Chapter 1 - The importance of chemical toxicants in Water, Sanitation, and Hygiene (WASH) provision

1.3 Moving towards transformational WASH

Biochar water treatment workshop in Kyae Kadaut Ywar village, Karen State, Burma/Myanmar lead by Myat Thandar Aung (front, right), Aqueous Solutions, May 2016.

My colleagues and I argue that achieving transformational WASH outcomes will require, at a minimum, addressing biological and chemical forms of pollution. To make this point, let’s consider some of the evidence regarding the effectiveness of the conventional WASH paradigm, which is only concerned about the biological dimensions of water quality. Conclusive evidence has emerged recently showing that – despite the several billion dollars spent annually promoting the conventional approach – WASH interventions that target pathogens alone fail to achieve key human health metrics[23]. 

The recent publication of the results from three large-scale trials of water, sanitation, and hygiene interventions, in different combinations with one another (e.g., water-alone, sanitation-alone, water+sanitation, sanitation+hygiene, all three together, and so on…) as well as coupled with nutrition interventions, sent shockwaves through the WASH sector*. The WASH Benefits trials in Bangladesh and Kenya, and the Sanitation, Hygiene, Infant Nutrition Efficacy (SHINE) trial in Zimbabwe revealed that conventional household WASH interventions are unlikely to reduce diarrhea or improve child growth (i.e., prevent stunting)[26]. Reduction in the incidence of diarrhea in households and improvement of child growth are key headline indicators used by the WASH establishment to determine the success (or lack of success) of different WASH interventions. The fact that the largest and most robust studies to-date showed no benefit of conventional WASH interventions to improve key health indicators has presented a serious existential challenge to the WASH sector!

The past couple of years since the trials’ results were published has seen an efflorescence of theories about “why WASH doesn’t work.” For example, the WASH sector is beginning to pay more attention to multiple additional pathways by which people living in poor circumstances, such as peri-urban slums, are exposed to fecal pathogens and other infectious agents. Recent work has shown that for small scale drinking water technologies that remove or inactivate pathogens to reliably achieve health benefits, high levels of adherence – correct, consistent, and sustained use of the treatment system at a rate of at least 90% – are required[27]. These are important expansions of the WASH repertoire for controlling pathogen exposures. An additional theory that my colleagues and I have proposed is that, since exposure to many chemical toxicants damages the immune system in ways that make people more susceptible to infectious diseases, WASH interventions that tackle pathogens but don’t remove chemicals might not achieve desired health benefits[18, 28]. 

The linkages are well established that exposure to waterborne infectious microbial pathogens such as some viruses, strains of E. coli and other fecal bacteria, and parasites like giardia leads to diarrheal disease and irritation of the intestinal tract. This makes it difficult to absorb nutrients, and thereby causes growth stunting in infants and young children[29]. Accordingly, conventional WASH interventions are specifically designed to remove, kill, or inactivate (prevent from reproducing) pathogenic microbes. For example, handwashing with soap kills bacteria on the skin. Commonly used conventional WASH technologies for treating drinking water include filtration (e.g., the BioSand filter, ceramic filters, and hollow-fiber membrane filters such as units made by Sawyer and the Lifestraw family of products), and chlorine disinfection. The drinking water intervention studied in the WASH-Benefits and SHINE trials was chlorination by sodium hypochlorite solution[30-32]. However, these conventional WASH technologies are not designed to remove chemical toxicants from drinking water.

Chemicals cause diarrhea and stunting, too

Infectious microbes like E. coli aren’t the only things that can cause diarrhea and stunting though. Thanks to the work of environmental toxicologists, we know that exposure to many chemicals can dysregulate immune function in ways that lead to greater susceptibility to pathogens and reduced effectiveness of vaccinations against infectious diseases[7, 33-36]. The effects of chemicals on the immune system can be particularly severe during developmental windows of increased vulnerability, such as in pregnant women and newborn babies. In fact, low-dose exposures that occur during embryonic, fetal, and early postnatal life can have far greater and longer-lasting effects than high-dose exposure in adults[20, 37].

In the next chapter we’ll learn about various classes of chemicals that you’d rather not have slathered on your food or swimming around in your drinking water. For now, we can summarize that immunotoxicty has been demonstrated for: various organochlorine compounds, several flame retardants and plasticizers, which are used in nearly all consumer products (bisphenol-A, BPA, is a well-known example), numerous pesticides, a few fluorochemicals also known as “per-and poly-fluoroalkyl substances” or PFAS for short, as well as arsenic and heavy metals such as lead, cadmium, and mercury[38]. Immunotoxicity has also been attributed to the air pollutants carbon monoxide and particulate matter (PM)[39]. This is a major problem in countless homes throughout the developing world where cooking is done over an open fire. Many chemicals have been shown to cross the placenta (even PM)[40], and/or to accumulate in breast milk[34, 41]. Breast milk plays a crucial role facilitating infants’ digestive tract development and providing anti-inflammatory and immunomodulation[41]. Therefore, the presence of chemicals in breast milk that adversely affect immune-development and inflammation response in newborns and young children are especially consequential[41].

Exposure to many chemical immunotoxins is linked directly with gastroenteritis and diarrheal disease. For example, recent studies in Bangladesh[42], Thailand[43], Tanzania[44], and Pakistan[45] have revealed increased incidences of diarrhea (and other ailments) among farmers occupationally exposed to pesticides. Studies have found gastrointestinal symptoms including diarrhea statistically correlated with exposure to organochlorine and organophosphorus pesticides, and PCBs[42, 44, 46-48].. Parabens, phthalates, and phenols (including BPA) have been linked with inflammatory bowel disease and chronic diarrhea[49-51]. Maternal levels of some PFAS compounds have been associated with increased incidence of gastroenteritis in children[36].

Exposure to many chemical immunotoxins also linked with child stunting. An important cause of stunting is exposure to chronic, low-grade inflammation during fetal and early life[29]. In countries with poor WASH circumstances infections and chronic inflammation of the gut is a constant fact of life. Infectious microbes and chemical toxicants delivery a double-whammy on the intestinal tract and developing immune system. Maternal exposures to arsenic, cadmium, mercury, lead, various organochlorine compounds, flame retardants, PFAS, and carbon monoxide and particulate matter air pollutants are all associated with preterm birth, growth retardation of the fetus and low birth weight, along with other deleterious health effects [39, 52, 53].

I could go on, but you get the idea. (For further reading see my article, “The role of chemical exposures in reducing the effectiveness of water-sanitation-hygiene (WASH) interventions in Bangladesh, Kenya, and Zimbabwe”[18]. Clearly, many factors besides waterborne pathogens contribute to impaired fetus, infant, and child development, as well as to diseases throughout an individual’s lifespan. And WASH interventions that block pathogens but give a pass to toxic chemicals are unlikely to ensure good health.

* By “WASH Sector,” I refer to the amalgam of government development agencies, non-governmental organizations, philanthropies, charities religious and secular, entrepreneurs, and University researchers collectively tasked with providing safe drinking water, along with adequate sanitation facilities and personal hygiene systems, to roughly half of the world’s population who currently lack these essential services'.


[Next up: 1.4 The origins of biochar water treatment]