences

Most planetary health consequences for WASH services are felt through water resources. The relationship between climate and water resources is reviewed in the World Water Development Report 2020, and this paper provides a useful WASH-specific review. Impacts are likely to vary by geography, but will be felt via changes in: (i) levels and intensity of precipitation (with snow melt also being crucial in some regions, e.g. South Asia); (ii) extent of aquifer recharge and surface run-off; and (iii) sea levels. These factors will interact on a local basis and may not reflect the standard newspaper image of dried-out mud. For example, groundwater is less vulnerable to changes in rainfall than surface water, and availability may be resilient in some areas, depending on precipitation-recharge relationships.

There are three major WASH-relevant areas of impact from these changes, taken in turn below.

Availability and quality of groundwater and surface water

First is the availability and quality of groundwater and surface water, and thence the amount of usable source water for water supply. Considering piped water systems, the further that source water is from being of drinkable quality, the more extensive the treatment processes needed. The less the surplus of water production potential over demand, the higher the risk of “day zero” (see Cape Town and Chennai). Users relying on point sources (e.g. wells, springs) may see changes in water quality or quantity making their lives much more difficult. The lower the water availability, the less likely handwashing becomes. The sanitation consequences of such fluctuations are discussed below.

Considering other areas of planetary health, the ways in which agricultural practices impact on water and soil can in turn affect the availability and quality of groundwater and surface water (e.g. contamination with fertilisers, impact of soil degradation on run-off and suspended solids). Less obvious is that greater biodiversity (e.g. in algae) can be beneficial for water quality. Also, despite most planetary health consequences for WASH being felt through water resources, climate can have a direct impact, for example through higher air and water temperatures affecting treatment processes.

Floods, droughts and storms

The second area of impact is through increases in extreme events like storms, floods, and droughts. The high flows and carried debris resulting from storms and associated abnormal rainfall can damage infrastructure, particularly for sanitation and drainage but also water supply. Storms can also interrupt power supply and in turn the operation of infrastructure. The onset of flooding can be rapid or slow, but either kind can contaminate water supplies and/or increase loading of suspended solids to levels exceeding the capacity of water treatment plants. Floods and pit latrines are not a good mix – contents can be inundated from above, or rising water tables can flood them from below. Droughts have obvious consequences for water supply, discussed above, but can also negatively affect sanitation, for example if there are insufficient water flows for sewerage operation. More detail on sanitation is provided in a WHO discussion paper.

Sea level rise

The third area of impact via water resources is sea level rise. This can affect source water availability and quality by saline intrusion. Longer-term sea level rises threaten to overwhelm existing water and sanitation infrastructure in coastal regions. Consider that the majority of Lagos, Nigeria, is only a few metres above sea level and the mega-city already suffers from flooding.

Conclusion

We live in the anthropocene, the epoch in which humans are putting huge pressure on the planet, threatening our own health and survival. WASH services are part of the problem, to the extent that wastewater treatment and pit latrines contribute to GHG emissions. However, better WASH services are part of the solution in that they make people more resilient to shocks. Climate change is important but it is not everything. Other aspects of planetary health such as biodiversity have important interactions with WASH services both as a cause and consequence. Furthermore, in many of the poorest countries, there is likely to be more strain on water resources and WASH services from population growth, urbanisation and economic development than from climate change. Regardless of climate change, people’s lives will be improved if we make WASH services more resilient, whether to existing variability in water availability and quality, or to existing extreme events. Taking a planetary health perspective can help with this.

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*In this post I focus on the implications of planetary health for WASH services and vice versa, taking the impacts on health as given. I have also left out of the discussion (and diagram) how water demand might change in response to the trends described, e.g. through patterns of migration, urbanisation, population growth etc. Demand will also be affected by changes on the supply-side, including those influenced by planetary health factors. The diagram does not claim to be a complete picture of the relationships at play, just to capture the main ones. I also don’t consider this an area of much personal expertise. The main work I’ve done in this area was a three-country study with ODI focused on risk and options appraisal for climate adaptation in WASH. Therefore, I would welcome corrections or recommendations of things to read!